throughput: the upstream direction, counted by the only party that can

The client generates the traffic and the server counts it. No grant is involved
- the client is sending its own packets, so there is nothing to amplify - but it
does need the server's tally, because only the far end knows how much arrived.
Without that number a sender measures how fast it can transmit, which is usually
just the speed of the local NIC and is not the question being asked.

A new wire type the server counts and deliberately never answers: a reply would
double the traffic and drag the return path into a measurement that is
specifically about the outbound one.

The tally is a counter, not a list, and short-circuits before the observation
log. A five-second run at 20 Mbps is around ten thousand packets; one struct
each would turn a measurement into an allocation storm on a shared server, and
nothing needs the per-packet detail since the client holds the send-side record.
The gap between the two counts is the loss.

direction=up on the throughput action sends nothing - it zeroes the counter, so
a second run in one session measures itself instead of inheriting the first.

Same honesty rule as downstream: measures_network is false when what arrived
matches what was offered, because then the path was never the constraint.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -40,3 +40,9 @@ keystore.properties
 
 # wrangler build/dev artifacts
 web/.wrangler/
+
+# Eclipse/JDT output from the VSCodium Java extension — not a build artifact we own
+echolot-app/*/bin/
+
+# Kotlin compiler scratch/error logs
+echolot-app/.kotlin/

CLAUDE.md

@@ -32,10 +32,25 @@ Keep prober result IDs aligned with the measurement-schema test-type registry.
 
 ## Versioning
 
-Prefer **patch** bumps (`server-v0.3.1`) for additive/incremental work; reserve **minor** bumps
-for real milestones. Don't burn through minor versions. Tags are namespaced: `server-v*` for the
-Go server, `v*` for the app. Pushing a `server-v*` tag runs CI → binaries + Gitea release +
-registry image; the server on fmr can `--self-update` from those releases.
+Both artifacts are **SemVer**. Prefer **patch** bumps (`server-v0.3.1`) for additive/incremental
+work; reserve **minor** bumps for real milestones. Don't burn through minor versions. Tags are
+namespaced: `server-v*` for the Go server, `v*` for the app. Pushing a `server-v*` tag runs CI →
+binaries + Gitea release + registry image; the server on fmr can `--self-update` from those
+releases.
+
+The app's version lives once, as `appVersionName` in `app/build.gradle.kts`; **`versionCode` is
+derived from it** (`major*1e6 + minor*1e4 + patch*10`). Never set it by hand — a second number a
+human has to remember to bump eventually disagrees with the first.
+
+**Versions are load-bearing** (probe-protocol.md §8): the server refuses apps outside its window
+with `426`, and the app refuses servers outside its own. Two axes, kept separate:
+- `protocol_version` — *can* they talk. The correctness axis; below 1.0.0 the **minor** is the
+  breaking axis.
+- release-version window — *may* they, per policy. `[min, max)`, bounds at breaking boundaries so
+  a patch never strands a fleet. Client bounds: `Compat.kt`. Server: `ECHOLOT_MIN/MAX_APP_VERSION`.
+
+Raise a minimum only when older peers are actively harmful, and say why in the constant's comment.
+`GET /v1/profile` must stay ungated — it is how a refused client learns what it needs.
 
 ## Layout
 
@@ -52,6 +67,29 @@ echolot-prober/                the capability prober (self-contained Gradle buil
     ui/ProberScreen.kt         result cards colored by verdict
 ```
 
+## Client modules (echolot-app/)
+
+Pure Kotlin/JVM where possible, so the interesting logic is unit-testable without a device and can
+be exercised against the live server from the PC:
+
+- `core-protocol` — control plane (pinned TLS) + ELT1 UDP data plane. **One `ProbeSession` per
+  server session, for its whole lifetime**: a second one restarts sequence numbers, the server's
+  anti-replay window discards every packet, and granted sends then target the closed socket.
+- `core-measurement` — the schema types. `core-engine` — composes probes into documents.
+- `core-privacy` — the §8 anonymizer (`full` / `balanced` / `strict`). Field classification lives
+  in one table (`Classification.kt`); keep it there rather than annotating models.
+- `core-archive` — on-device run storage + retention. `enabled` is separate from the three
+  ceilings: all-zeros means "no limits", not "keep nothing".
+
+**The local archive keeps the unredacted document; anonymization happens per upload, on the way
+out.** Never redact what is stored locally.
+
+### Live testing without a device
+`echolot-app/scripts/test-fmr.sh [gradle-task] [test-filter]` mints an enrollment token over SSH,
+enrolls, computes the SPKI pin from the served cert and runs a `Live*Test` against fmr. This covers
+the whole server-facing vertical (granted sends, downstream MTU, uploads) with no phone involved —
+use it before asking the user to test on hardware.
+
 ## Conventions
 
 - Every probe returns a `ProbeResult` — never throws to the caller (MainActivity wraps anyway).
@@ -83,6 +121,36 @@ First build downloads AGP/Compose/Shizuku from Google Maven + Maven Central.
 - Known devices: OnePlus 15 (CPH2747, A16) — Shizuku UserService works;
   Lenovo TB330FU (A15, multi-user) — UserService never binds, the `newProcess` fallback carries
   it. Full history in build-status.md.
+- **Wireless-adb beacon** (`echolot-app/adb-beacon` + `tools/adb-beacon/receiver.py`): the
+  wireless-debug port rotates every couple of minutes on these devices; the beacon reads the live
+  port from adbd's own mDNS (`_adb-tls-connect._tcp`, filtered to the device's own IP) and POSTs
+  it to fmr:443 (cleartext allowed; over a validated net); a PC connector polls and reconnects.
+  Bootstrap needs one manual adb connection to install it, then it self-heals. Existing adb
+  connections survive port rotation — only fresh connects need the new port.
+  **Resolve adbd's mDNS advertisement exactly ONCE per service instance** (re-resolving makes
+  adbd re-arm the connection, which spams "wireless debugging connected" notifications); the
+  periodic heartbeat only re-POSTs the cached port. Rotation is still caught: onServiceLost
+  clears the guard, so the new advertisement is resolved once and reported within seconds
+  (verified: 37089 -> 33667 reported 6 s after rotation).
+  **Known limitation — do not run the beacon on the OnePlus.** On network churn (SSID jump, roam)
+  adbd repeatedly drops and re-publishes its advertisement, so lost/found cycles keep clearing the
+  resolve-guard; each resolve makes adbd re-arm and post a "wireless debugging connected"
+  notification. Guarding reduces but cannot eliminate this — resolving adbd's own mDNS record is
+  inherently noisy on that device. Use manual `ip:port` there (ask the user), or read the port via
+  Shizuku (`ss -tlnp | grep adbd`, no mDNS) if the shell tier is available.
+- **Shizuku start kills the adb bridge and the beacon can't auto-recover it.** Shizuku's non-root
+  start pairs over wireless debugging and runs its starter through adb, hijacking the channel:
+  adb goes device→offline→refused, and adbd keeps advertising the now-dead port over mDNS (stale),
+  so the beacon reports a port that no longer accepts connections. Workaround: after starting
+  Shizuku, **toggle Wireless debugging off/on** — Shizuku keeps running (separate process), a fresh
+  port + mDNS record appear, and the beacon/connector recover. Plan the Shizuku-tier dev loop
+  around this (or USB, if ever available).
+- **Empty-jar race with the IDE.** VSCodium's Java/Kotlin extension runs its own Gradle daemon on
+  the same project; when it overlaps a CLI build, a module's `build/libs/*.jar` can end up
+  containing only a manifest, and Gradle then considers `jar` up-to-date. Dependent modules fail
+  with "Unresolved reference" on symbols that plainly exist. Fix: `rm -f <module>/build/libs/*.jar`
+  and re-run the `jar` task. Suspect this whenever a reference resolves in one module but not in
+  its consumer.
 - As of the AGP 9.2.0 / Gradle 9.6.0 / Kotlin 2.2.10 bump, JDK 17+ (including 25) works —
   AGP 9 requires Gradle 9.1.0+ and Kotlin 2.2.10+ as its minimum KGP version. On machines with
   Android Studio, its `jbr` directory works as `JAVA_HOME`.
@@ -94,3 +162,11 @@ First build downloads AGP/Compose/Shizuku from Google Maven + Maven Central.
    are SUPPORTED on both known devices via `Os.recvmsg` + `StructMsghdr` reflection.
 3. Fold the confirmed capabilities + Shizuku dump-format samples back into the production
    `core-probe` / `core-shizuku` modules.
+
+## Enrolling a device with a server
+
+`echolot-app/scripts/enroll-link.sh [note]` mints a §2.1 bootstrap link on fmr over SSH and prints
+it (plus a QR if `qrencode` is installed, plus the `adb shell am start -a …VIEW -d '<uri>'` command
+when a device is attached). The link carries a single-use token — treat it as a secret until spent.
+Never hand-assemble one: the base64 pin needs percent-encoding, and a pin wrong by one character
+fails as an inscrutable TLS error rather than as a bad pin.

docs/build-status.md

@@ -254,3 +254,690 @@ caught a finding: **Google applies 0x20 case randomization** (mixed-case qname),
 not — captured via `case_preserved`. Capabilities now: udp-probe, delayed-echo, connect-back,
 tcp-echo, stun-5780, canary-dns. Kept the hand-rolled stdlib DNS (no miekg/dns) — validated
 against independent clients. Deployed via `--self-update` (v0.3.0→v0.3.1, checksum-verified).
+
+## Server v0.3.2 + v0.3.3 (2026-07-31)
+- **v0.3.2 — control-plane security (live on fmr, externally verified):** `POST /v1/echo`
+  reflects the received request head+body (b64) and observed TLS (version/cipher/SNI/ALPN) —
+  captured real SNI `fmr-1.echo-lot.app` and an injected header over public TLS1.3; `GET
+  /v1/tls-reference` returns the served DER chain + pin (cross-checked against the openssl-derived
+  pin). Optional cleartext echo listener (default off). Capability `http-echo`.
+- **v0.3.3 — MTU probe (data plane):** MTU_PROBE (0x09) → small MTU_ACK (0x0A) carrying the
+  received datagram size; client DF-probes increasing sizes to find path MTU / black holes. ACK
+  is tiny → never amplifies. Tested.
+- **Note on trains:** upstream trains (TRAIN_DATA 0x03) are already observable — every HMAC-valid
+  packet is recorded (seq/t_rx/size/type) with no per-packet response, so loss/reordering/inter-
+  arrival are visible via GET observations. The dedicated data-plane TRAIN_REPORT (0x05) is
+  deferred: §3.4 anti-amplification means it needs an asymmetric grant + columnar multi-datagram
+  encoding — a focused batch, not a corner to rush.
+Remaining spec: tls-echo (ClientHello+JA4), TRAIN_REPORT, big/frag-send, throughput, downtrain;
+real admin UI.
+
+## Server self-test + host tuning — v0.3.4/v0.3.5, fmr proven good (2026-07-31)
+The daemon now proves its own host is a clean measurement target:
+- **sysctl audit** (`GET /admin/selftest`, startup warnings): on first run it flagged exactly 4
+  real issues on fmr — accept_ra=1 on a static-v6 host, accept_redirects=1, send_redirects=1,
+  icmp_ratelimit=1000. Recommended `server/deploy/99-echolot-sysctl.conf` applied (v6 default
+  route/addrs are proto static with 0 RA-derived routes, so disabling accept_ra is safe —
+  verified v6 egress intact after). Now sysctl_ok=true, 0 warnings.
+- **egress-MTU self-proof**: DF PMTUD via IP_MTU_DISCOVER + getsockopt IP_MTU (v0.3.4 had a bug —
+  read IP_MTU without connecting → ENOTCONN; v0.3.5 connects first). fmr reports 1500 on both v4
+  and v6 → mtu_ok=true, so client MTU tests are trustworthy.
+- Both signals ride in the profile as `server_selftest{mtu_ok,sysctl_ok}` so a client can skip
+  MTU testing when the server can't support it honestly.
+fmr profile now: `{mtu_ok: true, sysctl_ok: true}`.
+
+## Server v0.3.6 — tls-echo / JA4: spec §4 COMPLETE (2026-07-31)
+The elt-echo TLS variant runs on the TCP-echo port (8441), multiplexed by a timed 0x16 peek
+(plain echo stays server-speaks-first; a TLS ClientHello routes to the TLS path). It captures
+the full ClientHello, returns it raw (b64) + as a JA4 fingerprint (FoxIO), then TLS byte-echoes —
+the sec.clienthello_echo evidence. Hand-rolled ClientHello parser (ciphers/exts/ALPN/
+supported_versions/sig-algs, GREASE-excluded), unit-tested. **Cross-client verified on fmr**:
+openssl → t13d3013eo (30 ciphers), python ssl → t13d1712eo (17) — different stacks, different
+fingerprints, correct _a structure both. Capability tls-echo.
+
+Spec §4 (TCP/TLS/HTTP/STUN) is now fully implemented. Server capabilities: udp-probe,
+delayed-echo, connect-back, http-echo, tcp-echo, tls-echo, stun-5780, canary-dns.
+Remaining spec: §5 heavy actions (downtrain/big_send/frag_send/throughput) + the TRAIN_REPORT
+retrieval path — all gated on the anti-amplification grant machinery (§3.4) — and a real admin UI.
+
+## Production app — echolot-app/, core-protocol proven live (2026-07-31)
+Started the Android client, bottom-up from the verifiable spine. `echolot-app/` is a multi-module
+Gradle build; `core-protocol` is a **pure Kotlin/JVM** module (no Android SDK) implementing the
+client half of probe-protocol.md: SPKI-pinned control plane (enroll/profile/session via
+HttpsURLConnection — Android-API-1 compatible, hostname verification off since trust is the pin),
+HKDF-SHA256 session keys, and the ELT1 UDP data plane (HMAC gate, ECHO+observation, MTU probe) —
+byte-compatible with the Go server. Unit tests pass incl. the RFC 5869 HKDF vector (so key
+derivation provably matches the server). **Verified END-TO-END against live fmr** via
+`scripts/test-fmr.sh` (mint token over SSH → enroll on public control plane → run LiveServerTest):
+profile (8 caps), session, ECHO rtt ~11ms with the observation block round-tripping the client's
+observed NAT port, MTU probe 1400→1400, observations 298B. Two client bugs found+fixed doing it:
+java.net.http did hostname verification (switched to HttpsURLConnection) and ECHO needed ≥72-byte
+requests for the full 40-byte observation to survive §3.4 anti-amplification. Next: core-measurement
+(schema types), core-probe (port prober probes), core-shizuku (dual-path), Compose UI.
+
+## App: core-measurement + core-engine — full server-facing vertical proven (2026-07-31)
+Two more pure-Kotlin/JVM modules, both verifiable without a device:
+- **core-measurement**: the measurement-schema.md document model (two-clock, columnar trains,
+  test-type registry, anonymization types, finding-requires-evidence). The §7.3 deterministic
+  verdict derivation is implemented + unit-tested; document JSON round-trips.
+- **core-engine**: the run engine composing core-protocol probes into core-measurement documents.
+  Injected clock/UUID source (pure, testable). Runs a server ECHO train → RTT distribution, loss,
+  and NAT-rebinding detection (from the server's observed source port) as train.udp_updown.
+  **Verified END-TO-END against fmr**: 20-packet train, 0% loss, RTT 1.7/2.5/6.9ms, single
+  observed port (no rebinding) → valid MeasurementDocument (2.3kB), overall GREEN.
+So the whole server-facing stack — protocol client → engine → schema document → verdict — is now
+proven against the live server, no device needed. Next modules (core-probe device-tier,
+core-shizuku dual-path, Compose app) are Android + need on-device verification.
+
+## App: installable APK — core-probe + Compose UI (2026-07-31)
+The production Android app assembles. Android toolchain in echolot-app mirrors the prober (AGP
+9.2 built-in Kotlin — do NOT also apply kotlin.android, it double-registers the `kotlin`
+extension; that was the one build gotcha). Modules added:
+- **core-probe** (Android lib): Probe→core-measurement Test abstraction; NetworkInventory
+  (LinkProperties → measurement networks[]), LinkSnapshotProbe (link.snapshot), IcmpProbe
+  (per-network icmp.ping4/6, ported from the prober's validated per-network logic).
+- **app** (Compose): RunViewModel orchestrates probes → assembles a MeasurementDocument with a
+  §7.3 summary + first-pass findings; Compose UI shows overall/ per-category traffic lights,
+  networks, tests (status/metrics), findings; JSON export via share intent. Survives rotation
+  (ViewModel). App-tier only for now; server-facing (core-engine) and Shizuku tier are additive
+  follow-ups (app degrades gracefully without them, like the prober).
+Debug APK: 9.5 MB, `echolot-app/app/build/outputs/apk/debug/app-debug.apk`. Not yet run on device
+(needs the user's phone). core-shizuku (dual-path executor) deferred as additive.
+
+## App verified on-device — both phones (2026-07-31)
+The production Echolot app runs on real hardware, on BOTH devices, via the beacon-managed adb:
+- OnePlus 15 (CPH2747, A16) and Lenovo TB330FU (A15): link.snapshot OK, icmp.ping4 OK
+  (per-network, RTT ~40ms), icmp.ping6 FAILED → finding "No IPv6 ICMP path on any active network"
+  → category ipv6 yellow → **Overall YELLOW**. The verdict is driven by the real broken-LAN IPv6
+  (RA default route, no global prefix) we first found with the prober — the product now surfaces
+  it end to end (probe → schema → verdict → traffic-light UI).
+Wireless-adb beacon (tools/adb-beacon) made this practical: both devices self-report their
+rotating wireless-debug port to fmr:443; a PC connector keeps adb connected. Debugged live
+against the restricted LAN (cleartext policy, egress filtering, shared-LAN mDNS crossing, fast
+port rotation) — all handled.
+
+## App: core-shizuku (shell tier) built + wired (2026-07-31)
+Ported the prober's validated Shizuku executor into the app as a library module:
+- AIDL IUserService + UserService (runs `sh -c` as shell/root in the Shizuku-spawned process),
+  Shizuku provider merged into the app manifest.
+- **ShizukuRunner: the build-4 dual-path executor** — bind the UserService (25s + retry) where it
+  works (OnePlus 7/7), fall back to the legacy `Shizuku.newProcess` reflection API where it never
+  binds (Lenovo). `exec_path` records which path ran.
+- ShizukuProbe: runs the shell battery (ip neigh / ip -6 route / ip addr / ip monitor /
+  network_stack DHCP / wifi dump) and emits a shizuku-tier `link.ip_monitor` Test with the raw
+  per-device dumps as evidence + commands_ok/exec_path metrics. Self-degrades to UNSUPPORTED when
+  Shizuku isn't running.
+Wired into RunViewModel (runs after app-tier probes; sets tiers.shizuku). App APK assembles clean.
+On-device test deferred: at build time no device was reachable (tablet wifi/beacon dropped on the
+churning LAN; phone wireless debugging disabled to stop reconnect notifications). Will verify on a
+device later — expecting UserService on the OnePlus, newProcess fallback on the Lenovo, per the
+prober.
+
+## App on-device: net.captive_portal verified, Shizuku degrades correctly (2026-07-31)
+Installed the app (core-shizuku + net.captive_portal) on the OnePlus 15 and ran it; report archived
+at `echolot-app/reports/CPH2747-app-run1.json`. Results:
+- **net.captive_portal works** — Android's NetworkMonitor logic reproduced: default + wifi both
+  returned HTTP **204** on the HTTPS *and* HTTP generate_204 probes → `validated`; **cellular
+  returned neither (-1/-1) → `no_internet`**. The per-network split immediately surfaces an
+  asymmetry the OS hides (wifi validated, cellular can't reach the checks at all).
+- **Shizuku tier degrades correctly**: `binder_alive:false` → test UNSUPPORTED, `tiers.shizuku:false`
+  (Shizuku isn't running on the phone). The dual-path *executing* path still needs an on-device
+  test with Shizuku started (expect UserService on this OnePlus).
+- 5 tests now: link.snapshot ok, icmp.ping4 ok, icmp.ping6 failed, net.captive_portal ok,
+  link.ip_monitor(shizuku) unsupported → overall YELLOW via the IPv6 finding.
+Also fixed this session: the beacon app itself caused the "wireless debugging connected"
+notification spam (it re-resolved adbd's own mDNS advertisement, making adbd re-arm each time);
+now resolves once per service instance and the heartbeat re-POSTs the cached port only.
+
+## App: dns.canary verified against the live server (2026-08-01)
+Built the client half of the canary-DNS measurement and verified it on the OnePlus against the
+deployed fmr zone (`echolot-app/reports/CPH2747-app-run2-dns.json`):
+- All four spec-frozen reference records matched byte-for-byte through the network's own resolver
+  (ttl-5→192.0.2.5, ttl-60→192.0.2.60, ttl-3600→192.0.2.36, ttl-86400→192.0.2.86) → nothing on
+  this path rewrites DNS answers (`dns.answer_integrity` in the green case).
+- The un-cacheable nonce name `1006ad16.adhoc.c.echo-lot.app` resolved to 192.0.2.21 →
+  `reached_authoritative: true`, proving the query actually reached the canary server rather than
+  being answered from a cache or an interceptor.
+Findings wired: `dns.answer_rewritten` (high) when a reference mismatches, and
+`dns.authoritative_unreachable` (medium) when the nonce isn't answered by the canary server.
+This closes the first full client↔server measurement loop: the Kotlin app measures against the Go
+server's canary zone on real hardware. 6 tests now run per measurement.
+
+## App: Shizuku shell tier VERIFIED on-device — the app is feature-complete for v1 tiers (2026-08-01)
+Ran the app on the OnePlus with Shizuku running (`echolot-app/reports/CPH2747-app-run3-shizuku.json`):
+- **`tiers: {app:true, shizuku:true}`**, shizuku test **ok**, **commands_ok 7/7**,
+  **`exec_path: UserService`** (the OnePlus binds it — matches the prober; the newProcess fallback
+  stays for the Lenovo).
+- Evidence is the real privileged material the production parsers need: live ARP/NDP neighbor
+  table, per-table IPv6 routes, `ip addr`, an actual `[NEIGH]` netlink event from `ip monitor`,
+  IpClient DHCP logs incl. APF capabilities, and the wifi state dump — all as shell(2000).
+Both privilege tiers now work end to end in the production app on real hardware, alongside the
+canary-DNS loop against the live server. 6 tests/run: link.snapshot, icmp.ping4, icmp.ping6,
+net.captive_portal, dns.canary, link.ip_monitor(shizuku).
+
+## App: nat.stun_5780 — NAT behavior discovery verified against the live server (2026-08-01)
+Client-side RFC 5389/5780 STUN (hand-rolled, stdlib only) exercising the server's `stun-5780`
+capability. Three binding requests from ONE socket: primary, the server's OTHER-ADDRESS
+(alternate IP), and CHANGE-REQUEST(port). Verified on the OnePlus
+(`echolot-app/reports/CPH2747-app-run4-stun.json`):
+- local `10.13.102.124` → mapped `178.191.120.247:53259`, `behind_nat: true`
+- `other_address 89.185.109.151:3479` — the server's second IP answered, so RFC 5780 works
+  end to end (client ↔ our own STUN implementation)
+- **mapping: endpoint-independent** (same external port toward a different destination → P2P
+  friendly); **filtering: address/port-dependent** (no reply to CHANGE-REQUEST → unsolicited
+  inbound is dropped). Classic full-cone-mapping + port-restricted-filtering NAT.
+Finding wired: `nat.symmetric` (medium) when mapping is address/port-dependent.
+Two bugs caught by running it for real: port preservation was misread as "no NAT" (now compares
+ADDRESSES), and an unbound socket reports the wildcard as its local address (now resolved via a
+throwaway connected socket). 7 tests/run.
+
+## App: autorun mode + IPv6 severity rework (2026-08-01)
+**IPv6 is no longer treated as a defect just for being absent.** The finding now depends on
+whether the network actually provisioned IPv6 (a global v6 address or a `::/0` route):
+- not provisioned → `ipv6.not_offered`, severity **INFO → green**. Most networks are still
+  IPv4-only and that is not a fault.
+- provisioned but ICMPv6 fails → `ipv6.broken`, severity **MEDIUM → yellow**. Half-configured
+  IPv6 is worse than none (Happy-Eyeballs stalls). Verified on the OnePlus: our LAN advertises a
+  v6 default route with no working path, so it correctly reports `ipv6.broken`.
+
+**Autorun mode** — one adb command runs a full measurement unattended and collects the result
+without any UI tapping or adb round-trip:
+```
+adb shell am start -n app.echo_lot.app/.MainActivity --ez autorun true
+curl http://<fmr>/reports            # list
+curl http://<fmr>/report/<name>      # fetch
+```
+The app runs the suite, POSTs the MeasurementDocument to the collection endpoint (receiver.py
+gained `POST /report`, `GET /reports`, `GET /report/<name>`), shows the result for 3 s, then
+finishes itself — leaving the device as it was found. On upload failure it stays open so the
+error is visible. Grant permissions once via `adb shell pm grant app.echo_lot.app
+android.permission.ACCESS_FINE_LOCATION` so nothing blocks on a dialog.
+
+## App: router identification, brand icons, DEV build variant (2026-08-01)
+**`link.ra_source` — who is advertising IPv6 here, and what box is it?** New app-tier probe
+(registry addition). Identification chain, each step recorded as evidence so nothing is guessed:
+1. RA source = next-hop of the `::/0` route per network (a `fe80::` link-local).
+2. **MAC recovered from the modified-EUI-64 link-local** (strip `ff:fe`, flip the U/L bit) —
+   e.g. `fe80::7a9a:18ff:fe54:b8f9` → `78:9a:18:54:b8:f9`. RFC 7217/privacy addresses don't encode
+   a MAC and are reported as such rather than guessed.
+3. Vendor via a curated OUI table (`Oui.kt` — SOHO/router vendors; unknown OUIs are printed
+   verbatim). Locally-administered (randomized) MACs are flagged.
+4. **UPnP/SSDP M-SEARCH** → the gateway's `SERVER:` banner + device-description XML gives
+   manufacturer / model / friendly name. This is what usually names the exact box.
+5. Reverse DNS for both gateways.
+All SSDP responders are recorded (not just the gateway) so a rogue RA sender that isn't the
+gateway can still be matched — and the MAC travels with every identity source, which is the hook
+for the future LLDP / mDNS cross-matching.
+UI: a "Router / IPv6 advertiser" panel above the network list, leading with the identified
+vendor/model.
+
+**Icons + DEV variant.** The branding adaptive icon is now the app icon: `icon-adaptive-*.svg`
+converted to Android vector drawables (SVG transform baked in, gradient background, monochrome
+layer for themed icons) plus PNG mipmaps for legacy launchers. The **debug build is a separate
+app**: `applicationIdSuffix .dev`, label "Echolot DEV", and a DEV-badged icon (layer-list =
+production foreground + generated amber DEV ribbon) so it is unmistakable next to a real install
+and both can be installed side by side.
+NOTE for tooling: the dev package is `app.echo_lot.app.dev`, activity `app.echo_lot.app.MainActivity`.
+
+### link.ra_source verified on-device — it named the actual router (2026-08-01)
+Run archived at `echolot-app/reports/CPH2747-app-run5-router-id.json`. On the wifi network the
+probe identified the RA sender completely, from an unprivileged app:
+- RA source `fe80::7a9a:18ff:fe54:b8f9` → **MAC 78:9A:18:54:B8:F9 recovered via EUI-64**
+  (matches the Shizuku neighbor table exactly) → vendor **MikroTik** by OUI
+- IPv4 gateway `10.13.102.1`, reverse DNS `router.hudelist.local`
+- UPnP: `RouterOS/7.23.2 UPnP/1.0 MikroTik` → manufacturer MikroTik, model Router OS,
+  friendly name "MikroTik Router"
+So the box advertising this LAN's broken IPv6 RA is a **MikroTik running RouterOS 7.23.2**, named
+by two independent methods (OUI from the address itself + UPnP device description) that corroborate.
+On cellular the carrier's RA source is an RFC 7217 privacy address and is correctly reported as
+"not EUI-64" rather than guessed.
+The SSDP sweep also inventoried the LAN (Synology DS1522+ DSM 7.3, a Sky ES160 gateway) — the
+raw material for the planned LLDP/mDNS cross-matching by MAC.
+Fixes from this run: added the confirmed MikroTik OUI 78:9A:18 (+ other RouterBOARD ranges), and
+an elvis-operator bug that printed "no UPnP response" even when UPnP data was present.
+
+### App UX: progress bar + ETA, cancel, and edge-to-edge insets (2026-08-01)
+- **Progress + ETA**: `Probe.estimatedMs` (per-probe, from measured on-device durations — the
+  timeout-bound probes dominate: icmp.ping6 ~7s on a v4-only net, captive-portal ~9s, SSDP ~7s,
+  STUN ~6s) drives a determinate bar plus "test N of M · ~Xs left". The Shizuku battery is counted
+  in the total so the bar covers the whole run.
+- **Cancel**: stops an in-flight run and shows what was measured so far, assembled into a normal
+  document (findings + verdict over the partial set). Deliberately **does not upload** — a partial
+  run is for the person looking at the screen, not for the record.
+- **Insets/cutout**: Android 15 draws edge-to-edge by default, so the title was running under the
+  status-bar clock and the camera cutout. The root column now uses `safeDrawingPadding()`, which
+  covers status bar, navigation bar and display cutout.
+
+### Shell-tier readiness shown before a run (2026-08-01)
+`ShizukuAvailability` distinguishes four states and the UI only speaks when it is actionable:
+- **NOT_INSTALLED → says nothing.** Users who don't use Shizuku are never nagged.
+- **INSTALLED_NOT_RUNNING → amber banner** "Shizuku is installed but not running — start it to
+  include shell-tier tests". This is the case worth reminding about: the user has it, but a
+  stopped service silently costs them the whole shell tier.
+- NEEDS_PERMISSION → "running but not authorised, it will ask on first use".
+- READY → green "shell-tier tests will run".
+Detection is listener-based (`addBinderReceivedListenerSticky` + binder-dead), because
+`pingBinder()` is only truthful once ShizukuProvider has delivered the binder — a one-shot poll at
+launch would show a false "not running". Installed-vs-not needs the `<queries>` package-visibility
+entry on Android 11+. Verified on-device: with shizuku_server stopped the banner appears correctly.
+
+### Shizuku banner is actionable; progress + cancel verified on-device (2026-08-01)
+Tapping the shell-tier banner now does the right thing per state: **installed-but-stopped** →
+deep-links into the Shizuku app (a third-party app *cannot* start Shizuku itself; the wireless-
+debugging pairing flow is privileged and lives in that app, so taking the user there in one tap is
+the best available), **running-but-unauthorised** → fires the Shizuku permission request directly.
+The hint line states which action the tap performs.
+Verified on-device in one screenshot: progress bar at "test 4 of 8 · icmp.ping6 · ~33s left",
+Cancel button beside the disabled Run button, title clear of the status bar/cutout, and the banner
+having live-switched from "installed but not running" to "running but not authorised" via the
+binder listener when Shizuku was started mid-session.
+
+### Why the Shizuku banner can't start wireless debugging directly (verified, 2026-08-01)
+Checked against Shizuku 13.6's own manifest (pulled the APK, `aapt2 dump xmltree`): the
+wireless-debugging entry points — `moe.shizuku.manager.adb.AdbPairingTutorialActivity`,
+`moe.shizuku.manager.adb.AdbPairingService`, `moe.shizuku.manager.starter.StarterActivity` —
+declare **no intent filters**, so they are not exported and a third-party app cannot launch them.
+`MainActivity` is the only reachable entry and answers MAIN/LAUNCHER only (no deep link), which is
+why the handoff lands on the screen whose primary action is the root start.
+Best available behavior, now implemented: the banner still opens Shizuku, but the hint names the
+exact steps there ("Pairing", then "Start"), and a second tap target opens **Developer options**
+(`Settings.ACTION_APPLICATION_DEVELOPMENT_SETTINGS` — public and exported) since Wireless
+debugging must be enabled first for Shizuku's wireless start to work at all.
+
+### Downstream measurements: asymmetric grants, DF-mode big_send (server-v0.4.0 … v0.4.2, 2026-08-01)
+The client can measure a round trip and the largest packet it can *send*. It cannot measure the
+largest packet it can *receive*, or downstream-only loss — those need the server to push, which is
+exactly what §3.4 gates behind an asymmetric grant. Implemented and verified live from the PC:
+
+- **`session.Grant`** — created per action, bound at creation to the session's *observed*
+  data-plane source (no grant without a verified destination), clamped to server limits, with a
+  byte budget, an average-rate ceiling and an expiry. Unit-tested for each of those refusals.
+- **`downtrain`** — N packets of size S every I µs; the client derives downstream loss,
+  reordering and inter-arrival spacing.
+- **`big_send`** — one datagram per requested size. **DF is on by default**, so the largest size
+  that arrives *is* the downstream path MTU. Without DF the kernel fragments and the result only
+  says whether fragments get through — a different fact, and the reason the schema has both
+  `mtu.pmtud_down` and `mtu.frag_delivery`. Sizes above the server's own egress MTU (from the
+  startup self-test) are refused up front and reported as `max_df_bytes`, so an absence caused by
+  our kernel is never read as a limit of the client's path.
+
+Live from the PC against fmr: downstream path MTU **1500** (1472 payload, DF), fragmented delivery
+up to **4000**, downstream train **100/100, 0 % loss, 0 reordered**, inter-arrival 3.3 ms for a
+3000 µs send interval.
+
+#### Two bugs this shook out, both invisible in a single-homed lab
+1. **Granted sends went out from the wrong local address** (fixed in server-v0.4.2). fmr binds two
+   IPv4 addresses; `connFor` returned whichever socket of the right family came first in the bind
+   list. A train for a session established on `.150` left from `.151` and every packet was dropped
+   by the client's NAT, which has no mapping for that pair. tcpdump showed all 50 leaving, the
+   client saw none — reported as *100 % downstream loss*, a confident measurement of something
+   that never happened. Sessions now record which of our own bound addresses received their
+   traffic and granted sends go back through that socket; `connfor_test.go` pins both that and the
+   family fallback.
+2. **A second `ProbeSession` on one server session is silently dead.** Sequence numbers restart at
+   zero client-side while the server's anti-replay window keeps counting, so every packet is
+   discarded as a replay — and because the server then never records the new source, the grant
+   still targets the closed socket. `ServerMeasurement` now uses one ProbeSession for the whole
+   run; `ProbeSession`'s doc comment states the constraint.
+
+### Run archive, anonymizer and uploads (2026-08-01)
+Three pieces, deliberately separate:
+
+- **`core-archive`** — one JSON file per run plus an index entry, in a plain directory the user can
+  inspect or delete with a file manager. Retention (max runs / max age / max total bytes) is
+  enforced on every save rather than by a sweeper. `enabled` is a separate flag from the three
+  ceilings because "no limits" and "keep nothing" are opposite intentions; collapsing them onto
+  all-zeros is how a user who turns the caps off ends up with an empty history. 13 tests.
+- **`core-privacy`** — the schema §8 anonymizer, three levels. `full` (your own server) changes
+  nothing; `balanced` pseudonymizes SSIDs/hostnames, keeps the OUI half of a MAC and the /16 of a
+  public IP, keeps RFC1918 verbatim (it describes topology, not a person), and *drops* neighbour
+  inventories (SSDP/ARP/scan results) rather than mangling them; `strict` keeps only metrics,
+  statuses and finding codes. Pseudonyms are consistent within a document and — by default — not
+  across documents, so an upload endpoint cannot link a device's runs; a stable salt is opt-in for
+  people diffing their own history. Classification is one readable table, not annotations spread
+  across modules. 14 tests, each pinning a property someone's privacy depends on.
+- **Server-side upload policy** — `off | anonymous | account`, plus max size, retention days, max
+  runs per device, and the *least* anonymization accepted. The profile advertises all of it so the
+  app presents the choice honestly instead of discovering the rules by being rejected. `account`
+  refuses today rather than falling back to anonymous: picking the strict setting before OIDC
+  lands must not silently mean the loose one.
+
+**The archive holds the unredacted document; redaction happens on the way out, per upload.** The
+local archive is the user's own data on their own device, and redacting it would destroy exactly
+the detail that makes a week-old run worth keeping.
+
+App-side: settings screen (archive limits, privacy level with a plain-language description of what
+each keeps, auto-upload off by default, server URL/pin/credential), history screen showing whether
+each run left the device, and a **preview of the exact bytes an upload would send** — an anonymizer
+the user cannot inspect is only a promise.
+
+Live round trip against fmr: uploaded a run, listed it, fetched it back and asserted the SSID, the
+SSDP neighbour name and the free-text note are absent from what the server stores while the
+finding code and the metrics survive, then deleted it.
+
+### Still open
+- `mtu.pmtud_up` (DF + errqueue), `frag_send`, `throughput`, TRAIN_REPORT retrieval.
+- Enrollment UI in the app (server URL/pin/credential are typed in by hand today).
+- Accounts/OIDC on the server, which is what `uploads=account` is waiting for.
+- Nothing in this entry has been exercised on a phone yet — all of it was verified from the PC
+  against the live server. On-device verification is the next step.
+
+### SemVer compatibility windows between app and server (server-v0.5.0 … v0.5.2, 2026-08-01)
+Both artifacts are SemVer, and each now declares — and enforces — which peer versions it will talk
+to. Spec: `docs/probe-protocol.md` §8.
+
+**Two axes, deliberately not conflated.** Release versions are a *proxy* for what actually has to
+match, so the real thing is checked first:
+- `protocol_version` — **can** these builds talk. Advertised in the profile; a peer in a different
+  breaking series is refused whatever its release version says. Below 1.0.0 the **minor** is the
+  breaking axis (SemVer §4).
+- release-version window — **may** they, per policy. `[min, max)`, min inclusive, max exclusive,
+  because the useful bound is always "the version that broke it".
+
+Bounds sit at breaking boundaries, not at releases, so shipping a patch never requires editing a
+range. The app requires server `>= 0.4.2` for a stated reason, not caution: earlier multi-homed
+servers mis-addressed granted sends and the client measured 100 % downstream loss that never
+happened. Operators override the server side with `ECHOLOT_MIN_APP_VERSION` /
+`ECHOLOT_MAX_APP_VERSION`; a malformed bound is fatal at startup rather than ignored, so a typo
+cannot silently disable a restriction.
+
+Three rules that shaped the implementation:
+1. **`GET /v1/profile` is never gated.** It is where a refused client learns which version it needs;
+   gating it leaves the user with a network error instead of an answer.
+2. **An unparseable or absent version is `unknown`, and is allowed.** Dev builds report `dev`, and a
+   client too old to send the header cannot be identified anyway.
+3. **Refusal is 426 with a body naming both versions and the window**, surfaced client-side as a
+   distinct `VersionRefused` rather than folded into "network error".
+
+The app's `versionCode` is now derived from its SemVer (`major*1e6 + minor*1e4 + patch*10`) instead
+of being a second number to remember.
+
+Verified live against fmr (`LiveCompatTest`): profile advertises the window and stays readable for a
+refused version; 0.1.0 and 99.0.0 are both refused with actionable messages; 0.2.0 and a missing
+header are both served.
+
+One user-visible bug caught in the process: Go's JSON encoder HTML-escapes `<`, `>` and `&` by
+default, so the refusal reached the client as `needs \u003e= 0.2.0`. Disabled at the encoder (this
+is an API, not a page), and the client now *parses* the error field instead of pattern-matching it,
+so it survives whatever a future encoder decides to escape.
+
+### Enrollment: the server mints the bootstrap link (server-v0.5.3 … v0.5.4, 2026-08-01)
+Until now a device was configured by hand-typing a control URL, a base64 SPKI pin and a
+credential. That is the step that goes wrong, and it goes wrong quietly: a pin off by one
+character does not fail loudly, it just never matches, and surfaces days later as an inscrutable
+TLS error.
+
+`POST /admin/enroll-tokens` now returns the whole §2.1 bootstrap link alongside the token, because
+the server is the only party holding all three parts at once. The app takes it from a paste or an
+`echolot://enroll` deep link (so a QR scan configures a server in one action) and writes URL, pin
+and credential **together or not at all** — a half-applied server fails later, somewhere else,
+with an error pointing at the wrong thing.
+
+The control URL comes from `ECHOLOT_PUBLIC_URL` (set on fmr to `https://fmr-1.echo-lot.app:8443`),
+falling back to the first control listen address; a wildcard bind warns rather than emitting a
+link to `0.0.0.0`.
+
+**The encoding trap, which is the whole reason this is tested across both languages.** The pin is
+base64, so it contains `+`, `/` and `=` — each of which means something else in a query string. An
+unencoded `+` decodes to a space, leaving the pin wrong by exactly one character. Base64 has no
+spaces, so the parser restores them; that cannot damage a correctly-encoded pin and it rescues
+every hand-assembled link. `LiveEnrollmentTest` redeems a link the *server* produced, which is the
+only way to catch a disagreement between the Go assembler and the Kotlin parser — a unit test on
+either side alone cannot see it. It also asserts the token is refused the second time.
+
+Also fixed a spec divergence found while reading §2.1: the spec names the field
+`device_credential`, the first implementation shipped `credential`. The server now sends both and
+the client prefers the spec's; the alias goes once nothing reads it.
+
+Two process notes from this round:
+- An edit to the admin handler silently failed to apply and the endpoint kept returning just the
+  token. Caught by deploying and *looking at the response*, not by trusting a green build.
+- The live suite is now six tests (`LiveServerTest`, `LiveMeasurement`, `LiveGranted`,
+  `LiveUpload`, `LiveCompat`, `LiveEnrollment`), all green against fmr from the PC with no device.
+
+### Directional loss: which way is the packet loss? (2026-08-01)
+A round trip can only report that *something* was lost somewhere, which is the least useful form
+of the answer — "3 % loss" sends an engineer looking in both directions at once. The server
+already records every packet it received per sequence number (§6), so the two cases are actually
+distinguishable, and `train.udp_updown` now reports them separately:
+
+- sent, never seen by the server → **upstream** loss
+- seen by the server, reply never arrived → **downstream** loss
+
+Findings name the direction and say what is *not* implicated, which is half the value:
+`connectivity.loss_upstream` ("the return path is not implicated: replies came back for everything
+that arrived"), `connectivity.loss_downstream`, `nat.udp_unreachable_upstream`.
+
+Two things the implementation gets deliberately right:
+- **Downstream loss is measured against what reached the server**, not against what was sent.
+  Using "sent" as the denominator counts every upstream loss a second time and overstates the
+  return path. Pinned by a test with loss in both directions at once.
+- **Per-direction jitter without synchronised clocks.** Absolute one-way delay would need clock
+  sync and we deliberately have none (the two-clock rule). But `server_rx − client_tx` carries a
+  constant unknown offset, and differencing successive samples cancels it — so RFC 3393 one-way
+  delay variation *is* honestly attributable to a direction even though latency is not. A test
+  pins that a 10-second clock offset changes nothing.
+
+Correlation is by **wire sequence number**, which is not the loop index: the counter is shared
+with every other packet type on the session, so "the nth echo" is not "sequence n". `ProbeSession`
+now exposes `lastSeq`, including for a probe that was lost — a lost packet still has a sequence
+number, and that number is exactly what tells you which way it was lost.
+
+Live against fmr: 20/20 both ways, and jitter of **0.08 ms upstream vs 0.85 ms downstream** — a
+tenfold asymmetry that a round-trip measurement cannot see at all.
+
+10 unit tests on the arithmetic (a wrong denominator here does not crash, it produces a plausible
+number pointing at the wrong half of the network) plus the live correlation check.
+
+### frag_send: crafted IP fragments, so *ordering* is testable (server-v0.6.0, 2026-08-01)
+`big_send` with `df=false` answers one question — do fragments get through. It cannot answer the
+more interesting one, because the kernel always emits fragments in order, first one first.
+
+The classic middlebox fault is exactly about that ordering. Only the **first** fragment carries the
+UDP header, and therefore the ports; a stateful firewall or NAT that has not seen it has no flow to
+match the rest against, and many simply drop them. That is invisible to every in-order test, and in
+the field it looks like "large DNS answers fail on this network" or "the tunnel breaks when the MTU
+drops" — it works until the network reorders, then fails intermittently, which is the hardest kind
+of fault to chase.
+
+So the server builds the fragments itself (raw socket, `IP_HDRINCL`) and controls their order:
+`in_order` (baseline), `reversed` (last fragment first), `first_last` (first fragment held back
+250 ms). The datagram is assembled and **signed whole** before being cut up, so what the client
+reassembles is indistinguishable from an ordinary packet — otherwise the test would be measuring
+our sender rather than the path. New test type `mtu.frag_ordering`; findings
+`mtu.fragments_blocked` and `mtu.fragment_reorder_sensitive`.
+
+Two details that would otherwise produce confidently wrong answers:
+- **The UDP checksum is computed, not left zero.** Zero is legal in IPv4 and would be less code,
+  but zero-checksum datagrams are dropped by some middleboxes — and that drop would be recorded as
+  a fragmentation failure, which is the wrong conclusion entirely.
+- **Fragment offsets are in 8-byte units**, so non-final fragments are rounded down to a multiple
+  of 8. A 100-byte fragment is not an error; it is a datagram no host will ever reassemble.
+
+`frag-send` is advertised only when a raw socket can actually be opened — checked by opening one,
+because a permission model has more ways to say no (userns, seccomp, LSM) than a capability bit has
+to say yes. fmr runs as root with `cap_net_raw` in its bounding set, so it is available there.
+
+Fragment ordering runs only after `mtu.frag_delivery` shows fragments arrive at all; otherwise the
+three orderings would each report "not delivered" and read as three faults instead of one.
+
+The header arithmetic is unit-tested (reassembly coverage with no gaps or double-delivery, MF
+flags, shared IP ID, 8-byte offsets, checksum verification over odd and even lengths). Because the
+code is `//go:build linux`, the tests are **cross-compiled and run on fmr** — there is no Go
+toolchain there, so `go test -c` plus scp is the loop.
+
+Live against fmr: 4 fragments per burst, and all three orderings reassembled — a healthy path, and
+the baseline against which a mobile network will be interesting.
+
+### Testing state (2026-08-01)
+Six live tests against fmr, all green, no device involved: `LiveServerTest`, `LiveMeasurement`,
+`LiveGranted`, `LiveDownstream`, `LiveUpload`, `LiveCompat`, `LiveEnrollment`. Plus 74 client unit
+tests and the full Go suite. Everything in the last several entries is verified from the PC; the
+app's UI (settings, history, deep-link enrollment) and `mtu.pmtud_up` remain device-only.
+
+### throughput: a rate, plus the qualifier that makes it a measurement (server-v0.6.1 … v0.6.2)
+A throughput test reports the *smallest* limit on the path — and the sender's own ceiling is one of
+the candidates. If the server is asked for 50 Mbps and 50 Mbps arrives, the network was never the
+constraint and "50 Mbps" says nothing about it. So `perf.throughput_udp` always carries
+`limited_by` (duration | budget | rate | send_error) and `measures_network`, and a finding is
+raised only when the path is actually implicated. The live run against fmr reports 20 Mbit/s with
+`measures_network: false`, which is the correct and useful answer.
+
+Loss is computed against the **sender's own count**, fetched from the observations API, not against
+the requested rate. A receiver alone cannot tell "the network dropped it" from "the sender never
+sent it", and guessing turns a healthy server-side limit into a phantom network fault. The server
+keeps one summary per action rather than per-packet records — a ten-second run at 50 Mbps is half a
+million packets, and a struct each would turn a measurement into memory exhaustion.
+
+Sending is **paced**, on an absolute schedule. Unpaced would measure the server's NIC and the first
+queue it meets, then collapse into loss that reads as a network fault; sleep-per-packet would
+accumulate scheduler error and drift the rate down over a ten-second run.
+
+Throughput gets its own grant budget sized from the request, so every *other* action stays bounded
+at 8 MiB. When the byte cap binds before the clock does, the **duration is shortened and reported**
+rather than the run being truncated: promising thirty seconds and delivering twenty-one is the same
+information with a surprise attached, and it keeps "the clock ended the run" as the normal case —
+the only case where the rate is a clean property of the path. That behaviour came out of a test
+that failed honestly (30 s at 100 Mbps needs 375 MB against a 256 MB cap).
+
+It is **opt-in** in the run config, default off. A 5-second run at 50 Mbps moves ~30 MB; on a
+metered mobile connection that is the user's money, and a tool that spends it without being asked
+is not one people keep installed.
+
+#### The bug the live test found
+The first live run delivered 104 packets and stopped after 50 ms. The grant's rate check exempted
+the first 50 ms entirely, meaning to be lenient at startup — the effect was the opposite. A sender
+could dump an unbounded burst into that free window, and the instant the check switched on it
+compared those bytes against 50 ms worth of allowance and refused everything until real time caught
+up. **Every short test passed** (downtrain sends 50 packets, big_send seven); every sustained send
+died fifty milliseconds in.
+
+Replaced with a token bucket (`allowance = burst + rate × elapsed`), which is smooth from t=0.
+The burst is 100 ms of the allowed rate, floored at one ordinary datagram — deliberately one, since
+at 8 kbps a 64 KB floor is sixty-four seconds' worth, exactly the instant dump the ceiling exists to
+prevent. The pre-existing rate test caught that when I first tried the generous floor, and it was
+right to. Second half of the same bug: callers treated *any* refusal as terminal, so `TryAllow` now
+says why — a sender paces through a transient "too fast just now" and still stops dead on a spent
+budget or an expired grant. Both halves are pinned by regression tests.
+
+### Findings registry (2026-08-01)
+Closes open item 1 of measurement-schema.md §9. A finding code is the stable, machine-readable half
+of a result — what a dashboard groups by and what someone greps a year of archived runs for — and
+that only holds if a code means exactly one thing forever. Ad-hoc string literals at fifteen call
+sites cannot promise that, and by the time the registry was written the failure had already
+happened.
+
+**Two emitters had independently produced `connectivity.downstream_loss` and
+`connectivity.loss_downstream` for the same claim**, and nothing anywhere objected. Anyone
+aggregating either one would have silently seen half their data. Merged into
+`connectivity.loss_downstream`, paired with `loss_upstream` so the two directions read as a set.
+
+**Two codes were also renamed out of `nat.*`.** `nat.udp_unreachable` is not about NAT — it means
+no replies came back — but the prefix determines the category, and the category determines which
+verdict light the finding rolls up into (§7.3). A `nat.*` code landing under *connectivity* is not
+a naming quibble; it changes which light turns red. Cheap to fix now, a breaking change later.
+
+Codes are now declared as typed `FindingSpec`s carrying their category and default severity, and
+emitters reference the spec instead of retyping the string — so a typo is a compile error and two
+call sites cannot disagree about a finding's category.
+
+`docs/findings-registry.md` is the contract, and a test reads it: it fails when the document and
+the registry have codes the other lacks, or when a severity differs. Documentation that drifts from
+its implementation is worse than none, because it still looks authoritative. The check scopes
+itself to table rows, so the prose can keep explaining which codes were retired and why.
+
+Six tests: uniqueness, declared-vs-listed, prefix↔category agreement, naming convention, a
+word-order-anagram check (the shape the duplication actually took), and the document agreement.
+
+### A real privacy leak, found by starting on the machine-readable schema (2026-08-01)
+The intent was `measurement.schema.json` (§8's promised companion). The first step — checking
+whether the anonymizer actually covers the fields the schema declares as sensitive — found that it
+did not, so that became the work.
+
+**At the `balanced` level, five identifying values were being uploaded verbatim:**
+
+| value | field | why it matters |
+|---|---|---|
+| `2001:…::150` | `networks[].link.addresses[].addr` | the device's own global IPv6 address — a strong, geolocatable device identifier |
+| `2a02:…::1` | `networks[].link.routes[].gateway` | identifies the ISP allocation |
+| `203.0.113.77` | `networks[].link.dns.servers[]` | the configured resolver |
+| `nas.example.lan` | `private_dns_hostname` | an internal hostname |
+| `example.lan` | `search_domains[]` | the internal domain |
+
+The settings screen describes that level as pseudonymizing addresses. It was not.
+
+**Root cause:** classification keyed on field *names*, and the schema's actual names (`addr`,
+`gateway`, `dst`, `servers`, `search_domains`, `private_dns_hostname`) had never been added to the
+table. Not a subtle bug — just an unfalsifiable design. The existing tests all passed, because each
+one checked a field somebody had remembered to write a case for.
+
+**Two fixes, one of them structural:**
+1. The missing names were added.
+2. More importantly, a **shape-based backstop**: when a field name is unrecognised, the *value* is
+   inspected, and anything shaped like an IPv4/IPv6 address or a MAC is treated as one. A name
+   table can only protect fields someone thought of, which is precisely the wrong property for a
+   privacy control. Hostnames are deliberately *not* inferred by shape — `train.udp_updown` is
+   indistinguishable from a domain, and mangling a test type would corrupt the document to protect
+   nothing.
+
+`LeakTest` is the new guard and is written to fail for fields nobody has considered: it plants
+identifying values wherever one can actually occur and asserts none survive, rather than checking
+a list of known cases. It also pins that RFC1918 addresses still come through readable, so the
+test cannot pass by over-redacting everything.
+
+Route prefixes and the unspecified address needed care in the transform: `0.0.0.0/0` and `::/0`
+must stay themselves, or a routing table becomes unreadable for no privacy gain.
+
+**Still outstanding:** `measurement.schema.json` itself. Worth noting what this episode implies for
+it — much of a document's payload lives in `evidence`/`metrics`/`params`, which are per-test-type
+`JsonObject` by design and therefore *outside* any schema. A schema-driven anonymizer would have
+less coverage there than the name-plus-shape one now does, so the schema should be built for
+validation and external tooling, not as a replacement for the classifier.
+
+### ULA prefixes are pseudonymized whole (2026-08-01)
+Spotted in a real uploaded run from the phone: the server had
+`fda1:3fb1:ff92:6696::2662` for a DNS server. The general IPv6 path preserves the leading two
+groups (deliberately — for a global address that keeps the ISP allocation, which is the
+diagnostically useful part), and for a ULA that passed through **32 of the 40 random bits** of the
+global ID.
+
+ULA looks like the v6 equivalent of RFC1918 and the instinct is to treat it the same. That
+reasoning does not carry over, and the difference is the whole point: an RFC1918 prefix is shared
+by millions of networks and identifies none of them, while a ULA global ID is random and unique to
+one network by construction (RFC 4193). The prefix *is* the identifier — it is a network
+fingerprint that was surviving redaction.
+
+Now pseudonymized as a unit, so two addresses on the same ULA subnet still land on the same
+pseudonymous prefix: "these hosts are on one network" survives, "this is *that* network" does not.
+Three tests, one of which uses the exact value observed on the wire.
+
+Worth recording as a reasoning trap: I had originally raised this as "ULA should probably be kept
+verbatim, like RFC1918, for consistency". The surface analogy pointed the wrong way, and the
+correct answer was the opposite.
+
+### Registry adopted everywhere; v6 findings renamed; Back works (2026-08-01)
+The findings registry was only adopted in `core-engine`. The app module still emitted seven codes
+as raw strings, so the registry test passed while codes existed outside it — including
+`ipv6.broken`, which fired on a real network and was in no registry at all.
+
+All seven now reference registry entries for code, category and severity, so those three cannot
+disagree at a call site. A grep for `code = "…"` across the app, engine and probe modules returns
+nothing.
+
+**`ipv6.*` → `v6.*`.** The third instance of rule 1: they declared `Category.IPV6` while the prefix
+map only knows `v6`, so `TestType.category("ipv6.broken")` fell through to *connectivity* and the
+finding rolled up under the wrong verdict light. The test-type registry already used `v6.`.
+
+Two severities reconciled while merging:
+- `connectivity.captive_portal` is **medium**, not high. The registry had guessed high; the probe
+  that emits it had always said medium, and the probe was the considered value — a captive portal
+  on hotel wifi is what should be there, and logging in clears it. `connectivity.no_internet` is
+  the high one, because nothing the user does locally fixes that.
+- `v6.not_offered` is **info, and the registry says it must stay info**. Most networks still do not
+  offer IPv6 and that is not a fault; a warning here lights a yellow verdict on a healthy network,
+  which teaches people to ignore the light.
+
+Also: a `BackHandler` now returns from Settings/History to the run screen. The screen was a plain
+state variable with nothing connecting it to the back stack, so the system Back gesture left the
+app entirely. Enabled only when there is somewhere to go back to, so Back still exits from the run
+screen.

docs/findings-registry.md

@@ -0,0 +1,106 @@
+<!--
+SPDX-FileCopyrightText: 2026 Echolot contributors
+SPDX-License-Identifier: CC-BY-4.0
+-->
+
+# Echolot findings registry
+
+Closes open item 1 of `measurement-schema.md` §9.
+
+A **finding code** is the stable, machine-readable half of a result. The prose around it changes
+freely; the code is what a dashboard groups by, what a diff between two runs keys on, and what
+someone greps a year of archived runs for. That only works if a code means exactly one thing,
+forever.
+
+This document is the contract. It is kept in step with
+`echolot-app/core-measurement/.../FindingRegistry.kt` by a test that fails when either side has a
+code the other does not — a registry that drifts from its documentation is worse than none,
+because it looks authoritative.
+
+## Rules
+
+1. **The prefix determines the category**, and the category determines which verdict light the
+   finding rolls up into (§7.3). A `nat.*` code appearing under *connectivity* is not a naming
+   quibble; it changes which light turns red. Two codes were renamed from `nat.*` to
+   `connectivity.*` for exactly this reason.
+2. **One code per concept.** Two emitters independently produced `connectivity.downstream_loss`
+   and `connectivity.loss_downstream` for the same claim before this registry existed. Anyone
+   aggregating either would have silently seen half their data.
+3. **Codes are declared, not typed.** Emitters reference a `FindingSpec`, so a typo is a compile
+   error and no two call sites can disagree about a finding's category or default severity.
+4. **Severity in the registry is the default.** An emitter may escalate for a specific run; it may
+   not quietly reclassify the finding in general.
+5. **Say what is ruled out**, where that is the useful half. "Loss upstream" is worth far more
+   when it also states that the return path is clean, because that halves where to look next.
+6. **Renaming a code is a breaking change** once runs are archived at scale. Before 1.0 it is
+   cheap; after, it needs an alias and a deprecation window.
+
+## Registry
+
+### connectivity
+
+| code | severity | means | rules out |
+|---|---|---|---|
+| `connectivity.udp_unreachable` | high | No UDP echo replies came back from the server at all. | — |
+| `connectivity.udp_unreachable_upstream` | high | The server received none of the probes, so traffic is dropped on the way out. | The return path: nothing arrived to be replied to. |
+| `connectivity.udp_loss` | medium | A large fraction of round-trip probes were lost, direction unknown. | — |
+| `connectivity.loss_upstream` | medium | Probes were lost on the way to the server. | The return path: replies came back for everything that arrived. |
+| `connectivity.loss_downstream` | medium | Packets were lost on the way back from the server. | The outbound path: the server received what it was answering. |
+| `connectivity.downstream_blocked` | high | Server-initiated packets never arrive, although round trips work. | Basic reachability: the path forwards replies, just not unsolicited traffic. |
+| `connectivity.downstream_reorder` | low | Downstream packets arrive in a different order than they were sent. | — |
+| `connectivity.captive_portal` | medium | A captive portal is intercepting connectivity checks. | — |
+| `connectivity.no_internet` | high | Android's own connectivity checks fail on this network. | — |
+
+### mtu
+
+| code | severity | means | rules out |
+|---|---|---|---|
+| `mtu.reduced_downstream` | low | The downstream path MTU is below the usual 1500 bytes. | — |
+| `mtu.downstream_blackhole` | medium | Datagrams above the path MTU are dropped downstream, fragmented or not. | — |
+| `mtu.fragments_blocked` | medium | IP fragments do not reach this device even when sent in order. | — |
+| `mtu.fragment_reorder_sensitive` | low | Fragments are delivered in order but dropped when reordered or delayed. | Fragmentation itself: in-order fragments arrive fine. |
+
+### nat
+
+| code | severity | means | rules out |
+|---|---|---|---|
+| `nat.udp_rebinding` | medium | A NAT remapped the UDP source port mid-flow. | — |
+| `nat.symmetric` | medium | The NAT assigns a different external port per destination. | — |
+
+### perf
+
+| code | severity | means | rules out |
+|---|---|---|---|
+| `perf.throughput_no_delivery` | high | No throughput traffic arrived, although the server sent it. | — |
+| `perf.throughput_below_offered` | low | Less throughput arrived than the server sent for the whole run. | — |
+
+### dns
+
+| code | severity | means | rules out |
+|---|---|---|---|
+| `dns.answer_rewritten` | high | A resolver returned an answer that differs from the authoritative record. | — |
+| `dns.authoritative_unreachable` | medium | The canary zone's authoritative server could not be reached. | — |
+
+### v6
+
+The prefix is `v6.`, matching the test-type registry (`v6.brokenness`, `v6.happy_eyeballs`, …).
+These were `ipv6.*` while declaring `Category.IPV6`; since the prefix map only knows `v6`, they
+rolled up under *connectivity* instead — the third occurrence of rule 1 being broken.
+
+| code | severity | means | rules out |
+|---|---|---|---|
+| `v6.broken` | medium | IPv6 is configured on this network but does not work. | Absence of IPv6: it is provisioned, it simply fails. |
+| `v6.not_offered` | info | This network does not offer IPv6. | — |
+
+`v6.not_offered` is **info and must stay info**. Most networks still do not offer IPv6 and that is
+not a fault; reporting it as a warning lights a yellow verdict on a healthy network, which teaches
+people to ignore the light — the one thing a diagnostic must never do.
+
+## Adding a finding
+
+1. Add a `FindingSpec` to `FindingRegistry`, and to its `all` list.
+2. Add the row here, under the section its prefix names.
+3. Emit it with `finding(FindingRegistry.YOUR_CODE, …)`.
+
+The registry test checks 1 and 2 agree, that every prefix maps to the category it claims, and that
+no two entries share a code.

docs/measurement-schema.md

@@ -269,7 +269,7 @@ The JSON Schema (machine-readable companion, `measurement.schema.json`, generate
 
 | type | example fields | v2 anonymizer transform |
 |---|---|---|
-| `ip4`, `ip6` | addresses, routes, hops, DNS answers | prefix-preserving pseudonymization, consistent per document; well-known/reserved ranges kept verbatim |
+| `ip4`, `ip6` | addresses, routes, hops, DNS answers | prefix-preserving pseudonymization, consistent per document; well-known/reserved ranges kept verbatim. **Exception: ULA (`fc00::/7`) has its whole prefix pseudonymized as a unit.** It resembles RFC1918 but is not analogous: a ULA global ID is 40 random bits, unique to one network by construction (RFC 4193), so the prefix *is* the identifier, whereas `192.168.0.0/16` is shared by millions of networks and identifies none. Pseudonymizing it as a unit keeps "these hosts are on one subnet" while dropping "this is that subnet". |
 | `mac`, `bssid` | wifi, arp_watch | OUI kept, NIC part pseudonymized |
 | `fqdn` | DNS names, reverse lookups | per-label pseudonyms, public-suffix kept |
 | `ssid` | wifi | pseudonym |
@@ -279,7 +279,8 @@ Free-text fields (`notes`, `error.detail`, dump excerpts from Shizuku parsers) c
 
 ## 9. Open items
 
-1. Findings registry document — start alongside the first implemented tests.
+1. ~~Findings registry document~~ — done: `findings-registry.md`, kept in step with
+   `FindingRegistry.kt` by a test that fails when the two disagree.
 2. Whether Shizuku raw-dump excerpts (dumpsys/ip output) are embedded in `evidence` verbatim (auditable, but large and hard to anonymize) or parsed-only with an optional "attach raw dumps" toggle. Proposal: toggle, default on for local archive, default off for export.
 3. Peer-mode documents: each device produces its own run; the coordinator embeds the peer's findings summary and cross-references by `run.id`. Full merge format deferred.
 4. Size guardrails: soft cap 20 MB uncompressed per run; trains beyond that downsample evidence (keep aggregates + first/last N + all anomalies) and record `"evidence_truncated": true`.

docs/probe-protocol.md

@@ -24,11 +24,34 @@ echolot://enroll?v=1&u=<control-URL, urlencoded>&p=pin-sha256:<b64 SPKI hash>&t=
 
 ```
 POST /v1/enroll        Authorization: Bearer <enrollment-token>
-→ 200 { "device_credential": "<random 256-bit, b64url>",
-        "device_id": "uuid",
-        "profile": { ... §2.2 ... } }
+→ 201 { "device_credential": "<random 256-bit, b64url>",
+        "device_id": "uuid" }
 ```
 
+The **server assembles the bootstrap link**, because it is the only party holding all three parts
+at once, and the part an operator gets wrong by hand is the base64 pin — which does not fail
+loudly, it just never matches, and surfaces later as an inscrutable TLS error:
+
+```
+POST /admin/enroll-tokens
+→ { "token": "…", "expires_in_s": 86400,
+    "enroll_uri": "echolot://enroll?v=1&u=…&p=…&t=…" }
+```
+
+The control URL in the link comes from `ECHOLOT_PUBLIC_URL`, falling back to the first control
+listen address. A wildcard bind has no single right answer, so it warns rather than guessing.
+
+Encoding notes that matter in practice:
+- `u`, `p` and `t` are **percent-encoded**. The pin is base64, so it contains `+`, `/` and `=`,
+  every one of which means something else in a query string.
+- A `+` that was *not* encoded decodes to a space. Base64 contains no spaces, so a parser SHOULD
+  restore them — the alternative is a pin wrong by one character and a failure that points nowhere
+  near the cause.
+- The control URL MUST be `https://`. The pin only protects a TLS connection; a cleartext URL
+  would hand the token to anyone on the path.
+- **The link is a secret** while it is live: it carries a bearer token, so anyone who sees it
+  before the device does can enroll instead.
+
 Enrollment tokens are single-use with expiry, created in the admin UI, scoped `enroll`. The device credential is a long-lived bearer secret, scoped `run-tests`; it is also the HKDF input for session keys. Revocation = deleting the device in the admin UI.
 
 ### 2.2 Profile
@@ -192,14 +215,77 @@ Note: exact RDATA constants to be frozen in the implementation's `dns_reference.
 
 Same daemon, separate listener (default localhost-only): health + self-test (are both IPs live, is the canary zone delegated correctly, is UDP reachable from outside — tested via a public echolot "mirror" if configured), enrollment token management (create/expire/scope), device list + revocation, retention settings, QR rendering (client-side JS). Out of scope for this spec beyond the endpoints above.
 
-## 8. Cross-references to the measurement schema
+## 8. Version compatibility
+
+Both artifacts are versioned with **SemVer**: the Go server (`server-vX.Y.Z` tags) and the Android
+app (`versionName`; `versionCode` is derived from it, never maintained separately). Two independent
+things are checked, and conflating them is the mistake this section exists to prevent.
+
+### 8.1 Protocol version — *can* these builds talk?
+
+`protocol_version` is the version of **this document**. It is advertised in the profile
+(`compat.protocol_version`) and is the correctness axis: a peer in a different breaking series
+cannot be talked to, whatever its release version says. Below `1.0.0` the **minor** is the breaking
+axis (SemVer §4); at and above it, the major is. A patch bump of the protocol never splits a fleet.
+
+### 8.2 Release-version window — *should* they, per policy?
+
+Each side declares the range of peer release versions it will work with, as `[min, max)` —
+**minimum inclusive, maximum exclusive**, because the useful bound is always "the version that
+broke it" and writing that literally is unambiguous. An empty maximum means unbounded.
+
+The server advertises its window and enforces it:
+
+```jsonc
+"compat": {
+  "protocol_version": "1.0.0",
+  "schema_version": "1.0.0",
+  "app_min": "0.2.0",
+  "app_max": "1.0.0"     // exclusive; "" = no upper bound
+}
+```
+
+Operators override it with `ECHOLOT_MIN_APP_VERSION` / `ECHOLOT_MAX_APP_VERSION` (or
+`--min-app-version` / `--max-app-version`). A malformed bound is **fatal at startup**, not ignored:
+a typo must not silently disable a restriction the operator meant to set.
+
+The app sends its version on every control-plane request:
+
+```
+X-Echolot-App-Version: 0.2.0
+```
+
+and carries its own bounds for the server (`MIN_SERVER` / `MAX_SERVER` in `Compat.kt`). It checks
+the profile in **both** directions — is the server in our range, and are we in the server's — so a
+mismatch is reported before a run starts rather than discovered halfway through one.
+
+### 8.3 Rules
+
+1. **`GET /v1/profile` is never gated.** It is where a refused client learns which version it needs.
+   Gating it leaves the user with a network error instead of an answer, defeating the check.
+2. **Refusal is `426 Upgrade Required`**, with a body naming both versions and the accepted window:
+   ```json
+   { "error": "app 0.1.0 is older than this build supports (needs >= 0.2.0, < 1.0.0). Update the app.",
+     "app_version": "0.1.0", "accepts_app": ">= 0.2.0, < 1.0.0",
+     "server_version": "0.5.0", "protocol_version": "1.0.0" }
+   ```
+3. **An unparseable or absent version is `unknown`, and is allowed.** Development builds report
+   `dev`, and a client too old to send the header cannot be identified anyway. The check exists to
+   turn confusing failures into clear ones; refusing what it cannot identify does the opposite.
+4. **Bounds move at breaking boundaries, not at releases.** Shipping a patch must never require
+   editing a range. A minimum is raised only when older peers are actually harmful — e.g. the app
+   requires server `>= 0.4.2` because earlier multi-homed servers sent granted traffic from an
+   address the session never used, which the client measured as 100 % downstream loss. A
+   confidently wrong measurement is worse than a refused one.
+
+## 9. Cross-references to the measurement schema
 
 - Observation-block fields (§3.3) appear as `*_seen_by_server` columns in `train` evidence (schema §6.2).
 - `TIMESYNC` (§3.2) produces the `time.server_offset` test; without it, cross-clock fields must not be compared (schema §6.2 note).
 - Capability strings (§2.3) are copied verbatim into `server_sessions[].capabilities` (schema §5); tests skipped for missing capability get `status: "unsupported"`.
 - `session_id` maps to `server_sessions[].session_id`; `action_id`s appear in test `params`.
 
-## 9. Open items
+## 10. Open items
 
 1. Whether TRAIN_REPORT should also stream during long trains (partial reports every N packets) for live UI feedback — leaning yes, same type with a `flags` bit.
 2. Throughput methodology (fixed streams vs BBR-style ramp) — decide with `perf.*` test design.

echolot-app/.gitignore

@@ -0,0 +1,6 @@
+.gradle/
+build/
+/local.properties
+/.idea/
+*.iml
+.DS_Store

echolot-app/README.md

@@ -0,0 +1,35 @@
+# Echolot app
+
+The production Android client ([spec](../docs/)). Native Kotlin + Jetpack Compose. Multi-module;
+built bottom-up from a verifiable protocol spine.
+
+## Modules
+
+| Module | Type | Status |
+|---|---|---|
+| `core-protocol` | pure Kotlin/JVM | **done** — client half of `probe-protocol.md`, verified live against the server |
+| `core-measurement` | pure Kotlin/JVM | planned — `measurement-schema.md` types |
+| `core-probe` | Android lib | planned — app-tier probes, ported from `echolot-prober` |
+| `core-shizuku` | Android lib | planned — dual-path executor (UserService + newProcess fallback) |
+| `app` | Android app | planned — Compose UI |
+
+`core-protocol` is deliberately Android-free so it builds and unit-tests on any JDK (no Android
+SDK) and can run **integration tests against a live server**.
+
+## core-protocol
+
+Implements the control plane (SPKI-pinned enrollment/profile/sessions via `HttpsURLConnection` —
+Android-API-1 compatible, hostname verification off because trust is the pin), the HKDF-SHA256
+session-key schedule, and the binary ELT1 UDP data plane (HMAC gate, ECHO + observation block,
+MTU probe) — byte-compatible with the Go server.
+
+```sh
+./gradlew :core-protocol:test              # unit tests (crypto vectors, wire round-trip)
+scripts/test-fmr.sh                         # live end-to-end test against the deployed server
+```
+
+`test-fmr.sh` mints an enrollment token over SSH, enrolls via the public control plane, computes
+the SPKI pin from the served cert, and runs `LiveServerTest` — proving the client speaks the wire
+protocol to the real server (enroll → profile → session → echo+observation → MTU → observations).
+The live test self-skips when `ECHOLOT_LIVE_*` env vars are absent, so unit runs and CI stay green
+offline.

echolot-app/adb-beacon/.gitignore

@@ -0,0 +1 @@
+/build

echolot-app/adb-beacon/build.gradle.kts

@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    // AGP 9 built-in Kotlin (no kotlin.android — see core-probe note).
+    alias(libs.plugins.android.application)
+}
+
+// Dev tool (NOT the product app): reports this phone's rotating wireless-debug
+// endpoint to the fmr beacon so the PC can keep `adb connect` current. Reads
+// the connect port from adbd's own mDNS advertisement (_adb-tls-connect._tcp)
+// via NsdManager — no root, no Shizuku.
+android {
+    namespace = "app.echo_lot.adbbeacon"
+    compileSdk = 36
+
+    defaultConfig {
+        applicationId = "app.echo_lot.adbbeacon"
+        minSdk = 26
+        targetSdk = 36
+        versionCode = 1
+        versionName = "0.1.0"
+        // Prefilled beacon config (dev tool — secret in the APK is fine).
+        buildConfigField("String", "BEACON_URL", "\"http://89.185.109.150:443/beacon\"")
+        buildConfigField("String", "BEACON_SECRET", "\"D4OmG5gGJsElqVVbtYIZbR\"")
+    }
+    buildTypes { release { isMinifyEnabled = false } }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    buildFeatures { buildConfig = true }
+}
+
+dependencies {
+    implementation(libs.kotlinx.coroutines.android)
+    implementation(libs.androidx.core.ktx)
+    implementation("androidx.activity:activity:1.9.3")
+}

echolot-app/adb-beacon/src/main/AndroidManifest.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-FileCopyrightText: 2026 Echolot contributors
+     SPDX-License-Identifier: GPL-3.0-or-later -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_SPECIAL_USE" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+
+    <application
+        android:allowBackup="false"
+        android:label="Echolot ADB Beacon"
+        android:usesCleartextTraffic="true"
+        android:theme="@android:style/Theme.Material.Light">
+
+        <activity android:name=".MainActivity" android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <service
+            android:name=".BeaconService"
+            android:exported="false"
+            android:foregroundServiceType="specialUse">
+            <property
+                android:name="android.app.PROPERTY_SPECIAL_USE_FGS_SUBTYPE"
+                android:value="wireless-debug-endpoint-beacon" />
+        </service>
+    </application>
+</manifest>

echolot-app/adb-beacon/src/main/kotlin/app/echo_lot/adbbeacon/BeaconService.kt

@@ -0,0 +1,226 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.adbbeacon
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.Service
+import android.content.Context
+import android.content.Intent
+import android.net.nsd.NsdManager
+import android.net.nsd.NsdServiceInfo
+import android.os.Build
+import android.os.IBinder
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import java.net.HttpURLConnection
+import java.net.Inet4Address
+import java.net.NetworkInterface
+import java.net.URL
+
+/**
+ * Foreground service that tracks this phone's wireless-debug endpoint and reports it to the fmr
+ * beacon. The port comes from adbd's own mDNS advertisement (`_adb-tls-connect._tcp`) via
+ * NsdManager — continuous discovery, so a port rotation re-fires and re-reports within seconds.
+ * The IP is the wlan0 private IPv4 (what the PC routes to). No root, no Shizuku.
+ */
+class BeaconService : Service() {
+
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.IO)
+    private lateinit var nsd: NsdManager
+    private var discoveryListener: NsdManager.DiscoveryListener? = null
+
+    @Volatile private var currentPort: Int = -1
+    /** Service instances already resolved — prevents repeat resolves (notification spam). */
+    private val resolvedOnce = java.util.Collections.synchronizedSet(mutableSetOf<String>())
+    private var heartbeat: Job? = null
+
+    override fun onBind(intent: Intent?): IBinder? = null
+
+    override fun onCreate() {
+        super.onCreate()
+        nsd = getSystemService(Context.NSD_SERVICE) as NsdManager
+        startForeground(1, buildNotification("Starting…"))
+        startDiscovery()
+        // Re-assert the endpoint periodically, but do NOT re-resolve mDNS each time:
+        // resolving adbd's own advertisement provokes it to re-arm the connection, which fires
+        // Android's "wireless debugging connected" notification — every cycle. Discovery runs
+        // once; we only re-POST the cached port (cheap, silent).
+        heartbeat = scope.launch {
+            while (true) {
+                delay(60_000)
+                report()
+            }
+        }
+        Status.set("watching for wireless-debug port…")
+    }
+
+    private fun startDiscovery() {
+        val listener = object : NsdManager.DiscoveryListener {
+            override fun onStartDiscoveryFailed(t: String?, code: Int) { Status.set("NSD start failed ($code)") }
+            override fun onStopDiscoveryFailed(t: String?, code: Int) {}
+            override fun onDiscoveryStarted(t: String?) {}
+            override fun onDiscoveryStopped(t: String?) {}
+            override fun onServiceLost(s: NsdServiceInfo?) {
+                // adbd stops advertising when Wireless debugging is turned off.
+                currentPort = -1
+                s?.serviceName?.let { resolvedOnce.remove(it) } // allow one re-resolve when it returns
+                val warn = "⚠ Wireless debugging appears OFF (adb mDNS service gone) — re-enable it"
+                Status.set(warn)
+                updateNotification(warn)
+            }
+            override fun onServiceFound(s: NsdServiceInfo?) {
+                if (s == null) return
+                // Resolve ONCE per discovered service instance. Repeatedly resolving adbd's own
+                // advertisement makes it re-arm the connection and spam the user with
+                // "wireless debugging connected" notifications.
+                val key = s.serviceName ?: return
+                if (!resolvedOnce.add(key)) return
+                resolve(s)
+            }
+        }
+        discoveryListener = listener
+        runCatching {
+            nsd.discoverServices("_adb-tls-connect._tcp", NsdManager.PROTOCOL_DNS_SD, listener)
+        }.onFailure { Status.set("NSD unavailable: ${it.message}") }
+    }
+
+    @Suppress("DEPRECATION")
+    private fun resolve(info: NsdServiceInfo) {
+        nsd.resolveService(info, object : NsdManager.ResolveListener {
+            override fun onResolveFailed(s: NsdServiceInfo?, code: Int) {}
+            override fun onServiceResolved(s: NsdServiceInfo?) {
+                s ?: return
+                // On a shared LAN, NsdManager discovers EVERY device's adb
+                // advertisement — accept only the one whose host is THIS device's
+                // own IP, else we'd report a neighbour's port for our IP.
+                val host = s.host?.hostAddress
+                val mine = wifiIpv4()
+                if (host != null && mine != null && host != mine) return
+                currentPort = s.port
+                scope.launch { report() }
+            }
+        })
+    }
+
+    private fun report() {
+        val ip = wifiIpv4() ?: run { Status.set("no wlan0 IPv4 (is wifi up?)"); return }
+        val port = currentPort
+        if (port <= 0) {
+            // No adb advertisement: either discovery hasn't landed yet, or (usually) Wireless
+            // debugging is off. Say so plainly.
+            val warn = "⚠ $ip — no wireless-debug port. Is Wireless debugging ON?"
+            Status.set(warn); updateNotification(warn)
+            return
+        }
+        val device = android.os.Build.MODEL.replace(Regex("[^A-Za-z0-9_.-]"), "_")
+        val body = """{"device":"$device","ip":"$ip","port":$port}"""
+        // Send over a VALIDATED internet network — the wireless-debug wifi is often a restricted
+        // LAN with no real internet TCP egress, so bind the report to cellular/whatever actually
+        // reaches the beacon.
+        val net = internetNetwork()
+        val ok = runCatching {
+            val url = URL(BuildConfig.BEACON_URL)
+            val conn = (net?.openConnection(url) ?: url.openConnection()) as HttpURLConnection
+            conn.run {
+                requestMethod = "POST"
+                connectTimeout = 5000; readTimeout = 5000
+                doOutput = true
+                setRequestProperty("Content-Type", "application/json")
+                setRequestProperty("X-Beacon-Secret", BuildConfig.BEACON_SECRET)
+                outputStream.use { it.write(body.toByteArray()) }
+                responseCode == 200
+            }
+        }.getOrDefault(false)
+        val via = if (net != null) "via ${netLabel(net)}" else "via default net"
+        val line = if (ok) {
+            "reported [$device] $ip:$port ✓  $via\n→ ${BuildConfig.BEACON_URL}"
+        } else {
+            "report FAILED for [$device] $ip:$port  $via\n→ POST ${BuildConfig.BEACON_URL}"
+        }
+        Status.set(line)
+        updateNotification(if (ok) "reported $ip:$port ✓" else "report failed for $ip:$port")
+    }
+
+    /** A network with validated internet access, preferring cellular (the wireless-debug wifi is
+     *  frequently a restricted LAN that can't reach the beacon over TCP). */
+    private fun internetNetwork(): android.net.Network? {
+        val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as android.net.ConnectivityManager
+        var fallback: android.net.Network? = null
+        for (n in cm.allNetworks) {
+            val c = cm.getNetworkCapabilities(n) ?: continue
+            if (!c.hasCapability(android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET)) continue
+            if (!c.hasCapability(android.net.NetworkCapabilities.NET_CAPABILITY_VALIDATED)) continue
+            if (c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_CELLULAR)) return n
+            fallback = n
+        }
+        return fallback
+    }
+
+    private fun netLabel(n: android.net.Network): String {
+        val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as android.net.ConnectivityManager
+        val c = cm.getNetworkCapabilities(n) ?: return "net"
+        return when {
+            c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_CELLULAR) -> "cellular"
+            c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_WIFI) -> "wifi"
+            c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_ETHERNET) -> "ethernet"
+            else -> "net"
+        }
+    }
+
+    /** The wlan0 (or first private) IPv4 the PC routes to. */
+    private fun wifiIpv4(): String? {
+        return runCatching {
+            NetworkInterface.getNetworkInterfaces().asSequence()
+                .filter { it.isUp && !it.isLoopback }
+                .sortedByDescending { it.name.startsWith("wlan") } // prefer wlan0
+                .flatMap { it.inetAddresses.asSequence() }
+                .filterIsInstance<Inet4Address>()
+                .firstOrNull { it.isSiteLocalAddress }
+                ?.hostAddress
+        }.getOrNull()
+    }
+
+    private fun buildNotification(text: String): Notification {
+        val channelId = "beacon"
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            val nm = getSystemService(NotificationManager::class.java)
+            nm.createNotificationChannel(
+                NotificationChannel(channelId, "ADB Beacon", NotificationManager.IMPORTANCE_LOW)
+            )
+        }
+        return Notification.Builder(this, channelId)
+            .setContentTitle("Echolot ADB Beacon")
+            .setContentText(text)
+            .setSmallIcon(android.R.drawable.stat_sys_data_bluetooth)
+            .setOngoing(true)
+            .build()
+    }
+
+    private fun updateNotification(text: String) {
+        getSystemService(NotificationManager::class.java).notify(1, buildNotification(text))
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int = START_STICKY
+
+    override fun onDestroy() {
+        discoveryListener?.let { runCatching { nsd.stopServiceDiscovery(it) } }
+        heartbeat?.cancel()
+        scope.cancel()
+        Status.set("stopped")
+        super.onDestroy()
+    }
+}
+
+/** Tiny shared status the activity polls (keeps the app dependency-free of observers). */
+object Status {
+    @Volatile var line: String = "idle"; private set
+    fun set(s: String) { line = s }
+}

echolot-app/adb-beacon/src/main/kotlin/app/echo_lot/adbbeacon/MainActivity.kt

@@ -0,0 +1,74 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.adbbeacon
+
+import android.Manifest
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.os.Build
+import android.os.Bundle
+import android.os.Handler
+import android.os.Looper
+import android.view.Gravity
+import android.widget.Button
+import android.widget.LinearLayout
+import android.widget.TextView
+import androidx.activity.ComponentActivity
+import androidx.core.content.ContextCompat
+
+/**
+ * Minimal control surface for the beacon: Start/Stop the foreground service and show its live
+ * status. Deliberately plain (no Compose) — it's a dev tool.
+ */
+class MainActivity : ComponentActivity() {
+
+    private lateinit var status: TextView
+    private val ui = Handler(Looper.getMainLooper())
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        if (Build.VERSION.SDK_INT >= 33 &&
+            ContextCompat.checkSelfPermission(this, Manifest.permission.POST_NOTIFICATIONS) != PackageManager.PERMISSION_GRANTED
+        ) {
+            requestPermissions(arrayOf(Manifest.permission.POST_NOTIFICATIONS), 1)
+        }
+
+        val root = LinearLayout(this).apply {
+            orientation = LinearLayout.VERTICAL
+            setPadding(48, 64, 48, 48)
+        }
+        val title = TextView(this).apply { text = "Echolot ADB Beacon"; textSize = 22f }
+        val subtitle = TextView(this).apply {
+            text = "Reports this phone's wireless-debug endpoint to fmr so the PC can keep adb connected.\n\n" +
+                "Enable Wireless debugging, then Start."
+            textSize = 13f; setPadding(0, 16, 0, 32)
+        }
+        status = TextView(this).apply { text = Status.line; textSize = 14f; gravity = Gravity.START }
+
+        val start = Button(this).apply {
+            text = "Start beacon"
+            setOnClickListener {
+                val i = Intent(this@MainActivity, BeaconService::class.java)
+                ContextCompat.startForegroundService(this@MainActivity, i)
+            }
+        }
+        val stop = Button(this).apply {
+            text = "Stop beacon"
+            setOnClickListener { stopService(Intent(this@MainActivity, BeaconService::class.java)) }
+        }
+
+        root.addView(title); root.addView(subtitle)
+        root.addView(start); root.addView(stop)
+        root.addView(TextView(this).apply { text = "\nStatus:"; setPadding(0, 32, 0, 8) })
+        root.addView(status)
+        setContentView(root)
+
+        poll()
+    }
+
+    private fun poll() {
+        status.text = Status.line
+        ui.postDelayed({ poll() }, 1000)
+    }
+}

echolot-app/app/.gitignore

@@ -0,0 +1 @@
+/build

echolot-app/app/build.gradle.kts

@@ -0,0 +1,83 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    // AGP 9 built-in Kotlin — no kotlin.android here (see core-probe note).
+    alias(libs.plugins.android.application)
+    alias(libs.plugins.kotlin.compose)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+// The app's version is SemVer and lives here, once. versionCode is derived from it rather than
+// maintained alongside: Play/F-Droid need a monotonically increasing integer, but a second number
+// that a human has to remember to bump is a number that eventually disagrees with the first — and
+// the version is now load-bearing, since the server decides whether to serve us by it.
+//
+// major*1_000_000 + minor*10_000 + patch*10 leaves room for 9 patch-level rebuilds (the trailing
+// digit) without disturbing the mapping, and stays inside the 2_100_000_000 ceiling until major 2100.
+val appVersionName = "0.2.0"
+
+fun versionCodeOf(semver: String): Int {
+    val (major, minor, patch) = semver.substringBefore('-').split(".").map(String::toInt)
+    return major * 1_000_000 + minor * 10_000 + patch * 10
+}
+
+android {
+    namespace = "app.echo_lot.app"
+    compileSdk = 36
+
+    defaultConfig {
+        applicationId = "app.echo_lot.app"
+        minSdk = 26
+        targetSdk = 36
+        versionCode = versionCodeOf(appVersionName)
+        versionName = appVersionName
+        // Automation: `adb shell am start -n app.echo_lot.app/.MainActivity --ez autorun true`
+        // runs a measurement immediately and POSTs the report here (dev collection endpoint).
+        buildConfigField("String", "REPORT_UPLOAD_URL", "\"http://89.185.109.150:443/report\"")
+        buildConfigField("String", "REPORT_UPLOAD_SECRET", "\"D4OmG5gGJsElqVVbtYIZbR\"")
+        // The bare SemVer, without the debug build's "-dev" suffix stripped away by the server's
+        // parser anyway — sent to servers so they can apply their compatibility window.
+        buildConfigField("String", "APP_SEMVER", "\"$appVersionName\"")
+    }
+    buildTypes {
+        release { isMinifyEnabled = false }
+        debug {
+            // The dev build is a separate app: own package (installs alongside a real
+            // Echolot), own label and a DEV-badged icon (src/debug/res).
+            applicationIdSuffix = ".dev"
+            versionNameSuffix = "-dev"
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    buildFeatures {
+        compose = true
+        buildConfig = true
+    }
+}
+
+dependencies {
+    implementation(project(":core-measurement"))
+    implementation(project(":core-protocol"))
+    implementation(project(":core-engine"))
+    implementation(project(":core-probe"))
+    implementation(project(":core-shizuku"))
+    implementation(project(":core-privacy"))
+    implementation(project(":core-archive"))
+
+    implementation(libs.kotlinx.serialization.json)
+    implementation(libs.kotlinx.coroutines.android)
+    implementation(libs.androidx.core.ktx)
+    implementation(libs.androidx.lifecycle.runtime.ktx)
+    implementation(libs.androidx.lifecycle.viewmodel.compose)
+    implementation(libs.androidx.activity.compose)
+    implementation(platform(libs.androidx.compose.bom))
+    implementation(libs.androidx.ui)
+    implementation(libs.androidx.ui.graphics)
+    implementation(libs.androidx.ui.tooling.preview)
+    implementation(libs.androidx.material3)
+    debugImplementation(libs.androidx.ui.tooling)
+}

echolot-app/app/src/debug/res/drawable/ic_launcher_foreground_dev.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-License-Identifier: GPL-3.0-or-later
+     Debug foreground: the production mark with a DEV ribbon so the dev build is
+     unmistakable on the launcher next to a real install. -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@drawable/ic_launcher_foreground"/>
+    <item android:drawable="@drawable/ic_dev_badge"/>
+</layer-list>

echolot-app/app/src/debug/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground_dev"/>
+</adaptive-icon>

echolot-app/app/src/debug/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground_dev"/>
+</adaptive-icon>

echolot-app/app/src/debug/res/values/strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">Echolot DEV</string>
+</resources>

echolot-app/app/src/main/AndroidManifest.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-FileCopyrightText: 2026 Echolot contributors
+     SPDX-License-Identifier: GPL-3.0-or-later -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
+    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
+    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
+
+    <application
+        android:allowBackup="false"
+        android:label="@string/app_name"
+        android:icon="@mipmap/ic_launcher"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:usesCleartextTraffic="true"
+        android:theme="@style/Theme.Echolot">
+
+        <activity
+            android:name=".MainActivity"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+            <!--
+              Enrollment bootstrap (probe-protocol.md §2.1): echolot://enroll?v=1&u=…&p=…&t=…
+              Scanning a QR or tapping a link the operator sent configures the server in one
+              action, instead of transcribing a URL, a base64 pin and a token by hand — the pin
+              in particular fails silently when it is wrong by one character.
+            -->
+            <intent-filter android:autoVerify="false">
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="echolot" android:host="enroll" />
+            </intent-filter>
+        </activity>
+
+        <provider
+            android:name="androidx.core.content.FileProvider"
+            android:authorities="${applicationId}.fileprovider"
+            android:exported="false"
+            android:grantUriPermissions="true">
+            <meta-data
+                android:name="android.support.FILE_PROVIDER_PATHS"
+                android:resource="@xml/file_paths" />
+        </provider>
+    </application>
+</manifest>

echolot-app/app/src/main/kotlin/app/echo_lot/app/HistoryScreen.kt

@@ -0,0 +1,116 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.safeDrawingPadding
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material3.Card
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.unit.dp
+import app.echo_lot.archive.ArchivedRun
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+
+/**
+ * Archived runs, newest first.
+ *
+ * Each row states plainly whether the run left the device, because "is this backed up / did I
+ * share this?" is the question a history list actually gets asked.
+ */
+@Composable
+fun HistoryScreen(
+    runs: List<ArchivedRun>,
+    status: String?,
+    onOpen: (String) -> Unit,
+    onUpload: (String) -> Unit,
+    onDelete: (String) -> Unit,
+    onBack: () -> Unit,
+) {
+    Column(Modifier.fillMaxWidth().safeDrawingPadding().padding(16.dp), verticalArrangement = Arrangement.spacedBy(10.dp)) {
+        Row(verticalAlignment = Alignment.CenterVertically) {
+            TextButton(onClick = onBack) { Text("‹ Back") }
+            Text("History", style = MaterialTheme.typography.titleLarge)
+        }
+        status?.let { Text(it, style = MaterialTheme.typography.bodySmall) }
+
+        if (runs.isEmpty()) {
+            Text(
+                "No archived runs yet. Finished runs are kept here automatically unless you turn " +
+                    "archiving off in settings.",
+                style = MaterialTheme.typography.bodyMedium,
+            )
+            return@Column
+        }
+
+        LazyColumn(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+            items(runs, key = { it.id }) { r ->
+                Card(Modifier.fillMaxWidth()) {
+                    Column(Modifier.padding(12.dp), verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                        Row(verticalAlignment = Alignment.CenterVertically) {
+                            Text(
+                                r.verdict?.uppercase() ?: "—",
+                                color = verdictTint(r.verdict),
+                                style = MaterialTheme.typography.titleMedium,
+                            )
+                            Text(
+                                "  " + humanTime(r.savedAtEpochMs),
+                                style = MaterialTheme.typography.bodyMedium,
+                            )
+                        }
+                        Text(
+                            "${r.findingCount} finding(s) · ${r.sizeBytes / 1024} kB · " +
+                                "kept complete on this device",
+                            style = MaterialTheme.typography.bodySmall,
+                        )
+                        // The upload line names the level the upload was made at, not the
+                        // archive's. They describe different documents, and showing the archive's
+                        // level here claimed more had left the device than actually did.
+                        Text(
+                            if (r.uploaded) {
+                                "uploaded to ${r.uploadedTo ?: "a server"}" +
+                                    (r.uploadedAs?.let { " as $it" } ?: "")
+                            } else {
+                                "on this device only"
+                            },
+                            style = MaterialTheme.typography.bodySmall,
+                            color = if (r.uploaded) Color(0xFF7FD17F) else Color(0xFFBBBBBB),
+                        )
+                        Row(horizontalArrangement = Arrangement.spacedBy(4.dp)) {
+                            TextButton(onClick = { onOpen(r.id) }) { Text("Export") }
+                            TextButton(onClick = { onUpload(r.id) }) {
+                                Text(if (r.uploaded) "Upload again" else "Upload")
+                            }
+                            TextButton(onClick = { onDelete(r.id) }) { Text("Delete") }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+private fun verdictTint(v: String?): Color = when (v?.lowercase()) {
+    "green", "ok", "pass" -> Color(0xFF7FD17F)
+    "yellow", "warn" -> Color(0xFFE0C060)
+    "red", "fail" -> Color(0xFFE07070)
+    else -> Color(0xFFBBBBBB)
+}
+
+private val stamp: DateTimeFormatter =
+    DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm").withZone(ZoneId.systemDefault())
+
+private fun humanTime(epochMs: Long): String = stamp.format(Instant.ofEpochMilli(epochMs))

echolot-app/app/src/main/kotlin/app/echo_lot/app/MainActivity.kt

@@ -0,0 +1,450 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import android.Manifest
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.os.Build
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.core.content.ContextCompat
+import androidx.lifecycle.lifecycleScope
+import kotlinx.coroutines.launch
+import androidx.lifecycle.viewmodel.compose.viewModel
+import app.echo_lot.measurement.*
+
+/** The app's three top-level screens. */
+private enum class Screen { RUN, HISTORY, SETTINGS }
+
+class MainActivity : ComponentActivity() {
+
+    private val permissionLauncher =
+        registerForActivityResult(ActivityResultContracts.RequestMultiplePermissions()) { /* proceed regardless */ }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        requestRuntimePermissions()
+        setContent {
+            MaterialTheme(colorScheme = darkColorScheme()) {
+                Surface(color = MaterialTheme.colorScheme.background) {
+                    val vm: RunViewModel = viewModel()
+                    // Three flat screens, so a plain state variable beats a navigation library:
+                    // there is no back stack to model beyond "return to the run screen".
+                    var screen by remember { mutableStateOf(Screen.RUN) }
+                    var preview by remember { mutableStateOf<String?>(null) }
+                    // Automation entry point:
+                    //   adb shell am start -n app.echo_lot.app/.MainActivity --ez autorun true
+                    // starts a run immediately and uploads the report, so an unattended
+                    // measurement needs no UI tapping and no adb round-trip to collect.
+                    val autorun = intent?.getBooleanExtra("autorun", false) == true
+
+                    // An echolot://enroll link (QR scan, or a link the operator sent) opens the
+                    // app straight into settings with the enrollment already done, so the user
+                    // sees the result rather than a form they still have to fill in.
+                    val enrollUri = intent?.takeIf { it.action == Intent.ACTION_VIEW }?.dataString
+                    androidx.compose.runtime.LaunchedEffect(enrollUri) {
+                        if (enrollUri != null) {
+                            vm.enroll(enrollUri)
+                            screen = Screen.SETTINGS
+                        }
+                    }
+                    androidx.compose.runtime.LaunchedEffect(autorun) {
+                        if (autorun) vm.run(devUpload = true)
+                    }
+                    // In autorun the app is a batch job: once the run is done AND the upload
+                    // succeeded, show the result briefly, then close so the device is left as it
+                    // was found. On failure it stays open so the error is visible.
+                    val st = vm.state
+                    androidx.compose.runtime.LaunchedEffect(autorun, st.running, st.uploadStatus) {
+                        if (autorun && !st.running && st.document != null &&
+                            st.uploadStatus?.startsWith("uploaded") == true
+                        ) {
+                            kotlinx.coroutines.delay(3000)
+                            finish()
+                        }
+                    }
+                    // Without this, the system Back gesture leaves the activity from Settings or
+                    // History instead of returning to the run screen — the screen is a plain state
+                    // variable, so nothing connects it to the back stack. Registered only when
+                    // there is somewhere to go back to, so Back still exits from the run screen.
+                    androidx.activity.compose.BackHandler(enabled = screen != Screen.RUN) {
+                        screen = Screen.RUN
+                    }
+
+                    when (screen) {
+                      Screen.SETTINGS -> SettingsScreen(
+                        settings = vm.settings,
+                        archivedRuns = vm.archivedRunCount(),
+                        archivedBytes = vm.archivedBytes(),
+                        onApplyRetention = vm::applyRetention,
+                        onDeleteAll = vm::deleteAllRuns,
+                        onPreviewUpload = {
+                            // Preview the newest run, since that is the one the user just made
+                            // and the one they are deciding about.
+                            vm.state.history.firstOrNull()?.let { r ->
+                                lifecycleScope.launch { preview = vm.uploadPreview(r.id) }
+                            }
+                        },
+                        onCheckServer = vm::checkServer,
+                        onEnroll = vm::enroll,
+                        serverStatus = vm.state.archiveStatus,
+                        onBack = { screen = Screen.RUN },
+                      )
+                      Screen.HISTORY -> HistoryScreen(
+                        runs = vm.state.history,
+                        status = vm.state.archiveStatus,
+                        onOpen = { id ->
+                            lifecycleScope.launch {
+                                vm.readRun(id)?.let { text ->
+                                    startActivity(
+                                        Intent.createChooser(
+                                            Report.shareJson(this@MainActivity, id, text),
+                                            "Export Echolot run",
+                                        )
+                                    )
+                                }
+                            }
+                        },
+                        onUpload = vm::uploadRun,
+                        onDelete = vm::deleteRun,
+                        onBack = { screen = Screen.RUN },
+                      )
+                      Screen.RUN -> EcholotScreen(
+                        state = vm.state,
+                        onRun = { vm.run() },
+                        onCancel = vm::cancel,
+                        onDeveloperOptions = {
+                            runCatching {
+                                startActivity(
+                                    app.echo_lot.shizuku.ShizukuAvailability.developerOptionsIntent()
+                                )
+                            }
+                        },
+                        onShizukuAction = {
+                            // Shizuku can only be started from its own app (the pairing flow lives
+                            // there), so send the user straight to it; if it is already running we
+                            // just need permission.
+                            when (vm.state.shizukuState) {
+                                app.echo_lot.shizuku.ShizukuAvailability.State.NEEDS_PERMISSION ->
+                                    app.echo_lot.shizuku.ShizukuAvailability.requestPermission()
+                                app.echo_lot.shizuku.ShizukuAvailability.State.INSTALLED_NOT_RUNNING ->
+                                    app.echo_lot.shizuku.ShizukuAvailability.launchIntent(this)
+                                        ?.let { startActivity(it) }
+                                else -> Unit
+                            }
+                        },
+                        onExport = { doc -> startActivity(Intent.createChooser(Report.share(this, doc), "Export Echolot run")) },
+                        onOpenSettings = { screen = Screen.SETTINGS },
+                        onOpenHistory = { vm.refreshHistory(); screen = Screen.HISTORY },
+                      )
+                    }
+                    preview?.let { text ->
+                        UploadPreviewDialog(text) { preview = null }
+                    }
+                }
+            }
+        }
+    }
+
+    private fun requestRuntimePermissions() {
+        val perms = mutableListOf(Manifest.permission.ACCESS_FINE_LOCATION)
+        val missing = perms.filter {
+            ContextCompat.checkSelfPermission(this, it) != PackageManager.PERMISSION_GRANTED
+        }
+        if (missing.isNotEmpty()) permissionLauncher.launch(missing.toTypedArray())
+    }
+}
+
+private fun verdictColor(v: Verdict): Color = when (v) {
+    Verdict.GREEN -> Color(0xFF2E7D32)
+    Verdict.YELLOW -> Color(0xFFF9A825)
+    Verdict.RED -> Color(0xFFC62828)
+    Verdict.INCONCLUSIVE -> Color(0xFF616161)
+}
+
+private fun statusColor(s: TestStatus): Color = when (s) {
+    TestStatus.OK -> Color(0xFF66BB6A)
+    TestStatus.PARTIAL -> Color(0xFFFFB300)
+    TestStatus.FAILED -> Color(0xFFEF5350)
+    TestStatus.UNSUPPORTED, TestStatus.SKIPPED -> Color(0xFF9E9E9E)
+}
+
+@Composable
+private fun EcholotScreen(
+    state: UiState,
+    onRun: () -> Unit,
+    onCancel: () -> Unit,
+    onShizukuAction: () -> Unit,
+    onDeveloperOptions: () -> Unit,
+    onExport: (MeasurementDocument) -> Unit,
+    onOpenSettings: () -> Unit,
+    onOpenHistory: () -> Unit,
+) {
+    Column(
+        Modifier
+            .fillMaxSize()
+            // Android 15 draws edge-to-edge by default: without this the title runs under the
+            // status-bar clock and the camera cutout. safeDrawing covers status/navigation bars
+            // AND the display cutout, so text never lands where it can't be read.
+            .safeDrawingPadding()
+            .padding(16.dp)
+            .verticalScroll(rememberScrollState()),
+        verticalArrangement = Arrangement.spacedBy(12.dp),
+    ) {
+        Row(Modifier.fillMaxWidth(), verticalAlignment = Alignment.CenterVertically) {
+            Column(Modifier.weight(1f)) {
+                Text("Echolot", fontSize = 26.sp, fontWeight = FontWeight.SemiBold)
+                Text("measure, don't guess",
+                    color = MaterialTheme.colorScheme.onSurfaceVariant, fontSize = 13.sp)
+            }
+            TextButton(onClick = onOpenHistory) { Text("History") }
+            TextButton(onClick = onOpenSettings) { Text("Settings") }
+        }
+
+        // Shell-tier readiness, before the run. Nothing is shown when Shizuku isn't installed —
+        // only users who actually use it get reminded that it must be running.
+        state.shizukuNotice?.let { notice ->
+            Card(
+                Modifier.fillMaxWidth().let { m ->
+                    if (state.shizukuHint != null) m.clickable { onShizukuAction() } else m
+                },
+                colors = CardDefaults.cardColors(
+                    containerColor = if (state.shizukuReady) Color(0xFF14301F) else Color(0xFF3A2E12),
+                ),
+            ) {
+                Column(Modifier.padding(10.dp)) {
+                    Text(
+                        notice, fontSize = 12.sp,
+                        color = if (state.shizukuReady) Color(0xFF9CCFA8) else Color(0xFFFFD08A),
+                    )
+                    state.shizukuHint?.let {
+                        Text(it, fontSize = 11.sp, fontWeight = FontWeight.SemiBold,
+                            color = Color(0xFFFFB454))
+                    }
+                    // Wireless debugging must be ON before Shizuku's wireless start works, and
+                    // that screen (unlike Shizuku's pairing activity) is publicly launchable.
+                    if (state.shizukuState ==
+                        app.echo_lot.shizuku.ShizukuAvailability.State.INSTALLED_NOT_RUNNING
+                    ) {
+                        Text(
+                            "Wireless debugging settings →",
+                            Modifier.padding(top = 6.dp).clickable { onDeveloperOptions() },
+                            fontSize = 11.sp, color = Color(0xFF35E0C4),
+                        )
+                    }
+                }
+            }
+        }
+
+        Row(horizontalArrangement = Arrangement.spacedBy(12.dp), verticalAlignment = Alignment.CenterVertically) {
+            Button(onClick = onRun, enabled = !state.running) {
+                Text(if (state.running) "Running…" else "Run measurement")
+            }
+            if (state.running) {
+                OutlinedButton(onClick = onCancel) { Text("Cancel") }
+            }
+            state.document?.let { doc ->
+                OutlinedButton(onClick = { onExport(doc) }) { Text("Export JSON") }
+            }
+        }
+
+        state.archiveStatus?.let {
+            Text(it, fontSize = 12.sp, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        }
+
+        state.uploadStatus?.let {
+            Text(it, fontSize = 12.sp, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        }
+
+        if (state.running) {
+            Column(verticalArrangement = Arrangement.spacedBy(6.dp)) {
+                val frac = if (state.stepsTotal > 0)
+                    state.stepsDone.toFloat() / state.stepsTotal else 0f
+                LinearProgressIndicator(
+                    progress = { frac },
+                    modifier = Modifier.fillMaxWidth(),
+                )
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    Text(
+                        if (state.stepsTotal > 0)
+                            "test ${state.stepsDone + 1} of ${state.stepsTotal}" else "starting",
+                        fontSize = 12.sp, fontWeight = FontWeight.Medium,
+                    )
+                    Text(state.currentStep ?: "…", fontSize = 12.sp,
+                        fontFamily = FontFamily.Monospace, modifier = Modifier.weight(1f))
+                    if (state.etaSeconds > 0) {
+                        Text("~${state.etaSeconds}s left", fontSize = 12.sp,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant)
+                    }
+                }
+            }
+        }
+
+        state.document?.let { doc -> Results(doc) }
+    }
+}
+
+@Composable
+private fun Results(doc: MeasurementDocument) {
+    val summary = doc.summary
+    if (summary != null) {
+        Card(colors = CardDefaults.cardColors(containerColor = verdictColor(summary.overall))) {
+            Column(Modifier.fillMaxWidth().padding(16.dp)) {
+                Text("Overall: ${summary.overall}", color = Color.White, fontWeight = FontWeight.Bold, fontSize = 18.sp)
+            }
+        }
+        FlowCategories(summary.categories)
+    }
+
+    RouterPanel(doc)
+
+    SectionTitle("Networks (${doc.networks.size})")
+    for (n in doc.networks) {
+        Text("• ${n.transport.name.lowercase()} ${n.iface ?: ""} — " +
+            n.link.addresses.joinToString(", ") { "${it.addr}/${it.prefixLen}" },
+            fontSize = 13.sp, fontFamily = FontFamily.Monospace)
+    }
+
+    SectionTitle("Tests (${doc.tests.size})")
+    for (t in doc.tests) {
+        Card(Modifier.fillMaxWidth()) {
+            Column(Modifier.padding(12.dp)) {
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp), verticalAlignment = Alignment.CenterVertically) {
+                    Dot(statusColor(t.status))
+                    Text(t.type, fontWeight = FontWeight.Medium, modifier = Modifier.weight(1f))
+                    Text(t.status.name, color = statusColor(t.status), fontSize = 12.sp)
+                }
+                val ms = (t.endedMonoNs - t.startedMonoNs) / 1_000_000
+                Text("${t.tier.name.lowercase()} · ${ms} ms", fontSize = 11.sp, color = MaterialTheme.colorScheme.onSurfaceVariant)
+                t.metrics?.let { Text(it.toString(), fontSize = 11.sp, fontFamily = FontFamily.Monospace, color = MaterialTheme.colorScheme.onSurfaceVariant) }
+            }
+        }
+    }
+
+    if (doc.findings.isNotEmpty()) {
+        SectionTitle("Findings (${doc.findings.size})")
+        for (f in doc.findings) {
+            Card(Modifier.fillMaxWidth()) {
+                Column(Modifier.padding(12.dp)) {
+                    Text(f.title, fontWeight = FontWeight.Medium)
+                    Text("${f.category.name.lowercase()} · ${f.severity.name.lowercase()}", fontSize = 11.sp, color = MaterialTheme.colorScheme.onSurfaceVariant)
+                    Text(f.description, fontSize = 12.sp)
+                }
+            }
+        }
+    }
+}
+
+/**
+ * Who advertises IPv6 here, and what box is it? Pulled from the link.ra_source evidence and shown
+ * up front — a rogue/misconfigured RA sender is a top cause of broken IPv6, and "some router" is
+ * not actionable without an identity.
+ */
+@Composable
+private fun RouterPanel(doc: MeasurementDocument) {
+    val test = doc.tests.firstOrNull { it.type == TestType.LINK_RA_SOURCE } ?: return
+    val nets = (test.evidence?.get("networks") as? kotlinx.serialization.json.JsonArray) ?: return
+    if (nets.isEmpty()) return
+
+    SectionTitle("Router / IPv6 advertiser")
+    for (el in nets) {
+        val o = el as? kotlinx.serialization.json.JsonObject ?: continue
+        fun f(k: String): String? =
+            (o[k] as? kotlinx.serialization.json.JsonPrimitive)?.content?.takeIf { it.isNotBlank() }
+        val ra = f("ra_source")
+        Card(Modifier.fillMaxWidth()) {
+            Column(Modifier.padding(12.dp), verticalArrangement = Arrangement.spacedBy(2.dp)) {
+                Text(f("network") ?: "network", fontWeight = FontWeight.Medium)
+                // The identity line: vendor/model if we could pin it down.
+                val identity = listOfNotNull(
+                    f("upnp_manufacturer"), f("upnp_model"), f("ra_source_vendor"),
+                ).distinct().joinToString(" · ").ifBlank { null }
+                identity?.let {
+                    Text(it, fontWeight = FontWeight.SemiBold, color = Color(0xFF35E0C4), fontSize = 15.sp)
+                }
+                f("upnp_friendly_name")?.let { Row0("name", it) }
+                ra?.let { Row0("RA source", it) }
+                f("ra_source_mac")?.let { Row0("RA source MAC", it) }
+                f("ra_source_reverse_dns")?.takeIf { it != "(none)" }?.let { Row0("reverse DNS", it) }
+                f("v4_gateway")?.let { Row0("IPv4 gateway", it) }
+                f("v4_gateway_reverse_dns")?.takeIf { it != "(none)" }?.let { Row0("gateway rDNS", it) }
+                f("upnp_server")?.let { Row0("UPnP server", it) }
+            }
+        }
+    }
+}
+
+@Composable
+private fun Row0(label: String, value: String) {
+    Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+        Text("$label:", fontSize = 12.sp, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        Text(value, fontSize = 12.sp, fontFamily = FontFamily.Monospace)
+    }
+}
+
+@Composable
+private fun FlowCategories(categories: Map<String, CategorySummary>) {
+    Column(verticalArrangement = Arrangement.spacedBy(6.dp)) {
+        for ((name, cat) in categories) {
+            Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                Dot(verdictColor(cat.verdict))
+                Text(name, modifier = Modifier.weight(1f))
+                Text("${cat.testsRun} run" + if (cat.testsFailed > 0) " · ${cat.testsFailed} failed" else "",
+                    fontSize = 11.sp, color = MaterialTheme.colorScheme.onSurfaceVariant)
+            }
+        }
+    }
+}
+
+@Composable
+private fun Dot(color: Color) {
+    Surface(color = color, shape = RoundedCornerShape(50), modifier = Modifier.size(12.dp)) {}
+}
+
+@Composable
+private fun SectionTitle(text: String) {
+    Text(text, fontWeight = FontWeight.SemiBold, fontSize = 15.sp, modifier = Modifier.padding(top = 8.dp))
+}
+
+/**
+ * Shows the exact JSON an upload would send.
+ *
+ * This exists because an anonymizer the user cannot inspect is just a promise. Being able to
+ * read the outgoing document — and find their own SSID absent from it — is what makes the
+ * privacy setting checkable rather than merely stated.
+ */
+@Composable
+private fun UploadPreviewDialog(text: String, onDismiss: () -> Unit) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        confirmButton = { TextButton(onClick = onDismiss) { Text("Close") } },
+        title = { Text("This is what would be uploaded") },
+        text = {
+            Column(Modifier.heightIn(max = 420.dp).verticalScroll(rememberScrollState())) {
+                Text(text, fontSize = 10.sp, fontFamily = FontFamily.Monospace)
+            }
+        },
+    )
+}

echolot-app/app/src/main/kotlin/app/echo_lot/app/Report.kt

@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import android.content.Context
+import android.content.Intent
+import androidx.core.content.FileProvider
+import app.echo_lot.measurement.MeasurementDocument
+import kotlinx.serialization.json.Json
+import java.io.File
+
+/** Serializes a measurement run to JSON and builds a share intent (measurement-schema.md §2). */
+object Report {
+    private val json = Json { prettyPrint = true; encodeDefaults = true }
+
+    fun toJson(doc: MeasurementDocument): String =
+        json.encodeToString(MeasurementDocument.serializer(), doc)
+
+    fun share(ctx: Context, doc: MeasurementDocument): Intent =
+        shareJson(ctx, doc.run.id, toJson(doc))
+
+    /**
+     * Shares an already-serialized run — an archived one, whose bytes must go out exactly as
+     * stored rather than being re-serialized through the model (which would silently drop
+     * anything a newer schema version added).
+     */
+    fun shareJson(ctx: Context, runId: String, json: String): Intent {
+        val dir = File(ctx.cacheDir, "reports").apply { mkdirs() }
+        val file = File(dir, "echolot-run-$runId.json")
+        file.writeText(json)
+        val uri = FileProvider.getUriForFile(ctx, "${ctx.packageName}.fileprovider", file)
+        return Intent(Intent.ACTION_SEND).apply {
+            type = "application/json"
+            putExtra(Intent.EXTRA_STREAM, uri)
+            addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+        }
+    }
+}

echolot-app/app/src/main/kotlin/app/echo_lot/app/ReportUploader.kt

@@ -0,0 +1,44 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import app.echo_lot.measurement.MeasurementDocument
+import java.net.HttpURLConnection
+import java.net.URL
+
+/**
+ * Dev/automation helper: uploads a finished run to the collection endpoint so an unattended run
+ * (see MainActivity's `autorun` extra) needs no adb round-trip to retrieve its result. Off unless
+ * an upload URL is configured. Never throws — a failed upload must not lose the local report.
+ */
+object ReportUploader {
+
+    data class Result(val ok: Boolean, val detail: String)
+
+    fun upload(doc: MeasurementDocument): Result {
+        val url = BuildConfig.REPORT_UPLOAD_URL
+        if (url.isBlank()) return Result(false, "no upload URL configured")
+        return try {
+            val body = Report.toJson(doc).toByteArray()
+            val conn = (URL(url).openConnection() as HttpURLConnection).apply {
+                requestMethod = "POST"
+                connectTimeout = 10_000
+                readTimeout = 15_000
+                doOutput = true
+                setRequestProperty("Content-Type", "application/json")
+                if (BuildConfig.REPORT_UPLOAD_SECRET.isNotBlank()) {
+                    setRequestProperty("X-Beacon-Secret", BuildConfig.REPORT_UPLOAD_SECRET)
+                }
+            }
+            conn.outputStream.use { it.write(body) }
+            val code = conn.responseCode
+            val resp = (if (code in 200..299) conn.inputStream else conn.errorStream)
+                ?.bufferedReader()?.use { it.readText() } ?: ""
+            conn.disconnect()
+            Result(code in 200..299, "HTTP $code ${resp.take(120)}")
+        } catch (t: Throwable) {
+            Result(false, t.message ?: t.javaClass.simpleName)
+        }
+    }
+}

echolot-app/app/src/main/kotlin/app/echo_lot/app/RunStore.kt

@@ -0,0 +1,179 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import android.content.Context
+import app.echo_lot.archive.ArchivedRun
+import app.echo_lot.archive.RunArchive
+import app.echo_lot.measurement.MeasurementDocument
+import app.echo_lot.privacy.Anonymizer
+import app.echo_lot.privacy.PrivacyLevel
+import app.echo_lot.privacy.Salt
+import app.echo_lot.protocol.Compat
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.UploadRefused
+import app.echo_lot.protocol.VersionRefused
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.jsonObject
+import java.io.File
+import java.security.SecureRandom
+
+/**
+ * Ties together the three things that happen to a finished run: it gets archived, it may get
+ * anonymized, and it may get uploaded — in that order, and with the archive always holding the
+ * *unredacted* document.
+ *
+ * That ordering is the important decision. The local archive is the user's own data on their own
+ * device, and redacting it would destroy exactly the detail that makes a week-old run worth
+ * keeping; the anonymizer exists for the moment data crosses to someone else's machine. So
+ * redaction happens on the way out, per upload, and the archive is never the lossy copy.
+ */
+class RunStore(context: Context, private val settings: Settings) {
+
+    private val archive = RunArchive(File(context.filesDir, "runs"))
+    private val json = Json { encodeDefaults = true; explicitNulls = true }
+
+    fun list(): List<ArchivedRun> = archive.list()
+    fun read(id: String): String? = archive.read(id)
+    fun delete(id: String) = archive.delete(id)
+    fun deleteAll(): Int = archive.deleteAll()
+    fun totalBytes(): Long = archive.totalBytes()
+
+    /** Archives a finished run under the user's retention policy. Null when archiving is off. */
+    fun archive(doc: MeasurementDocument): ArchivedRun? =
+        archive.save(Report.toJson(doc), settings.retention())
+
+    /** Applies retention now — e.g. after the user tightens the limits in settings. */
+    fun purgeNow() = archive.purge(settings.retention())
+
+    /**
+     * Produces exactly the bytes an upload would send, so the UI can show the user their own
+     * document as the server will see it *before* it goes. "Preview what you're about to share"
+     * is the only honest way to present an anonymizer: its correctness is not something a user
+     * should have to take on faith.
+     */
+    fun redactedForUpload(docJson: String, level: PrivacyLevel = settings.privacyLevel): String {
+        val parsed = runCatching { json.parseToJsonElement(docJson).jsonObject }.getOrNull()
+            ?: return docJson
+        return json.encodeToString(JsonObject.serializer(), Anonymizer(level, salt()).anonymize(parsed))
+    }
+
+    private fun salt(): Salt =
+        if (settings.stableSalt) Salt.stable(settings.saltSecret())
+        else Salt.perRun(ByteArray(32).also { SecureRandom().nextBytes(it) })
+
+    sealed interface UploadOutcome {
+        data class Sent(val serverName: String, val detail: String) : UploadOutcome
+        /** The operator's policy says no. Not retryable, and not the user's fault. */
+        data class Refused(val reason: String) : UploadOutcome
+        /**
+         * The two builds do not go together. Kept apart from [Refused] and [Failed] because the
+         * remedy is different and specific — install a particular version — and a message that
+         * says so is worth more than one that says "upload failed".
+         */
+        data class Incompatible(val reason: String) : UploadOutcome
+        data class Failed(val detail: String) : UploadOutcome
+        data object NotConfigured : UploadOutcome
+    }
+
+    private fun client() = ControlClient(
+        settings.serverUrl, setOf(settings.serverPin), BuildConfig.APP_SEMVER,
+    )
+
+    /**
+     * Checks the configured server without uploading anything: reachable, pinned, compatible, and
+     * willing to accept runs. Lets the user find out in settings rather than from a failed run.
+     */
+    fun checkServer(): String {
+        if (!settings.serverConfigured) return "Fill in the server URL, pin and credential first."
+        return try {
+            val profile = client().profile(settings.serverCredential)
+            val compat = Compat.check(profile, BuildConfig.APP_SEMVER)
+            val head = "${profile.name} · server ${profile.serverVersion} · " +
+                "protocol ${profile.compat.protocolVersion.ifBlank { "unstated" }}"
+            when {
+                compat.message != null -> head + "\n" + compat.message
+                else -> {
+                    val uploads = profile.uploads.refusalReason()
+                        ?: "uploads accepted (min anonymization: ${profile.uploads.minAnonymization})"
+                    head + "\nCompatible. " + uploads
+                }
+            }
+        } catch (e: VersionRefused) {
+            "This server will not serve this app: ${e.message}"
+        } catch (t: Throwable) {
+            "Could not reach the server: ${t.message ?: t.javaClass.simpleName}"
+        }
+    }
+
+    /**
+     * Redeems an enrollment link and stores the resulting server configuration (§2.1).
+     *
+     * Everything is written at once or not at all: a half-applied server — say a URL and pin with
+     * no credential — fails later, somewhere else, with an error that points at the wrong thing.
+     * Blocking; callers run it off the main thread.
+     */
+    fun enroll(link: String, deviceName: String?): String {
+        val parsed = app.echo_lot.protocol.EnrollmentLink.parse(link)
+            ?: return "That does not look like an Echolot enrollment link. It should start with " +
+                "echolot://enroll and carry a URL, a pin and a token."
+        return try {
+            val enrolled = parsed.redeem(deviceName, BuildConfig.APP_SEMVER)
+            val compat = Compat.check(enrolled.profile, BuildConfig.APP_SEMVER)
+            settings.serverUrl = enrolled.controlUrl
+            settings.serverPin = enrolled.pin
+            settings.serverCredential = enrolled.credential
+            val head = "Enrolled with ${enrolled.profile.name} " +
+                "(server ${enrolled.profile.serverVersion})."
+            if (compat.message != null) head + " " + compat.message else head
+        } catch (e: VersionRefused) {
+            "That server will not serve this app: ${e.message}"
+        } catch (t: Throwable) {
+            // The commonest causes are a spent token and a wrong pin, and they look nothing alike
+            // in the message — so pass it through rather than flattening it to "enrollment failed".
+            "Enrollment failed: ${t.message ?: t.javaClass.simpleName}"
+        }
+    }
+
+    /**
+     * Uploads one archived run to the configured server, redacting first.
+     *
+     * The server's advertised minimum wins over the user's preference when it is stricter — a
+     * server may demand more anonymization than the user chose, never less. Blocking; callers
+     * run it off the main thread.
+     */
+    fun upload(runId: String): UploadOutcome {
+        if (!settings.serverConfigured) return UploadOutcome.NotConfigured
+        val docJson = read(runId) ?: return UploadOutcome.Failed("run $runId is not in the archive")
+        return try {
+            val client = client()
+            val profile = client.profile(settings.serverCredential)
+
+            // Compatibility before policy: an incompatible server may well advertise an upload
+            // policy it would never actually apply to us.
+            val compat = Compat.check(profile, BuildConfig.APP_SEMVER)
+            if (!compat.usable) return UploadOutcome.Incompatible(compat.message ?: "incompatible versions")
+
+            profile.uploads.refusalReason()?.let { return UploadOutcome.Refused(it) }
+
+            val level = PrivacyLevel.max(
+                settings.privacyLevel,
+                PrivacyLevel.fromWire(profile.uploads.minAnonymization),
+            )
+            val body = redactedForUpload(docJson, level)
+            val reply = client.uploadRun(settings.serverCredential, body)
+            archive.markUploaded(runId, profile.name, level.wire)
+            // Deliberately not echoing `reply`: it is the server's index entry as raw JSON, and
+            // it ended up rendered verbatim in the UI. Size and level are what a person wants.
+            UploadOutcome.Sent(profile.name, "as $level, ${body.toByteArray().size} bytes")
+        } catch (e: VersionRefused) {
+            UploadOutcome.Incompatible(e.message ?: "the server refused this app's version")
+        } catch (e: UploadRefused) {
+            UploadOutcome.Refused(e.message ?: "refused by the server")
+        } catch (t: Throwable) {
+            UploadOutcome.Failed(t.message ?: t.javaClass.simpleName)
+        }
+    }
+}

echolot-app/app/src/main/kotlin/app/echo_lot/app/RunViewModel.kt

@@ -0,0 +1,460 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import android.app.Application
+import android.os.Build
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.viewModelScope
+import app.echo_lot.measurement.*
+import app.echo_lot.probe.CaptivePortalProbe
+import app.echo_lot.probe.DnsCanaryProbe
+import app.echo_lot.probe.IcmpProbe
+import app.echo_lot.probe.LinkSnapshotProbe
+import app.echo_lot.probe.StunProbe
+import app.echo_lot.probe.NetworkInventory
+import app.echo_lot.probe.Probe
+import app.echo_lot.probe.ProbeIds
+import app.echo_lot.probe.RouterIdentityProbe
+import app.echo_lot.shizuku.ShizukuAvailability
+import app.echo_lot.shizuku.ShizukuProbe
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import java.time.Instant
+import java.util.UUID
+
+data class UiState(
+    val running: Boolean = false,
+    val currentStep: String? = null,
+    val document: MeasurementDocument? = null,
+    /** Result line of an automated upload (autorun mode); null when not attempted. */
+    val uploadStatus: String? = null,
+    /** Progress: tests finished / total, and a rough ETA from the remaining probes' estimates. */
+    val stepsDone: Int = 0,
+    val stepsTotal: Int = 0,
+    val etaSeconds: Int = 0,
+    /** Where the finished run went: archived locally, uploaded, or neither (and why). */
+    val archiveStatus: String? = null,
+    /** History, newest first. Refreshed after every run and whenever the history screen opens. */
+    val history: List<app.echo_lot.archive.ArchivedRun> = emptyList(),
+    /** Shell-tier readiness, shown before a run; null message = say nothing (Shizuku not installed). */
+    val shizukuNotice: String? = null,
+    val shizukuReady: Boolean = false,
+    val shizukuHint: String? = null,
+    val shizukuState: ShizukuAvailability.State = ShizukuAvailability.State.NOT_INSTALLED,
+)
+
+/**
+ * Drives one measurement run: device-tier probes (link snapshot, per-network ICMP) always run;
+ * results assemble into a MeasurementDocument with a §7.3 summary. Lives in a ViewModel so a run
+ * survives rotation — a dropped run means a lost report. Server-facing tests (core-engine) are a
+ * follow-up once enrollment UI lands.
+ */
+class RunViewModel(app: Application) : AndroidViewModel(app) {
+
+    var state by mutableStateOf(UiState())
+        private set
+
+    val settings = Settings(app)
+    private val store = RunStore(app, settings)
+
+    private var runJob: kotlinx.coroutines.Job? = null
+    private val stopShizukuObserver: () -> Unit
+
+    init {
+        // Report shell-tier readiness up front. The binder arrives asynchronously, so this is a
+        // listener, not a one-shot poll — otherwise a running Shizuku would look "not running"
+        // for the first moment after launch.
+        stopShizukuObserver = ShizukuAvailability.observe(app) { st ->
+            state = state.copy(
+                shizukuNotice = ShizukuAvailability.describe(st),
+                shizukuReady = st == ShizukuAvailability.State.READY,
+                shizukuHint = ShizukuAvailability.actionHint(st),
+                shizukuState = st,
+            )
+        }
+    }
+
+    override fun onCleared() {
+        stopShizukuObserver()
+        super.onCleared()
+    }
+    // Results collected so far. A cancelled run must still be able to show what it measured.
+    private val collected = mutableListOf<Test>()
+    private var runIds: RunIds = RunIds()
+    private var runStartWall: String = ""
+    private var runNetworks: List<app.echo_lot.measurement.Network> = emptyList()
+    private var runShizukuOk = false
+
+    /** Two-clock ids: UUIDs + monotonic ns relative to a per-run origin. */
+    private class RunIds : ProbeIds {
+        val originNanos = System.nanoTime()
+        override fun uuid(): String = UUID.randomUUID().toString()
+        override fun monoNs(): Long = System.nanoTime() - originNanos
+    }
+
+    /**
+     * Runs one measurement, then archives it and — if the user has turned that on — uploads it.
+     *
+     * [devUpload] is the separate autorun/adb path (BuildConfig collection endpoint), kept apart
+     * from the user-facing upload so a debugging convenience can never be mistaken for, or
+     * silently satisfy, the consent-gated one.
+     */
+    fun run(devUpload: Boolean = false) {
+        if (state.running) return
+        collected.clear()
+        state = state.copy(running = true, currentStep = "starting", document = null,
+            uploadStatus = null, archiveStatus = null)
+        runJob = viewModelScope.launch {
+            val doc = withContext(Dispatchers.IO) { measure() }
+
+            step("archiving")
+            val archived = withContext(Dispatchers.IO) { store.archive(doc) }
+            var archiveStatus = if (archived != null) {
+                "archived locally (${store.list().size} runs kept)"
+            } else {
+                "not archived — archiving is off in settings"
+            }
+
+            var status: String? = null
+            if (devUpload) {
+                state = state.copy(currentStep = "uploading report")
+                val r = withContext(Dispatchers.IO) { ReportUploader.upload(doc) }
+                status = if (r.ok) "uploaded ✓ ${r.detail}" else "upload failed: ${r.detail}"
+            }
+            if (archived != null && settings.autoUpload) {
+                state = state.copy(currentStep = "uploading to server")
+                val outcome = withContext(Dispatchers.IO) { store.upload(archived.id) }
+                archiveStatus += " · " + describe(outcome)
+            }
+
+            state = UiState(
+                running = false, currentStep = null, document = doc,
+                uploadStatus = status, archiveStatus = archiveStatus,
+                history = withContext(Dispatchers.IO) { store.list() },
+            )
+        }
+    }
+
+    private fun describe(o: RunStore.UploadOutcome): String = when (o) {
+        is RunStore.UploadOutcome.Sent -> "uploaded to ${o.serverName} (${o.detail})"
+        is RunStore.UploadOutcome.Refused -> "server refused the upload: ${o.reason}"
+        is RunStore.UploadOutcome.Incompatible -> "version mismatch: ${o.reason}"
+        is RunStore.UploadOutcome.Failed -> "upload failed: ${o.detail}"
+        RunStore.UploadOutcome.NotConfigured -> "no server configured, so nothing was uploaded"
+    }
+
+    // ---- history ---------------------------------------------------------------------
+
+    fun refreshHistory() {
+        viewModelScope.launch {
+            state = state.copy(history = withContext(Dispatchers.IO) { store.list() })
+        }
+    }
+
+    fun deleteRun(id: String) {
+        viewModelScope.launch {
+            withContext(Dispatchers.IO) { store.delete(id) }
+            state = state.copy(history = withContext(Dispatchers.IO) { store.list() })
+        }
+    }
+
+    fun deleteAllRuns() {
+        viewModelScope.launch {
+            val n = withContext(Dispatchers.IO) { store.deleteAll() }
+            state = state.copy(
+                history = emptyList(),
+                archiveStatus = "deleted $n archived run(s)",
+            )
+        }
+    }
+
+    /** Uploads one already-archived run on demand, regardless of the auto-upload setting. */
+    fun uploadRun(id: String) {
+        viewModelScope.launch {
+            state = state.copy(archiveStatus = "uploading …")
+            val outcome = withContext(Dispatchers.IO) { store.upload(id) }
+            state = state.copy(
+                archiveStatus = describe(outcome),
+                history = withContext(Dispatchers.IO) { store.list() },
+            )
+        }
+    }
+
+    /** The archived document as stored, for export. */
+    suspend fun readRun(id: String): String? = withContext(Dispatchers.IO) { store.read(id) }
+
+    /** The exact bytes an upload would send, for the settings screen's preview. */
+    suspend fun uploadPreview(id: String): String? = withContext(Dispatchers.IO) {
+        store.read(id)?.let { store.redactedForUpload(it) }
+    }
+
+    fun archivedBytes(): Long = store.totalBytes()
+
+    /** Counted from the archive itself, not from [UiState.history], which is empty until the
+     *  history screen has been opened - the two disagreeing read as data loss. */
+    fun archivedRunCount(): Int = store.list().size
+
+    /** Redeems an enrollment link, from a paste or from an echolot:// deep link. */
+    fun enroll(link: String, deviceName: String? = android.os.Build.MODEL) {
+        viewModelScope.launch {
+            state = state.copy(archiveStatus = "enrolling …")
+            state = state.copy(archiveStatus = withContext(Dispatchers.IO) { store.enroll(link, deviceName) })
+        }
+    }
+
+    /** Settings-screen action: report what the configured server is and whether we can use it. */
+    fun checkServer() {
+        viewModelScope.launch {
+            state = state.copy(archiveStatus = "checking server …")
+            state = state.copy(archiveStatus = withContext(Dispatchers.IO) { store.checkServer() })
+        }
+    }
+
+    /** Re-applies retention after the user changes the limits. */
+    fun applyRetention() {
+        viewModelScope.launch {
+            val result = withContext(Dispatchers.IO) { store.purgeNow() }
+            state = state.copy(
+                history = withContext(Dispatchers.IO) { store.list() },
+                archiveStatus = if (result.isEmpty) "nothing to purge"
+                else "purged ${result.removed.size} run(s), freed ${result.freedBytes / 1024} kB",
+            )
+        }
+    }
+
+    /**
+     * Stops an in-flight run and shows what was measured so far. Deliberately does NOT upload:
+     * a partial run is for the person looking at the screen, not for the record.
+     */
+    fun cancel() {
+        if (!state.running) return
+        runJob?.cancel()
+        val doc = buildDocument(collected.toList())
+        state = UiState(
+            running = false, currentStep = null, document = doc,
+            uploadStatus = "cancelled after ${collected.size} test(s) — shown locally, not uploaded",
+            archiveStatus = "partial run — not archived",
+            history = state.history,
+        )
+    }
+
+    private suspend fun measure(): MeasurementDocument {
+        val ctx = getApplication<Application>()
+        val ids = RunIds().also { runIds = it }
+        val startWall = Instant.now().toString().also { runStartWall = it }
+
+        step("reading networks")
+        val entries = NetworkInventory.snapshot(ctx)
+        val networks = entries.map { it.model }.also { runNetworks = it }
+
+        val probes: List<Probe> = listOf(
+            LinkSnapshotProbe(entries),
+            RouterIdentityProbe(entries),
+            IcmpProbe(entries, v6 = false),
+            IcmpProbe(entries, v6 = true),
+            CaptivePortalProbe(entries),
+            // Canary zone served by the Echolot probe server (probe-protocol §6.1). Hardcoded to
+            // the reference deployment until profiles/enrollment land in the UI.
+            DnsCanaryProbe(canaryZone = "c.echo-lot.app", sessionPrefix = "adhoc"),
+            StunProbe(serverHost = "fmr-1.echo-lot.app"),
+        )
+
+        // Plan the run first: the Shizuku battery is counted alongside the app-tier probes so
+        // the bar reflects the whole run. Estimates are per-probe (see Probe.estimatedMs).
+        val shizukuEstimateMs = 8_000L
+        val totalSteps = probes.size + 1
+        var remainingMs = probes.sumOf { it.estimatedMs } + shizukuEstimateMs
+        state = state.copy(stepsDone = 0, stepsTotal = totalSteps,
+            etaSeconds = ((remainingMs + 999) / 1000).toInt())
+
+        val tests = ArrayList<Test>()
+        for ((i, p) in probes.withIndex()) {
+            step(p.type, done = i, total = totalSteps, etaMs = remainingMs)
+            val result = (
+                try {
+                    p.run(ctx, ids)
+                } catch (t: Throwable) {
+                    Test(
+                        id = ids.uuid(), type = p.type, tier = p.tier,
+                        startedMonoNs = ids.monoNs(), endedMonoNs = ids.monoNs(),
+                        status = TestStatus.FAILED,
+                        error = TestError("uncaught", t.message ?: t.javaClass.simpleName),
+                    )
+                }
+            )
+            tests.add(result); collected.add(result)
+            remainingMs -= p.estimatedMs
+        }
+
+        // Shizuku shell tier — self-degrades to UNSUPPORTED when Shizuku isn't running.
+        step("link.ip_monitor (shizuku)", done = probes.size, total = totalSteps, etaMs = shizukuEstimateMs)
+        val shizukuTest = try {
+            ShizukuProbe().run(ctx, ids::uuid, ids::monoNs)
+        } catch (t: Throwable) {
+            Test(
+                id = ids.uuid(), type = TestType.LINK_IP_MONITOR, tier = Tier.SHIZUKU,
+                startedMonoNs = ids.monoNs(), endedMonoNs = ids.monoNs(),
+                status = TestStatus.FAILED, error = TestError("uncaught", t.message ?: t.javaClass.simpleName),
+            )
+        }
+        tests.add(shizukuTest); collected.add(shizukuTest)
+        runShizukuOk = shizukuTest.status == TestStatus.OK || shizukuTest.status == TestStatus.PARTIAL
+
+        return buildDocument(tests)
+    }
+
+    /** Assembles a document from whatever tests are in hand — used for both full and cancelled runs. */
+    private fun buildDocument(tests: List<Test>): MeasurementDocument {
+        val findings = deriveFindings(tests, runNetworks)
+        return MeasurementDocument(
+            run = Run(
+                id = runIds.uuid(), trigger = Trigger.MANUAL, startedAt = runStartWall,
+                endedAt = Instant.now().toString(),
+                clock = Clock(monoOriginWall = runStartWall),
+                app = AppInfo(
+                    version = BuildConfig.VERSION_NAME, build = BuildConfig.VERSION_CODE, flavor = "app",
+                ),
+                device = DeviceInfo(
+                    manufacturer = Build.MANUFACTURER, model = Build.MODEL,
+                    androidSdk = Build.VERSION.SDK_INT, androidRelease = Build.VERSION.RELEASE,
+                ),
+                tiers = Tiers(app = true, shizuku = runShizukuOk),
+            ),
+            networks = runNetworks,
+            tests = tests,
+            findings = findings,
+            summary = Verdicts.derive(tests, findings),
+        )
+    }
+
+    /**
+     * Was IPv6 actually provisioned on any network? A global (non-link-local) v6 address or a
+     * v6 default route means the network claims to offer IPv6 — link-local only does not count.
+     */
+    private fun ipv6Provisioned(networks: List<app.echo_lot.measurement.Network>): Boolean =
+        networks.any { n ->
+            n.link.addresses.any { a ->
+                a.addr.contains(':') &&
+                    !a.addr.startsWith("fe80", ignoreCase = true) &&
+                    !a.addr.startsWith("::1")
+            } || n.link.routes.any { it.dst == "::/0" }
+        }
+
+    /** Minimal first-pass findings from device-tier evidence; the registry grows with the suite. */
+    private fun deriveFindings(tests: List<Test>, networks: List<app.echo_lot.measurement.Network>): List<Finding> {
+        val out = ArrayList<Finding>()
+        val ids = RunIds()
+        for (t in tests) {
+            if (t.type == TestType.NET_CAPTIVE_PORTAL) {
+                val ev = t.evidence?.toString() ?: ""
+                when {
+                    ev.contains("\"captive_portal\"") -> out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.CAPTIVE_PORTAL.code,
+                            category = FindingRegistry.CAPTIVE_PORTAL.category,
+                            severity = FindingRegistry.CAPTIVE_PORTAL.severity, confidence = Confidence.HIGH,
+                            title = "Captive portal intercepting connections",
+                            description = "The generate_204 check returned a redirect or a page instead of HTTP 204 — a captive portal (login/splash page) is intercepting traffic on this network.",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                    t.status == TestStatus.FAILED -> out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.NO_INTERNET.code,
+                            category = FindingRegistry.NO_INTERNET.category,
+                            severity = FindingRegistry.NO_INTERNET.severity, confidence = Confidence.HIGH,
+                            title = "No working internet on any network",
+                            description = "Android's own generate_204 connectivity checks failed on every active network (no HTTP 204) — this device has no validated internet path.",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                }
+            }
+            if (t.type == TestType.DNS_CANARY) {
+                val ev = t.evidence?.toString() ?: ""
+                if (ev.contains("MISMATCH")) {
+                    out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.DNS_ANSWER_REWRITTEN.code,
+                            category = FindingRegistry.DNS_ANSWER_REWRITTEN.category,
+                            severity = FindingRegistry.DNS_ANSWER_REWRITTEN.severity, confidence = Confidence.HIGH,
+                            title = "DNS answers are being rewritten",
+                            description = "A canary reference record returned different RDATA than the spec-defined ground truth — something on the path is rewriting DNS answers (interception, filtering, or a middlebox).",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                } else if (ev.contains("\"reached_authoritative\":false")) {
+                    out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.DNS_AUTHORITATIVE_UNREACHABLE.code,
+                            category = FindingRegistry.DNS_AUTHORITATIVE_UNREACHABLE.category,
+                            severity = FindingRegistry.DNS_AUTHORITATIVE_UNREACHABLE.severity, confidence = Confidence.MEDIUM,
+                            title = "Canary queries don't reach the authoritative server",
+                            description = "A per-run nonce name (which cannot be cached) was not answered by the canary server — the resolver is intercepting or failing to reach it.",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                }
+            }
+            if (t.type == TestType.NAT_STUN_5780 && t.status == TestStatus.OK) {
+                val ev = t.evidence?.toString() ?: ""
+                if (ev.contains("address/port-dependent (symmetric NAT")) {
+                    out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.NAT_SYMMETRIC.code,
+                            category = FindingRegistry.NAT_SYMMETRIC.category,
+                            severity = FindingRegistry.NAT_SYMMETRIC.severity, confidence = Confidence.HIGH,
+                            title = "Symmetric NAT — peer-to-peer connections need a relay",
+                            description = "The NAT assigns a different external port per destination (address/port-dependent mapping). Direct peer-to-peer connections (calls, games, file transfer) will usually fail and fall back to relays.",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                }
+            }
+            if (t.type == TestType.ICMP_PING6 && t.status == TestStatus.FAILED) {
+                // A network with no IPv6 at all is NORMAL — most networks are still IPv4-only,
+                // and that is not a defect. What IS a defect is IPv6 that the network claims to
+                // provide (a global address or a default route from RA/DHCPv6) but that does not
+                // work: that causes Happy-Eyeballs delays, timeouts and hangs. So the severity
+                // depends on whether v6 was provisioned at all.
+                if (ipv6Provisioned(networks)) {
+                    out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.V6_BROKEN.code,
+                            category = FindingRegistry.V6_BROKEN.category,
+                            severity = FindingRegistry.V6_BROKEN.severity, confidence = Confidence.HIGH,
+                            title = "IPv6 is configured but not working",
+                            description = "This network advertises IPv6 (a global address and/or a default route), but ICMPv6 got no reply on any network. Half-configured IPv6 is worse than none: connections try IPv6 first and stall before falling back.",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                } else {
+                    out.add(
+                        Finding(
+                            id = ids.uuid(), code = FindingRegistry.V6_NOT_OFFERED.code,
+                            category = FindingRegistry.V6_NOT_OFFERED.category,
+                            severity = FindingRegistry.V6_NOT_OFFERED.severity, confidence = Confidence.HIGH,
+                            title = "IPv4-only network (no IPv6 offered)",
+                            description = "No IPv6 address or default route was provisioned, so IPv6 tests could not run. This is normal — many networks are still IPv4-only and it is not a fault.",
+                            evidenceRefs = listOf(EvidenceRef(t.id)),
+                        )
+                    )
+                }
+            }
+        }
+        return out
+    }
+
+    private fun step(s: String, done: Int = state.stepsDone, total: Int = state.stepsTotal, etaMs: Long = -1) {
+        state = state.copy(
+            currentStep = s, stepsDone = done, stepsTotal = total,
+            etaSeconds = if (etaMs >= 0) ((etaMs + 999) / 1000).toInt() else state.etaSeconds,
+        )
+    }
+}

echolot-app/app/src/main/kotlin/app/echo_lot/app/Settings.kt

@@ -0,0 +1,124 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import android.content.Context
+import android.content.SharedPreferences
+import app.echo_lot.archive.RetentionPolicy
+import app.echo_lot.privacy.PrivacyLevel
+import java.security.SecureRandom
+
+/**
+ * User settings for archiving, uploading and anonymization.
+ *
+ * Defaults are the conservative reading of "an engineer's tool that still respects the person
+ * holding it": keep history (that is the point of the archive), never upload without being asked,
+ * and when uploading, strip identifiers unless the user says this is their own server.
+ *
+ * SharedPreferences rather than DataStore because these are a dozen scalars read synchronously at
+ * the start of a run; a coroutine-flow store would add a dependency and a lifecycle for nothing.
+ */
+class Settings(context: Context) {
+
+    private val prefs: SharedPreferences =
+        context.getSharedPreferences("echolot-settings", Context.MODE_PRIVATE)
+
+    // ---- archive ---------------------------------------------------------------------
+
+    var archiveEnabled: Boolean
+        get() = prefs.getBoolean(ARCHIVE_ENABLED, true)
+        set(v) = prefs.edit().putBoolean(ARCHIVE_ENABLED, v).apply()
+
+    /** 0 = no ceiling. */
+    var maxRuns: Int
+        get() = prefs.getInt(MAX_RUNS, 100)
+        set(v) = prefs.edit().putInt(MAX_RUNS, v.coerceAtLeast(0)).apply()
+
+    var maxAgeDays: Int
+        get() = prefs.getInt(MAX_AGE_DAYS, 90)
+        set(v) = prefs.edit().putInt(MAX_AGE_DAYS, v.coerceAtLeast(0)).apply()
+
+    var maxTotalMb: Int
+        get() = prefs.getInt(MAX_TOTAL_MB, 64)
+        set(v) = prefs.edit().putInt(MAX_TOTAL_MB, v.coerceAtLeast(0)).apply()
+
+    fun retention(): RetentionPolicy = RetentionPolicy(
+        enabled = archiveEnabled,
+        maxRuns = maxRuns,
+        maxAgeDays = maxAgeDays,
+        maxTotalBytes = maxTotalMb.toLong() * 1024 * 1024,
+    )
+
+    // ---- upload ----------------------------------------------------------------------
+
+    /**
+     * Off by default. Measurement data describes the network the user is standing in; sending it
+     * anywhere is a decision they make, not one they discover after the fact.
+     */
+    var autoUpload: Boolean
+        get() = prefs.getBoolean(AUTO_UPLOAD, false)
+        set(v) = prefs.edit().putBoolean(AUTO_UPLOAD, v).apply()
+
+    /** Anonymization applied before a run leaves the device. Never applied to the local archive. */
+    var privacyLevel: PrivacyLevel
+        get() = PrivacyLevel.fromWire(prefs.getString(PRIVACY_LEVEL, PrivacyLevel.BALANCED.wire))
+        set(v) = prefs.edit().putString(PRIVACY_LEVEL, v.wire).apply()
+
+    /**
+     * Whether pseudonyms stay stable across runs. That makes history diffable ("same SSID as
+     * last week") and is what someone wants on their own server — but it also produces an
+     * identifier that links a device's uploads, so it is off unless chosen.
+     */
+    var stableSalt: Boolean
+        get() = prefs.getBoolean(STABLE_SALT, false)
+        set(v) = prefs.edit().putBoolean(STABLE_SALT, v).apply()
+
+    /**
+     * The device-local secret behind stable pseudonyms. Generated once, never leaves the device,
+     * and clearing it (via [resetSalt]) breaks the link to everything uploaded before.
+     */
+    fun saltSecret(): ByteArray {
+        prefs.getString(SALT_SECRET, null)?.let { return hex(it) }
+        val fresh = ByteArray(32).also { SecureRandom().nextBytes(it) }
+        prefs.edit().putString(SALT_SECRET, fresh.joinToString("") { "%02x".format(it) }).apply()
+        return fresh
+    }
+
+    fun resetSalt() = prefs.edit().remove(SALT_SECRET).apply()
+
+    // ---- server ----------------------------------------------------------------------
+
+    var serverUrl: String
+        get() = prefs.getString(SERVER_URL, "") ?: ""
+        set(v) = prefs.edit().putString(SERVER_URL, v.trim()).apply()
+
+    var serverPin: String
+        get() = prefs.getString(SERVER_PIN, "") ?: ""
+        set(v) = prefs.edit().putString(SERVER_PIN, v.trim()).apply()
+
+    var serverCredential: String
+        get() = prefs.getString(SERVER_CRED, "") ?: ""
+        set(v) = prefs.edit().putString(SERVER_CRED, v.trim()).apply()
+
+    val serverConfigured: Boolean
+        get() = serverUrl.isNotBlank() && serverPin.isNotBlank() && serverCredential.isNotBlank()
+
+    private fun hex(s: String) = ByteArray(s.length / 2) {
+        ((Character.digit(s[it * 2], 16) shl 4) or Character.digit(s[it * 2 + 1], 16)).toByte()
+    }
+
+    private companion object {
+        const val ARCHIVE_ENABLED = "archive_enabled"
+        const val MAX_RUNS = "archive_max_runs"
+        const val MAX_AGE_DAYS = "archive_max_age_days"
+        const val MAX_TOTAL_MB = "archive_max_total_mb"
+        const val AUTO_UPLOAD = "auto_upload"
+        const val PRIVACY_LEVEL = "privacy_level"
+        const val STABLE_SALT = "stable_salt"
+        const val SALT_SECRET = "salt_secret"
+        const val SERVER_URL = "server_url"
+        const val SERVER_PIN = "server_pin"
+        const val SERVER_CRED = "server_credential"
+    }
+}

echolot-app/app/src/main/kotlin/app/echo_lot/app/SettingsScreen.kt

@@ -0,0 +1,259 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.app
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.safeDrawingPadding
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.Button
+import androidx.compose.material3.Card
+import androidx.compose.material3.FilterChip
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Switch
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.unit.dp
+import app.echo_lot.privacy.PrivacyLevel
+
+/**
+ * Archiving, upload and anonymization settings.
+ *
+ * The screen is written to make the consequences legible rather than to look tidy: every toggle
+ * says what it means for the user's data in a sentence, and the privacy levels are described by
+ * what survives them, because "balanced" on its own tells nobody anything.
+ */
+@Composable
+fun SettingsScreen(
+    settings: Settings,
+    archivedRuns: Int,
+    archivedBytes: Long,
+    onApplyRetention: () -> Unit,
+    onDeleteAll: () -> Unit,
+    onPreviewUpload: () -> Unit,
+    onCheckServer: () -> Unit,
+    onEnroll: (String) -> Unit,
+    serverStatus: String?,
+    onBack: () -> Unit,
+) {
+    // SharedPreferences is not observable, so mirror each value into Compose state and write
+    // through on change. A dozen scalars; a store with flows would be ceremony for nothing.
+    var archiveEnabled by remember { mutableStateOf(settings.archiveEnabled) }
+    var maxRuns by remember { mutableStateOf(settings.maxRuns.toString()) }
+    var maxAgeDays by remember { mutableStateOf(settings.maxAgeDays.toString()) }
+    var maxTotalMb by remember { mutableStateOf(settings.maxTotalMb.toString()) }
+    var autoUpload by remember { mutableStateOf(settings.autoUpload) }
+    var privacy by remember { mutableStateOf(settings.privacyLevel) }
+    var stableSalt by remember { mutableStateOf(settings.stableSalt) }
+    var enrollLink by remember { mutableStateOf("") }
+    var serverUrl by remember { mutableStateOf(settings.serverUrl) }
+    var serverPin by remember { mutableStateOf(settings.serverPin) }
+    var serverCred by remember { mutableStateOf(settings.serverCredential) }
+
+    Column(
+        Modifier.fillMaxWidth().safeDrawingPadding().verticalScroll(rememberScrollState()).padding(16.dp),
+        verticalArrangement = Arrangement.spacedBy(12.dp),
+    ) {
+        Row(verticalAlignment = Alignment.CenterVertically) {
+            TextButton(onClick = onBack) { Text("‹ Back") }
+            Text("Settings", style = MaterialTheme.typography.titleLarge)
+        }
+
+        // ---- archive ----
+        Card(Modifier.fillMaxWidth()) {
+            Column(Modifier.padding(14.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("Archive", style = MaterialTheme.typography.titleMedium)
+                Toggle(
+                    label = "Keep finished runs on this device",
+                    detail = "History is what makes a run comparable later. Archived runs are " +
+                        "stored complete and unredacted — anonymization only applies to uploads.",
+                    checked = archiveEnabled,
+                ) { archiveEnabled = it; settings.archiveEnabled = it }
+
+                Text(
+                    "Purge automatically when a run exceeds any of these. 0 turns that limit off.",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+                NumberField("Keep at most (runs)", maxRuns) {
+                    maxRuns = it; settings.maxRuns = it.toIntOrNull() ?: 0
+                }
+                NumberField("Delete older than (days)", maxAgeDays) {
+                    maxAgeDays = it; settings.maxAgeDays = it.toIntOrNull() ?: 0
+                }
+                NumberField("Keep at most (MB)", maxTotalMb) {
+                    maxTotalMb = it; settings.maxTotalMb = it.toIntOrNull() ?: 0
+                }
+                Text(
+                    "$archivedRuns run(s), ${archivedBytes / 1024} kB stored",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    Button(onClick = onApplyRetention) { Text("Apply now") }
+                    TextButton(onClick = onDeleteAll) { Text("Delete all runs") }
+                }
+            }
+        }
+
+        // ---- privacy ----
+        Card(Modifier.fillMaxWidth()) {
+            Column(Modifier.padding(14.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("What leaves the device", style = MaterialTheme.typography.titleMedium)
+                Text(
+                    "Applied to uploads only. Measurements, verdicts and finding codes survive " +
+                        "every level — only the parts that identify you or your network change.",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+                Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                    for (level in PrivacyLevel.entries) {
+                        FilterChip(
+                            selected = privacy == level,
+                            onClick = { privacy = level; settings.privacyLevel = level },
+                            label = { Text(level.wire) },
+                        )
+                    }
+                }
+                Text(privacyExplanation(privacy), style = MaterialTheme.typography.bodySmall)
+
+                Toggle(
+                    label = "Stable pseudonyms across runs",
+                    detail = "Lets you compare uploaded runs over time (same SSID reads the same " +
+                        "each time). It also links your uploads together, so leave it off on a " +
+                        "server you don't run yourself.",
+                    checked = stableSalt,
+                ) { stableSalt = it; settings.stableSalt = it }
+
+                TextButton(onClick = onPreviewUpload) { Text("Preview what an upload would send") }
+            }
+        }
+
+        // ---- upload ----
+        Card(Modifier.fillMaxWidth()) {
+            Column(Modifier.padding(14.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("Upload", style = MaterialTheme.typography.titleMedium)
+                Toggle(
+                    label = "Upload finished runs automatically",
+                    detail = "Sends each completed run to the server below, anonymized to the " +
+                        "level above. The server may require more anonymization than you chose; " +
+                        "it can never require less.",
+                    checked = autoUpload,
+                ) { autoUpload = it; settings.autoUpload = it }
+
+                // Enrollment first, because it is the path that works: one link carries the
+                // URL, the pin and a single-use token. The three fields below exist for when
+                // someone has to reconstruct a configuration by hand, not as the normal route.
+                Text(
+                    "Paste an enrollment link from your server operator, or scan its QR code. " +
+                        "It fills in all three fields below. The link contains a one-time token — " +
+                        "treat it like a password until it is used.",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+                OutlinedTextField(
+                    value = enrollLink, onValueChange = { enrollLink = it },
+                    label = { Text("echolot://enroll?…") }, singleLine = true,
+                    textStyle = MaterialTheme.typography.bodySmall.copy(fontFamily = FontFamily.Monospace),
+                    modifier = Modifier.fillMaxWidth(),
+                )
+                Button(
+                    onClick = {
+                        onEnroll(enrollLink)
+                        enrollLink = "" // spent either way; leaving it around invites a retry
+                        serverUrl = settings.serverUrl
+                        serverPin = settings.serverPin
+                        serverCred = settings.serverCredential
+                    },
+                    enabled = enrollLink.isNotBlank(),
+                ) { Text("Enroll") }
+
+                OutlinedTextField(
+                    value = serverUrl, onValueChange = { serverUrl = it; settings.serverUrl = it },
+                    label = { Text("Server URL") }, singleLine = true, modifier = Modifier.fillMaxWidth(),
+                )
+                OutlinedTextField(
+                    value = serverPin, onValueChange = { serverPin = it; settings.serverPin = it },
+                    label = { Text("Certificate pin (SPKI, base64)") }, singleLine = true,
+                    textStyle = MaterialTheme.typography.bodySmall.copy(fontFamily = FontFamily.Monospace),
+                    modifier = Modifier.fillMaxWidth(),
+                )
+                OutlinedTextField(
+                    value = serverCred,
+                    onValueChange = { serverCred = it; settings.serverCredential = it },
+                    label = { Text("Device credential") }, singleLine = true,
+                    textStyle = MaterialTheme.typography.bodySmall.copy(fontFamily = FontFamily.Monospace),
+                    modifier = Modifier.fillMaxWidth(),
+                )
+                Row(verticalAlignment = Alignment.CenterVertically) {
+                    Button(onClick = onCheckServer) { Text("Check server") }
+                    Text(
+                        "  " + if (settings.serverConfigured) "Configured."
+                        else "Uploads stay off until all three fields are set.",
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+                // Version compatibility is checked here rather than discovered mid-run: a server
+                // that will refuse this build should say so before a measurement is wasted.
+                serverStatus?.let {
+                    Text(it, style = MaterialTheme.typography.bodySmall)
+                }
+                Text(
+                    "This app is ${BuildConfig.APP_SEMVER} and speaks probe protocol " +
+                        "${app.echo_lot.protocol.Compat.PROTOCOL_VERSION}. It works with servers " +
+                        "${app.echo_lot.protocol.Compat.serverRange}.",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+            }
+        }
+        Spacer(Modifier.height(24.dp))
+    }
+}
+
+private fun privacyExplanation(level: PrivacyLevel): String = when (level) {
+    PrivacyLevel.FULL ->
+        "Nothing is removed: SSIDs, MAC addresses, hostnames and discovered neighbours are sent " +
+            "as measured. Appropriate for a server you run yourself."
+    PrivacyLevel.BALANCED ->
+        "Network names and hostnames become pseudonyms, MAC addresses keep only their vendor " +
+            "prefix, public IP addresses keep only their /16, and discovered neighbours (SSDP, " +
+            "ARP, nearby networks) are dropped entirely. Private addresses stay readable, since " +
+            "192.168.1.1 describes the topology and not the person."
+    PrivacyLevel.STRICT ->
+        "Only numbers: test results, metrics and finding codes. No network description, no raw " +
+            "evidence, no finding text. Nothing left can identify a network."
+}
+
+@Composable
+private fun Toggle(label: String, detail: String, checked: Boolean, onChange: (Boolean) -> Unit) {
+    Row(Modifier.fillMaxWidth(), verticalAlignment = Alignment.Top) {
+        Column(Modifier.weight(1f)) {
+            Text(label, style = MaterialTheme.typography.bodyMedium)
+            Text(detail, style = MaterialTheme.typography.bodySmall)
+        }
+        Switch(checked = checked, onCheckedChange = onChange)
+    }
+}
+
+@Composable
+private fun NumberField(label: String, value: String, onChange: (String) -> Unit) {
+    OutlinedTextField(
+        value = value,
+        onValueChange = { s -> onChange(s.filter { it.isDigit() }.take(7)) },
+        label = { Text(label) },
+        singleLine = true,
+        modifier = Modifier.fillMaxWidth(),
+    )
+}

echolot-app/app/src/main/res/drawable/ic_launcher_background.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-License-Identifier: GPL-3.0-or-later
+     Adaptive-icon background: the brand "tile" gradient (assets/branding). -->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="108dp" android:height="108dp"
+    android:viewportWidth="108" android:viewportHeight="108">
+    <path android:pathData="M0,0h108v108h-108z">
+        <aapt:attr name="android:fillColor">
+            <gradient android:startX="54" android:startY="0" android:endX="54" android:endY="108"
+                android:type="linear">
+                <item android:offset="0" android:color="#FF0E2433"/>
+                <item android:offset="1" android:color="#FF071522"/>
+            </gradient>
+        </aapt:attr>
+    </path>
+</vector>

echolot-app/app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-License-Identifier: GPL-3.0-or-later
+     Adaptive-icon foreground: the Focus mark (assets/branding/icon-adaptive-foreground.svg),
+     SVG transform baked in so the art sits inside the 66dp safe circle. -->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp" android:height="108dp"
+    android:viewportWidth="108" android:viewportHeight="108">
+    <path android:fillColor="#FF1E4A5C" android:pathData="M32.72,34.8 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M51.92,34.8 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M71.12,34.8 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M32.72,54.0 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M71.12,54.0 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M32.72,73.2 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M51.92,73.2 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:fillColor="#FF1E4A5C" android:pathData="M71.12,73.2 a2.08,2.08 0 1,0 4.16,0 a2.08,2.08 0 1,0 -4.16,0"/>
+    <path android:strokeColor="#FFB454" android:strokeAlpha="0.3" android:strokeWidth="1.6" android:fillColor="#00000000" android:pathData="M47.6,54.0 a6.4,6.4 0 1,0 12.8,0 a6.4,6.4 0 1,0 -12.8,0"/>
+    <path android:fillColor="#FFFFB454" android:pathData="M50.4,54.0 a3.6,3.6 0 1,0 7.2,0 a3.6,3.6 0 1,0 -7.2,0"/>
+    <path android:strokeColor="#FF35E0C4" android:strokeWidth="2.8" android:strokeLineCap="round" android:strokeLineJoin="round" android:fillColor="#00000000" android:pathData="M42.0,48.4 V42.0 H48.4"/>
+    <path android:strokeColor="#FF35E0C4" android:strokeWidth="2.8" android:strokeLineCap="round" android:strokeLineJoin="round" android:fillColor="#00000000" android:pathData="M59.6,42.0 H66.0 V48.4"/>
+    <path android:strokeColor="#FF35E0C4" android:strokeWidth="2.8" android:strokeLineCap="round" android:strokeLineJoin="round" android:fillColor="#00000000" android:pathData="M66.0,59.6 V66.0 H59.6"/>
+    <path android:strokeColor="#FF35E0C4" android:strokeWidth="2.8" android:strokeLineCap="round" android:strokeLineJoin="round" android:fillColor="#00000000" android:pathData="M48.4,66.0 H42.0 V59.6"/>
+</vector>

echolot-app/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+    <monochrome android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>

echolot-app/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+    <monochrome android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>

echolot-app/app/src/main/res/values/strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">Echolot</string>
+</resources>

echolot-app/app/src/main/res/values/themes.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-License-Identifier: GPL-3.0-or-later -->
+<resources>
+    <style name="Theme.Echolot" parent="android:Theme.Material.NoActionBar" />
+</resources>

echolot-app/app/src/main/res/xml/file_paths.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- SPDX-License-Identifier: GPL-3.0-or-later -->
+<paths>
+    <cache-path name="reports" path="reports/" />
+</paths>

echolot-app/build.gradle.kts

@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    alias(libs.plugins.android.application) apply false
+    alias(libs.plugins.android.library) apply false
+    alias(libs.plugins.kotlin.jvm) apply false
+    alias(libs.plugins.kotlin.android) apply false
+    alias(libs.plugins.kotlin.compose) apply false
+    alias(libs.plugins.kotlin.serialization) apply false
+}

echolot-app/core-archive/build.gradle.kts

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+// The on-device run archive: measurement documents on disk, with retention.
+// Pure Kotlin/JVM (it takes a directory, not a Context) so the retention rules
+// — the part with edge cases — are unit-testable without a device.
+dependencies {
+    implementation(libs.kotlinx.serialization.json)
+    testImplementation(kotlin("test"))
+}
+
+kotlin {
+    jvmToolchain(21)
+    compilerOptions { jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17) }
+}
+java { sourceCompatibility = JavaVersion.VERSION_17; targetCompatibility = JavaVersion.VERSION_17 }
+
+tasks.test { useJUnitPlatform() }

echolot-app/core-archive/src/main/kotlin/app/echo_lot/archive/RunArchive.kt

@@ -0,0 +1,225 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Package archive keeps completed measurement runs on the device.
+//
+// The point of an archive is the second run: "this network was fine on Tuesday" is only
+// answerable if Tuesday was kept. But an app that silently accumulates network dumps forever is
+// its own privacy problem, so retention is a first-class part of the type rather than a cleanup
+// job somebody remembers to write — every save enforces it.
+//
+// Storage is one JSON file per run plus a small index entry, in a plain directory. Nothing here
+// needs a database, and a plain directory is something a user can inspect, copy off, or delete
+// with a file manager. Files are written to a temp name and renamed, so a run interrupted mid-
+// write never leaves a half-document that reads as real.
+package app.echo_lot.archive
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+import java.io.File
+
+/** Index entry for one archived run — enough for a history list without opening the documents. */
+@Serializable
+data class ArchivedRun(
+    val id: String,
+    @SerialName("saved_at_epoch_ms") val savedAtEpochMs: Long,
+    @SerialName("started_at") val startedAt: String? = null,
+    val verdict: String? = null,
+    @SerialName("finding_count") val findingCount: Int = 0,
+    @SerialName("size_bytes") val sizeBytes: Long = 0,
+    /**
+     * How the *archived* document is redacted. Always "full" in practice, because the archive
+     * deliberately keeps the unredacted run - see the package doc. This is not what was uploaded.
+     */
+    val anonymization: String = "full",
+    /** Whether this run has been accepted by a server, so history can show what is backed up. */
+    val uploaded: Boolean = false,
+    @SerialName("uploaded_to") val uploadedTo: String? = null,
+    /**
+     * The level the run was *uploaded* at, which is a different document from the archived one.
+     *
+     * Kept separately because conflating the two is actively misleading: the history row showed
+     * the archive's own level ("full") directly beneath "uploaded to fmr", which reads as "the
+     * complete data was uploaded" when a redacted copy had been sent. A privacy display that
+     * overstates what left the device is worse than none.
+     */
+    @SerialName("uploaded_as") val uploadedAs: String? = null,
+)
+
+/**
+ * Retention limits. All three are independent ceilings; a run is dropped when it violates any of
+ * them. Zero disables that limit.
+ *
+ * The default keeps a hundred runs or three months, whichever comes first. That is enough to see
+ * a pattern ("it degrades every evening") without turning the phone into an archive of every
+ * network its owner ever walked past.
+ */
+@Serializable
+data class RetentionPolicy(
+    /**
+     * Whether to archive at all. Separate from the limits because "no limits" (every limit zero)
+     * and "keep nothing" are opposite intentions, and collapsing them onto the same value is how
+     * a user who turns all the caps off ends up with an empty history.
+     */
+    val enabled: Boolean = true,
+    @SerialName("max_runs") val maxRuns: Int = 100,
+    @SerialName("max_age_days") val maxAgeDays: Int = 90,
+    @SerialName("max_total_bytes") val maxTotalBytes: Long = 64L * 1024 * 1024,
+) {
+    companion object {
+        /** Archiving off: runs are shown once and never written. */
+        val KeepNothing = RetentionPolicy(enabled = false)
+
+        /** Archiving on with no ceilings. Every run is kept until the user deletes it. */
+        val Unlimited = RetentionPolicy(maxRuns = 0, maxAgeDays = 0, maxTotalBytes = 0)
+
+        val Default = RetentionPolicy()
+    }
+
+    val keepsAnything: Boolean get() = enabled
+}
+
+/** What a purge removed, so the UI can say "dropped 3 old runs" instead of silently deleting. */
+data class PurgeResult(val removed: List<String>, val freedBytes: Long) {
+    val isEmpty: Boolean get() = removed.isEmpty()
+}
+
+class RunArchive(private val dir: File, private val now: () -> Long = System::currentTimeMillis) {
+
+    private val json = Json { ignoreUnknownKeys = true; encodeDefaults = true }
+
+    init {
+        dir.mkdirs()
+    }
+
+    /**
+     * Writes one run and applies retention. Returns the index entry, or null when the policy
+     * keeps nothing at all — in which case nothing is written, rather than written and instantly
+     * deleted (the difference matters on flash storage and to anyone watching the filesystem).
+     */
+    fun save(runJson: String, policy: RetentionPolicy = RetentionPolicy.Default): ArchivedRun? {
+        if (!policy.keepsAnything) return null
+        val doc = runCatching { json.parseToJsonElement(runJson).jsonObject }.getOrNull() ?: return null
+        val meta = indexOf(doc, runJson.toByteArray().size.toLong()) ?: return null
+
+        writeAtomically(File(dir, meta.id + EXT), runJson)
+        writeAtomically(File(dir, meta.id + META_EXT), json.encodeToString(ArchivedRun.serializer(), meta))
+        purge(policy)
+        return meta
+    }
+
+    /** History, newest first. */
+    fun list(): List<ArchivedRun> =
+        (dir.listFiles { f -> f.name.endsWith(META_EXT) } ?: emptyArray())
+            .mapNotNull { f ->
+                runCatching { json.decodeFromString(ArchivedRun.serializer(), f.readText()) }.getOrNull()
+            }
+            .sortedByDescending { it.savedAtEpochMs }
+
+    fun read(id: String): String? = File(dir, safe(id) + EXT).takeIf { it.isFile }?.readText()
+
+    fun delete(id: String): Boolean {
+        val s = safe(id)
+        val doc = File(dir, s + EXT).delete()
+        File(dir, s + META_EXT).delete()
+        return doc
+    }
+
+    fun deleteAll(): Int = list().count { delete(it.id) }
+
+    /** Records that a server accepted this run, so history can distinguish backed-up from local. */
+    fun markUploaded(id: String, serverName: String, uploadedAs: String? = null) {
+        val f = File(dir, safe(id) + META_EXT)
+        val meta = runCatching { json.decodeFromString(ArchivedRun.serializer(), f.readText()) }.getOrNull()
+            ?: return
+        writeAtomically(
+            f,
+            json.encodeToString(
+                ArchivedRun.serializer(),
+                meta.copy(uploaded = true, uploadedTo = serverName, uploadedAs = uploadedAs),
+            ),
+        )
+    }
+
+    fun totalBytes(): Long = list().sumOf { it.sizeBytes }
+
+    /**
+     * Enforces the policy. Age first, then total size, then count: dropping stale runs may already
+     * satisfy the other two, and it is the limit a user reasons about ("keep three months"), so it
+     * should not be pre-empted by a size sweep deleting last week instead.
+     */
+    fun purge(policy: RetentionPolicy): PurgeResult {
+        val removed = ArrayList<String>()
+        var freed = 0L
+        fun drop(r: ArchivedRun) {
+            if (delete(r.id)) {
+                removed.add(r.id)
+                freed += r.sizeBytes
+            }
+        }
+
+        var kept = list()
+        if (policy.maxAgeDays > 0) {
+            val cutoff = now() - policy.maxAgeDays * 24L * 60 * 60 * 1000
+            val (fresh, stale) = kept.partition { it.savedAtEpochMs >= cutoff }
+            stale.forEach(::drop)
+            kept = fresh
+        }
+        if (policy.maxTotalBytes > 0) {
+            var total = kept.sumOf { it.sizeBytes }
+            // Oldest first until we are under the ceiling.
+            for (r in kept.reversed()) {
+                if (total <= policy.maxTotalBytes) break
+                drop(r)
+                total -= r.sizeBytes
+            }
+            kept = kept.filter { it.id !in removed }
+        }
+        if (policy.maxRuns > 0 && kept.size > policy.maxRuns) {
+            kept.drop(policy.maxRuns).forEach(::drop) // list() is newest-first
+        }
+        return PurgeResult(removed, freed)
+    }
+
+    // ---- internals ---------------------------------------------------------------------
+
+    private fun indexOf(doc: JsonObject, size: Long): ArchivedRun? {
+        val run = doc["run"]?.jsonObject ?: return null
+        val id = run["id"]?.jsonPrimitive?.content?.let(::safe)?.takeIf { it.isNotEmpty() } ?: return null
+        return ArchivedRun(
+            id = id,
+            savedAtEpochMs = now(),
+            startedAt = run["started_at"]?.jsonPrimitive?.content,
+            // The schema calls it `overall` (Summary.overall); reading `verdict` here silently
+            // yielded null for every run, so the history list's most prominent element - the
+            // coloured verdict - was blank on every row.
+            verdict = doc["summary"]?.jsonObject?.get("overall")?.jsonPrimitive?.content,
+            findingCount = (doc["findings"] as? kotlinx.serialization.json.JsonArray)?.size ?: 0,
+            sizeBytes = size,
+            anonymization = run["privacy"]?.jsonObject?.get("anonymization")?.jsonPrimitive?.content ?: "full",
+        )
+    }
+
+    private fun writeAtomically(target: File, content: String) {
+        val tmp = File(target.parentFile, target.name + ".tmp")
+        tmp.writeText(content)
+        if (!tmp.renameTo(target)) {
+            target.delete()
+            tmp.renameTo(target)
+        }
+    }
+
+    /** Run ids reach the filesystem; keep them to characters that cannot climb out of [dir]. */
+    private fun safe(id: String): String = buildString {
+        for (c in id) if (c.isLetterOrDigit() || c == '-' || c == '_') append(c)
+    }.take(64)
+
+    private companion object {
+        const val EXT = ".json"
+        const val META_EXT = ".meta.json"
+    }
+}

echolot-app/core-archive/src/test/kotlin/app/echo_lot/archive/RunArchiveTest.kt

@@ -0,0 +1,197 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.archive
+
+import java.io.File
+import java.nio.file.Files
+import kotlin.test.AfterTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class RunArchiveTest {
+
+    private val dir: File = Files.createTempDirectory("echolot-archive").toFile()
+    private var clock = 1_000_000_000_000L // fixed: retention is time arithmetic, not wall time
+
+    private fun archive() = RunArchive(dir) { clock }
+
+    @AfterTest fun cleanup() { dir.deleteRecursively() }
+
+    private fun doc(id: String, findings: Int = 1, pad: Int = 0): String {
+        val f = (1..findings).joinToString(",") { """{"id":"f$it"}""" }
+        return """{"run":{"id":"$id","started_at":"2026-08-01T10:00:00Z","privacy":{"anonymization":"balanced"}},""" +
+            """"findings":[$f],"summary":{"overall":"warn"},"pad":"${"x".repeat(pad)}"}"""
+    }
+
+    @Test
+    fun savedRunsComeBackNewestFirst() {
+        val a = archive()
+        for (i in 1..3) {
+            a.save(doc("run-$i"))
+            clock += 60_000
+        }
+        assertEquals(listOf("run-3", "run-2", "run-1"), a.list().map { it.id })
+    }
+
+    @Test
+    fun theIndexSummarisesTheDocument() {
+        val meta = assertNotNull(archive().save(doc("run-1", findings = 4)))
+        assertEquals("warn", meta.verdict)
+        assertEquals(4, meta.findingCount)
+        assertEquals("balanced", meta.anonymization)
+        assertEquals("2026-08-01T10:00:00Z", meta.startedAt)
+        assertFalse(meta.uploaded)
+    }
+
+    @Test
+    fun theDocumentComesBackByteForByte() {
+        val a = archive()
+        val original = doc("run-1")
+        a.save(original)
+        assertEquals(original, a.read("run-1"))
+    }
+
+    @Test
+    fun countLimitKeepsTheNewest() {
+        val a = archive()
+        val policy = RetentionPolicy(maxRuns = 3, maxAgeDays = 0, maxTotalBytes = 0)
+        for (i in 1..7) {
+            a.save(doc("run-$i"), policy)
+            clock += 60_000
+        }
+        assertEquals(listOf("run-7", "run-6", "run-5"), a.list().map { it.id })
+        assertNull(a.read("run-1"), "purged run's document should be gone, not just its index entry")
+    }
+
+    @Test
+    fun ageLimitDropsRunsPastTheWindow() {
+        val a = archive()
+        val policy = RetentionPolicy(maxRuns = 0, maxAgeDays = 7, maxTotalBytes = 0)
+        a.save(doc("old"), policy)
+        clock += 30L * 24 * 60 * 60 * 1000 // a month later
+        a.save(doc("new"), policy)
+        assertEquals(listOf("new"), a.list().map { it.id })
+    }
+
+    @Test
+    fun sizeLimitDropsOldestUntilUnderTheCeiling() {
+        val a = archive()
+        val one = doc("x", pad = 900).toByteArray().size.toLong()
+        val policy = RetentionPolicy(maxRuns = 0, maxAgeDays = 0, maxTotalBytes = one * 2 + 10)
+        for (i in 1..5) {
+            a.save(doc("run-$i", pad = 900), policy)
+            clock += 60_000
+        }
+        val kept = a.list()
+        assertTrue(kept.size <= 2, "size ceiling not enforced: kept ${kept.size}")
+        assertEquals("run-5", kept.first().id, "the newest run must always survive")
+        assertTrue(a.totalBytes() <= policy.maxTotalBytes)
+    }
+
+    // A policy that keeps nothing must not write-then-delete: the run should never touch storage.
+    @Test
+    fun keepNothingWritesNothing() {
+        val a = archive()
+        assertNull(a.save(doc("run-1"), RetentionPolicy.KeepNothing))
+        assertTrue(a.list().isEmpty())
+        assertEquals(0, dir.listFiles()?.size ?: 0, "files were written for a keep-nothing policy")
+    }
+
+    // "no ceilings" and "keep nothing" must not be the same policy, however a user arrives at
+    // one: turning every limit off should keep everything, not wipe the history.
+    @Test
+    fun unlimitedKeepsEverythingWhileKeepNothingKeepsNone() {
+        val a = archive()
+        for (i in 1..5) {
+            a.save(doc("run-$i"), RetentionPolicy.Unlimited)
+            clock += 60_000
+        }
+        assertEquals(5, a.list().size)
+        assertNull(a.save(doc("run-6"), RetentionPolicy.KeepNothing))
+        assertEquals(5, a.list().size, "keep-nothing must not touch what is already archived")
+    }
+
+    @Test
+    fun uploadStateIsRecorded() {
+        val a = archive()
+        a.save(doc("run-1"))
+        a.markUploaded("run-1", "fmr", "balanced")
+        val meta = a.list().single()
+        assertTrue(meta.uploaded)
+        assertEquals("fmr", meta.uploadedTo)
+        assertEquals("run-1", meta.id, "marking upload must not disturb the rest of the entry")
+    }
+
+    // The archive's own level and the level a run was uploaded at describe *different documents*.
+    // Showing the archive's ("full", because the archive is deliberately unredacted) next to
+    // "uploaded to fmr" reads as "the complete data was uploaded" when a redacted copy was sent —
+    // a privacy display that overstates what left the device is worse than none.
+    @Test
+    fun theUploadedLevelIsRecordedSeparatelyFromTheArchivedOne() {
+        val a = archive()
+        // A real archived document carries no privacy stamp: the anonymizer never runs on the
+        // archive. The shared doc() fixture has one, which is exactly the unrealism that let this
+        // confusion through in the first place.
+        a.save("""{"run":{"id":"run-1"},"findings":[],"summary":{"overall":"green"}}""")
+        a.markUploaded("run-1", "fmr", "balanced")
+        val meta = a.list().single()
+        assertEquals("full", meta.anonymization, "the archived copy is unredacted, by design")
+        assertEquals("balanced", meta.uploadedAs, "the uploaded copy was redacted, and must say so")
+    }
+
+    // The verdict is read from `summary.overall` — the schema's actual field name. Reading
+    // `summary.verdict` silently yielded null for every run, so the history list's most prominent
+    // element was blank on every row while everything else looked fine.
+    @Test
+    fun theVerdictComesFromTheSchemasOverallField() {
+        val a = archive()
+        a.save("""{"run":{"id":"r1"},"findings":[],"summary":{"overall":"yellow"}}""")
+        assertEquals("yellow", a.list().single().verdict)
+    }
+
+    @Test
+    fun deleteRemovesBothFiles() {
+        val a = archive()
+        a.save(doc("run-1"))
+        assertTrue(a.delete("run-1"))
+        assertTrue(a.list().isEmpty())
+        assertNull(a.read("run-1"))
+        assertEquals(0, dir.listFiles()?.size ?: 0)
+    }
+
+    @Test
+    fun malformedInputIsRejectedRatherThanArchived() {
+        val a = archive()
+        assertNull(a.save("not json"))
+        assertNull(a.save("""{"summary":{"verdict":"ok"}}"""), "a document with no run id has no identity")
+        assertTrue(a.list().isEmpty())
+    }
+
+    // Run ids come from a document that may have been produced elsewhere; they must not be able
+    // to write outside the archive directory.
+    @Test
+    fun runIdsCannotEscapeTheArchiveDirectory() {
+        val a = archive()
+        a.save(doc("../../evil"))
+        val strays = dir.parentFile.listFiles { f -> f.name.contains("evil") } ?: emptyArray()
+        assertTrue(strays.isEmpty(), "wrote outside the archive: ${strays.toList()}")
+    }
+
+    @Test
+    fun purgeReportsWhatItRemoved() {
+        val a = archive()
+        for (i in 1..5) {
+            a.save(doc("run-$i"), RetentionPolicy.Unlimited)
+            clock += 60_000
+        }
+        val result = a.purge(RetentionPolicy(maxRuns = 2, maxAgeDays = 0, maxTotalBytes = 0))
+        assertEquals(3, result.removed.size)
+        assertTrue(result.freedBytes > 0)
+        assertEquals(2, a.list().size)
+    }
+}

echolot-app/core-engine/build.gradle.kts

@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+// The measurement run engine: composes core-protocol probes into
+// core-measurement documents. Pure Kotlin/JVM, so it is unit-testable and can
+// run a full server-facing measurement against a live server.
+dependencies {
+    implementation(project(":core-protocol"))
+    implementation(project(":core-measurement"))
+    implementation(project(":core-privacy"))
+    implementation(libs.kotlinx.serialization.json)
+    testImplementation(kotlin("test"))
+}
+
+kotlin {
+    jvmToolchain(21)
+    compilerOptions { jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17) }
+}
+java { sourceCompatibility = JavaVersion.VERSION_17; targetCompatibility = JavaVersion.VERSION_17 }
+
+tasks.test {
+    useJUnitPlatform()
+    listOf("ECHOLOT_LIVE_URL","ECHOLOT_LIVE_PIN","ECHOLOT_LIVE_CRED","ECHOLOT_LIVE_UDP","ECHOLOT_LIVE_TARGET","ECHOLOT_ENROLL_URI")
+        .forEach { k -> System.getenv(k)?.let { environment(k, it) } }
+}

echolot-app/core-engine/src/main/kotlin/app/echo_lot/engine/Directional.kt

@@ -0,0 +1,107 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/**
+ * Splits a round-trip train into its two directions using what the server witnessed.
+ *
+ * A round trip can only report that *something* was lost somewhere. That is the least useful form
+ * of the answer: "3 % loss" sends an engineer looking in both directions at once. The server
+ * records every packet it received, per sequence number (probe-protocol.md §6), so the two cases
+ * are actually distinguishable:
+ *
+ *   - sent, never seen by the server  → **upstream** loss
+ *   - seen by the server, reply never arrived → **downstream** loss
+ *
+ * The same records give one-way delay *variation* per direction. Absolute one-way delay would
+ * need synchronised clocks and we deliberately have none (measurement-schema.md's two-clock rule),
+ * but the variation does not: (server_rx − client_tx) contains an unknown constant clock offset,
+ * and differencing successive samples cancels it. So jitter is honestly attributable to a
+ * direction even though latency is not.
+ */
+object Directional {
+
+    /** One probe as the client saw it. [tRxNs] null means no reply came back. */
+    data class Sample(val seq: Int, val tTxNs: Long, val tRxNs: Long?)
+
+    /** One probe as the server saw it: its own receive and transmit stamps, on its own clock. */
+    data class ServerSighting(val seq: Int, val tRxNs: Long, val tTxNs: Long)
+
+    fun analyse(sent: List<Sample>, seen: List<ServerSighting>): DirectionalMetrics {
+        val byServerSeq = seen.associateBy { it.seq }
+        // Only sequences we actually sent count. A server record for a sequence we have no note
+        // of is not evidence about this train — it is a bug or a stray, and silently folding it
+        // in would produce loss percentages above 100 or below zero.
+        val relevant = sent.filter { byServerSeq.containsKey(it.seq) }
+
+        val nSent = sent.size
+        val nSeen = relevant.size
+        val nReplied = sent.count { it.tRxNs != null }
+
+        // A reply can only exist if the request arrived, so downstream loss is measured against
+        // what the server saw, not against what we sent — otherwise upstream loss is counted twice.
+        val lostUp = nSent - nSeen
+        val lostDown = (nSeen - nReplied).coerceAtLeast(0)
+
+        val upDeltas = relevant.sortedBy { it.seq }
+            .map { byServerSeq.getValue(it.seq).tRxNs - it.tTxNs }
+        val downDeltas = sent.filter { it.tRxNs != null && byServerSeq.containsKey(it.seq) }
+            .sortedBy { it.seq }
+            .map { it.tRxNs!! - byServerSeq.getValue(it.seq).tTxNs }
+
+        return DirectionalMetrics(
+            sent = nSent,
+            seenByServer = nSeen,
+            repliesReceived = nReplied,
+            lostUpstream = lostUp,
+            lostDownstream = lostDown,
+            lossUpstreamPct = pct(lostUp, nSent),
+            // Denominator is what reached the server: of the packets that got there, how many
+            // replies came back.
+            lossDownstreamPct = pct(lostDown, nSeen),
+            jitterUpstreamMs = jitterMs(upDeltas),
+            jitterDownstreamMs = jitterMs(downDeltas),
+            /** True when the server saw nothing at all, which is a different fault from loss. */
+            noneReachedServer = nSent > 0 && nSeen == 0,
+        )
+    }
+
+    /**
+     * Mean absolute difference between consecutive one-way samples (RFC 3393 IPDV, averaged).
+     *
+     * Differencing is what makes this legitimate without synchronised clocks: each sample carries
+     * the same unknown offset between the two clocks, and the difference cancels it. Fewer than
+     * two samples yields null rather than zero — "no jitter" and "not enough data to say" are
+     * different claims and only one of them is true here.
+     */
+    private fun jitterMs(oneWayNs: List<Long>): Double? {
+        if (oneWayNs.size < 2) return null
+        val deltas = oneWayNs.zipWithNext { a, b -> kotlin.math.abs(b - a) }
+        return round2(deltas.average() / 1_000_000.0)
+    }
+
+    private fun pct(part: Int, whole: Int): Double =
+        if (whole <= 0) 0.0 else round2(part * 100.0 / whole)
+
+    private fun round2(v: Double) = Math.round(v * 100.0) / 100.0
+}
+
+/** Directional metrics for train.udp_updown; recomputable from the columnar evidence. */
+@Serializable
+data class DirectionalMetrics(
+    val sent: Int,
+    @SerialName("seen_by_server") val seenByServer: Int,
+    @SerialName("replies_received") val repliesReceived: Int,
+    @SerialName("lost_upstream") val lostUpstream: Int,
+    @SerialName("lost_downstream") val lostDownstream: Int,
+    @SerialName("loss_upstream_pct") val lossUpstreamPct: Double,
+    @SerialName("loss_downstream_pct") val lossDownstreamPct: Double,
+    /** One-way delay variation (RFC 3393), per direction. Null when there were too few samples. */
+    @SerialName("jitter_upstream_ms") val jitterUpstreamMs: Double? = null,
+    @SerialName("jitter_downstream_ms") val jitterDownstreamMs: Double? = null,
+    @SerialName("none_reached_server") val noneReachedServer: Boolean = false,
+)

echolot-app/core-engine/src/main/kotlin/app/echo_lot/engine/DownstreamMeasurement.kt

@@ -0,0 +1,493 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.measurement.*
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.ProbeSession
+import app.echo_lot.protocol.Wire
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.encodeToJsonElement
+
+/**
+ * The measurements only the far end can make: what the *downstream* path does to traffic the
+ * client never asked for packet-by-packet.
+ *
+ * A client alone can measure a round trip, and it can find the largest packet it can *send*. It
+ * cannot find the largest packet it can *receive*, or whether the network drops downstream
+ * packets independently of upstream ones — those need a server willing to push, which is why the
+ * protocol gates them behind an asymmetric grant (probe-protocol.md §3.4).
+ *
+ * Three separate facts come out, and keeping them separate is the point:
+ *   - `mtu.pmtud_down` — the largest datagram that arrives *unfragmented*. This is the number
+ *     that matters for anything setting DF, and it is only meaningful because the server sets DF.
+ *   - `mtu.frag_delivery` — whether larger datagrams arrive once the network is allowed to
+ *     fragment them. A path can be fine for one and broken for the other; conflating them is how
+ *     you get "MTU is 4000" on a link that drops every DF packet over 1400.
+ *   - `train.udp_downstream` — loss, reordering and arrival spacing in the download direction.
+ */
+class DownstreamMeasurement(private val ids: IdSource) {
+
+    private val json = Json { encodeDefaults = true; explicitNulls = true }
+
+    /** How long to wait for a granted burst after the server accepts the action. */
+    private val collectWindowMs = 4_000L
+
+    /**
+     * Shorter, but long enough to cover the first_last mode's deliberate 250 ms hold plus a
+     * reassembly. A fragment burst is one datagram: it is here quickly or not at all.
+     */
+    private val fragWindowMs = 1_500L
+
+    /**
+     * Asks the server to send one deliberately-fragmented datagram per ordering, and reports
+     * which orderings survive the path.
+     *
+     * Kernel fragmentation always emits fragments in order, first one first, so an oversized
+     * datagram can only answer "do fragments get through at all". The interesting fault is about
+     * ordering: only the *first* fragment carries the UDP ports, so a stateful firewall that has
+     * not seen it has nothing to match the rest against, and many drop them. That failure is
+     * invisible to every in-order test and shows up in the field as "large DNS answers fail here"
+     * or "the tunnel breaks when the MTU drops".
+     */
+    fun fragmentOrdering(
+        credential: String,
+        sessionId: String,
+        control: ControlClient,
+        probe: ProbeSession,
+        sessionRef: String,
+        sizeBytes: Int = 2000,
+        fragBytes: Int = 576,
+    ): Pair<Test, List<Finding>> {
+        val testId = ids.uuid()
+        val started = ids.monoNs()
+        val delivered = LinkedHashMap<String, Boolean>()
+        val fragmentCounts = LinkedHashMap<String, Int>()
+        var unsupported = false
+
+        for (mode in FRAG_MODES) {
+            val reply = runCatching {
+                control.action(
+                    credential, sessionId,
+                    """{"action":"frag_send","size_bytes":$sizeBytes,"mode":"$mode","frag_bytes":$fragBytes}""",
+                )
+            }
+            if (reply.isFailure) {
+                // A server without a raw socket says so; that is a missing capability, not a
+                // property of the network, and must not be recorded as a failed delivery.
+                unsupported = true
+                break
+            }
+            parseInt(reply.getOrNull(), "fragments")?.let { fragmentCounts[mode] = it }
+            // The burst is already on the wire when the action returns (it is sent
+            // synchronously), so anything that survived is either here or lost.
+            val got = probe.collectGranted(fragWindowMs).any { it.type == Wire.TYPE_FRAG_DATA }
+            delivered[mode] = got
+        }
+
+        if (unsupported) {
+            return Test(
+                id = testId, type = TestType.MTU_FRAG_ORDERING, sessionRef = sessionRef, tier = Tier.APP,
+                startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                status = TestStatus.UNSUPPORTED,
+                error = TestError("no_raw_socket", "this server cannot craft fragments"),
+            ) to emptyList()
+        }
+
+        val metrics = json.encodeToJsonElement(
+            FragOrderingMetrics(
+                sizeBytes = sizeBytes,
+                fragBytes = fragBytes,
+                fragmentsPerBurst = fragmentCounts,
+                deliveredByMode = delivered,
+                inOrderDelivered = delivered[FRAG_IN_ORDER] == true,
+                reorderedDelivered = delivered[FRAG_REVERSED] == true,
+                delayedFirstDelivered = delivered[FRAG_FIRST_LAST] == true,
+            ),
+        ) as JsonObject
+
+        val findings = ArrayList<Finding>()
+        val inOrder = delivered[FRAG_IN_ORDER] == true
+        val reversed = delivered[FRAG_REVERSED] == true
+        val firstLast = delivered[FRAG_FIRST_LAST] == true
+
+        if (!inOrder) {
+            findings.add(
+                finding(
+                    FindingRegistry.FRAGMENTS_BLOCKED, testId,
+                    "IP fragments do not reach this device",
+                    "A fragmented datagram sent in the normal order never arrived. Anything that " +
+                        "relies on fragmentation — large DNS answers over UDP, some VPN traffic — " +
+                        "will fail here rather than slow down.",
+                ),
+            )
+        } else if (!reversed || !firstLast) {
+            // The precise and useful finding: fragments work, but only if they arrive tidily.
+            val which = buildList {
+                if (!reversed) add("out of order")
+                if (!firstLast) add("with the first fragment delayed")
+            }.joinToString(" or ")
+            findings.add(
+                finding(
+                    FindingRegistry.FRAGMENT_REORDER_SENSITIVE, testId,
+                    "Fragments are dropped when they arrive $which",
+                    "In-order fragments are delivered, but the same datagram sent $which is not. " +
+                        "Something on the path only reassembles when the first fragment (the one " +
+                        "carrying the UDP ports) arrives first — typical of a stateful firewall " +
+                        "or NAT. It works until the network reorders, then fails intermittently, " +
+                        "which is the hardest kind of fault to chase.",
+                ),
+            )
+        }
+        return Test(
+            id = testId, type = TestType.MTU_FRAG_ORDERING, sessionRef = sessionRef, tier = Tier.APP,
+            startedMonoNs = started, endedMonoNs = ids.monoNs(),
+            status = if (inOrder) TestStatus.OK else TestStatus.PARTIAL,
+            metrics = metrics,
+        ) to findings
+    }
+
+    /**
+     * Runs all three against an already-primed session.
+     *
+     * [session] must already have sent at least one ECHO: the grant is bound to the source the
+     * server has actually observed, so an unprimed session gets a 409 rather than a grant. That
+     * is the anti-amplification rule doing its job, not an error to work around.
+     */
+    fun run(
+        credential: String,
+        sessionId: String,
+        control: ControlClient,
+        probe: ProbeSession,
+        sessionRef: String,
+        sizes: List<Int> = DEFAULT_SIZES,
+        trainCount: Int = 100,
+        trainSizeBytes: Int = 300,
+        trainIntervalUs: Int = 3_000,
+    ): Pair<List<Test>, List<Finding>> {
+        val tests = ArrayList<Test>()
+        val findings = ArrayList<Finding>()
+
+        val df = bigSend(credential, sessionId, control, probe, sessionRef, sizes, df = true)
+        val frag = bigSend(credential, sessionId, control, probe, sessionRef, sizes, df = false)
+        val train = downTrain(
+            credential, sessionId, control, probe, sessionRef, trainCount, trainSizeBytes, trainIntervalUs,
+        )
+
+        tests.add(df.test); tests.add(frag.test); tests.add(train.test)
+
+        // Fragment ordering only makes sense once we know fragments arrive at all; when they do
+        // not, the ordering variants would all report "not delivered" and read as three faults
+        // instead of one.
+        if (frag.largestDelivered != null) {
+            val (fragTest, fragFindings) =
+                fragmentOrdering(credential, sessionId, control, probe, sessionRef)
+            tests.add(fragTest)
+            findings.addAll(fragFindings)
+        }
+
+        // A downstream MTU below the classic 1500-byte Ethernet payload is worth saying out loud:
+        // it is the usual cause of "small requests work, large responses hang".
+        val pathMtu = df.largestDelivered
+        if (pathMtu != null && pathMtu > 0) {
+            val ipMtu = pathMtu + IP_UDP_OVERHEAD4
+            if (ipMtu < 1500) {
+                findings.add(
+                    finding(
+                        FindingRegistry.MTU_REDUCED_DOWNSTREAM, df.test.id,
+                        "Downstream path MTU is $ipMtu bytes, below 1500",
+                        "The largest datagram that reached this device without fragmenting was " +
+                            "$pathMtu bytes of payload ($ipMtu on the wire). Tunnels (PPPoE, VPN, " +
+                            "IPv6-in-IPv4) commonly do this; it is only a fault when something " +
+                            "on the path also blocks the ICMP messages that let senders discover it.",
+                    ),
+                )
+            }
+            // The dangerous combination: unfragmented large packets vanish AND fragments do too,
+            // so a sender that never gets told will retransmit into a black hole.
+            val fragLargest = frag.largestDelivered ?: 0
+            if (fragLargest <= pathMtu && sizes.any { it > pathMtu }) {
+                findings.add(
+                    finding(
+                        FindingRegistry.MTU_DOWNSTREAM_BLACKHOLE, frag.test.id,
+                        "Datagrams above $pathMtu bytes are dropped downstream, fragmented or not",
+                        "Nothing larger than $pathMtu bytes arrived, even when the network was " +
+                            "free to fragment it. Traffic that relies on large responses will " +
+                            "stall rather than fail cleanly.",
+                    ),
+                )
+            }
+        }
+
+        if (train.received == 0) {
+            findings.add(
+                finding(
+                    FindingRegistry.DOWNSTREAM_BLOCKED, train.test.id,
+                    "No server-initiated packets arrived",
+                    "The server sent ${train.sent} packets toward this device and none arrived, " +
+                        "while the round-trip echo worked. Something on the path forwards replies " +
+                        "but drops traffic the device did not individually solicit.",
+                ),
+            )
+        } else if (train.lossPct >= 5.0) {
+            findings.add(
+                finding(
+                    FindingRegistry.LOSS_DOWNSTREAM, train.test.id,
+                    "Downstream loss of ${round1(train.lossPct)}%",
+                    "${train.sent - train.received} of ${train.sent} packets sent toward this " +
+                        "device were lost. Downstream loss is invisible to a round-trip test, " +
+                        "which reports only that *something* was lost somewhere.",
+                ),
+            )
+        }
+        if (train.reordered > 0) {
+            findings.add(
+                finding(
+                    FindingRegistry.DOWNSTREAM_REORDER, train.test.id,
+                    "${train.reordered} downstream packet(s) arrived out of order",
+                    "Packets arrived in a different order than they were sent. Usually per-packet " +
+                        "load balancing across links; harmless for most traffic, not for all of it.",
+                ),
+            )
+        }
+        return tests to findings
+    }
+
+    // ---- big_send ---------------------------------------------------------------------
+
+    private class SizeResult(val test: Test, val largestDelivered: Int?)
+
+    private fun bigSend(
+        credential: String, sessionId: String, control: ControlClient, probe: ProbeSession,
+        sessionRef: String, sizes: List<Int>, df: Boolean,
+    ): SizeResult {
+        val testId = ids.uuid()
+        val started = ids.monoNs()
+        val requested = sizes.joinToString(",")
+
+        val reply = runCatching {
+            control.action(
+                credential, sessionId,
+                """{"action":"big_send","df":$df,"sizes_bytes":[$requested]}""",
+            )
+        }
+        if (reply.isFailure) {
+            return SizeResult(
+                Test(
+                    id = testId, type = if (df) TestType.MTU_PMTUD_DOWN else TestType.MTU_FRAG_DELIVERY,
+                    sessionRef = sessionRef, tier = Tier.APP,
+                    startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                    status = TestStatus.UNSUPPORTED,
+                    error = TestError("action_refused", reply.exceptionOrNull()?.message ?: "big_send refused"),
+                ),
+                null,
+            )
+        }
+
+        // The server tells us which sizes it actually put on the wire. With DF it refuses
+        // anything above its own egress MTU, and treating those as "lost downstream" would
+        // blame the client's network for our own limit.
+        val accepted = parseIntArray(reply.getOrNull(), "sizes_bytes").ifEmpty { sizes }
+        val serverMaxDf = parseInt(reply.getOrNull(), "max_df_bytes")
+
+        val arrived = probe.collectGranted(collectWindowMs)
+            .filter { it.type == Wire.TYPE_BIG_SEND }
+            .map { it.sizeBytes }
+            .distinct()
+            .sorted()
+        val largest = arrived.maxOrNull()
+
+        val metrics = json.encodeToJsonElement(
+            BigSendMetrics(
+                requestedBytes = sizes,
+                sentBytes = accepted,
+                deliveredBytes = arrived,
+                largestDeliveredBytes = largest,
+                dontFragment = df,
+                serverMaxDfBytes = serverMaxDf,
+                // Only meaningful for the DF run; the IP-level MTU is the payload plus headers.
+                pathMtuBytes = if (df && largest != null) largest + IP_UDP_OVERHEAD4 else null,
+            ),
+        ) as JsonObject
+
+        val status = when {
+            arrived.isEmpty() -> TestStatus.FAILED
+            arrived.size < accepted.size -> TestStatus.PARTIAL
+            else -> TestStatus.OK
+        }
+        return SizeResult(
+            Test(
+                id = testId, type = if (df) TestType.MTU_PMTUD_DOWN else TestType.MTU_FRAG_DELIVERY,
+                sessionRef = sessionRef, tier = Tier.APP,
+                startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                status = status, metrics = metrics,
+            ),
+            largest,
+        )
+    }
+
+    // ---- downtrain --------------------------------------------------------------------
+
+    private class TrainResult(
+        val test: Test, val sent: Int, val received: Int, val lossPct: Double, val reordered: Int,
+    )
+
+    private fun downTrain(
+        credential: String, sessionId: String, control: ControlClient, probe: ProbeSession,
+        sessionRef: String, count: Int, sizeBytes: Int, intervalUs: Int,
+    ): TrainResult {
+        val testId = ids.uuid()
+        val started = ids.monoNs()
+
+        val reply = runCatching {
+            control.action(
+                credential, sessionId,
+                """{"action":"downtrain","count":$count,"size_bytes":$sizeBytes,"interval_us":$intervalUs}""",
+            )
+        }
+        if (reply.isFailure) {
+            return TrainResult(
+                Test(
+                    id = testId, type = TestType.TRAIN_UDP_DOWNSTREAM, sessionRef = sessionRef,
+                    tier = Tier.APP, startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                    status = TestStatus.UNSUPPORTED,
+                    error = TestError("action_refused", reply.exceptionOrNull()?.message ?: "downtrain refused"),
+                ),
+                0, 0, 0.0, 0,
+            )
+        }
+        val sent = parseInt(reply.getOrNull(), "count") ?: count
+
+        val got = probe.collectGranted(collectWindowMs).filter { it.type == Wire.TYPE_DOWNTRAIN_DATA }
+        val received = got.size
+        val lossPct = if (sent == 0) 0.0 else (sent - received) * 100.0 / sent
+
+        // Reordering: a packet whose sequence is below the highest already seen. Counting
+        // inversions rather than "not sorted" keeps one late packet from being reported as
+        // dozens of reorder events.
+        var highest = -1
+        var reordered = 0
+        for (p in got) {
+            if (p.seq < highest) reordered++ else highest = p.seq
+        }
+
+        // Columnar evidence per the schema: what arrived, when, and how big — so every metric
+        // above is recomputable by a reader who does not trust our arithmetic.
+        val evidence = TrainEvidence(
+            epochMonoNs = started,
+            seq = got.map { it.seq },
+            tTxNs = got.map { null },
+            tRxNs = got.map { it.tRxNs },
+            sizeBytes = got.map { it.sizeBytes },
+        ).toEvidence()
+
+        val interArrival = got.zipWithNext { a, b -> (b.tRxNs - a.tRxNs) / 1_000_000.0 }
+        val metrics = json.encodeToJsonElement(
+            DownTrainMetrics(
+                sent = sent, received = received, lossPct = round1(lossPct),
+                reorderedPackets = reordered,
+                sizeBytes = sizeBytes,
+                interArrivalMsAvg = interArrival.average().takeIf { interArrival.isNotEmpty() }?.let(::round1),
+                interArrivalMsMax = interArrival.maxOrNull()?.let(::round1),
+                sendIntervalUs = intervalUs,
+            ),
+        ) as JsonObject
+
+        val status = when {
+            received == 0 -> TestStatus.FAILED
+            received < sent -> TestStatus.PARTIAL
+            else -> TestStatus.OK
+        }
+        return TrainResult(
+            Test(
+                id = testId, type = TestType.TRAIN_UDP_DOWNSTREAM, sessionRef = sessionRef, tier = Tier.APP,
+                startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                status = status, evidence = evidence, metrics = metrics,
+            ),
+            sent, received, lossPct, reordered,
+        )
+    }
+
+    // ---- helpers ----------------------------------------------------------------------
+
+    /**
+     * Builds a finding from a registry entry, which supplies the code, category and severity.
+     *
+     * Taking a [FindingSpec] rather than three loose values is the point: a typo becomes a
+     * compile error, and two call sites cannot disagree about which category a finding belongs
+     * to - a disagreement that would split one fault across two verdict lights.
+     */
+    private fun finding(spec: FindingSpec, testId: String, title: String, desc: String) =
+        Finding(
+            id = ids.uuid(), code = spec.code, category = spec.category, severity = spec.severity,
+            confidence = Confidence.HIGH,
+            title = title, description = desc, evidenceRefs = listOf(EvidenceRef(testId)),
+        )
+
+    /** Minimal scalar extraction from the action reply; the shape is small and server-owned. */
+    private fun parseInt(body: String?, key: String): Int? =
+        body?.let { Regex("\"$key\"\\s*:\\s*(-?\\d+)").find(it)?.groupValues?.get(1)?.toIntOrNull() }
+
+    private fun parseIntArray(body: String?, key: String): List<Int> =
+        body?.let { b ->
+            Regex("\"$key\"\\s*:\\s*\\[([^\\]]*)\\]").find(b)?.groupValues?.get(1)
+                ?.split(",")?.mapNotNull { it.trim().toIntOrNull() }
+        } ?: emptyList()
+
+    private companion object {
+        /** IPv4 (20) + UDP (8). The v6 case is 48; reported per-family once v6 sessions land. */
+        const val IP_UDP_OVERHEAD4 = 28
+
+        const val FRAG_IN_ORDER = "in_order"
+        const val FRAG_REVERSED = "reversed"
+        const val FRAG_FIRST_LAST = "first_last"
+        val FRAG_MODES = listOf(FRAG_IN_ORDER, FRAG_REVERSED, FRAG_FIRST_LAST)
+
+        /** Straddles the usual suspects: 1500 Ethernet, 1492 PPPoE, 1400-ish tunnels. */
+        val DEFAULT_SIZES = listOf(600, 1200, 1372, 1400, 1450, 1472, 1500, 2000, 4000)
+
+        fun round1(v: Double) = Math.round(v * 10.0) / 10.0
+    }
+}
+
+/** Metrics for mtu.pmtud_down / mtu.frag_delivery. */
+@Serializable
+data class BigSendMetrics(
+    @SerialName("requested_bytes") val requestedBytes: List<Int>,
+    @SerialName("sent_bytes") val sentBytes: List<Int>,
+    @SerialName("delivered_bytes") val deliveredBytes: List<Int>,
+    @SerialName("largest_delivered_bytes") val largestDeliveredBytes: Int? = null,
+    @SerialName("dont_fragment") val dontFragment: Boolean,
+    /** The server's own DF ceiling; sizes above it were never sent and are not path evidence. */
+    @SerialName("server_max_df_bytes") val serverMaxDfBytes: Int? = null,
+    @SerialName("path_mtu_bytes") val pathMtuBytes: Int? = null,
+)
+
+/** Metrics for mtu.frag_ordering. */
+@Serializable
+data class FragOrderingMetrics(
+    @SerialName("size_bytes") val sizeBytes: Int,
+    @SerialName("frag_bytes") val fragBytes: Int,
+    @SerialName("fragments_per_burst") val fragmentsPerBurst: Map<String, Int>,
+    @SerialName("delivered_by_mode") val deliveredByMode: Map<String, Boolean>,
+    @SerialName("in_order_delivered") val inOrderDelivered: Boolean,
+    @SerialName("reordered_delivered") val reorderedDelivered: Boolean,
+    @SerialName("delayed_first_delivered") val delayedFirstDelivered: Boolean,
+)
+
+/** Metrics for train.udp_downstream. */
+@Serializable
+data class DownTrainMetrics(
+    val sent: Int,
+    val received: Int,
+    @SerialName("loss_pct") val lossPct: Double,
+    @SerialName("reordered_packets") val reorderedPackets: Int,
+    @SerialName("size_bytes") val sizeBytes: Int,
+    @SerialName("inter_arrival_ms_avg") val interArrivalMsAvg: Double? = null,
+    @SerialName("inter_arrival_ms_max") val interArrivalMsMax: Double? = null,
+    @SerialName("send_interval_us") val sendIntervalUs: Int,
+)

echolot-app/core-engine/src/main/kotlin/app/echo_lot/engine/ServerMeasurement.kt

@@ -0,0 +1,298 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Package engine composes core-protocol probes into core-measurement documents — the run engine
+// the app drives. This file covers the server-facing vertical (control plane + UDP data plane);
+// device-tier probes (link snapshot, Shizuku, local discovery) plug in from the Android modules.
+package app.echo_lot.engine
+
+import app.echo_lot.measurement.*
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.ProbeSession
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonArray
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.encodeToJsonElement
+import kotlinx.serialization.json.intOrNull
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+import kotlinx.serialization.json.longOrNull
+
+/**
+ * Runs the server-facing measurements against one target and assembles a [MeasurementDocument]:
+ * an ECHO train (RTT distribution, loss, and NAT-rebinding detection from the server's observed
+ * source port) as `train.udp_updown`. Everything is real evidence with recomputable metrics, and
+ * findings are derived deterministically. IDs/timestamps are injected so the engine stays pure
+ * (no clocks/UUIDs of its own) and unit-testable.
+ */
+class ServerMeasurement(
+    private val ids: IdSource,
+    private val app: AppInfo,
+    private val device: DeviceInfo,
+) {
+    private val json = Json { encodeDefaults = true; explicitNulls = true }
+
+    data class Config(
+        val controlUrl: String,
+        val pins: Set<String>,
+        val credential: String,
+        val target: String,
+        val udpHost: String,
+        val udpPort: Int,
+        val echoCount: Int = 20,
+        val echoPaddingBytes: Int = 64,
+        /**
+         * Whether to ask the server to push traffic back (downstream MTU and downstream train).
+         * Costs a few hundred kB of download and needs a server that advertises the grants, so
+         * it is a flag rather than an assumption.
+         */
+        val downstream: Boolean = true,
+        /**
+         * Throughput moves real data — a 5-second run at 50 Mbps is about 30 MB — so it is off
+         * unless asked for. On a metered mobile connection that is the user's money, and a
+         * measurement tool that spends it without being told to is not one people keep installed.
+         */
+        val throughput: Boolean = false,
+        @Suppress("unused") val throughputSeconds: Int = 5,
+        @Suppress("unused") val throughputKbps: Int = 50_000,
+    )
+
+    fun run(cfg: Config): MeasurementDocument {
+        val runId = ids.uuid()
+        val startWall = ids.nowWall()
+        val startMono = ids.monoNs()
+
+        val control = ControlClient(cfg.controlUrl, cfg.pins)
+        val profile = control.profile(cfg.credential)
+        val session = control.createSession(cfg.credential, cfg.target)
+
+        val serverSession = ServerSession(
+            id = "sess-1",
+            profileName = profile.name,
+            controlUrl = cfg.controlUrl,
+            serverVersion = profile.serverVersion,
+            capabilities = profile.capabilities,
+            sessionId = session.sessionId,
+            target = SessionTarget(ip4 = cfg.udpHost, udpPort = cfg.udpPort),
+        )
+
+        val tests = ArrayList<Test>()
+        val allFindings = ArrayList<Finding>()
+
+        // One ProbeSession for the whole run. A second one would open a new socket and restart
+        // the sequence counter, which the server's anti-replay window correctly rejects — so the
+        // re-primed source is never recorded and every granted send goes to the old, closed port.
+        // Session identity lives on the server; the socket must live as long as it does.
+        ProbeSession(cfg.credential, session, cfg.udpHost, cfg.udpPort).use { ps ->
+            val (test, findings) = echoTrain(cfg, ps, startMono, control, session.sessionId)
+            tests.add(test)
+            allFindings.addAll(findings)
+
+            // Downstream needs a session the server has already seen traffic from — the echo
+            // train just provided that — and a server that advertises the grants. Skipped
+            // quietly against an older server rather than reported as a failure of the network.
+            if (cfg.downstream && profile.supports("downtrain") && profile.supports("big-send")) {
+                val (dsTests, dsFindings) = DownstreamMeasurement(ids)
+                    .run(cfg.credential, session.sessionId, control, ps, sessionRef = "sess-1")
+                tests.addAll(dsTests)
+                allFindings.addAll(dsFindings)
+            }
+
+            if (cfg.throughput && profile.supports("throughput")) {
+                val (tpTest, tpFindings) = ThroughputMeasurement(ids).run(
+                    cfg.credential, session.sessionId, control, ps, sessionRef = "sess-1",
+                    durationS = cfg.throughputSeconds, kbps = cfg.throughputKbps,
+                )
+                tests.add(tpTest)
+                allFindings.addAll(tpFindings)
+            }
+        }
+
+        control.deleteSession(cfg.credential, session.sessionId)
+
+        val summary = Verdicts.derive(tests, allFindings)
+        return MeasurementDocument(
+            run = Run(
+                id = runId, trigger = Trigger.MANUAL, startedAt = startWall, endedAt = ids.nowWall(),
+                clock = Clock(monoOriginWall = startWall),
+                app = app, device = device,
+                tiers = Tiers(app = true),
+            ),
+            serverSessions = listOf(serverSession),
+            tests = tests,
+            findings = allFindings,
+            summary = summary,
+        )
+    }
+
+    private fun echoTrain(
+        cfg: Config, ps: ProbeSession, startMono: Long,
+        control: ControlClient? = null, sessionId: String? = null,
+    ): Pair<Test, List<Finding>> {
+        val testId = ids.uuid()
+        val seqs = ArrayList<Int>()
+        val tTx = ArrayList<Long?>()
+        val tRx = ArrayList<Long?>()
+        val sizes = ArrayList<Int>()
+        val rtts = ArrayList<Double>()
+        val observedPorts = LinkedHashSet<Int>()
+
+        // Wire sequence numbers, kept so the server's observations can be correlated packet by
+        // packet. They are not 0..n-1: the counter is shared with every other packet type on the
+        // session, so "the nth echo" is not "sequence n".
+        val wireSeqs = ArrayList<Int>()
+
+        for (i in 0 until cfg.echoCount) {
+            val txMono = ids.monoNs() - startMono
+            val r = ps.echo(cfg.echoPaddingBytes)
+            wireSeqs.add(ps.lastSeq)
+            seqs.add(i)
+            tTx.add(txMono)
+            sizes.add(Wire_HEADER + cfg.echoPaddingBytes)
+            if (r != null) {
+                tRx.add(ids.monoNs() - startMono)
+                rtts.add(r.rttMs)
+                r.observation?.observedPort?.let { observedPorts.add(it) }
+            } else {
+                tRx.add(null)
+            }
+        }
+
+        // Ask the server what it actually received. This is what turns "3 % loss somewhere" into
+        // "3 % loss upstream" - the least useful form of the answer into a usable one.
+        val directional: DirectionalMetrics? =
+            if (control != null && sessionId != null) {
+                runCatching {
+                    val samples = wireSeqs.indices.map {
+                        Directional.Sample(wireSeqs[it], tTx[it] ?: 0L, tRx[it])
+                    }
+                    Directional.analyse(samples, serverSightings(control, cfg, sessionId))
+                }.getOrNull() // an older server without the endpoint simply yields no split
+            } else {
+                null
+            }
+
+        val sent = cfg.echoCount
+        val received = rtts.size
+        val lossPct = if (sent == 0) 0.0 else (sent - received) * 100.0 / sent
+        val natRebinding = observedPorts.size > 1
+
+        val evidence: JsonObject = TrainEvidence(
+            epochMonoNs = startMono, seq = seqs, tTxNs = tTx, tRxNs = tRx, sizeBytes = sizes,
+        ).toEvidence()
+
+        val directionalJson = directional?.let {
+            json.encodeToJsonElement(DirectionalMetrics.serializer(), it) as JsonObject
+        }
+        val metrics: JsonObject = json.encodeToJsonElement(
+            EchoMetrics(
+                sent = sent, received = received, lossPct = round1(lossPct),
+                rttMsMin = rtts.minOrNull()?.let(::round1),
+                rttMsAvg = rtts.average().takeIf { received > 0 }?.let(::round1),
+                rttMsMax = rtts.maxOrNull()?.let(::round1),
+                observedPorts = observedPorts.toList(),
+                natRebindingDetected = natRebinding,
+            )
+        ).let { base -> JsonObject((base as JsonObject) + (directionalJson ?: JsonObject(emptyMap()))) }
+
+        val status = when {
+            received == 0 -> TestStatus.FAILED
+            received < sent -> TestStatus.PARTIAL
+            else -> TestStatus.OK
+        }
+        val test = Test(
+            id = testId, type = TestType.TRAIN_UDP_UPDOWN, sessionRef = "sess-1", tier = Tier.APP,
+            startedMonoNs = startMono, endedMonoNs = ids.monoNs(), status = status,
+            evidence = evidence, metrics = metrics,
+        )
+
+        val findings = ArrayList<Finding>()
+        if (received == 0) {
+            findings.add(finding(FindingRegistry.UDP_UNREACHABLE, testId,
+                "No UDP echo replies from the server",
+                "Every ECHO probe to the server's UDP data plane was lost — the path blocks or drops the session's UDP traffic."))
+        } else if (lossPct >= 20.0) {
+            findings.add(finding(FindingRegistry.UDP_LOSS, testId,
+                "High UDP loss to the server (${round1(lossPct)}%)",
+                "A large fraction of ECHO probes were lost, indicating an unreliable UDP path."))
+        }
+        // Naming the direction is the entire value of the split, so the findings do.
+        directional?.let { d ->
+            when {
+                d.noneReachedServer && received == 0 -> findings.add(
+                    finding(FindingRegistry.UDP_UNREACHABLE_UPSTREAM, testId,
+                        "Nothing reached the server",
+                        "The server received none of the ${d.sent} probes, so the traffic is being " +
+                            "dropped on the way out, not on the way back. A firewall or NAT on " +
+                            "this side of the path is the place to look."),
+                )
+                d.lossUpstreamPct >= 2.0 -> findings.add(
+                    finding(FindingRegistry.LOSS_UPSTREAM, testId,
+                        "${d.lossUpstreamPct} % of probes were lost on the way to the server",
+                        "${d.lostUpstream} of ${d.sent} probes never reached the server. The " +
+                            "return path is not implicated: replies came back for everything that " +
+                            "arrived."),
+                )
+            }
+            if (d.lossDownstreamPct >= 2.0) {
+                findings.add(
+                    finding(FindingRegistry.LOSS_DOWNSTREAM, testId,
+                        "${d.lossDownstreamPct} % of replies were lost on the way back",
+                        "The server received ${d.seenByServer} probes and answered them, but " +
+                            "${d.lostDownstream} of those replies never arrived. The outbound path " +
+                            "is fine; the fault is on the return leg."),
+                )
+            }
+        }
+
+        if (natRebinding) {
+            findings.add(finding(FindingRegistry.NAT_UDP_REBINDING, testId,
+                "NAT remapped the UDP source port mid-flow",
+                "The server observed more than one source port for this session (${observedPorts.joinToString()}), i.e. a NAT with a short UDP mapping or per-packet remapping."))
+        }
+        return test to findings
+    }
+
+    /**
+     * The server's per-packet record of this session's echoes (spec section 6). Filtered to
+     * ECHO_REQ, because the observation list also holds MTU probes and anything else we sent -
+     * counting those as train packets would invent loss that is not there.
+     */
+    private fun serverSightings(
+        control: ControlClient, cfg: Config, sessionId: String,
+    ): List<Directional.ServerSighting> {
+        val body = control.observations(cfg.credential, sessionId)
+        val packets = Json.parseToJsonElement(body).jsonObject["udp"]
+            ?.jsonObject?.get("packets") as? JsonArray ?: return emptyList()
+        return packets.mapNotNull { el ->
+            val o = el as? JsonObject ?: return@mapNotNull null
+            val type = o["type"]?.jsonPrimitive?.intOrNull ?: return@mapNotNull null
+            if (type != ECHO_REQ_TYPE) return@mapNotNull null
+            Directional.ServerSighting(
+                seq = o["seq"]?.jsonPrimitive?.intOrNull ?: return@mapNotNull null,
+                tRxNs = o["t_rx_ns"]?.jsonPrimitive?.longOrNull ?: return@mapNotNull null,
+                tTxNs = o["t_tx_ns"]?.jsonPrimitive?.longOrNull ?: return@mapNotNull null,
+            )
+        }
+    }
+
+    /**
+     * Builds a finding from a registry entry, which supplies the code, category and severity.
+     *
+     * Taking a [FindingSpec] rather than three loose values is the point: a typo becomes a
+     * compile error, and two call sites cannot disagree about which category a finding belongs
+     * to - a disagreement that would split one fault across two verdict lights.
+     */
+    private fun finding(spec: FindingSpec, testId: String, title: String, desc: String) =
+        Finding(
+            id = ids.uuid(), code = spec.code, category = spec.category, severity = spec.severity,
+            confidence = Confidence.HIGH,
+            title = title, description = desc, evidenceRefs = listOf(EvidenceRef(testId)),
+        )
+
+    private companion object {
+        const val Wire_HEADER = 32
+        const val ECHO_REQ_TYPE = 0x01
+        fun round1(v: Double) = Math.round(v * 10.0) / 10.0
+    }
+}

echolot-app/core-engine/src/main/kotlin/app/echo_lot/engine/Support.kt

@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import java.time.Instant
+import java.util.UUID
+
+/**
+ * Clock/ID source, injected so the engine has no hidden nondeterminism and stays unit-testable.
+ * The default uses wall + monotonic clocks and random UUIDs; tests supply deterministic ones.
+ */
+interface IdSource {
+    fun uuid(): String
+    fun monoNs(): Long
+    fun nowWall(): String
+}
+
+class SystemIdSource : IdSource {
+    override fun uuid(): String = UUID.randomUUID().toString()
+    override fun monoNs(): Long = System.nanoTime()
+    override fun nowWall(): String = Instant.now().toString()
+}
+
+/** Metrics for train.udp_updown; recomputable from the columnar evidence. */
+@Serializable
+data class EchoMetrics(
+    val sent: Int,
+    val received: Int,
+    @SerialName("loss_pct") val lossPct: Double,
+    @SerialName("rtt_ms_min") val rttMsMin: Double? = null,
+    @SerialName("rtt_ms_avg") val rttMsAvg: Double? = null,
+    @SerialName("rtt_ms_max") val rttMsMax: Double? = null,
+    @SerialName("observed_ports") val observedPorts: List<Int> = emptyList(),
+    @SerialName("nat_rebinding_detected") val natRebindingDetected: Boolean = false,
+)

echolot-app/core-engine/src/main/kotlin/app/echo_lot/engine/ThroughputMeasurement.kt

@@ -0,0 +1,338 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.measurement.*
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.ProbeSession
+import app.echo_lot.protocol.Wire
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.encodeToJsonElement
+import kotlinx.serialization.json.jsonArray
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+
+/**
+ * Downstream throughput: the server sends at a paced rate for a bounded time and the client
+ * measures what arrives (`perf.throughput_udp`).
+ *
+ * The number this produces is only meaningful with a qualifier attached, and getting that
+ * qualifier right is most of the work here. A throughput test reports the *smallest* limit on the
+ * path, and the sender's own ceiling is one of the candidates: if the server was asked for 50 Mbps
+ * and 50 Mbps arrived, the network was never the constraint and "50 Mbps" says nothing about it.
+ * Reporting that as a capacity measurement would be a confident lie, so the result always carries
+ * [ThroughputMetrics.limitedBy] and a finding is only raised when the network is actually
+ * implicated.
+ *
+ * Comparing against the *sender's* count rather than the requested rate is the other half: the
+ * server reports how much it actually put on the wire, and the gap between that and what arrived
+ * is the loss. A receiver alone cannot tell "the network dropped it" from "the sender never sent
+ * it", and guessing turns a healthy server-side limit into a phantom network fault.
+ */
+class ThroughputMeasurement(private val ids: IdSource) {
+
+    private val json = Json { encodeDefaults = true; explicitNulls = true }
+
+    fun run(
+        credential: String,
+        sessionId: String,
+        control: ControlClient,
+        probe: ProbeSession,
+        sessionRef: String,
+        durationS: Int = 5,
+        kbps: Int = 50_000,
+        sizeBytes: Int = 1200,
+    ): Pair<Test, List<Finding>> {
+        val testId = ids.uuid()
+        val started = ids.monoNs()
+
+        val reply = runCatching {
+            control.action(
+                credential, sessionId,
+                """{"action":"throughput","direction":"down","duration_s":$durationS,""" +
+                    """"kbps":$kbps,"size_bytes":$sizeBytes}""",
+            )
+        }
+        if (reply.isFailure) {
+            return Test(
+                id = testId, type = TestType.PERF_THROUGHPUT_UDP, sessionRef = sessionRef, tier = Tier.APP,
+                startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                status = TestStatus.UNSUPPORTED,
+                error = TestError("action_refused", reply.exceptionOrNull()?.message ?: "throughput refused"),
+            ) to emptyList()
+        }
+
+        // The server may have shortened the run to fit its own byte budget; listen for what it
+        // actually promised, not for what we asked.
+        val plannedMs = parseInt(reply.getOrNull(), "duration_ms") ?: (durationS * 1000)
+
+        // A margin past the planned end so the tail of the run is not counted as loss: packets
+        // still in flight when we stop listening were not dropped, they were merely late.
+        val received = probe.collectGranted(plannedMs + 1_500L)
+            .filter { it.type == Wire.TYPE_THROUGHPUT_DATA }
+
+        val bytes = received.sumOf { it.sizeBytes.toLong() }
+        val spanNs = if (received.size >= 2) {
+            received.maxOf { it.tRxNs } - received.minOf { it.tRxNs }
+        } else {
+            0L
+        }
+        // Measured over the arrival span rather than our listening window, which includes the
+        // request round trip and the trailing margin and would understate the rate.
+        val receivedKbps = if (spanNs > 0) (bytes * 8 * 1_000_000 / spanNs).toInt() else 0
+
+        val sender = senderReport(control, credential, sessionId)
+        val sentPackets = sender?.packets ?: 0
+        val lossPct = if (sentPackets > 0) {
+            round2((sentPackets - received.size).coerceAtLeast(0) * 100.0 / sentPackets)
+        } else {
+            null
+        }
+
+        // Only a run the *clock* ended measured the network. One stopped by our own byte budget
+        // or rate ceiling measured this server.
+        val limitedBy = sender?.limitedBy ?: "unknown"
+        val networkLimited = limitedBy == "duration" &&
+            sender != null && receivedKbps > 0 && receivedKbps < sender.kbps * 9 / 10
+
+        val metrics = json.encodeToJsonElement(
+            ThroughputMetrics(
+                requestedKbps = kbps,
+                plannedDurationMs = plannedMs,
+                packetsReceived = received.size,
+                bytesReceived = bytes,
+                receivedKbps = receivedKbps,
+                senderPackets = sender?.packets,
+                senderBytes = sender?.bytes,
+                senderKbps = sender?.kbps,
+                lossPct = lossPct,
+                limitedBy = limitedBy,
+                measuresNetwork = networkLimited,
+            ),
+        ) as JsonObject
+
+        val findings = ArrayList<Finding>()
+        when {
+            sender == null -> Unit // no sender report: nothing can be concluded, so nothing is
+            received.isEmpty() -> findings.add(
+                finding(
+                    FindingRegistry.THROUGHPUT_NO_DELIVERY, testId,
+                    "No throughput traffic arrived",
+                    "The server sent ${sender.packets} packets and none arrived. This is a " +
+                        "connectivity fault rather than a slow link.",
+                ),
+            )
+            networkLimited -> findings.add(
+                finding(
+                    FindingRegistry.THROUGHPUT_BELOW_OFFERED, testId,
+                    "Downstream throughput ${receivedKbps / 1000} Mbit/s, below the " +
+                        "${sender.kbps / 1000} Mbit/s offered",
+                    "The server sent at ${sender.kbps / 1000} Mbit/s for the full run and " +
+                        "${receivedKbps / 1000} Mbit/s arrived" +
+                        (lossPct?.let { ", losing $it % of packets" } ?: "") +
+                        ". The path could not carry what was offered.",
+                ),
+            )
+        }
+
+        return Test(
+            id = testId, type = TestType.PERF_THROUGHPUT_UDP, sessionRef = sessionRef, tier = Tier.APP,
+            startedMonoNs = started, endedMonoNs = ids.monoNs(),
+            status = if (received.isEmpty()) TestStatus.FAILED else TestStatus.OK,
+            metrics = metrics,
+        ) to findings
+    }
+
+    /**
+     * Upstream throughput: the client sends, the server counts.
+     *
+     * The mirror image of the downstream case, and it needs no grant — the client is generating
+     * its own traffic, so there is no amplification to gate. What it does need is the server's
+     * count: only the far end knows how much arrived, and without that number a sender can
+     * measure how fast it can *transmit*, which is not the same question and is usually just the
+     * speed of the local NIC.
+     */
+    fun runUpstream(
+        credential: String,
+        sessionId: String,
+        control: ControlClient,
+        probe: ProbeSession,
+        sessionRef: String,
+        durationS: Int = 5,
+        kbps: Int = 20_000,
+        sizeBytes: Int = 1200,
+    ): Pair<Test, List<Finding>> {
+        val testId = ids.uuid()
+        val started = ids.monoNs()
+
+        // Zeroes the server's counter so this run measures itself rather than inheriting the
+        // packets of an earlier one on the same session.
+        val reply = runCatching {
+            control.action(credential, sessionId, """{"action":"throughput","direction":"up"}""")
+        }
+        if (reply.isFailure) {
+            return Test(
+                id = testId, type = TestType.PERF_THROUGHPUT_UDP, sessionRef = sessionRef, tier = Tier.APP,
+                startedMonoNs = started, endedMonoNs = ids.monoNs(),
+                status = TestStatus.UNSUPPORTED,
+                error = TestError("action_refused", reply.exceptionOrNull()?.message ?: "refused"),
+            ) to emptyList()
+        }
+
+        val sent = probe.sendThroughput(durationS * 1000L, kbps, sizeBytes)
+        // A moment for the tail of the run to arrive; counting still-in-flight packets as lost
+        // would inflate the loss figure by whatever the path's delay happens to be.
+        Thread.sleep(500)
+        val seen = upstreamCount(control, credential, sessionId)
+
+        val lossPct = if (sent.packets > 0 && seen != null) {
+            round2((sent.packets - seen.packets).coerceAtLeast(0) * 100.0 / sent.packets)
+        } else {
+            null
+        }
+        // The receiver's rate is the measurement. The sender's is what we managed to emit, which
+        // is a property of this phone and its radio, not of the network.
+        val achievedKbps = seen?.kbps ?: 0
+
+        val metrics = json.encodeToJsonElement(
+            UpstreamThroughputMetrics(
+                requestedKbps = kbps,
+                sentPackets = sent.packets,
+                sentBytes = sent.bytes,
+                sentKbps = sent.kbps,
+                receivedPackets = seen?.packets,
+                receivedBytes = seen?.bytes,
+                receivedKbps = achievedKbps,
+                lossPct = lossPct,
+                // Same honesty rule as downstream: if what arrived matches what we offered, the
+                // path was never the constraint and this number says nothing about it.
+                measuresNetwork = seen != null && achievedKbps > 0 && achievedKbps < sent.kbps * 9 / 10,
+            ),
+        ) as JsonObject
+
+        val findings = ArrayList<Finding>()
+        if (seen != null && seen.packets == 0 && sent.packets > 0) {
+            findings.add(
+                finding(
+                    FindingRegistry.THROUGHPUT_NO_DELIVERY, testId,
+                    "No upstream traffic reached the server",
+                    "This device sent ${sent.packets} packets and the server received none. " +
+                        "That is a connectivity fault on the outbound path rather than a slow link.",
+                ),
+            )
+        } else if (lossPct != null && lossPct >= 2.0) {
+            findings.add(
+                finding(
+                    FindingRegistry.THROUGHPUT_BELOW_OFFERED, testId,
+                    "Upstream loss of $lossPct % at ${sent.kbps / 1000} Mbit/s",
+                    "The server received ${seen?.packets} of the ${sent.packets} packets this " +
+                        "device sent. The outbound path could not carry what was offered.",
+                ),
+            )
+        }
+
+        return Test(
+            id = testId, type = TestType.PERF_THROUGHPUT_UDP, sessionRef = sessionRef, tier = Tier.APP,
+            startedMonoNs = started, endedMonoNs = ids.monoNs(),
+            status = if (seen == null || seen.packets == 0) TestStatus.FAILED else TestStatus.OK,
+            metrics = metrics,
+        ) to findings
+    }
+
+    private data class UpstreamCount(val packets: Int, val bytes: Long, val kbps: Int)
+
+    /** The server's tally for this session's upstream run. */
+    private fun upstreamCount(
+        control: ControlClient, credential: String, sessionId: String,
+    ): UpstreamCount? = runCatching {
+        val o = Json.parseToJsonElement(control.observations(credential, sessionId))
+            .jsonObject["throughput_up"]?.jsonObject ?: return null
+        UpstreamCount(
+            packets = o["packets"]?.jsonPrimitive?.content?.toIntOrNull() ?: 0,
+            bytes = o["bytes"]?.jsonPrimitive?.content?.toLongOrNull() ?: 0,
+            kbps = o["kbps"]?.jsonPrimitive?.content?.toIntOrNull() ?: 0,
+        )
+    }.getOrNull()
+
+    private data class SenderReport(
+        val packets: Int, val bytes: Long, val kbps: Int, val limitedBy: String,
+    )
+
+    /** The server's own account of the run, from the observations API. */
+    private fun senderReport(
+        control: ControlClient, credential: String, sessionId: String,
+    ): SenderReport? = runCatching {
+        val arr = Json.parseToJsonElement(control.observations(credential, sessionId))
+            .jsonObject["throughput"]?.jsonArray ?: return null
+        val last = arr.lastOrNull()?.jsonObject ?: return null
+        SenderReport(
+            packets = last["packets"]?.jsonPrimitive?.content?.toIntOrNull() ?: 0,
+            bytes = last["bytes"]?.jsonPrimitive?.content?.toLongOrNull() ?: 0,
+            kbps = last["kbps"]?.jsonPrimitive?.content?.toIntOrNull() ?: 0,
+            limitedBy = last["limited_by"]?.jsonPrimitive?.content ?: "unknown",
+        )
+    }.getOrNull()
+
+    private fun parseInt(body: String?, key: String): Int? =
+        body?.let { Regex("\"$key\"\\s*:\\s*(-?\\d+)").find(it)?.groupValues?.get(1)?.toIntOrNull() }
+
+    /**
+     * Builds a finding from a registry entry, which supplies the code, category and severity.
+     *
+     * Taking a [FindingSpec] rather than three loose values is the point: a typo becomes a
+     * compile error, and two call sites cannot disagree about which category a finding belongs
+     * to - a disagreement that would split one fault across two verdict lights.
+     */
+    private fun finding(spec: FindingSpec, testId: String, title: String, desc: String) =
+        Finding(
+            id = ids.uuid(), code = spec.code, category = spec.category, severity = spec.severity,
+            confidence = Confidence.HIGH,
+            title = title, description = desc, evidenceRefs = listOf(EvidenceRef(testId)),
+        )
+
+    private fun round2(v: Double) = Math.round(v * 100.0) / 100.0
+}
+
+/** Metrics for perf.throughput_udp in the upstream direction. */
+@Serializable
+data class UpstreamThroughputMetrics(
+    val direction: String = "up",
+    @SerialName("requested_kbps") val requestedKbps: Int,
+    @SerialName("sent_packets") val sentPackets: Int,
+    @SerialName("sent_bytes") val sentBytes: Long,
+    /** What this device managed to emit — a property of the phone and its radio, not the path. */
+    @SerialName("sent_kbps") val sentKbps: Int,
+    @SerialName("received_packets") val receivedPackets: Int? = null,
+    @SerialName("received_bytes") val receivedBytes: Long? = null,
+    /** What arrived, measured by the only party that can measure it. This is the result. */
+    @SerialName("received_kbps") val receivedKbps: Int,
+    @SerialName("loss_pct") val lossPct: Double? = null,
+    @SerialName("measures_network") val measuresNetwork: Boolean,
+)
+
+/** Metrics for perf.throughput_udp. */
+@Serializable
+data class ThroughputMetrics(
+    val direction: String = "down",
+    @SerialName("requested_kbps") val requestedKbps: Int,
+    @SerialName("planned_duration_ms") val plannedDurationMs: Int,
+    @SerialName("packets_received") val packetsReceived: Int,
+    @SerialName("bytes_received") val bytesReceived: Long,
+    @SerialName("received_kbps") val receivedKbps: Int,
+    @SerialName("sender_packets") val senderPackets: Int? = null,
+    @SerialName("sender_bytes") val senderBytes: Long? = null,
+    @SerialName("sender_kbps") val senderKbps: Int? = null,
+    /** Against the sender's count, so a server-side limit is never counted as network loss. */
+    @SerialName("loss_pct") val lossPct: Double? = null,
+    /** What ended the run: duration | budget | rate | send_error | unknown. */
+    @SerialName("limited_by") val limitedBy: String,
+    /**
+     * Whether this number says anything about the network. False when the sender's own ceiling
+     * was the binding constraint — in which case the rate is a property of the test, not the path.
+     */
+    @SerialName("measures_network") val measuresNetwork: Boolean,
+)

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/DirectionalTest.kt

@@ -0,0 +1,155 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.engine.Directional.Sample
+import app.echo_lot.engine.Directional.ServerSighting
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * The arithmetic that turns "3 % loss somewhere" into "3 % loss upstream". Getting a denominator
+ * wrong here does not crash anything — it produces a plausible number pointing at the wrong half
+ * of the network, which is worse than no number at all. Hence a test per claim.
+ */
+class DirectionalTest {
+
+    /** A clean train: every packet sent, seen and answered. Server clock offset by a constant. */
+    private fun clean(n: Int, offsetNs: Long = 5_000_000_000L): Pair<List<Sample>, List<ServerSighting>> {
+        val sent = (1..n).map { Sample(it, tTxNs = it * 10_000_000L, tRxNs = it * 10_000_000L + 4_000_000L) }
+        val seen = (1..n).map {
+            ServerSighting(it, tRxNs = offsetNs + it * 10_000_000L + 2_000_000L,
+                tTxNs = offsetNs + it * 10_000_000L + 2_100_000L)
+        }
+        return sent to seen
+    }
+
+    @Test
+    fun aCleanTrainReportsNoLossInEitherDirection() {
+        val (sent, seen) = clean(10)
+        val m = Directional.analyse(sent, seen)
+        assertEquals(10, m.sent)
+        assertEquals(10, m.seenByServer)
+        assertEquals(10, m.repliesReceived)
+        assertEquals(0.0, m.lossUpstreamPct)
+        assertEquals(0.0, m.lossDownstreamPct)
+        assertFalse(m.noneReachedServer)
+    }
+
+    // The whole point: a packet the server never saw was lost on the way there.
+    @Test
+    fun packetsTheServerNeverSawAreUpstreamLoss() {
+        val (sent, seen) = clean(10)
+        val m = Directional.analyse(sent, seen.filter { it.seq !in setOf(3, 7) })
+        assertEquals(2, m.lostUpstream)
+        assertEquals(0, m.lostDownstream)
+        assertEquals(20.0, m.lossUpstreamPct)
+        assertEquals(0.0, m.lossDownstreamPct, "a packet that never arrived cannot be lost coming back")
+    }
+
+    @Test
+    fun repliesThatNeverArrivedAreDownstreamLoss() {
+        val (sent, seen) = clean(10)
+        val withHoles = sent.map { if (it.seq in setOf(2, 5)) it.copy(tRxNs = null) else it }
+        val m = Directional.analyse(withHoles, seen)
+        assertEquals(0, m.lostUpstream)
+        assertEquals(2, m.lostDownstream)
+        assertEquals(20.0, m.lossDownstreamPct)
+    }
+
+    // Downstream loss is measured against what actually reached the server. Using "sent" as the
+    // denominator would count every upstream loss a second time and overstate the return path.
+    @Test
+    fun downstreamLossIsRelativeToWhatReachedTheServer() {
+        val (sent, seen) = clean(10)
+        // 5 lost on the way there; of the 5 that arrived, 1 reply is lost coming back.
+        val seenPartial = seen.filter { it.seq > 5 }
+        val withHole = sent.map {
+            when {
+                it.seq <= 5 -> it.copy(tRxNs = null) // never got there, so never came back
+                it.seq == 6 -> it.copy(tRxNs = null) // arrived, reply lost
+                else -> it
+            }
+        }
+        val m = Directional.analyse(withHole, seenPartial)
+        assertEquals(5, m.lostUpstream)
+        assertEquals(50.0, m.lossUpstreamPct)
+        assertEquals(1, m.lostDownstream)
+        assertEquals(20.0, m.lossDownstreamPct, "1 of the 5 that arrived, not 1 of 10")
+    }
+
+    @Test
+    fun aServerThatSawNothingIsCalledOutSeparately() {
+        val (sent, _) = clean(6)
+        val m = Directional.analyse(sent.map { it.copy(tRxNs = null) }, emptyList())
+        assertTrue(m.noneReachedServer)
+        assertEquals(100.0, m.lossUpstreamPct)
+        assertEquals(0.0, m.lossDownstreamPct, "with nothing arriving there is no return path to blame")
+    }
+
+    // Jitter is legitimate without synchronised clocks because the offset cancels when successive
+    // one-way samples are differenced. This pins that: a huge constant offset must not show up.
+    @Test
+    fun jitterIsUnaffectedByTheClockOffsetBetweenTheTwoMachines() {
+        val (sent, near) = clean(10, offsetNs = 0)
+        val (_, far) = clean(10, offsetNs = 9_999_999_999L)
+        val a = Directional.analyse(sent, near)
+        val b = Directional.analyse(sent, far)
+        assertEquals(a.jitterUpstreamMs, b.jitterUpstreamMs,
+            "a constant clock offset must cancel when consecutive samples are differenced")
+        assertEquals(0.0, assertNotNull(a.jitterUpstreamMs), "an evenly spaced train has no jitter")
+    }
+
+    @Test
+    fun jitterReflectsUnevenArrival() {
+        val sent = listOf(
+            Sample(1, 0, 10_000_000),
+            Sample(2, 10_000_000, 20_000_000),
+            Sample(3, 20_000_000, 30_000_000),
+        )
+        // Server receive times drift: +2ms, +7ms, +3ms relative to send.
+        val seen = listOf(
+            ServerSighting(1, 2_000_000, 2_100_000),
+            ServerSighting(2, 17_000_000, 17_100_000),
+            ServerSighting(3, 23_000_000, 23_100_000),
+        )
+        val m = Directional.analyse(sent, seen)
+        // one-way samples: 2ms, 7ms, 3ms → |7-2| and |3-7| → mean 4.5ms
+        assertEquals(4.5, assertNotNull(m.jitterUpstreamMs))
+    }
+
+    // "No jitter" and "not enough data to say" are different claims, and only one is true here.
+    @Test
+    fun tooFewSamplesReportsNoJitterRatherThanZero() {
+        val m = Directional.analyse(
+            listOf(Sample(1, 0, 10_000_000)),
+            listOf(ServerSighting(1, 2_000_000, 2_100_000)),
+        )
+        assertNull(m.jitterUpstreamMs)
+        assertNull(m.jitterDownstreamMs)
+    }
+
+    // A server record for a sequence we never sent is not evidence about this train; folding it
+    // in would yield loss percentages outside 0–100.
+    @Test
+    fun strayServerRecordsAreIgnored() {
+        val (sent, seen) = clean(5)
+        val m = Directional.analyse(sent, seen + ServerSighting(99, 1, 2) + ServerSighting(100, 3, 4))
+        assertEquals(5, m.seenByServer)
+        assertEquals(0.0, m.lossUpstreamPct)
+        assertTrue(m.lossDownstreamPct in 0.0..100.0)
+    }
+
+    @Test
+    fun anEmptyTrainDoesNotDivideByZero() {
+        val m = Directional.analyse(emptyList(), emptyList())
+        assertEquals(0.0, m.lossUpstreamPct)
+        assertEquals(0.0, m.lossDownstreamPct)
+        assertFalse(m.noneReachedServer, "nothing sent is not the same as nothing arriving")
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveCompatTest.kt

@@ -0,0 +1,71 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.protocol.Compat
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.VersionRefused
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+import kotlin.test.fail
+
+/**
+ * Checks the version gate against a LIVE server — the half that unit tests cannot reach, because
+ * the whole point is that two independently-built artifacts agree. Self-skips without
+ * ECHOLOT_LIVE_*.
+ */
+class LiveCompatTest {
+
+    private val url = System.getenv("ECHOLOT_LIVE_URL")
+    private val pin = System.getenv("ECHOLOT_LIVE_PIN")
+    private val cred = System.getenv("ECHOLOT_LIVE_CRED")
+
+    private fun clientAs(version: String) = ControlClient(url!!, setOf(pin!!), version)
+
+    @Test
+    fun theServerAdvertisesAndEnforcesItsWindow() {
+        if (url == null || pin == null || cred == null) {
+            println("LiveCompatTest skipped (no ECHOLOT_LIVE_* env)"); return
+        }
+
+        // The profile must state the window — without it the app cannot pre-empt a refusal.
+        val profile = clientAs("0.2.0").profile(cred)
+        println("server ${profile.serverVersion} protocol=${profile.compat.protocolVersion} " +
+            "accepts app [${profile.compat.appMin}, ${profile.compat.appMax})")
+        assertTrue(profile.compat.protocolVersion.isNotBlank(), "profile omits protocol_version")
+        assertTrue(profile.compat.appMin.isNotBlank(), "profile omits app_min")
+
+        // This build must be inside it, or every other live test here is meaningless.
+        val verdict = Compat.check(profile, "0.2.0")
+        assertEquals(Compat.Verdict.OK, verdict.verdict, verdict.message ?: "")
+
+        // The profile stays reachable for a version the server would otherwise refuse: that is
+        // how a refused client discovers what it needs.
+        val ancient = clientAs("0.1.0")
+        val stillReadable = ancient.profile(cred)
+        assertEquals(profile.serverVersion, stillReadable.serverVersion,
+            "the profile endpoint must never be gated on app version")
+
+        // And a gated endpoint refuses it, with a message naming the window.
+        try {
+            ancient.createSession(cred, System.getenv("ECHOLOT_LIVE_TARGET") ?: "fmr")
+            fail("server accepted a session from an out-of-window app")
+        } catch (e: VersionRefused) {
+            val msg = assertNotNull(e.message)
+            println("refused as expected: $msg")
+            assertTrue(msg.contains("0.1.0"), "refusal should name the offending version: $msg")
+            assertTrue(msg.contains(profile.compat.appMin), "refusal should name the window: $msg")
+        }
+
+        // Too new is refused the same way — the window is a range, not a floor.
+        try {
+            clientAs("99.0.0").createSession(cred, System.getenv("ECHOLOT_LIVE_TARGET") ?: "fmr")
+            fail("server accepted a session from an app above its window")
+        } catch (e: VersionRefused) {
+            println("too-new refused as expected: ${e.message}")
+        }
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveDownstreamTest.kt

@@ -0,0 +1,81 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.measurement.TestStatus
+import app.echo_lot.measurement.TestType
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.ProbeSession
+import kotlin.test.Test as JTest
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+
+/**
+ * Runs DownstreamMeasurement against a LIVE server and checks the *documents* it produces, not
+ * just that packets moved: the tests must carry recomputable metrics and land on the right test
+ * types, because that is what an archived run is read back as. Self-skips without ECHOLOT_LIVE_*.
+ */
+class LiveDownstreamTest {
+
+    private val url = System.getenv("ECHOLOT_LIVE_URL")
+    private val pin = System.getenv("ECHOLOT_LIVE_PIN")
+    private val cred = System.getenv("ECHOLOT_LIVE_CRED")
+    private val udp = System.getenv("ECHOLOT_LIVE_UDP")
+    private val target = System.getenv("ECHOLOT_LIVE_TARGET") ?: "fmr"
+
+    @JTest
+    fun producesDownstreamTestsAndFindings() {
+        if (url == null || pin == null || cred == null || udp == null) {
+            println("LiveDownstreamTest skipped (no ECHOLOT_LIVE_* env)"); return
+        }
+        val control = ControlClient(url, setOf(pin))
+        val session = control.createSession(cred, target)
+        val (host, port) = udp.split(":").let { it[0] to it[1].toInt() }
+
+        val (tests, findings) = ProbeSession(cred, session, host, port).use { ps ->
+            ps.echo() // prime: the grant binds to the source the server has actually observed
+            DownstreamMeasurement(SystemIdSource())
+                .run(cred, session.sessionId, control, ps, sessionRef = "sess-1")
+        }
+        control.deleteSession(cred, session.sessionId)
+
+        for (t in tests) println("${t.type}  status=${t.status}  metrics=${t.metrics}")
+        for (f in findings) println("finding ${f.code} [${f.severity}] ${f.title}")
+
+        // Assert on what is present, not on how many: adding a measurement should not be a
+        // test edit. (It was, once — hence the note.)
+        assertTrue(tests.size >= 3, "expected at least the three downstream tests, got ${tests.size}")
+        val byType = tests.associateBy { it.type }
+
+        val pmtud = assertNotNull(byType[TestType.MTU_PMTUD_DOWN], "no mtu.pmtud_down test")
+        assertTrue(pmtud.status == TestStatus.OK || pmtud.status == TestStatus.PARTIAL,
+            "DF probe did not deliver anything: ${pmtud.status}")
+        val pathMtu = pmtud.metrics?.get("path_mtu_bytes")?.toString()?.toIntOrNull()
+        assertNotNull(pathMtu, "pmtud_down must report a path MTU")
+        assertTrue(pathMtu in 576..9000, "implausible downstream path MTU: $pathMtu")
+        println("downstream path MTU = $pathMtu bytes")
+
+        val frag = assertNotNull(byType[TestType.MTU_FRAG_DELIVERY], "no mtu.frag_delivery test")
+        assertNotNull(frag.metrics?.get("largest_delivered_bytes"))
+
+        // Fragment ordering runs only when fragments arrive at all, and only against a server
+        // that can craft them — so it is checked when present rather than required.
+        byType[TestType.MTU_FRAG_ORDERING]?.let { fo ->
+            val m = fo.metrics?.toString() ?: ""
+            println("fragment ordering: ${fo.status} $m")
+            if (fo.status != TestStatus.UNSUPPORTED) {
+                assertTrue(m.contains("in_order"), "no per-ordering result: $m")
+                assertTrue(m.contains("reversed"), "reversed ordering was never attempted: $m")
+            }
+        }
+
+        val train = assertNotNull(byType[TestType.TRAIN_UDP_DOWNSTREAM], "no downstream train")
+        assertNotNull(train.evidence, "a train without columnar evidence is not recomputable")
+        val received = train.metrics?.get("received")?.toString()?.toIntOrNull() ?: 0
+        assertTrue(received > 0, "no downstream train packets arrived")
+        println("downstream train: $received received, loss=${train.metrics?.get("loss_pct")}, " +
+            "reordered=${train.metrics?.get("reordered_packets")}")
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveEnrollmentTest.kt

@@ -0,0 +1,63 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.protocol.EnrollmentLink
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+import kotlin.test.fail
+
+/**
+ * Enrolls against a LIVE server using the link the server itself minted (probe-protocol.md §2.1).
+ *
+ * This is the test that matters for enrollment, because the failure mode it guards against is a
+ * *disagreement* between two programs: the Go side assembles the link, the Kotlin side takes it
+ * apart, and if they differ by one percent-encoding the pin is wrong by one character — which
+ * does not fail loudly, it fails as an inscrutable TLS error days later. A unit test on either
+ * side alone cannot see that.
+ *
+ * Needs ECHOLOT_ENROLL_URI (minted over SSH by scripts/test-fmr.sh); self-skips without it.
+ */
+class LiveEnrollmentTest {
+
+    private val enrollUri = System.getenv("ECHOLOT_ENROLL_URI")
+
+    @Test
+    fun enrollsFromTheServersOwnLink() {
+        if (enrollUri.isNullOrBlank()) {
+            println("LiveEnrollmentTest skipped (no ECHOLOT_ENROLL_URI)"); return
+        }
+        println("link: ${enrollUri.take(60)}…")
+
+        val link = assertNotNull(
+            EnrollmentLink.parse(enrollUri),
+            "the client could not parse a link the server produced — the two sides disagree",
+        )
+        println("parsed: url=${link.controlUrl} pin=${link.pin.take(12)}… token=${link.token.take(8)}…")
+
+        // Redeeming applies the pin to the very request that spends the token, so a wrong pin
+        // fails here at the handshake rather than after the token is gone.
+        val enrolled = link.redeem(deviceName = "live-test", appVersion = "0.2.0")
+        assertTrue(enrolled.credential.isNotBlank(), "no credential came back")
+        assertTrue(enrolled.deviceId.isNotBlank(), "no device id came back")
+        println("enrolled: device=${enrolled.deviceId} server=${enrolled.profile.name} " +
+            "${enrolled.profile.serverVersion}")
+
+        // The credential must actually work, and the pin from the link must be the one that
+        // verifies the server — that is the whole claim the link is making.
+        assertEquals(link.controlUrl, enrolled.controlUrl)
+        assertTrue(enrolled.profile.capabilities.contains("udp-probe"),
+            "profile fetched with the new credential looks wrong: ${enrolled.profile.capabilities}")
+
+        // Single-use: a token that still works after redemption is a token an attacker can reuse.
+        try {
+            link.redeem(deviceName = "should-not-happen", appVersion = "0.2.0")
+            fail("the enrollment token was accepted twice — it must be single-use")
+        } catch (t: Throwable) {
+            println("second redemption correctly refused: ${t.message?.take(120)}")
+        }
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveGrantedTest.kt

@@ -0,0 +1,89 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.ProbeSession
+import app.echo_lot.protocol.Wire
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+/**
+ * Exercises the server's §5 granted sends against a LIVE server: downtrain (downstream loss /
+ * ordering) and big_send (downstream MTU). Self-skips without ECHOLOT_LIVE_*.
+ *
+ * This is the direction a client cannot measure alone — only the far end can push large or
+ * numerous packets toward it — so it is also the direction that needs the anti-amplification
+ * grant, and this test is the proof that the grant path works end to end.
+ */
+class LiveGrantedTest {
+
+    private val url = System.getenv("ECHOLOT_LIVE_URL")
+    private val pin = System.getenv("ECHOLOT_LIVE_PIN")
+    private val cred = System.getenv("ECHOLOT_LIVE_CRED")
+    private val udp = System.getenv("ECHOLOT_LIVE_UDP")
+    private val target = System.getenv("ECHOLOT_LIVE_TARGET") ?: "fmr"
+
+    @Test
+    fun downstreamTrainAndBigSend() {
+        if (url == null || pin == null || cred == null || udp == null) {
+            println("LiveGrantedTest skipped (no ECHOLOT_LIVE_* env)"); return
+        }
+        val control = ControlClient(url, setOf(pin))
+        val profile = control.profile(cred)
+        println("capabilities: ${profile.capabilities}")
+        val session = control.createSession(cred, target)
+        val (host, port) = udp.split(":").let { it[0] to it[1].toInt() }
+
+        ProbeSession(cred, session, host, port).use { ps ->
+            // The grant is bound to the OBSERVED data-plane source, so we must be seen first.
+            val echo = ps.echo()
+            println("primed with echo rtt=${echo?.rttMs}")
+
+            // --- downtrain: 50 packets of 300 bytes, 5ms apart ---
+            val dtResp = control.action(
+                cred, session.sessionId,
+                """{"action":"downtrain","count":50,"size_bytes":300,"interval_us":5000}""",
+            )
+            println("downtrain accepted: ${dtResp.take(160)}")
+            val down = ps.collectGranted(windowMs = 4000)
+                .filter { it.type == Wire.TYPE_DOWNTRAIN_DATA }
+            val seqs = down.map { it.seq }.toSet()
+            println("downtrain received ${down.size}/50 packets, distinct seqs=${seqs.size}, " +
+                "sizes=${down.map { it.sizeBytes }.distinct()}")
+            assertTrue(down.isNotEmpty(), "no DOWNTRAIN_DATA arrived — granted send path is broken")
+
+            // --- big_send with DF: the largest size that arrives is the downstream path MTU ---
+            val sizes = listOf(600, 1200, 1400, 1472, 1500, 2000, 4000)
+            val dfResp = control.action(
+                cred, session.sessionId,
+                """{"action":"big_send","df":true,"sizes_bytes":${sizes}}""",
+            )
+            println("big_send(df) accepted: ${dfResp.take(200)}")
+            val dfArrived = ps.collectGranted(windowMs = 4000)
+                .filter { it.type == Wire.TYPE_BIG_SEND }.map { it.sizeBytes }.sorted()
+            println("big_send(df) arrived: $dfArrived")
+            assertTrue(dfArrived.isNotEmpty(), "no unfragmented BIG_SEND packets arrived")
+            val pathMtu = dfArrived.max()
+
+            // --- and without DF, to see whether fragments get through above that ---
+            val fragResp = control.action(
+                cred, session.sessionId,
+                """{"action":"big_send","df":false,"sizes_bytes":${sizes}}""",
+            )
+            println("big_send(frag) accepted: ${fragResp.take(200)}")
+            val fragArrived = ps.collectGranted(windowMs = 4000)
+                .filter { it.type == Wire.TYPE_BIG_SEND }.map { it.sizeBytes }.sorted()
+            println("big_send(frag) arrived: $fragArrived")
+
+            // The distinction the DF flag exists for: fragmented delivery may exceed the
+            // unfragmented path MTU, and reporting the former as the latter would be a lie.
+            println("downstream path MTU (payload bytes) = $pathMtu; " +
+                "largest fragmented delivery = ${fragArrived.maxOrNull()}")
+            assertTrue((fragArrived.maxOrNull() ?: 0) >= pathMtu,
+                "fragmented delivery should reach at least as far as unfragmented")
+        }
+        control.deleteSession(cred, session.sessionId)
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveMeasurementTest.kt

@@ -0,0 +1,79 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.measurement.*
+import kotlinx.serialization.json.Json
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+
+/**
+ * Runs the full server-facing engine against a live server and validates the produced
+ * MeasurementDocument. Self-skips without ECHOLOT_LIVE_* (same contract as core-protocol's live
+ * test). This is the whole vertical: protocol client → engine → schema document → verdict.
+ */
+class LiveMeasurementTest {
+
+    private val url = System.getenv("ECHOLOT_LIVE_URL")
+    private val pin = System.getenv("ECHOLOT_LIVE_PIN")
+    private val cred = System.getenv("ECHOLOT_LIVE_CRED")
+    private val udp = System.getenv("ECHOLOT_LIVE_UDP")
+    private val target = System.getenv("ECHOLOT_LIVE_TARGET") ?: "fmr"
+
+    @Test
+    fun producesValidDocumentFromLiveServer() {
+        if (url == null || pin == null || cred == null || udp == null) {
+            println("LiveMeasurementTest skipped (no ECHOLOT_LIVE_* env)")
+            return
+        }
+        val (host, port) = udp.split(":").let { it[0] to it[1].toInt() }
+        val engine = ServerMeasurement(
+            ids = SystemIdSource(),
+            app = AppInfo(version = "0.1.0", build = 1, flavor = "test"),
+            device = DeviceInfo("test", "jvm", 0, "n/a"),
+        )
+        val doc = engine.run(
+            ServerMeasurement.Config(
+                controlUrl = url, pins = setOf(pin), credential = cred,
+                target = target, udpHost = host, udpPort = port, echoCount = 20,
+            )
+        )
+
+        // The document must round-trip and carry the expected structure.
+        val encoded = Json { encodeDefaults = true }.encodeToString(MeasurementDocument.serializer(), doc)
+        println("document (${encoded.length} bytes): overall=${doc.summary?.overall}")
+
+        assertEquals(1, doc.serverSessions.size)
+        assertTrue(doc.serverSessions[0].capabilities.contains("udp-probe"))
+        // A full run is the echo train plus the three downstream tests; assert on the one this
+        // test is about rather than on the count, so adding a measurement is not a test edit.
+        for (t in doc.tests) println("  ${t.type} → ${t.status}")
+        for (f in doc.findings) println("  finding ${f.code} [${f.severity}] ${f.title}")
+        val test = doc.tests.first { it.type == TestType.TRAIN_UDP_UPDOWN }
+        assertTrue(test.status == TestStatus.OK || test.status == TestStatus.PARTIAL,
+            "expected replies from live server, got ${test.status}")
+
+        val metrics = Json.parseToJsonElement(test.metrics.toString())
+        println("metrics: $metrics")
+        assertTrue(metrics.toString().contains("rtt_ms_avg"))
+
+        // The directional split is the point of asking the server what it saw: without it a
+        // lossy path is reported as "loss" with no direction, which sends an engineer looking
+        // in both at once. Correlation is by wire sequence number, so a mismatch here means the
+        // two sides disagree about which packet is which.
+        val m = metrics.toString()
+        assertTrue(m.contains("seen_by_server"), "no directional split in the metrics: $m")
+        val seen = Regex(""""seen_by_server":(\d+)""").find(m)?.groupValues?.get(1)?.toInt()
+        assertNotNull(seen, "seen_by_server missing")
+        assertEquals(20, seen, "the server should have seen every probe on a healthy path")
+        assertTrue(m.contains("jitter_upstream_ms"), "no per-direction jitter: $m")
+        println("directional: $m")
+
+        assertTrue(doc.summary != null)
+        // A healthy local->fmr path should be green (no loss, no rebinding) or yellow.
+        println("summary: ${doc.summary}")
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveThroughputTest.kt

@@ -0,0 +1,68 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.measurement.TestStatus
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.ProbeSession
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+
+/**
+ * Downstream throughput against a LIVE server. Self-skips without ECHOLOT_LIVE_*.
+ *
+ * The assertions are about *honesty* rather than speed: a rate is only a measurement if the run
+ * was ended by the clock and the sender's own count backs it up. A test that just asserted "some
+ * Mbps arrived" would pass equally well against a broken implementation.
+ */
+class LiveThroughputTest {
+
+    private val url = System.getenv("ECHOLOT_LIVE_URL")
+    private val pin = System.getenv("ECHOLOT_LIVE_PIN")
+    private val cred = System.getenv("ECHOLOT_LIVE_CRED")
+    private val udp = System.getenv("ECHOLOT_LIVE_UDP")
+    private val target = System.getenv("ECHOLOT_LIVE_TARGET") ?: "fmr"
+
+    @Test
+    fun measuresDownstreamRateAndSaysWhatLimitedIt() {
+        if (url == null || pin == null || cred == null || udp == null) {
+            println("LiveThroughputTest skipped (no ECHOLOT_LIVE_* env)"); return
+        }
+        val control = ControlClient(url, setOf(pin), "0.2.0")
+        val session = control.createSession(cred, target)
+        val (host, port) = udp.split(":").let { it[0] to it[1].toInt() }
+
+        val (test, findings) = ProbeSession(cred, session, host, port).use { ps ->
+            ps.echo() // prime: the grant binds to the observed source
+            ThroughputMeasurement(SystemIdSource()).run(
+                cred, session.sessionId, control, ps, sessionRef = "sess-1",
+                durationS = 3, kbps = 20_000,
+            )
+        }
+        control.deleteSession(cred, session.sessionId)
+
+        val m = assertNotNull(test.metrics).toString()
+        println("throughput: ${test.status} $m")
+        for (f in findings) println("finding ${f.code} [${f.severity}] ${f.title}")
+
+        assertEquals(TestStatus.OK, test.status, "no throughput traffic arrived: $m")
+
+        // The sender's own count must be present — without it, loss cannot be attributed and the
+        // number is not a measurement.
+        assertTrue(m.contains("sender_packets"), "no sender report to compare against: $m")
+        assertTrue(m.contains("limited_by"), "the result must say what ended the run: $m")
+
+        val received = Regex(""""received_kbps":(\d+)""").find(m)?.groupValues?.get(1)?.toInt()
+        assertNotNull(received)
+        assertTrue(received > 0, "measured 0 kbps: $m")
+        println("received ${received / 1000} Mbit/s")
+
+        // A run this short and this far below the ceiling should end on the clock. Anything else
+        // means the grant was the constraint, and then the rate says nothing about the path.
+        assertTrue(m.contains(""""limited_by":"duration""""),
+            "the run did not end on the clock, so the rate measures the server, not the path: $m")
+    }
+}

echolot-app/core-engine/src/test/kotlin/app/echo_lot/engine/LiveUploadTest.kt

@@ -0,0 +1,102 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.engine
+
+import app.echo_lot.privacy.Anonymizer
+import app.echo_lot.privacy.PrivacyLevel
+import app.echo_lot.privacy.Salt
+import app.echo_lot.protocol.ControlClient
+import app.echo_lot.protocol.UploadRefused
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.jsonObject
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+/**
+ * Drives the upload path against a LIVE server: anonymize, upload, list, fetch back, delete.
+ *
+ * The point is not that the HTTP works — it is that what comes *back off the server* has been
+ * stripped. Uploading and then re-reading the stored document is the only check that proves the
+ * anonymizer ran on the bytes that actually left, rather than on a copy. Self-skips without
+ * ECHOLOT_LIVE_*.
+ */
+class LiveUploadTest {
+
+    private val url = System.getenv("ECHOLOT_LIVE_URL")
+    private val pin = System.getenv("ECHOLOT_LIVE_PIN")
+    private val cred = System.getenv("ECHOLOT_LIVE_CRED")
+    private val json = Json { prettyPrint = false }
+
+    private fun sampleRun(id: String) = """
+        {
+          "schema": "echolot/measurement",
+          "run": {
+            "id": "$id", "trigger": "manual", "started_at": "2026-08-01T10:00:00Z",
+            "notes": "kitchen table",
+            "device": {"manufacturer": "OnePlus", "model": "CPH2747"}
+          },
+          "networks": [{
+            "id": "net-1", "ssid": "Rambossek WLAN", "bssid": "78:9a:18:aa:bb:cc",
+            "gateway_ip4": "192.168.1.1", "public_ip4": "203.0.113.77",
+            "ssdp_responders": [{"friendly_name": "Living Room TV"}]
+          }],
+          "tests": [{"id": "t1", "type": "train.udp_updown", "status": "ok",
+                     "metrics": {"rtt_ms_avg": 12.4, "loss_pct": 0.0}}],
+          "findings": [{"id": "f1", "code": "nat.udp_rebinding", "severity": "medium"}],
+          "summary": {"verdict": "warn"}
+        }
+    """.trimIndent()
+
+    @Test
+    fun uploadRoundTrip() {
+        if (url == null || pin == null || cred == null) {
+            println("LiveUploadTest skipped (no ECHOLOT_LIVE_* env)"); return
+        }
+        val control = ControlClient(url, setOf(pin))
+        val profile = control.profile(cred)
+        val policy = profile.uploads
+        println("upload policy: mode=${policy.mode} min_anon=${policy.minAnonymization} " +
+            "max_bytes=${policy.maxBytes} retention_days=${policy.retentionDays}")
+
+        val runId = "livetest-" + System.nanoTime().toString().takeLast(10)
+        val level = PrivacyLevel.max(PrivacyLevel.BALANCED, PrivacyLevel.fromWire(policy.minAnonymization))
+        val redacted = json.encodeToString(
+            JsonObject.serializer(),
+            Anonymizer(level, Salt.perRun(ByteArray(32) { 9 }))
+                .anonymize(json.parseToJsonElement(sampleRun(runId)).jsonObject),
+        )
+        assertFalse(redacted.contains("Rambossek"), "the anonymizer did not strip the SSID before upload")
+
+        if (!policy.accepted) {
+            // A server configured to refuse must refuse — that is the behaviour worth asserting.
+            try {
+                control.uploadRun(cred, redacted)
+                throw AssertionError("server advertises mode=${policy.mode} but accepted an upload")
+            } catch (e: UploadRefused) {
+                println("upload correctly refused: ${e.message?.take(140)}")
+                return
+            }
+        }
+
+        val created = control.uploadRun(cred, redacted)
+        println("stored: ${created.take(200)}")
+
+        val listed = control.listRuns(cred)
+        assertTrue(listed.contains(runId), "uploaded run is missing from the server's list")
+
+        val fetched = control.getRun(cred, runId)
+        assertFalse(fetched.contains("Rambossek"), "the SSID is sitting on the server")
+        assertFalse(fetched.contains("Living Room TV"), "an SSDP neighbour name is sitting on the server")
+        assertFalse(fetched.contains("kitchen table"), "a free-text note is sitting on the server")
+        assertTrue(fetched.contains("nat.udp_rebinding"), "the finding code should survive — it is the point")
+        assertTrue(fetched.contains("12.4"), "metrics should survive anonymization")
+        println("round trip verified: identifiers stripped, measurements intact")
+
+        control.deleteRun(cred, runId)
+        assertFalse(control.listRuns(cred).contains(runId), "delete did not remove the run")
+        println("deleted")
+    }
+}

echolot-app/core-measurement/build.gradle.kts

@@ -0,0 +1,33 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+// Pure Kotlin/JVM: the client half of probe-protocol.md. No Android deps, so
+// the Android app modules can depend on it and it stays unit-testable (incl.
+// live integration tests) on any JDK. Crypto, HTTP and UDP come from the JDK
+// (javax.crypto, java.net.http, java.net) — only JSON needs a library.
+dependencies {
+    implementation(libs.kotlinx.serialization.json)
+    testImplementation(kotlin("test"))
+}
+
+kotlin {
+    // Build with the available JDK (Android Studio's JBR is 21) but emit
+    // Java-17 bytecode so the Android app modules can consume this library.
+    jvmToolchain(21)
+    compilerOptions {
+        jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
+    }
+}
+java {
+    sourceCompatibility = JavaVersion.VERSION_17
+    targetCompatibility = JavaVersion.VERSION_17
+}
+
+tasks.test {
+    useJUnitPlatform()
+}

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/Document.kt

@@ -0,0 +1,100 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Package measurement models one measurement run (measurement-schema.md) — the archived,
+// diffable, exportable unit. Design rules honored in the types: observation/interpretation
+// separated (tests[] vs findings[]), two clocks (wall RFC3339 for humans, *_mono_ns for math),
+// units in field names, columnar trains. params/evidence/metrics are per-test-type, so they are
+// carried as JsonObject (the probe engine fills them; consumers ignore unknown fields).
+package app.echo_lot.measurement
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonObject
+
+@Serializable
+data class MeasurementDocument(
+    val schema: String = "echolot/measurement",
+    @SerialName("schema_version") val schemaVersion: String = "1.0.0",
+    val run: Run,
+    val networks: List<Network> = emptyList(),
+    @SerialName("server_sessions") val serverSessions: List<ServerSession> = emptyList(),
+    val tests: List<Test> = emptyList(),
+    val findings: List<Finding> = emptyList(),
+    val summary: Summary? = null,
+)
+
+@Serializable
+data class Run(
+    val id: String, // UUIDv7
+    val trigger: Trigger,
+    @SerialName("started_at") val startedAt: String, // RFC3339 UTC, human correlation only
+    @SerialName("ended_at") val endedAt: String? = null,
+    val clock: Clock,
+    val app: AppInfo,
+    val device: DeviceInfo,
+    val tiers: Tiers,
+    @SerialName("profiles_used") val profilesUsed: List<String> = emptyList(),
+    val notes: String? = null,
+)
+
+@Serializable
+enum class Trigger {
+    @SerialName("manual") MANUAL,
+    @SerialName("scheduled") SCHEDULED,
+    @SerialName("monitor") MONITOR,
+    @SerialName("peer") PEER,
+}
+
+/** The two-clock anchor: mono_origin_wall maps the monotonic epoch to a wall time for humans;
+ *  all math uses *_mono_ns relative to that monotonic origin. */
+@Serializable
+data class Clock(
+    @SerialName("mono_origin_wall") val monoOriginWall: String,
+    @SerialName("ntp_offset_ms") val ntpOffsetMs: Double? = null,
+    @SerialName("ntp_offset_source") val ntpOffsetSource: String? = null,
+)
+
+@Serializable
+data class AppInfo(
+    val version: String,
+    val build: Int,
+    val git: String? = null,
+    val flavor: String? = null,
+)
+
+@Serializable
+data class DeviceInfo(
+    val manufacturer: String,
+    val model: String,
+    @SerialName("android_sdk") val androidSdk: Int,
+    @SerialName("android_release") val androidRelease: String,
+    @SerialName("security_patch") val securityPatch: String? = null,
+)
+
+/** What each tier was *available*; each test records what it *used*. */
+@Serializable
+data class Tiers(
+    val app: Boolean = true,
+    val shizuku: Boolean = false,
+    val root: Boolean = false,
+)
+
+@Serializable
+data class ServerSession(
+    val id: String,
+    @SerialName("profile_id") val profileId: String? = null,
+    @SerialName("profile_name") val profileName: String? = null,
+    @SerialName("control_url") val controlUrl: String,
+    @SerialName("server_version") val serverVersion: String? = null,
+    val capabilities: List<String> = emptyList(),
+    @SerialName("session_id") val sessionId: String,
+    val target: SessionTarget,
+)
+
+@Serializable
+data class SessionTarget(
+    val ip4: String? = null,
+    val ip6: String? = null,
+    @SerialName("udp_port") val udpPort: Int = 0,
+)

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/Evidence.kt

@@ -0,0 +1,85 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.encodeToJsonElement
+
+/**
+ * Typed builders for the per-test-type evidence shapes the schema fixes (§6.2/§6.3/§6.4). Probe
+ * code fills these and folds them into [Test.evidence] via [toEvidence]; keeping them typed here
+ * means the columnar/traceroute/resolver contracts live in one place.
+ */
+
+@PublishedApi
+internal val evidenceJson = Json { encodeDefaults = true; explicitNulls = true }
+
+/** Serialize any typed evidence object into the JsonObject the Test envelope carries. */
+inline fun <reified T> T.toEvidence(): JsonObject =
+    evidenceJson.encodeToJsonElement(this) as JsonObject
+
+/**
+ * Packet-train evidence (§6.2): columnar parallel arrays, one index per probe packet. Missing
+ * observations are null at that index — a 10k-packet train stays in the hundreds of kB. Server
+ * columns use the server session epoch; only differences within one clock are meaningful unless a
+ * time.server_offset test maps them.
+ */
+@Serializable
+data class TrainEvidence(
+    @SerialName("epoch_mono_ns") val epochMonoNs: Long,
+    val seq: List<Int>,
+    @SerialName("t_tx_ns") val tTxNs: List<Long?>,
+    @SerialName("t_srv_rx_ns") val tSrvRxNs: List<Long?> = emptyList(),
+    @SerialName("t_srv_tx_ns") val tSrvTxNs: List<Long?> = emptyList(),
+    @SerialName("t_rx_ns") val tRxNs: List<Long?>,
+    @SerialName("size_bytes") val sizeBytes: List<Int>,
+    @SerialName("dscp_sent") val dscpSent: Int? = null,
+    @SerialName("dscp_seen_by_server") val dscpSeenByServer: List<Int?> = emptyList(),
+    @SerialName("ecn_sent") val ecnSent: Int? = null,
+    @SerialName("ecn_seen_by_server") val ecnSeenByServer: List<Int?> = emptyList(),
+    @SerialName("ttl_seen_by_server") val ttlSeenByServer: List<Int?> = emptyList(),
+    @SerialName("evidence_truncated") val evidenceTruncated: Boolean = false,
+)
+
+/** Traceroute evidence (§6.3): fixed-tuple flow + per-TTL probe replies. */
+@Serializable
+data class TracerouteEvidence(val flow: Flow, val hops: List<Hop>)
+
+@Serializable
+data class Flow(
+    @SerialName("src_port") val srcPort: Int,
+    @SerialName("dst_port") val dstPort: Int,
+    @SerialName("fixed_tuple") val fixedTuple: Boolean = true,
+)
+
+@Serializable
+data class Hop(val ttl: Int, val probes: List<HopProbe>)
+
+@Serializable
+data class HopProbe(
+    @SerialName("reply_from") val replyFrom: String? = null,
+    @SerialName("rtt_ns") val rttNs: Long? = null,
+    val icmp: String? = null,
+    @SerialName("reply_ttl") val replyTtl: Int? = null,
+)
+
+/** Resolver under test (§6.4); every dns.* test carries this in params. */
+@Serializable
+data class ResolverSpec(
+    val source: ResolverSource,
+    val address: String? = null,
+    val port: Int = 53,
+    val transport: String, // do53-udp | do53-tcp | dot | doh
+    @SerialName("doh_url") val dohUrl: String? = null,
+)
+
+@Serializable
+enum class ResolverSource {
+    @SerialName("system") SYSTEM,
+    @SerialName("manual") MANUAL,
+    @SerialName("server-recursive") SERVER_RECURSIVE,
+}

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/Finding.kt

@@ -0,0 +1,68 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/** Interpretation with references back to evidence (measurement-schema.md §7.1). A finding with
+ *  no evidence_refs is invalid — every finding must be re-derivable from the evidence alone. */
+@Serializable
+data class Finding(
+    val id: String, // UUIDv7
+    val code: String, // stable registry (findings-registry.md), lint-rule style
+    val category: Category,
+    val severity: Severity,
+    val confidence: Confidence,
+    @SerialName("network_ref") val networkRef: String? = null,
+    val title: String,
+    val description: String,
+    @SerialName("evidence_refs") val evidenceRefs: List<EvidenceRef>,
+    val recommendation: String? = null,
+) {
+    init {
+        require(evidenceRefs.isNotEmpty()) { "a finding must reference at least one piece of evidence" }
+    }
+}
+
+@Serializable
+data class EvidenceRef(val test: String, val pointer: String? = null)
+
+/** Fixed §7.2 categories; each maps to one traffic light. */
+@Serializable
+enum class Category {
+    @SerialName("connectivity") CONNECTIVITY,
+    @SerialName("dns") DNS,
+    @SerialName("nat") NAT,
+    @SerialName("mtu") MTU,
+    @SerialName("ipv6") IPV6,
+    @SerialName("security") SECURITY,
+    @SerialName("performance") PERFORMANCE,
+    @SerialName("local") LOCAL,
+    @SerialName("wifi") WIFI,
+}
+
+/** Ordered worst→best via [rank]; drives the §7.3 light mapping. */
+@Serializable
+enum class Severity(val rank: Int) {
+    @SerialName("critical") CRITICAL(4),
+    @SerialName("high") HIGH(3),
+    @SerialName("medium") MEDIUM(2),
+    @SerialName("low") LOW(1),
+    @SerialName("info") INFO(0);
+
+    /** §7.3: critical|high → red, medium|low → yellow, info → green. */
+    fun toLight(): Verdict = when (this) {
+        CRITICAL, HIGH -> Verdict.RED
+        MEDIUM, LOW -> Verdict.YELLOW
+        INFO -> Verdict.GREEN
+    }
+}
+
+@Serializable
+enum class Confidence {
+    @SerialName("high") HIGH,
+    @SerialName("medium") MEDIUM,
+    @SerialName("low") LOW,
+}

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/FindingRegistry.kt

@@ -0,0 +1,205 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+/**
+ * The registry of finding codes (measurement-schema.md §9, open item 1).
+ *
+ * A finding code is the stable, machine-readable half of a result: the prose changes, the code is
+ * what a dashboard groups by and what someone greps a year of archived runs for. That only holds
+ * if a code means exactly one thing forever — which is not something ad-hoc string literals at
+ * fifteen call sites can promise.
+ *
+ * The failure this exists to prevent had already happened by the time it was written. Two
+ * independently-added emitters produced `connectivity.downstream_loss` and
+ * `connectivity.loss_downstream` for the same concept, and nothing anywhere objected. Anyone
+ * aggregating either one would have silently seen half their data.
+ *
+ * So codes are declared here as typed specs, each carrying its category and default severity, and
+ * emitters reference the spec rather than retyping the string. That makes a typo a compile error,
+ * and makes it impossible for two call sites to disagree about which category a finding belongs
+ * to — a disagreement that would otherwise split one fault across two verdict lights.
+ */
+data class FindingSpec(
+    val code: String,
+    val category: Category,
+    /** Severity when nothing about the specific run argues otherwise; emitters may escalate. */
+    val severity: Severity,
+    /** One line: what this finding asserts. Present tense, no hedging. */
+    val meaning: String,
+    /**
+     * What the finding rules *out*, where that is the useful half. "Loss upstream" is worth much
+     * more when it also says the return path is fine, because that halves where to look next.
+     */
+    val rulesOut: String? = null,
+)
+
+object FindingRegistry {
+
+    // ---- connectivity ----------------------------------------------------------------
+
+    // Renamed from nat.* before anything shipped: neither of these is about NAT, and the
+    // prefix is what decides which category - and therefore which verdict light - a finding
+    // rolls up into. A nat.* code landing under connectivity would be a permanent puzzle.
+    val UDP_UNREACHABLE = FindingSpec(
+        "connectivity.udp_unreachable", Category.CONNECTIVITY, Severity.HIGH,
+        "No UDP echo replies came back from the server at all.",
+    )
+
+    val UDP_UNREACHABLE_UPSTREAM = FindingSpec(
+        "connectivity.udp_unreachable_upstream", Category.CONNECTIVITY, Severity.HIGH,
+        "The server received none of the probes, so traffic is dropped on the way out.",
+        rulesOut = "The return path: nothing arrived to be replied to.",
+    )
+
+    val UDP_LOSS = FindingSpec(
+        "connectivity.udp_loss", Category.CONNECTIVITY, Severity.MEDIUM,
+        "A large fraction of round-trip probes were lost, direction unknown.",
+    )
+
+    val LOSS_UPSTREAM = FindingSpec(
+        "connectivity.loss_upstream", Category.CONNECTIVITY, Severity.MEDIUM,
+        "Probes were lost on the way to the server.",
+        rulesOut = "The return path: replies came back for everything that arrived.",
+    )
+
+    /**
+     * The single code for "lost on the return path", whichever measurement found it.
+     *
+     * Two emitters had independently invented `connectivity.downstream_loss` and
+     * `connectivity.loss_downstream` for this, and nothing objected. Anyone aggregating either
+     * one would have silently seen half their data. Paired with [LOSS_UPSTREAM] so the two
+     * directions read as a set.
+     */
+    val LOSS_DOWNSTREAM = FindingSpec(
+        "connectivity.loss_downstream", Category.CONNECTIVITY, Severity.MEDIUM,
+        "Packets were lost on the way back from the server.",
+        rulesOut = "The outbound path: the server received what it was answering.",
+    )
+
+    val DOWNSTREAM_BLOCKED = FindingSpec(
+        "connectivity.downstream_blocked", Category.CONNECTIVITY, Severity.HIGH,
+        "Server-initiated packets never arrive, although round trips work.",
+        rulesOut = "Basic reachability: the path forwards replies, just not unsolicited traffic.",
+    )
+
+    val DOWNSTREAM_REORDER = FindingSpec(
+        "connectivity.downstream_reorder", Category.CONNECTIVITY, Severity.LOW,
+        "Downstream packets arrive in a different order than they were sent.",
+    )
+
+    // MEDIUM, not HIGH: a captive portal is a condition to report, not necessarily a fault - on
+    // hotel or cafe wifi it is exactly what should be there, and logging in clears it. NO_INTERNET
+    // is the HIGH one, because nothing the user does locally fixes that. The registry first said
+    // HIGH; the probe emitting it had always said MEDIUM, and the probe was the considered value.
+    val CAPTIVE_PORTAL = FindingSpec(
+        "connectivity.captive_portal", Category.CONNECTIVITY, Severity.MEDIUM,
+        "A captive portal is intercepting connectivity checks.",
+    )
+
+    val NO_INTERNET = FindingSpec(
+        "connectivity.no_internet", Category.CONNECTIVITY, Severity.HIGH,
+        "Android's own connectivity checks fail on this network.",
+    )
+
+    // ---- mtu -------------------------------------------------------------------------
+
+    val MTU_REDUCED_DOWNSTREAM = FindingSpec(
+        "mtu.reduced_downstream", Category.MTU, Severity.LOW,
+        "The downstream path MTU is below the usual 1500 bytes.",
+    )
+
+    val MTU_DOWNSTREAM_BLACKHOLE = FindingSpec(
+        "mtu.downstream_blackhole", Category.MTU, Severity.MEDIUM,
+        "Datagrams above the path MTU are dropped downstream, fragmented or not.",
+    )
+
+    val FRAGMENTS_BLOCKED = FindingSpec(
+        "mtu.fragments_blocked", Category.MTU, Severity.MEDIUM,
+        "IP fragments do not reach this device even when sent in order.",
+    )
+
+    val FRAGMENT_REORDER_SENSITIVE = FindingSpec(
+        "mtu.fragment_reorder_sensitive", Category.MTU, Severity.LOW,
+        "Fragments are delivered in order but dropped when reordered or delayed.",
+        rulesOut = "Fragmentation itself: in-order fragments arrive fine.",
+    )
+
+    // ---- nat -------------------------------------------------------------------------
+
+    val NAT_UDP_REBINDING = FindingSpec(
+        "nat.udp_rebinding", Category.NAT, Severity.MEDIUM,
+        "A NAT remapped the UDP source port mid-flow.",
+    )
+
+    val NAT_SYMMETRIC = FindingSpec(
+        "nat.symmetric", Category.NAT, Severity.MEDIUM,
+        "The NAT assigns a different external port per destination.",
+    )
+
+    // ---- perf ------------------------------------------------------------------------
+
+    val THROUGHPUT_NO_DELIVERY = FindingSpec(
+        "perf.throughput_no_delivery", Category.PERFORMANCE, Severity.HIGH,
+        "No throughput traffic arrived, although the server sent it.",
+    )
+
+    val THROUGHPUT_BELOW_OFFERED = FindingSpec(
+        "perf.throughput_below_offered", Category.PERFORMANCE, Severity.LOW,
+        "Less throughput arrived than the server sent for the whole run.",
+    )
+
+    // ---- dns -------------------------------------------------------------------------
+
+    val DNS_ANSWER_REWRITTEN = FindingSpec(
+        "dns.answer_rewritten", Category.DNS, Severity.HIGH,
+        "A resolver returned an answer that differs from the authoritative record.",
+    )
+
+    val DNS_AUTHORITATIVE_UNREACHABLE = FindingSpec(
+        "dns.authoritative_unreachable", Category.DNS, Severity.MEDIUM,
+        "The canary zone's authoritative server could not be reached.",
+    )
+
+    // ---- v6 ----------------------------------------------------------------------------
+    //
+    // Prefix is `v6.`, matching the test-type registry (v6.brokenness, v6.happy_eyeballs, ...).
+    // These were `ipv6.*` while declaring Category.IPV6, but the prefix map only knows "v6", so
+    // they silently rolled up under connectivity: the third instance of a prefix disagreeing with
+    // its category and quietly moving a fault to a different verdict light.
+
+    val V6_BROKEN = FindingSpec(
+        "v6.broken", Category.IPV6, Severity.MEDIUM,
+        "IPv6 is configured on this network but does not work.",
+        rulesOut = "Absence of IPv6: it is provisioned, it simply fails.",
+    )
+
+    /**
+     * INFO deliberately, and it needs to stay that way.
+     *
+     * Most networks still do not offer IPv6, and that is not a fault. Reporting it as a warning
+     * lights a yellow verdict on a perfectly healthy network, which teaches people to ignore the
+     * light — the one thing a diagnostic must never do.
+     */
+    val V6_NOT_OFFERED = FindingSpec(
+        "v6.not_offered", Category.IPV6, Severity.INFO,
+        "This network does not offer IPv6.",
+    )
+
+    /** Every registered finding, in declaration order. */
+    val all: List<FindingSpec> = listOf(
+        UDP_UNREACHABLE, UDP_UNREACHABLE_UPSTREAM, UDP_LOSS, LOSS_UPSTREAM, LOSS_DOWNSTREAM,
+        DOWNSTREAM_BLOCKED, DOWNSTREAM_REORDER, CAPTIVE_PORTAL, NO_INTERNET,
+        MTU_REDUCED_DOWNSTREAM, MTU_DOWNSTREAM_BLACKHOLE, FRAGMENTS_BLOCKED,
+        FRAGMENT_REORDER_SENSITIVE,
+        NAT_UDP_REBINDING, NAT_SYMMETRIC,
+        THROUGHPUT_NO_DELIVERY, THROUGHPUT_BELOW_OFFERED,
+        DNS_ANSWER_REWRITTEN, DNS_AUTHORITATIVE_UNREACHABLE,
+        V6_BROKEN, V6_NOT_OFFERED,
+    )
+
+    private val byCode: Map<String, FindingSpec> = all.associateBy { it.code }
+
+    fun byCode(code: String): FindingSpec? = byCode[code]
+}

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/Network.kt

@@ -0,0 +1,113 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonObject
+
+/** One Android Network in play (measurement-schema.md §4). Shizuku-tier fields (route proto,
+ *  lifetimes) are absent at app tier — absence means "not observed", never "not present". */
+@Serializable
+data class Network(
+    val id: String,
+    val transport: Transport,
+    @SerialName("interface") val iface: String? = null,
+    val link: Link,
+    val wifi: Wifi? = null,
+    val cellular: Cellular? = null,
+    val changes: List<NetworkChange> = emptyList(),
+)
+
+@Serializable
+enum class Transport {
+    @SerialName("wifi") WIFI,
+    @SerialName("cellular") CELLULAR,
+    @SerialName("ethernet") ETHERNET,
+    @SerialName("vpn") VPN,
+    @SerialName("other") OTHER,
+}
+
+@Serializable
+data class Link(
+    val mtu: Int? = null,
+    val addresses: List<Address> = emptyList(),
+    val routes: List<Route> = emptyList(),
+    val dns: DnsConfig? = null,
+    val dhcp: Dhcp? = null,
+    @SerialName("captive_portal") val captivePortal: CaptivePortal? = null,
+)
+
+@Serializable
+data class Address(
+    val addr: String, // ip4 | ip6 (logical type, §8)
+    @SerialName("prefix_len") val prefixLen: Int,
+    val scope: String? = null,
+    val flags: List<String> = emptyList(),
+    @SerialName("valid_lft_s") val validLftS: Long? = null,
+    @SerialName("pref_lft_s") val prefLftS: Long? = null,
+)
+
+@Serializable
+data class Route(
+    val dst: String,
+    val gateway: String? = null,
+    val iface: String? = null,
+    val proto: RouteProto? = null, // shizuku tier; null = not observed
+    @SerialName("expires_s") val expiresS: Long? = null,
+)
+
+@Serializable
+enum class RouteProto {
+    @SerialName("dhcp") DHCP,
+    @SerialName("ra") RA,
+    @SerialName("static") STATIC,
+    @SerialName("unknown") UNKNOWN,
+}
+
+@Serializable
+data class DnsConfig(
+    val servers: List<String> = emptyList(),
+    @SerialName("private_dns_mode") val privateDnsMode: String? = null,
+    @SerialName("private_dns_hostname") val privateDnsHostname: String? = null,
+    @SerialName("search_domains") val searchDomains: List<String> = emptyList(),
+    @SerialName("nat64_prefix") val nat64Prefix: String? = null,
+)
+
+@Serializable
+data class Dhcp(val server: String? = null, @SerialName("lease_s") val leaseS: Long? = null)
+
+@Serializable
+data class CaptivePortal(
+    val detected: Boolean = false,
+    @SerialName("api_url") val apiUrl: String? = null,
+    @SerialName("venue_url") val venueUrl: String? = null,
+)
+
+@Serializable
+data class Wifi(
+    val ssid: String? = null,          // ssid (logical type)
+    val bssid: String? = null,         // bssid (logical type)
+    @SerialName("rssi_dbm") val rssiDbm: Int? = null,
+    @SerialName("link_speed_mbps") val linkSpeedMbps: Int? = null,
+    @SerialName("frequency_mhz") val frequencyMhz: Int? = null,
+    @SerialName("channel_width_mhz") val channelWidthMhz: Int? = null,
+    val standard: String? = null,
+    val security: String? = null,
+    @SerialName("mac_randomization") val macRandomization: Boolean? = null,
+)
+
+@Serializable
+data class Cellular(
+    val rat: String? = null,
+    val operator: String? = null,
+    val band: String? = null,
+)
+
+@Serializable
+data class NetworkChange(
+    @SerialName("at_mono_ns") val atMonoNs: Long,
+    val kind: String, // lost | gained | link_changed
+    val detail: JsonObject? = null,
+)

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/Summary.kt

@@ -0,0 +1,90 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+enum class Verdict {
+    @SerialName("green") GREEN,
+    @SerialName("yellow") YELLOW,
+    @SerialName("red") RED,
+    @SerialName("inconclusive") INCONCLUSIVE,
+}
+
+@Serializable
+data class Summary(
+    val overall: Verdict,
+    val categories: Map<String, CategorySummary>,
+)
+
+@Serializable
+data class CategorySummary(
+    val verdict: Verdict,
+    @SerialName("worst_finding") val worstFinding: String? = null,
+    @SerialName("tests_run") val testsRun: Int,
+    @SerialName("tests_failed") val testsFailed: Int,
+)
+
+/**
+ * Deterministic verdict derivation, fixed by measurement-schema.md §7.3:
+ *
+ * - A category's verdict = the light of its worst-severity finding
+ *   (critical|high → red, medium|low → yellow, info/none → green).
+ * - A category is `inconclusive` when > 50% of its tests are failed/unsupported.
+ * - Overall = the worst category light; `inconclusive` only when ALL categories are.
+ *
+ * The mapping test-type → category comes from [TestType.category]. Only categories that have
+ * findings or tests appear in the summary.
+ */
+object Verdicts {
+
+    private fun isInconclusiveTest(s: TestStatus) =
+        s == TestStatus.FAILED || s == TestStatus.UNSUPPORTED
+
+    fun derive(tests: List<Test>, findings: List<Finding>): Summary {
+        val testsByCat = tests.groupBy { TestType.category(it.type) }
+        val findingsByCat = findings.groupBy { it.category }
+        val categories = (testsByCat.keys + findingsByCat.keys)
+
+        val perCat = LinkedHashMap<String, CategorySummary>()
+        for (cat in Category.entries) {
+            if (cat !in categories) continue
+            val catTests = testsByCat[cat].orEmpty()
+            val catFindings = findingsByCat[cat].orEmpty()
+
+            val failed = catTests.count { isInconclusiveTest(it.status) }
+            val inconclusive = catTests.isNotEmpty() && failed * 2 > catTests.size
+
+            val worst = catFindings.maxByOrNull { it.severity.rank }
+            val verdict = when {
+                inconclusive -> Verdict.INCONCLUSIVE
+                worst == null -> Verdict.GREEN
+                else -> worst.severity.toLight()
+            }
+            perCat[serialName(cat)] = CategorySummary(
+                verdict = verdict,
+                worstFinding = worst?.id,
+                testsRun = catTests.size,
+                testsFailed = failed,
+            )
+        }
+
+        val overall = deriveOverall(perCat.values)
+        return Summary(overall = overall, categories = perCat)
+    }
+
+    /** Overall = worst light; inconclusive only if every category is inconclusive. */
+    private fun deriveOverall(cats: Collection<CategorySummary>): Verdict {
+        if (cats.isEmpty()) return Verdict.INCONCLUSIVE
+        if (cats.all { it.verdict == Verdict.INCONCLUSIVE }) return Verdict.INCONCLUSIVE
+        val rank = mapOf(Verdict.GREEN to 0, Verdict.YELLOW to 1, Verdict.RED to 2)
+        // Non-inconclusive categories decide the overall light.
+        return cats.filter { it.verdict != Verdict.INCONCLUSIVE }
+            .maxByOrNull { rank.getValue(it.verdict) }!!.verdict
+    }
+
+    private fun serialName(cat: Category): String = cat.name.lowercase()
+}

echolot-app/core-measurement/src/main/kotlin/app/echo_lot/measurement/Test.kt

@@ -0,0 +1,153 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonObject
+
+/** The generic test envelope (measurement-schema.md §6). params must fully reproduce the test;
+ *  evidence is append-only raw truth; metrics must be recomputable from evidence. All three are
+ *  per-test-type JSON, so they are carried as JsonObject. */
+@Serializable
+data class Test(
+    val id: String, // UUIDv7
+    val type: String, // TestType registry (§6.1)
+    @SerialName("network_ref") val networkRef: String? = null,
+    @SerialName("session_ref") val sessionRef: String? = null, // null for local-only tests
+    val tier: Tier,
+    @SerialName("started_mono_ns") val startedMonoNs: Long,
+    @SerialName("ended_mono_ns") val endedMonoNs: Long,
+    val status: TestStatus,
+    val error: TestError? = null,
+    val params: JsonObject? = null,
+    val evidence: JsonObject? = null,
+    val metrics: JsonObject? = null,
+)
+
+@Serializable
+enum class Tier {
+    @SerialName("app") APP,
+    @SerialName("shizuku") SHIZUKU,
+    @SerialName("root") ROOT,
+}
+
+@Serializable
+enum class TestStatus {
+    @SerialName("ok") OK,
+    @SerialName("failed") FAILED,
+    @SerialName("unsupported") UNSUPPORTED,
+    @SerialName("skipped") SKIPPED,
+    @SerialName("partial") PARTIAL,
+}
+
+@Serializable
+data class TestError(val code: String, val detail: String? = null)
+
+/**
+ * The v1 test-type registry (§6.1). String constants (dotted, family-first) so probe code and the
+ * server's measurement-schema test-type registry stay aligned. [category] maps a type to one of
+ * the fixed §7.2 categories for verdict rollup.
+ */
+object TestType {
+    // link
+    const val LINK_SNAPSHOT = "link.snapshot"
+    const val LINK_DHCP_RENEWAL_WATCH = "link.dhcp_renewal_watch"
+    const val LINK_IP_MONITOR = "link.ip_monitor"
+    /** Who advertises IPv6 on this link (+ gateway identity). Registry addition, v1.1. */
+    const val LINK_RA_SOURCE = "link.ra_source"
+    // net — connectivity validation (reproduces Android's NetworkMonitor generate_204 checks)
+    const val NET_CAPTIVE_PORTAL = "net.captive_portal"
+    // icmp
+    const val ICMP_PING4 = "icmp.ping4"
+    const val ICMP_PING6 = "icmp.ping6"
+    // trace
+    const val TRACEROUTE_UDP4 = "traceroute.udp4"
+    const val TRACEROUTE_UDP6 = "traceroute.udp6"
+    const val TRACEROUTE_ICMP4 = "traceroute.icmp4"
+    const val TRACEROUTE_ICMP6 = "traceroute.icmp6"
+    // train
+    const val TRAIN_UDP_UPDOWN = "train.udp_updown"
+    /** Server-to-client train under a §3.4 grant: the direction a round trip cannot separate. */
+    const val TRAIN_UDP_DOWNSTREAM = "train.udp_downstream"
+    // mtu
+    const val MTU_PMTUD_UP = "mtu.pmtud_up"
+    const val MTU_PMTUD_DOWN = "mtu.pmtud_down"
+    const val MTU_BLACKHOLE = "mtu.blackhole"
+    const val MTU_MSS_OBSERVED = "mtu.mss_observed"
+    const val MTU_FRAG_DELIVERY = "mtu.frag_delivery"
+    /** Whether fragments survive arriving out of order, not merely whether they survive. */
+    const val MTU_FRAG_ORDERING = "mtu.frag_ordering"
+    // nat
+    const val NAT_STUN_5780 = "nat.stun_5780"
+    const val NAT_MAPPING_LIFETIME_UDP = "nat.mapping_lifetime_udp"
+    const val NAT_MAPPING_LIFETIME_TCP = "nat.mapping_lifetime_tcp"
+    const val NAT_HAIRPIN = "nat.hairpin"
+    const val NAT_CONNECT_BACK = "nat.connect_back"
+    const val NAT_CGNAT_DETECT = "nat.cgnat_detect"
+    // dns
+    const val DNS_RESOLVER_INVENTORY = "dns.resolver_inventory"
+    const val DNS_CANARY = "dns.canary"
+    const val DNS_INTERCEPTION = "dns.interception"
+    const val DNS_TTL_INTEGRITY = "dns.ttl_integrity"
+    const val DNS_ANSWER_INTEGRITY = "dns.answer_integrity"
+    const val DNS_DNSSEC = "dns.dnssec"
+    const val DNS_NXDOMAIN_WILDCARD = "dns.nxdomain_wildcard"
+    const val DNS_REBIND_FILTER = "dns.rebind_filter"
+    const val DNS_AAAA_FILTER = "dns.aaaa_filter"
+    const val DNS_DNS64 = "dns.dns64"
+    const val DNS_COMPARE = "dns.compare"
+    // sec
+    const val SEC_TLS_REFERENCE = "sec.tls_reference"
+    const val SEC_CLIENTHELLO_ECHO = "sec.clienthello_echo"
+    const val SEC_HTTP_ECHO = "sec.http_echo"
+    const val SEC_SNI_FILTER = "sec.sni_filter"
+    const val SEC_DSCP_ECN_SURVIVAL = "sec.dscp_ecn_survival"
+    const val SEC_ARP_WATCH = "sec.arp_watch"
+    // port
+    const val PORT_REACH_SWEEP = "port.reach_sweep"
+    const val PORT_UDP_USABILITY = "port.udp_usability"
+    // perf
+    const val PERF_THROUGHPUT_TCP = "perf.throughput_tcp"
+    const val PERF_THROUGHPUT_UDP = "perf.throughput_udp"
+    const val PERF_BUFFERBLOAT = "perf.bufferbloat"
+    const val PERF_RRC_LATENCY = "perf.rrc_latency"
+    // v6
+    const val V6_DUALSTACK_COMPARE = "v6.dualstack_compare"
+    const val V6_HAPPY_EYEBALLS = "v6.happy_eyeballs"
+    const val V6_BROKENNESS = "v6.brokenness"
+    const val V6_NAT64_CLAT = "v6.nat64_clat"
+    // wifi
+    const val WIFI_ENVIRONMENT_SCAN = "wifi.environment_scan"
+    const val WIFI_ROAM_LOG = "wifi.roam_log"
+    const val WIFI_SIGNAL_LOG = "wifi.signal_log"
+    // local
+    const val LOCAL_MDNS_INVENTORY = "local.mdns_inventory"
+    const val LOCAL_SSDP_INVENTORY = "local.ssdp_inventory"
+    const val LOCAL_LLMNR_INVENTORY = "local.llmnr_inventory"
+    const val LOCAL_GATEWAY_SERVICES = "local.gateway_services"
+    const val LOCAL_NTP = "local.ntp"
+    // peer
+    const val PEER_REACHABILITY = "peer.reachability"
+    const val PEER_ISOLATION = "peer.isolation"
+    const val PEER_MULTICAST = "peer.multicast"
+    const val PEER_LAN_TRAIN = "peer.lan_train"
+    const val PEER_LEASE_DIFF = "peer.lease_diff"
+    // time
+    const val TIME_SERVER_OFFSET = "time.server_offset"
+
+    /** Maps a dotted test type to its §7.2 category for verdict rollup. */
+    fun category(type: String): Category = when (type.substringBefore('.')) {
+        "link", "icmp", "trace", "traceroute", "train", "port", "time", "net" -> Category.CONNECTIVITY
+        "dns" -> Category.DNS
+        "nat" -> Category.NAT
+        "mtu" -> Category.MTU
+        "v6" -> Category.IPV6
+        "sec" -> Category.SECURITY
+        "perf" -> Category.PERFORMANCE
+        "local", "peer" -> Category.LOCAL
+        "wifi" -> Category.WIFI
+        else -> Category.CONNECTIVITY
+    }
+}

echolot-app/core-measurement/src/test/kotlin/app/echo_lot/measurement/FindingRegistryTest.kt

@@ -0,0 +1,133 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import java.io.File
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.fail
+
+/**
+ * Keeps the finding registry honest.
+ *
+ * The interesting test is the last one: it reads `docs/findings-registry.md` and fails when the
+ * document and the code disagree. Documentation that drifts from its implementation is worse than
+ * none, because it still looks authoritative — and a finding registry is precisely the artifact
+ * other people build tooling against.
+ */
+class FindingRegistryTest {
+
+    @Test
+    fun codesAreUnique() {
+        val dupes = FindingRegistry.all.groupBy { it.code }.filterValues { it.size > 1 }.keys
+        assertTrue(dupes.isEmpty(), "duplicate finding codes: $dupes")
+    }
+
+    @Test
+    fun everyDeclaredSpecIsInTheAllList() {
+        // Reflection over the object's properties: a spec that is declared but left out of `all`
+        // is invisible to the doc check and to any consumer enumerating the registry.
+        val declared = FindingRegistry::class.java.declaredMethods
+            .filter { it.parameterCount == 0 && it.returnType == FindingSpec::class.java }
+            .mapNotNull { runCatching { it.invoke(FindingRegistry) as FindingSpec }.getOrNull() }
+            .map { it.code }
+            .toSet()
+        val listed = FindingRegistry.all.map { it.code }.toSet()
+        assertEquals(declared, listed, "declared specs and the `all` list disagree")
+    }
+
+    // The prefix decides the category, and the category decides which verdict light the finding
+    // rolls up into. A code whose prefix disagrees with its category silently moves a fault to a
+    // different light — the exact bug that got two codes renamed out of nat.*.
+    @Test
+    fun everyPrefixMatchesItsCategory() {
+        for (spec in FindingRegistry.all) {
+            val fromPrefix = TestType.category(spec.code)
+            assertEquals(
+                fromPrefix, spec.category,
+                "${spec.code} is declared as ${spec.category} but its prefix maps to $fromPrefix",
+            )
+        }
+    }
+
+    @Test
+    fun codesFollowTheNamingConvention() {
+        val shape = Regex("^[a-z0-9]+\\.[a-z0-9_]+$")
+        for (spec in FindingRegistry.all) {
+            assertTrue(shape.matches(spec.code), "malformed code: ${spec.code}")
+            assertTrue(spec.meaning.isNotBlank(), "${spec.code} has no meaning")
+            assertTrue(
+                spec.meaning.trimEnd().endsWith("."),
+                "${spec.code}'s meaning should be a sentence: '${spec.meaning}'",
+            )
+        }
+    }
+
+    // Two near-identical codes are how one fault ends up split across two dashboards. This is a
+    // blunt check — it will not catch every synonym — but it catches the shape that already
+    // happened: the same words in a different order.
+    @Test
+    fun noTwoCodesAreAnagramsOfEachOther() {
+        val normalised = FindingRegistry.all.associate { spec ->
+            spec.code to spec.code.substringAfter('.').split('_').sorted().joinToString("_")
+        }
+        val clashes = normalised.entries.groupBy { it.value }.filterValues { it.size > 1 }
+        if (clashes.isNotEmpty()) {
+            fail("codes differing only in word order: ${clashes.values.map { g -> g.map { it.key } }}")
+        }
+    }
+
+    @Test
+    fun theDocumentAndTheRegistryAgree() {
+        val doc = findDoc() ?: run {
+            println("findings-registry.md not found from ${File(".").absolutePath} — skipping")
+            return
+        }
+        val text = doc.readText()
+
+        // Only table rows count as "documented". Prose may legitimately mention a code that no
+        // longer exists — the rules section explains why two were merged — and treating that as
+        // a registry entry would force the document to forget its own history.
+        val documented = text.lines()
+            .filter { it.trimStart().startsWith("|") }
+            .flatMap { row -> Regex("`([a-z0-9]+\\.[a-z0-9_]+)`").findAll(row).map { it.groupValues[1] } }
+            .toSet()
+        val registered = FindingRegistry.all.map { it.code }.toSet()
+
+        val missingFromDoc = registered - documented
+        val missingFromCode = documented - registered
+        assertTrue(
+            missingFromDoc.isEmpty(),
+            "these codes exist in FindingRegistry but not in docs/findings-registry.md: $missingFromDoc",
+        )
+        assertTrue(
+            missingFromCode.isEmpty(),
+            "docs/findings-registry.md documents codes that no longer exist: $missingFromCode",
+        )
+
+        // And the severities must match, or the document is describing a different system.
+        for (spec in FindingRegistry.all) {
+            val row = text.lines().firstOrNull {
+                it.trimStart().startsWith("|") && it.contains("`${spec.code}`")
+            } ?: continue
+            val severity = spec.severity.name.lowercase()
+            assertTrue(
+                row.contains("| $severity |"),
+                "${spec.code} is ${severity} in code but the doc row says otherwise: $row",
+            )
+        }
+    }
+
+    /** Walks up from the test's working directory to find the repo's docs/ folder. */
+    private fun findDoc(): File? {
+        var dir: File? = File(".").absoluteFile
+        repeat(6) {
+            val candidate = File(dir, "docs/findings-registry.md")
+            if (candidate.isFile) return candidate
+            dir = dir?.parentFile
+        }
+        return null
+    }
+}

echolot-app/core-measurement/src/test/kotlin/app/echo_lot/measurement/SerializationTest.kt

@@ -0,0 +1,71 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlinx.serialization.json.Json
+import kotlin.test.Test as JTest
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class SerializationTest {
+
+    private val json = Json { ignoreUnknownKeys = true; encodeDefaults = true }
+
+    @JTest
+    fun documentRoundTrips() {
+        val doc = MeasurementDocument(
+            run = Run(
+                id = "0198c5f2-0000-7000-8000-000000000000",
+                trigger = Trigger.MANUAL,
+                startedAt = "2026-07-31T14:03:21.114Z",
+                clock = Clock(monoOriginWall = "2026-07-31T14:03:21.114Z"),
+                app = AppInfo(version = "0.1.0", build = 1),
+                device = DeviceInfo("OnePlus", "CPH2747", 36, "16"),
+                tiers = Tiers(app = true, shizuku = true),
+            ),
+            networks = listOf(
+                Network(
+                    id = "net-1", transport = Transport.WIFI, iface = "wlan0",
+                    link = Link(mtu = 1500, addresses = listOf(Address("192.0.2.23", 24, "global"))),
+                    wifi = Wifi(ssid = "example", rssiDbm = -54),
+                ),
+            ),
+            tests = listOf(
+                Test(
+                    id = "t-1", type = TestType.ICMP_PING4, networkRef = "net-1", tier = Tier.APP,
+                    startedMonoNs = 0, endedMonoNs = 38_000_000, status = TestStatus.OK,
+                    evidence = TrainEvidence(
+                        epochMonoNs = 0, seq = listOf(0, 1), tTxNs = listOf(0L, 20_000_000L),
+                        tRxNs = listOf(16_500_000L, null), sizeBytes = listOf(64, 64),
+                    ).toEvidence(),
+                ),
+            ),
+        )
+
+        val encoded = json.encodeToString(MeasurementDocument.serializer(), doc)
+        val decoded = json.decodeFromString(MeasurementDocument.serializer(), encoded)
+        assertEquals(doc.run.id, decoded.run.id)
+        assertEquals(Transport.WIFI, decoded.networks[0].transport)
+        assertEquals(TestType.ICMP_PING4, decoded.tests[0].type)
+        // snake_case field names on the wire
+        assertTrue(encoded.contains("\"schema_version\""))
+        assertTrue(encoded.contains("\"mono_origin_wall\""))
+        assertTrue(encoded.contains("\"t_tx_ns\""))
+        // null preserved at train index 1
+        assertTrue(encoded.contains("[16500000,null]"))
+    }
+
+    @JTest
+    fun findingRequiresEvidence() {
+        try {
+            Finding(
+                id = "f-1", code = "x", category = Category.DNS, severity = Severity.INFO,
+                confidence = Confidence.LOW, title = "t", description = "d", evidenceRefs = emptyList(),
+            )
+            throw AssertionError("expected IllegalArgumentException for empty evidence_refs")
+        } catch (e: IllegalArgumentException) {
+            // expected — a finding with no evidence is invalid (§7.1)
+        }
+    }
+}

echolot-app/core-measurement/src/test/kotlin/app/echo_lot/measurement/VerdictsTest.kt

@@ -0,0 +1,109 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.measurement
+
+import kotlin.test.Test as JTest
+import kotlin.test.assertEquals
+
+class VerdictsTest {
+
+    private fun test(type: String, status: TestStatus, id: String = type): Test =
+        Test(id = id, type = type, tier = Tier.APP, startedMonoNs = 0, endedMonoNs = 1, status = status)
+
+    private fun finding(cat: Category, sev: Severity, id: String = "f-$cat-$sev"): Finding =
+        Finding(
+            id = id, code = "x.$cat", category = cat, severity = sev, confidence = Confidence.HIGH,
+            title = "t", description = "d", evidenceRefs = listOf(EvidenceRef("some-test")),
+        )
+
+    @JTest
+    fun categoryLightFromWorstSeverity() {
+        val tests = listOf(test(TestType.DNS_CANARY, TestStatus.OK))
+        val findings = listOf(
+            finding(Category.DNS, Severity.LOW),
+            finding(Category.DNS, Severity.HIGH), // worst → red
+            finding(Category.DNS, Severity.INFO),
+        )
+        val s = Verdicts.derive(tests, findings)
+        assertEquals(Verdict.RED, s.categories["dns"]!!.verdict)
+        assertEquals("f-DNS-HIGH", s.categories["dns"]!!.worstFinding)
+        assertEquals(Verdict.RED, s.overall)
+    }
+
+    @JTest
+    fun noFindingsIsGreen() {
+        val s = Verdicts.derive(listOf(test(TestType.MTU_BLACKHOLE, TestStatus.OK)), emptyList())
+        assertEquals(Verdict.GREEN, s.categories["mtu"]!!.verdict)
+        assertEquals(Verdict.GREEN, s.overall)
+    }
+
+    @JTest
+    fun mediumAndLowAreYellow() {
+        val s = Verdicts.derive(
+            listOf(test(TestType.SEC_HTTP_ECHO, TestStatus.OK)),
+            listOf(finding(Category.SECURITY, Severity.MEDIUM)),
+        )
+        assertEquals(Verdict.YELLOW, s.categories["security"]!!.verdict)
+    }
+
+    @JTest
+    fun majorityFailedIsInconclusive() {
+        // 2 of 3 dns tests failed → > 50% → inconclusive, even with a finding present.
+        val tests = listOf(
+            test(TestType.DNS_CANARY, TestStatus.FAILED, "a"),
+            test(TestType.DNS_TTL_INTEGRITY, TestStatus.UNSUPPORTED, "b"),
+            test(TestType.DNS_COMPARE, TestStatus.OK, "c"),
+        )
+        val s = Verdicts.derive(tests, listOf(finding(Category.DNS, Severity.HIGH)))
+        assertEquals(Verdict.INCONCLUSIVE, s.categories["dns"]!!.verdict)
+        assertEquals(2, s.categories["dns"]!!.testsFailed)
+        assertEquals(3, s.categories["dns"]!!.testsRun)
+    }
+
+    @JTest
+    fun exactlyHalfFailedIsNotInconclusive() {
+        // 1 of 2 failed → not > 50% → the finding decides.
+        val tests = listOf(
+            test(TestType.NAT_HAIRPIN, TestStatus.FAILED, "a"),
+            test(TestType.NAT_CONNECT_BACK, TestStatus.OK, "b"),
+        )
+        val s = Verdicts.derive(tests, listOf(finding(Category.NAT, Severity.CRITICAL)))
+        assertEquals(Verdict.RED, s.categories["nat"]!!.verdict)
+    }
+
+    @JTest
+    fun overallIsWorstCategory() {
+        val tests = listOf(
+            test(TestType.DNS_CANARY, TestStatus.OK, "d"),
+            test(TestType.MTU_BLACKHOLE, TestStatus.OK, "m"),
+        )
+        val findings = listOf(
+            finding(Category.DNS, Severity.MEDIUM),   // yellow
+            finding(Category.MTU, Severity.CRITICAL), // red
+        )
+        val s = Verdicts.derive(tests, findings)
+        assertEquals(Verdict.RED, s.overall)
+    }
+
+    @JTest
+    fun overallInconclusiveOnlyWhenAllAre() {
+        val tests = listOf(
+            test(TestType.DNS_CANARY, TestStatus.FAILED, "d"),    // dns inconclusive
+            test(TestType.MTU_BLACKHOLE, TestStatus.OK, "m"),     // mtu green
+        )
+        val s = Verdicts.derive(tests, emptyList())
+        assertEquals(Verdict.INCONCLUSIVE, s.categories["dns"]!!.verdict)
+        assertEquals(Verdict.GREEN, s.categories["mtu"]!!.verdict)
+        assertEquals(Verdict.GREEN, s.overall) // not all inconclusive → mtu decides
+    }
+
+    @JTest
+    fun categoryMappingCoversFamilies() {
+        assertEquals(Category.CONNECTIVITY, TestType.category(TestType.TRACEROUTE_UDP4))
+        assertEquals(Category.IPV6, TestType.category(TestType.V6_BROKENNESS))
+        assertEquals(Category.LOCAL, TestType.category(TestType.PEER_MULTICAST))
+        assertEquals(Category.PERFORMANCE, TestType.category(TestType.PERF_BUFFERBLOAT))
+        assertEquals(Category.CONNECTIVITY, TestType.category(TestType.TIME_SERVER_OFFSET))
+    }
+}

echolot-app/core-privacy/build.gradle.kts

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+// The anonymizer (measurement-schema.md §8). Pure Kotlin/JVM and deliberately
+// dependency-free beyond JSON: it must be trivially auditable, because a bug
+// here leaks a user's network onto someone else's server.
+dependencies {
+    implementation(libs.kotlinx.serialization.json)
+    testImplementation(kotlin("test"))
+}
+
+kotlin {
+    jvmToolchain(21)
+    compilerOptions { jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17) }
+}
+java { sourceCompatibility = JavaVersion.VERSION_17; targetCompatibility = JavaVersion.VERSION_17 }
+
+tasks.test { useJUnitPlatform() }

echolot-app/core-privacy/src/main/kotlin/app/echo_lot/privacy/Anonymizer.kt

@@ -0,0 +1,276 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Package privacy implements the anonymization contract of measurement-schema.md §8.
+//
+// The threat model is specific. An engineer running their own server wants the full document —
+// SSIDs and MACs are what make a run useful a week later. Someone measuring against a stranger's
+// server wants the numbers to survive and the identifiers not to. So this is a *transform*, not a
+// filter: the output is still a valid measurement document with the same tests, metrics and
+// findings; only the identifying scalars change, and consistently, so "same SSID as last run" is
+// still answerable from pseudonyms alone.
+//
+// Two properties are load-bearing and are what the tests pin:
+//   - Consistency within a document: one input value always maps to one pseudonym, so
+//     correlations inside a run survive.
+//   - No consistency *across* documents unless the user asks for it: the salt is per-run by
+//     default, so pseudonyms cannot be used to track a device between uploads. A stable salt is
+//     opt-in (`Salt.stable`) for people diffing their own history on their own server.
+package app.echo_lot.privacy
+
+import kotlinx.serialization.json.*
+import java.security.MessageDigest
+import java.util.Locale
+
+/** How much to strip. Ordered: FULL < BALANCED < STRICT. Wire values match the server's. */
+enum class PrivacyLevel(val wire: String) {
+    /** Nothing removed. The right choice for your own server. */
+    FULL("full"),
+
+    /**
+     * Identifiers pseudonymized, neighbour inventory dropped. Topology and timing survive:
+     * you can still see that the gateway is a MikroTik at a /24 boundary with 3 % loss, but not
+     * which MikroTik, on which SSID, next to whose Chromecast.
+     */
+    BALANCED("balanced"),
+
+    /**
+     * Numbers only: tests keep their metrics and status, evidence is dropped, findings keep their
+     * codes and severities but lose descriptions (which quote real names). What is left cannot
+     * identify a network, and is still enough for aggregate "how common is this fault" work.
+     */
+    STRICT("strict");
+
+    companion object {
+        fun fromWire(s: String?): PrivacyLevel =
+            entries.firstOrNull { it.wire == s?.lowercase(Locale.ROOT) } ?: FULL
+
+        /** The stricter of two levels — used to honour a server's minimum. */
+        fun max(a: PrivacyLevel, b: PrivacyLevel): PrivacyLevel = if (a.ordinal >= b.ordinal) a else b
+    }
+}
+
+/**
+ * The pseudonymization salt. Per-run by default: a fresh random salt means the same SSID uploaded
+ * twice yields two different pseudonyms, so an upload endpoint cannot link runs to a device.
+ * A stable salt trades that away for cross-run diffing and is only appropriate on a server you
+ * own — the app makes that an explicit choice, not a default.
+ */
+class Salt private constructor(internal val bytes: ByteArray, val stable: Boolean) {
+    companion object {
+        fun perRun(random: ByteArray): Salt = Salt(random.copyOf(), stable = false)
+        fun stable(secret: ByteArray): Salt = Salt(secret.copyOf(), stable = true)
+    }
+}
+
+/**
+ * Transforms a measurement document to [level].
+ *
+ * Field classification is by JSON key name, because the schema names things consistently
+ * (`ssid`, `bssid`, `mac`, `ip4`, `ip6`, `fqdn`, …) and a name-driven pass is auditable by
+ * reading one table. Anything unrecognized is treated as identifying when it is a string inside
+ * a known-sensitive container, and left alone otherwise — see [Classification].
+ */
+class Anonymizer(private val level: PrivacyLevel, private val salt: Salt) {
+
+    private val cache = HashMap<String, String>()
+
+    fun anonymize(doc: JsonObject): JsonObject {
+        if (level == PrivacyLevel.FULL) return stamp(doc)
+        val walked = walkObject(doc, path = emptyList())
+        val out = if (level == PrivacyLevel.STRICT) strip(walked) else walked
+        return stamp(out)
+    }
+
+    /** Records what was done, so a reader of the archived/uploaded document is never guessing. */
+    private fun stamp(doc: JsonObject): JsonObject {
+        val run = doc["run"]?.jsonObject ?: return doc
+        val privacy = buildJsonObject {
+            put("anonymization", level.wire)
+            put("salt", if (salt.stable) "stable" else "per_run")
+        }
+        return JsonObject(doc + ("run" to JsonObject(run + ("privacy" to privacy))))
+    }
+
+    // ---- the tree walk -------------------------------------------------------------------
+
+    private fun walkObject(obj: JsonObject, path: List<String>): JsonObject = buildJsonObject {
+        for ((k, v) in obj) {
+            val childPath = path + k
+            when {
+                Classification.dropAtBalanced(childPath) -> Unit // omit entirely
+                else -> put(k, walk(k, v, childPath))
+            }
+        }
+    }
+
+    private fun walk(key: String, v: JsonElement, path: List<String>): JsonElement = when (v) {
+        is JsonObject -> walkObject(v, path)
+        is JsonArray -> JsonArray(v.map { walk(key, it, path) })
+        is JsonPrimitive ->
+            if (v.isString) {
+                // Name first (it is precise), then shape (it is exhaustive). A field nobody
+                // classified must not be a field that leaks.
+                val type = Classification.typeOf(key, path) ?: Classification.inferFromValue(v.content)
+                JsonPrimitive(transform(type, v.content))
+            } else {
+                v
+            }
+    }
+
+    private fun transform(type: LogicalType?, value: String): String = when (type) {
+        null -> value
+        LogicalType.SSID -> pseudo("ssid", value) { "net-" + it.take(6) }
+        LogicalType.MAC, LogicalType.BSSID -> macPreservingOui(value)
+        LogicalType.IP4 -> ip4(value)
+        LogicalType.IP6 -> ip6(value)
+        LogicalType.FQDN -> fqdn(value)
+        LogicalType.OPAQUE_ID -> "redacted"
+        LogicalType.FREETEXT -> "[removed: may contain identifying text]"
+    }
+
+    // ---- per-type transforms -------------------------------------------------------------
+
+    /**
+     * Keeps the OUI (which vendor) and pseudonymizes the NIC part (which unit). Vendor is the
+     * diagnostically valuable half — "the RA comes from a MikroTik" survives, "…from THAT
+     * MikroTik" does not.
+     */
+    private fun macPreservingOui(value: String): String {
+        val sep = if (value.contains('-')) '-' else ':'
+        val parts = value.split(sep)
+        if (parts.size != 6 || parts.any { it.length != 2 }) return pseudo("mac", value) { "mac-" + it.take(8) }
+        val nic = pseudo("mac", value) { it }
+        return (parts.take(3) + listOf(nic.substring(0, 2), nic.substring(2, 4), nic.substring(4, 6)))
+            .joinToString(sep.toString())
+            .lowercase(Locale.ROOT)
+    }
+
+    /**
+     * Prefix-preserving within the same class, with reserved ranges kept verbatim: RFC1918 and
+     * CGNAT addresses say something about the topology and nothing about the person, and a run
+     * where 192.168.1.1 became a random public address would be actively misleading to read.
+     * Public addresses keep only their /16 so the network is still locatable at ISP granularity.
+     */
+    private fun ip4(value: String): String {
+        // A route destination carries a prefix length; pseudonymize the address and put it back,
+        // or "0.0.0.0/0" turns into nonsense and the routing table becomes unreadable.
+        value.substringAfter('/', "").takeIf { it.isNotEmpty() && value.contains('/') }?.let { len ->
+            return ip4(value.substringBefore('/')) + "/" + len
+        }
+        val o = value.split(".")
+        if (o.size != 4 || o.any { it.toIntOrNull() == null }) return value
+        val n = o.map { it.toInt() }
+        val reserved = n[0] == 10 ||
+            (n[0] == 172 && n[1] in 16..31) ||
+            (n[0] == 192 && n[1] == 168) ||
+            (n[0] == 169 && n[1] == 254) ||
+            (n[0] == 100 && n[1] in 64..127) ||
+            n[0] == 127 || n[0] == 0 || n[0] >= 224
+        if (reserved) return value
+        val h = pseudo("ip4", value) { it }
+        return "${n[0]}.${n[1]}.${h.substring(0, 2).toInt(16)}.${h.substring(2, 4).toInt(16)}"
+    }
+
+    /**
+     * IPv6 keeps the scope and the first 32 bits (so 2001:db8:… still reads as global unicast in
+     * the same allocation) and pseudonymizes the rest — the interface identifier is the part that
+     * is a device fingerprint, especially with EUI-64.
+     */
+    private fun ip6(value: String): String {
+        // Dotted quads reach here through the family-agnostic field names (addr, gateway, dst);
+        // hand them to the IPv4 path rather than mangling them as if they were v6.
+        if (value.count { it == ':' } < 2) return ip4(value)
+        if (value.contains('/')) {
+            return ip6(value.substringBefore('/')) + "/" + value.substringAfter('/')
+        }
+        val v = value.lowercase(Locale.ROOT)
+        // The unspecified address and the default route are not identities; mangling them would
+        // make a routing table unreadable for no privacy gain.
+        if (v == "::1" || v == "::" || v.startsWith("fe80:") || v.startsWith("ff")) return v
+
+        // Unique local addresses (fc00::/7) need the *whole* prefix replaced, not the tail.
+        //
+        // They look like the v6 equivalent of RFC1918, and the first instinct is to keep them for
+        // the same reason: private, topological, says nothing about anyone. That reasoning does
+        // not carry over. An RFC1918 prefix is shared by millions of networks and identifies
+        // none of them; a ULA global ID is 40 *random* bits, unique to one network by
+        // construction (RFC 4193). It is a network fingerprint. Passing the leading groups
+        // through - which is what the general path does - leaked 32 of those 40 bits.
+        //
+        // The prefix is pseudonymized as a unit, so two addresses on the same ULA subnet still
+        // land on the same pseudonymous prefix. "These hosts are on one network" survives;
+        // "this is *that* network" does not.
+        if (v.startsWith("fc") || v.startsWith("fd")) {
+            val groups = v.substringBefore('%').split(":")
+            val prefix = pseudo("ula-prefix", groups.take(3).joinToString(":")) { it }
+            val host = pseudo("ula-host", v) { it }
+            return "fd${prefix.substring(0, 2)}:${prefix.substring(2, 6)}:${prefix.substring(6, 10)}" +
+                "::${host.substring(0, 4)}"
+        }
+        val groups = v.substringBefore('%').split(":")
+        if (groups.size < 3) return v
+        val h = pseudo("ip6", value) { it }
+        return "${groups[0]}:${groups[1]}:${h.substring(0, 4)}:${h.substring(4, 8)}::${h.substring(8, 12)}"
+    }
+
+    /**
+     * Per-label pseudonyms with the public suffix kept, so "it resolved somewhere under .local"
+     * or "…under example.com" survives without naming the host. The suffix list is deliberately
+     * short: guessing wrong keeps *more* pseudonymized, never less.
+     */
+    private fun fqdn(value: String): String {
+        if (value.isEmpty()) return value
+        val trailing = value.endsWith(".")
+        val labels = value.trimEnd('.').split(".")
+        if (labels.size == 1) return pseudo("fqdn", value) { "host-" + it.take(6) }
+        val keep = if (labels.last() in publicSuffixes) 1 else 0
+        val head = labels.dropLast(keep).map { l -> pseudo("label", l) { "l-" + it.take(6) } }
+        return (head + labels.takeLast(keep)).joinToString(".") + if (trailing) "." else ""
+    }
+
+    // ---- STRICT ---------------------------------------------------------------------------
+
+    /**
+     * STRICT keeps the shape of the document and the numbers, and nothing that quotes the
+     * network back. Evidence goes (trains carry addresses and hostnames), finding prose goes
+     * (it interpolates real names), networks go entirely.
+     */
+    private fun strip(doc: JsonObject): JsonObject = buildJsonObject {
+        for ((k, v) in doc) {
+            when (k) {
+                "networks", "server_sessions" -> Unit
+                "tests" -> put(k, JsonArray((v as? JsonArray ?: JsonArray(emptyList())).map { t ->
+                    val o = t.jsonObject
+                    JsonObject(o.filterKeys { it != "evidence" && it != "params" })
+                }))
+                "findings" -> put(k, JsonArray((v as? JsonArray ?: JsonArray(emptyList())).map { f ->
+                    val o = f.jsonObject
+                    JsonObject(o.filterKeys { it != "description" && it != "title" && it != "evidence_refs" })
+                }))
+                "run" -> put(k, JsonObject(v.jsonObject.filterKeys { it != "notes" }))
+                else -> put(k, v)
+            }
+        }
+    }
+
+    // ---- pseudonym machinery ---------------------------------------------------------------
+
+    /** Deterministic per (domain, value, salt); memoized so one value maps to one pseudonym. */
+    private fun pseudo(domain: String, value: String, shape: (String) -> String): String =
+        cache.getOrPut("$domain$value") {
+            val md = MessageDigest.getInstance("SHA-256")
+            md.update(salt.bytes)
+            md.update(domain.toByteArray())
+            md.update(0)
+            md.update(value.lowercase(Locale.ROOT).toByteArray())
+            shape(md.digest().joinToString("") { "%02x".format(it) })
+        }
+
+    private companion object {
+        val publicSuffixes = setOf(
+            "local", "lan", "home", "internal", "arpa",
+            "com", "net", "org", "io", "app", "dev", "at", "de", "eu", "uk",
+        )
+    }
+}

echolot-app/core-privacy/src/main/kotlin/app/echo_lot/privacy/Classification.kt

@@ -0,0 +1,140 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.privacy
+
+/** The logical types of measurement-schema.md §8. */
+enum class LogicalType { IP4, IP6, MAC, BSSID, SSID, FQDN, OPAQUE_ID, FREETEXT }
+
+/**
+ * Which fields hold which logical type, and which whole subtrees are dropped below FULL.
+ *
+ * This is a table on purpose. The alternative — annotating the Kotlin models and reflecting over
+ * them — spreads the answer across every module and makes "what exactly gets uploaded?" a
+ * question you answer by reading the whole app. Here it is one file a reviewer can check against
+ * the spec in a sitting, and a new field that nobody classified stays visible in the output
+ * rather than being silently mangled.
+ *
+ * The bias is toward over-classifying: a metric wrongly pseudonymized is a bug someone reports;
+ * an SSID wrongly kept is a leak nobody notices.
+ */
+object Classification {
+
+    private val byKey: Map<String, LogicalType> = buildMap {
+        listOf(
+            "ip4", "ipv4", "gateway_ip4", "dns_ip4", "src_ip4", "dst_ip4", "public_ip4",
+            "observed_ip4", "hop_ip4", "answer_ip4", "address_ip4", "server_ip4",
+        ).forEach { put(it, LogicalType.IP4) }
+
+        listOf(
+            "ip6", "ipv6", "gateway_ip6", "dns_ip6", "src_ip6", "dst_ip6", "public_ip6",
+            "observed_ip6", "hop_ip6", "answer_ip6", "address_ip6", "server_ip6",
+            "link_local", "ra_source", "prefix",
+        ).forEach { put(it, LogicalType.IP6) }
+
+        // Family-agnostic address fields — the names the models actually use (Address.addr,
+        // Route.gateway, Route.dst, DnsConfig.servers). Their absence here was a real leak: the
+        // device's own global IPv6 address went out verbatim at the level whose description
+        // promises addresses are pseudonymized. Typed IP6 because the transform detects the
+        // family from the value, falling through to the IPv4 path for a dotted quad.
+        listOf(
+            "addr", "address", "gateway", "dst", "src", "servers", "server", "resolver",
+            "next_hop", "via", "public_ip", "observed_ip",
+        ).forEach { put(it, LogicalType.IP6) }
+
+        listOf("mac", "hw_addr", "gateway_mac", "router_mac", "sender_mac", "peer_mac")
+            .forEach { put(it, LogicalType.MAC) }
+        listOf("bssid", "ap_mac").forEach { put(it, LogicalType.BSSID) }
+        listOf("ssid", "network_name", "wifi_ssid").forEach { put(it, LogicalType.SSID) }
+
+        listOf(
+            "fqdn", "hostname", "host", "name", "reverse_dns", "ptr", "domain", "query_name",
+            "friendly_name", "server_name", "sni", "cname", "search_domain", "device_name",
+            // Plural and prefixed variants the models actually use.
+            "search_domains", "private_dns_hostname", "domains", "hostnames",
+        ).forEach { put(it, LogicalType.FQDN) }
+
+        listOf("session_id", "credential", "token", "device_id", "android_id", "serial", "imsi", "iccid")
+            .forEach { put(it, LogicalType.OPAQUE_ID) }
+
+        listOf("notes", "detail", "raw", "excerpt", "location", "model_description")
+            .forEach { put(it, LogicalType.FREETEXT) }
+    }
+
+    /**
+     * Whole subtrees that BALANCED removes rather than pseudonymizes.
+     *
+     * Neighbour inventories (SSDP/UPnP responders, ARP tables, discovered peers) are the clearest
+     * case: they describe other people's devices, they are a household fingerprint even with the
+     * names hashed, and no metric depends on them. Dropping beats mangling.
+     */
+    private val droppedPaths: List<List<String>> = listOf(
+        listOf("networks", "neighbors"),
+        listOf("networks", "arp"),
+        listOf("networks", "wifi", "scan_results"),
+        listOf("run", "device", "security_patch"),
+    )
+
+    /** Key suffixes whose whole value is a neighbour inventory wherever they appear. */
+    private val droppedKeys = setOf(
+        "ssdp_responders", "upnp", "neighbors", "arp_table", "scan_results",
+        "nearby_networks", "peers", "raw_dump", "dumpsys",
+    )
+
+    fun typeOf(key: String, path: List<String>): LogicalType? {
+        byKey[key]?.let { return it }
+        // Inside a discovery/neighbour container every string is someone's device name until
+        // proven otherwise, so classify unknown strings there as free text rather than passing
+        // them through.
+        if (path.any { it in droppedKeys }) return LogicalType.FREETEXT
+        return null
+    }
+
+    /**
+     * Last-resort classification from the *value*, when the field name is unrecognised.
+     *
+     * A name table can only protect fields somebody remembered to add, which is the wrong
+     * property for a privacy control: the dangerous field is the one nobody thought of. This
+     * exists because that failed once already — `addresses[].addr` holds the device's own global
+     * IPv6 address, the table had never heard of the name, and it went out verbatim.
+     *
+     * Only addresses and MACs are inferred, because only those have shapes that cannot be
+     * mistaken for something else. Hostnames deliberately are not: `train.udp_updown` is
+     * indistinguishable from a domain by shape, and mangling a test type would corrupt the
+     * document to protect nothing.
+     */
+    fun inferFromValue(value: String): LogicalType? {
+        val v = value.trim()
+        if (v.isEmpty() || v.length > 64) return null
+        if (looksLikeMac(v)) return LogicalType.MAC
+        if (looksLikeIp6(v)) return LogicalType.IP6
+        if (looksLikeIp4(v)) return LogicalType.IP4
+        return null
+    }
+
+    private fun isHex(c: Char) = c in '0'..'9' || c in 'a'..'f' || c in 'A'..'F'
+
+    private fun looksLikeMac(v: String): Boolean {
+        val parts = v.split(':', '-')
+        return parts.size == 6 && parts.all { p -> p.length == 2 && p.all(::isHex) }
+    }
+
+    private fun looksLikeIp4(v: String): Boolean {
+        val parts = v.substringBefore('/').split('.')
+        return parts.size == 4 && parts.all { p ->
+            p.isNotEmpty() && p.length <= 3 && p.all(Char::isDigit) && p.toInt() <= 255
+        }
+    }
+
+    private fun looksLikeIp6(v: String): Boolean {
+        val core = v.substringBefore('/').substringBefore('%')
+        // Two colons minimum, so a time or a MAC fragment does not qualify, and nothing but the
+        // characters an address may contain.
+        return core.count { it == ':' } >= 2 && core.all { it == ':' || isHex(it) }
+    }
+
+    fun dropAtBalanced(path: List<String>): Boolean {
+        if (path.isNotEmpty() && path.last() in droppedKeys) return true
+        return droppedPaths.any { dropped -> dropped.all { path.contains(it) } }
+    }
+}

echolot-app/core-privacy/src/test/kotlin/app/echo_lot/privacy/AnonymizerTest.kt

@@ -0,0 +1,228 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.privacy
+
+import kotlinx.serialization.json.*
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotEquals
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * These tests are the audit of the anonymizer: each one states a property someone's privacy
+ * depends on, so a regression here fails loudly rather than quietly leaking.
+ */
+class AnonymizerTest {
+
+    private val json = Json { prettyPrint = false }
+    private val salt = Salt.perRun(ByteArray(32) { it.toByte() })
+
+    private fun sample(): JsonObject = json.parseToJsonElement(
+        """
+        {
+          "schema": "echolot/measurement",
+          "run": {
+            "id": "0190-run", "trigger": "manual", "notes": "at Anna's flat",
+            "device": {"manufacturer": "OnePlus", "model": "CPH2747", "security_patch": "2026-06-05"}
+          },
+          "networks": [{
+            "id": "net-1", "ssid": "Rambossek WLAN", "bssid": "78:9a:18:aa:bb:cc",
+            "gateway_ip4": "192.168.1.1", "public_ip4": "89.185.109.150",
+            "gateway_ip6": "2001:1ad0:c4fe:6767::1", "link_local": "fe80::7a9a:18ff:feaa:bbcc",
+            "neighbors": [{"name": "Anna's Chromecast", "mac": "aa:bb:cc:dd:ee:ff"}],
+            "ssdp_responders": [{"friendly_name": "Living Room TV", "location": "http://192.168.1.44:8060/"}]
+          }],
+          "tests": [{
+            "id": "t1", "type": "train.udp_updown", "status": "ok",
+            "metrics": {"rtt_ms_avg": 12.4, "loss_pct": 0.0},
+            "evidence": {"seq": [0,1,2], "t_rx_ns": [1,2,3]}
+          }],
+          "findings": [{
+            "id": "f1", "code": "nat.udp_rebinding", "severity": "medium",
+            "title": "NAT remapped the port", "description": "server saw 89.185.109.150:41000"
+          }],
+          "summary": {"verdict": "warn"}
+        }
+        """.trimIndent(),
+    ).jsonObject
+
+    private fun anon(level: PrivacyLevel, doc: JsonObject = sample()) = Anonymizer(level, salt).anonymize(doc)
+
+    private fun flat(e: JsonElement): String = e.toString()
+
+    @Test
+    fun fullLeavesTheDocumentAloneButRecordsThat() {
+        val out = anon(PrivacyLevel.FULL)
+        assertEquals("Rambossek WLAN", out["networks"]!!.jsonArray[0].jsonObject["ssid"]!!.jsonPrimitive.content)
+        assertEquals("full", out["run"]!!.jsonObject["privacy"]!!.jsonObject["anonymization"]!!.jsonPrimitive.content)
+    }
+
+    @Test
+    fun balancedRemovesTheSsidAndTheNotes() {
+        val text = flat(anon(PrivacyLevel.BALANCED))
+        assertFalse(text.contains("Rambossek"), "SSID survived: $text")
+        assertFalse(text.contains("Anna"), "free-text note or neighbour name survived: $text")
+    }
+
+    @Test
+    fun balancedDropsNeighbourInventoriesEntirely() {
+        val net = anon(PrivacyLevel.BALANCED)["networks"]!!.jsonArray[0].jsonObject
+        assertNull(net["neighbors"], "neighbour list should be dropped, not pseudonymized")
+        assertNull(net["ssdp_responders"], "SSDP responders should be dropped, not pseudonymized")
+    }
+
+    @Test
+    fun balancedKeepsTheVendorHalfOfAMac() {
+        val bssid = anon(PrivacyLevel.BALANCED)["networks"]!!.jsonArray[0].jsonObject["bssid"]!!.jsonPrimitive.content
+        assertTrue(bssid.startsWith("78:9a:18"), "OUI should survive so the vendor is still known: $bssid")
+        assertFalse(bssid.endsWith("aa:bb:cc"), "NIC part should be pseudonymized: $bssid")
+    }
+
+    @Test
+    fun privateAddressesAreKeptVerbatimAndPublicOnesAreNot() {
+        val net = anon(PrivacyLevel.BALANCED)["networks"]!!.jsonArray[0].jsonObject
+        assertEquals("192.168.1.1", net["gateway_ip4"]!!.jsonPrimitive.content,
+            "RFC1918 says nothing about the user and everything about the topology")
+        assertNotEquals("89.185.109.150", net["public_ip4"]!!.jsonPrimitive.content)
+        assertTrue(net["public_ip4"]!!.jsonPrimitive.content.startsWith("89.185."),
+            "the /16 should survive for ISP-level context")
+    }
+
+    @Test
+    fun linkLocalIsKeptButGlobalV6IsNot() {
+        val net = anon(PrivacyLevel.BALANCED)["networks"]!!.jsonArray[0].jsonObject
+        assertEquals("fe80::7a9a:18ff:feaa:bbcc", net["link_local"]!!.jsonPrimitive.content)
+        assertNotEquals("2001:1ad0:c4fe:6767::1", net["gateway_ip6"]!!.jsonPrimitive.content)
+    }
+
+    @Test
+    fun metricsAndVerdictsAreNeverTouched() {
+        for (level in PrivacyLevel.entries) {
+            val out = anon(level)
+            val t = out["tests"]!!.jsonArray[0].jsonObject
+            assertEquals(12.4, t["metrics"]!!.jsonObject["rtt_ms_avg"]!!.jsonPrimitive.double, 1e-9,
+                "$level changed a metric")
+            assertEquals("ok", t["status"]!!.jsonPrimitive.content)
+            assertEquals("warn", out["summary"]!!.jsonObject["verdict"]!!.jsonPrimitive.content)
+        }
+    }
+
+    @Test
+    fun findingCodesSurviveEveryLevelSoAggregationStillWorks() {
+        for (level in PrivacyLevel.entries) {
+            val f = anon(level)["findings"]!!.jsonArray[0].jsonObject
+            assertEquals("nat.udp_rebinding", f["code"]!!.jsonPrimitive.content, "$level lost the finding code")
+            assertEquals("medium", f["severity"]!!.jsonPrimitive.content)
+        }
+    }
+
+    @Test
+    fun strictDropsEvidenceAndProse() {
+        val out = anon(PrivacyLevel.STRICT)
+        assertNull(out["networks"], "STRICT should not describe the network at all")
+        assertNull(out["tests"]!!.jsonArray[0].jsonObject["evidence"])
+        assertNull(out["findings"]!!.jsonArray[0].jsonObject["description"])
+        assertFalse(flat(out).contains("89.185.109.150"), "an address leaked through finding prose")
+    }
+
+    @Test
+    fun pseudonymsAreConsistentWithinADocument() {
+        val doc = json.parseToJsonElement(
+            """{"run":{"id":"r"},"networks":[{"ssid":"Home"},{"ssid":"Home"},{"ssid":"Other"}]}"""
+        ).jsonObject
+        val nets = anon(PrivacyLevel.BALANCED, doc)["networks"]!!.jsonArray
+        val a = nets[0].jsonObject["ssid"]!!.jsonPrimitive.content
+        val b = nets[1].jsonObject["ssid"]!!.jsonPrimitive.content
+        val c = nets[2].jsonObject["ssid"]!!.jsonPrimitive.content
+        assertEquals(a, b, "the same SSID must map to the same pseudonym inside one run")
+        assertNotEquals(a, c, "different SSIDs must not collide")
+    }
+
+    @Test
+    fun perRunSaltsDoNotLinkTwoUploadsOfTheSameNetwork() {
+        val doc = json.parseToJsonElement("""{"run":{"id":"r"},"networks":[{"ssid":"Home"}]}""").jsonObject
+        val one = Anonymizer(PrivacyLevel.BALANCED, Salt.perRun(ByteArray(32) { 1 })).anonymize(doc)
+        val two = Anonymizer(PrivacyLevel.BALANCED, Salt.perRun(ByteArray(32) { 2 })).anonymize(doc)
+        assertNotEquals(
+            one["networks"]!!.jsonArray[0].jsonObject["ssid"],
+            two["networks"]!!.jsonArray[0].jsonObject["ssid"],
+            "a per-run salt must not produce a cross-run tracking identifier",
+        )
+    }
+
+    @Test
+    fun aStableSaltDoesLinkThemBecauseThatIsWhatItIsFor() {
+        val doc = json.parseToJsonElement("""{"run":{"id":"r"},"networks":[{"ssid":"Home"}]}""").jsonObject
+        val secret = ByteArray(32) { 7 }
+        val one = Anonymizer(PrivacyLevel.BALANCED, Salt.stable(secret)).anonymize(doc)
+        val two = Anonymizer(PrivacyLevel.BALANCED, Salt.stable(secret)).anonymize(doc)
+        assertEquals(
+            one["networks"]!!.jsonArray[0].jsonObject["ssid"],
+            two["networks"]!!.jsonArray[0].jsonObject["ssid"],
+        )
+        assertEquals("stable", one["run"]!!.jsonObject["privacy"]!!.jsonObject["salt"]!!.jsonPrimitive.content)
+    }
+
+    @Test
+    fun theDeclaredLevelMatchesWhatWasApplied() {
+        for (level in PrivacyLevel.entries) {
+            assertEquals(
+                level.wire,
+                anon(level)["run"]!!.jsonObject["privacy"]!!.jsonObject["anonymization"]!!.jsonPrimitive.content,
+            )
+        }
+    }
+
+    @Test
+    fun serverMinimumWins() {
+        assertEquals(PrivacyLevel.STRICT, PrivacyLevel.max(PrivacyLevel.FULL, PrivacyLevel.STRICT))
+        assertEquals(PrivacyLevel.BALANCED, PrivacyLevel.max(PrivacyLevel.BALANCED, PrivacyLevel.FULL))
+        assertEquals(PrivacyLevel.FULL, PrivacyLevel.fromWire("nonsense"))
+    }
+
+    // A ULA looks like the v6 RFC1918 and is not. Its global ID is 40 random bits, unique to one
+    // network by construction (RFC 4193), so the prefix IS the identifier - unlike 192.168.x,
+    // which millions of networks share. Passing the leading groups through leaked most of it.
+    @Test
+    fun ulaPrefixesArePseudonymizedWhole() {
+        val doc = json.parseToJsonElement(
+            """{"run":{"id":"r"},"networks":[{"link":{"dns":{"servers":["fda1:3fb1:ff92:6696::2662"]}}}]}"""
+        ).jsonObject
+        val out = flat(anon(PrivacyLevel.BALANCED, doc))
+        assertFalse(out.contains("fda1"), "the ULA global ID survived: $out")
+        assertFalse(out.contains("3fb1"), "part of the ULA global ID survived: $out")
+        assertTrue(out.contains("fd"), "the result should still read as a ULA: $out")
+    }
+
+    // Pseudonymizing the prefix as a unit keeps the one fact that is diagnostically useful:
+    // whether two addresses sit on the same network.
+    @Test
+    fun addressesOnOneUlaSubnetStayRelated() {
+        val doc = json.parseToJsonElement(
+            """{"run":{"id":"r"},"networks":[{"link":{"dns":{"servers":[
+               "fda1:3fb1:ff92:6696::1","fda1:3fb1:ff92:6696::2","fdff:9999:8888:7777::1"]}}}]}"""
+        ).jsonObject
+        val servers = anon(PrivacyLevel.BALANCED, doc)["networks"]!!.jsonArray[0].jsonObject["link"]!!
+            .jsonObject["dns"]!!.jsonObject["servers"]!!.jsonArray.map { it.jsonPrimitive.content }
+        val prefixOf = { s: String -> s.substringBeforeLast("::") }
+        assertEquals(prefixOf(servers[0]), prefixOf(servers[1]),
+            "two addresses on one ULA subnet should share a pseudonymous prefix")
+        assertNotEquals(prefixOf(servers[0]), prefixOf(servers[2]),
+            "a different ULA network must not collide with the first")
+    }
+
+    // RFC1918 stays readable, and this is the contrast that justifies it: a shared, meaningless
+    // prefix is topology; a unique random one is identity.
+    @Test
+    fun rfc1918StaysReadableUnlikeUla() {
+        val doc = json.parseToJsonElement(
+            """{"run":{"id":"r"},"networks":[{"link":{"dns":{"servers":["192.168.1.1","10.13.102.1"]}}}]}"""
+        ).jsonObject
+        val out = flat(anon(PrivacyLevel.BALANCED, doc))
+        assertTrue(out.contains("192.168.1.1"), "RFC1918 should survive: $out")
+        assertTrue(out.contains("10.13.102.1"), "RFC1918 should survive: $out")
+    }
+}

echolot-app/core-privacy/src/test/kotlin/app/echo_lot/privacy/LeakTest.kt

@@ -0,0 +1,113 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.privacy
+
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.jsonObject
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+/**
+ * The blunt instrument: build a document with identifying values in every place one can actually
+ * occur, anonymize it, and assert none of them survive.
+ *
+ * [AnonymizerTest] checks that the fields the classification table knows about are handled
+ * correctly. This checks the other half — the fields it does *not* know about. A per-field test
+ * can only fail for a field someone remembered to write a case for, which is exactly the wrong
+ * property for a privacy check: the dangerous field is the one nobody thought of.
+ *
+ * Concretely, this is written the way it is because the schema's own field names disagree with
+ * the classifier's. `Address.addr` carries an IP and is documented as such in
+ * measurement-schema.md §8, but the classifier keys on names like `ip4` and `gateway_ip4` and had
+ * never heard of `addr`.
+ */
+class LeakTest {
+
+    private val json = Json { prettyPrint = false }
+    private val salt = Salt.perRun(ByteArray(32) { 3 })
+
+    /**
+     * Every string here is something that identifies a person, a household or a device, placed
+     * where the real models actually put it (`core-measurement`'s Network/Link/Address/DnsConfig).
+     */
+    private val secrets = listOf(
+        "Rambossek WLAN",              // ssid
+        "78:9a:18:aa:bb:cc",           // bssid
+        "aa:bb:cc:dd:ee:11",           // gateway mac
+        "2001:1ad0:c4fe:6767::150",    // global v6 address on the interface
+        "2a02:1748:dead:beef::1",      // v6 default gateway
+        "203.0.113.77",                // public v4
+        "nas.rambossek.lan",           // private-dns hostname
+        "rambossek.lan",               // search domain
+        "Anna's Chromecast",           // neighbour name
+        "kitchen table",               // free-text note
+    )
+
+    private fun document(): String = """
+        {
+          "schema": "echolot/measurement",
+          "run": {
+            "id": "run-1", "trigger": "manual", "notes": "${secrets[9]}",
+            "device": {"manufacturer": "OnePlus", "model": "CPH2747"}
+          },
+          "networks": [{
+            "id": "net-1", "transport": "wifi",
+            "link": {
+              "mtu": 1500,
+              "addresses": [
+                {"addr": "${secrets[3]}", "prefix_len": 64, "scope": "global"},
+                {"addr": "192.168.1.44", "prefix_len": 24, "scope": "global"}
+              ],
+              "routes": [
+                {"dst": "::/0", "gateway": "${secrets[4]}", "iface": "wlan0"},
+                {"dst": "0.0.0.0/0", "gateway": "192.168.1.1", "iface": "wlan0"}
+              ],
+              "dns": {
+                "servers": ["${secrets[5]}", "192.168.1.1"],
+                "private_dns_hostname": "${secrets[6]}",
+                "search_domains": ["${secrets[7]}"]
+              }
+            },
+            "wifi": {"ssid": "${secrets[0]}", "bssid": "${secrets[1]}"},
+            "neighbors": [{"name": "${secrets[8]}", "mac": "${secrets[2]}"}]
+          }],
+          "tests": [{"id": "t1", "type": "train.udp_updown", "status": "ok",
+                     "metrics": {"rtt_ms_avg": 12.4}}],
+          "findings": [],
+          "summary": {"verdict": "ok"}
+        }
+    """.trimIndent()
+
+    private fun anonymized(level: PrivacyLevel): String =
+        json.encodeToString(
+            kotlinx.serialization.json.JsonObject.serializer(),
+            Anonymizer(level, salt).anonymize(json.parseToJsonElement(document()).jsonObject),
+        )
+
+    @Test
+    fun nothingIdentifyingSurvivesBalanced() {
+        val out = anonymized(PrivacyLevel.BALANCED)
+        val leaked = secrets.filter { out.contains(it) }
+        assertTrue(
+            leaked.isEmpty(),
+            "these identifying values were uploaded verbatim at BALANCED: $leaked\n\n$out",
+        )
+    }
+
+    @Test
+    fun nothingIdentifyingSurvivesStrict() {
+        val out = anonymized(PrivacyLevel.STRICT)
+        val leaked = secrets.filter { out.contains(it) }
+        assertTrue(leaked.isEmpty(), "leaked at STRICT: $leaked\n\n$out")
+    }
+
+    // Private addresses are kept on purpose — they describe the topology and not the person — so
+    // this pins that the leak test above is not passing by accident of over-redaction.
+    @Test
+    fun privateAddressesAreStillReadable() {
+        val out = anonymized(PrivacyLevel.BALANCED)
+        assertTrue(out.contains("192.168.1.1"), "RFC1918 gateway should survive: $out")
+        assertTrue(out.contains("192.168.1.44"), "RFC1918 interface address should survive: $out")
+    }
+}

echolot-app/core-probe/build.gradle.kts

@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+plugins {
+    // AGP 9 has built-in Kotlin — do NOT also apply kotlin.android (double-registers
+    // the `kotlin` extension). Only the serialization compiler plugin is added.
+    alias(libs.plugins.android.library)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+// Device-tier probes (Android platform APIs), emitting core-measurement Test
+// objects. Ported/adapted from the validated echolot-prober. minSdk 26 to
+// match the prober and the feasibility findings.
+android {
+    namespace = "app.echo_lot.probe"
+    compileSdk = 36
+
+    defaultConfig {
+        minSdk = 26
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+}
+
+dependencies {
+    implementation(project(":core-measurement"))
+    implementation(libs.kotlinx.serialization.json)
+    implementation(libs.kotlinx.coroutines.android)
+}

echolot-app/core-probe/src/main/kotlin/app/echo_lot/probe/CaptivePortalProbe.kt

@@ -0,0 +1,119 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.probe
+
+import android.content.Context
+import android.net.Network
+import app.echo_lot.measurement.Test
+import app.echo_lot.measurement.TestStatus
+import app.echo_lot.measurement.TestType
+import app.echo_lot.measurement.Tier
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.put
+import kotlinx.serialization.json.putJsonObject
+import java.io.IOException
+import java.net.HttpURLConnection
+import java.net.URL
+
+/**
+ * Reproduces Android's own "do I have internet / is there a captive portal?" logic
+ * (NetworkMonitor): it fetches `generate_204` endpoints and checks for **HTTP 204 No Content**.
+ *
+ * Per active network (bound via Network.openConnection):
+ *  - **HTTPS 204** (`https://www.google.com/generate_204`) → real validated internet.
+ *  - **HTTP 204** (`http://connectivitycheck.gstatic.com/generate_204`) → a plain-HTTP path with
+ *    no interference. A 3xx redirect or a 200-with-body instead of 204 is the classic **captive
+ *    portal** signature (the portal's login page); the redirect Location is captured.
+ *  - timeout/IO error on both → no working internet on that network.
+ *
+ * These are the AOSP default probe URLs (Settings.Global CAPTIVE_PORTAL_HTTPS_URL /
+ * CAPTIVE_PORTAL_HTTP_URL). Redirects are NOT followed — an unfollowed 3xx is the evidence.
+ */
+class CaptivePortalProbe(private val entries: List<NetworkInventory.Entry>) : Probe {
+    override val type = TestType.NET_CAPTIVE_PORTAL
+    override val tier = Tier.APP
+    override val estimatedMs = 9_000L // two HTTP probes per network, 4s timeouts each
+
+    private val httpsUrl = "https://www.google.com/generate_204"
+    private val httpUrl = "http://connectivitycheck.gstatic.com/generate_204"
+
+    override suspend fun run(ctx: Context, ids: ProbeIds): Test = withContext(Dispatchers.IO) {
+        val b = TestBuilder(type, tier, ids)
+        val perNet = LinkedHashMap<String, ProbeResult>()
+
+        // Default network first, then each active network explicitly.
+        perNet["default"] = validate(null)
+        for (e in entries) {
+            perNet["${e.model.transport.name.lowercase()}:${e.model.id}"] = validate(e.handle)
+        }
+
+        val evidence: JsonObject = buildJsonObject {
+            put("https_url", httpsUrl); put("http_url", httpUrl)
+            for ((label, r) in perNet) putJsonObject(label) {
+                put("https_code", r.httpsCode); put("http_code", r.httpCode)
+                r.portalLocation?.let { put("portal_location", it) }
+                put("verdict", r.verdict)
+            }
+        }
+        // Best verdict across networks: validated > portal > none.
+        val anyValidated = perNet.values.any { it.verdict == "validated" }
+        val anyPortal = perNet.values.any { it.verdict == "captive_portal" }
+        val status = when {
+            anyValidated -> TestStatus.OK
+            anyPortal -> TestStatus.PARTIAL // reachable but intercepted
+            else -> TestStatus.FAILED       // no working internet anywhere
+        }
+        b.build(status, evidence = evidence)
+    }
+
+    private data class ProbeResult(
+        val httpsCode: Int, val httpCode: Int, val portalLocation: String?, val verdict: String,
+    )
+
+    private fun validate(network: Network?): ProbeResult {
+        val https = probe(network, httpsUrl)
+        val http = probe(network, httpUrl)
+        val portalLoc = http.location.takeIf { http.code in 300..399 }
+        val verdict = when {
+            https.code == 204 -> "validated"                              // real internet
+            http.code == 204 -> "validated_http_only"                     // HTTP clean, HTTPS blocked
+            http.code in 300..399 || (http.code == 200 && http.hadBody) -> "captive_portal"
+            https.code < 0 && http.code < 0 -> "no_internet"
+            else -> "inconclusive"
+        }
+        return ProbeResult(https.code, http.code, portalLoc, verdict)
+    }
+
+    private data class Resp(val code: Int, val location: String?, val hadBody: Boolean)
+
+    /** One probe: code (-1 on failure), Location header, and whether a body was present (204 has none). */
+    private fun probe(network: Network?, urlStr: String): Resp {
+        var conn: HttpURLConnection? = null
+        return try {
+            val url = URL(urlStr)
+            conn = (network?.openConnection(url) ?: url.openConnection()) as HttpURLConnection
+            conn.instanceFollowRedirects = false // an unfollowed 3xx is the portal signal
+            conn.connectTimeout = 4000
+            conn.readTimeout = 4000
+            conn.requestMethod = "GET"
+            conn.setRequestProperty("User-Agent", "Echolot")
+            conn.setRequestProperty("Connection", "close")
+            val code = conn.responseCode
+            val loc = conn.getHeaderField("Location")
+            val body = runCatching {
+                (conn.inputStream ?: conn.errorStream)?.use { it.read() != -1 }
+            }.getOrNull() ?: false
+            Resp(code, loc, body)
+        } catch (e: IOException) {
+            Resp(-1, null, false)
+        } catch (e: Throwable) {
+            Resp(-1, null, false)
+        } finally {
+            conn?.disconnect()
+        }
+    }
+}

echolot-app/core-probe/src/main/kotlin/app/echo_lot/probe/DnsCanaryProbe.kt

@@ -0,0 +1,112 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.probe
+
+import android.content.Context
+import app.echo_lot.measurement.Test
+import app.echo_lot.measurement.TestStatus
+import app.echo_lot.measurement.TestType
+import app.echo_lot.measurement.Tier
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.put
+import kotlinx.serialization.json.putJsonObject
+import java.net.InetAddress
+
+/**
+ * dns.canary / dns.answer_integrity — resolves the server's canary zone through the network's own
+ * resolver and compares against the spec-frozen ground truth (probe-protocol.md §6.1).
+ *
+ * Two things are checked, and they detect different failures:
+ *  - **Reference records** (`ttl-5`, `many-rr`, …) have FIXED RDATA fixed by the spec, so a
+ *    mismatch means the answer was rewritten in flight (interception/filtering).
+ *  - A **per-run nonce name** `<nonce>.<session>.<zone>` can never have been cached, so it proves
+ *    the query reached the authoritative server, and the answer is derived from the nonce itself.
+ *
+ * Resolution goes through the platform resolver (InetAddress), i.e. exactly the path apps use —
+ * so interception by the network's DNS is what we measure. The server side records who actually
+ * asked (its observation API), letting the app pair "what I got" with "who asked".
+ */
+class DnsCanaryProbe(
+    private val canaryZone: String,
+    private val sessionPrefix: String,
+    private val nonce: String = java.util.UUID.randomUUID().toString().take(8),
+) : Probe {
+    override val type = TestType.DNS_CANARY
+    override val tier = Tier.APP
+    override val estimatedMs = 3_000L // five resolutions through the platform resolver
+
+    /** Frozen ground truth from probe-protocol.md §6.1 — must match the server's dns_reference.go. */
+    private val references = listOf(
+        Reference("ttl-5", "192.0.2.5"),
+        Reference("ttl-60", "192.0.2.60"),
+        Reference("ttl-3600", "192.0.2.36"),
+        Reference("ttl-86400", "192.0.2.86"),
+    )
+
+    private data class Reference(val label: String, val expectedA: String)
+
+    override suspend fun run(ctx: Context, ids: ProbeIds): Test = withContext(Dispatchers.IO) {
+        val b = TestBuilder(type, tier, ids)
+        if (canaryZone.isBlank()) {
+            return@withContext b.build(
+                TestStatus.SKIPPED,
+                evidence = buildJsonObject { put("reason", "no canary zone configured (needs a server profile)") },
+            )
+        }
+
+        var matched = 0
+        var mismatched = 0
+        var failed = 0
+
+        val evidence: JsonObject = buildJsonObject {
+            put("zone", canaryZone)
+            putJsonObject("reference_records") {
+                for (r in references) {
+                    val fqdn = "${r.label}.$canaryZone"
+                    val got = resolveA(fqdn)
+                    putJsonObject(r.label) {
+                        put("fqdn", fqdn); put("expected", r.expectedA); put("got", got ?: "")
+                        val verdict = when {
+                            got == null -> { failed++; "resolve_failed" }
+                            got == r.expectedA -> { matched++; "match" }
+                            else -> { mismatched++; "MISMATCH (answer rewritten in flight)" }
+                        }
+                        put("verdict", verdict)
+                    }
+                }
+            }
+            // Cache-miss proof: a nonce name that cannot have been pre-cached.
+            val nonceFqdn = "$nonce.$sessionPrefix.$canaryZone"
+            val nonceGot = resolveA(nonceFqdn)
+            putJsonObject("nonce_query") {
+                put("fqdn", nonceFqdn)
+                put("got", nonceGot ?: "")
+                // The server answers nonce names from 192.0.2.0/24 (deterministic per nonce).
+                val reached = nonceGot?.startsWith("192.0.2.") == true
+                put("reached_authoritative", reached)
+                put("note", "a non-192.0.2.x answer means something other than the canary server replied")
+            }
+        }
+
+        val metrics = buildJsonObject {
+            put("references_matched", matched); put("references_mismatched", mismatched)
+            put("references_failed", failed)
+        }
+        val status = when {
+            mismatched > 0 -> TestStatus.PARTIAL   // answers altered — a finding
+            matched == 0 -> TestStatus.FAILED      // nothing resolved
+            failed > 0 -> TestStatus.PARTIAL
+            else -> TestStatus.OK
+        }
+        b.build(status, evidence = evidence, metrics = metrics)
+    }
+
+    /** First IPv4 answer via the platform resolver (the path a normal app takes), or null. */
+    private fun resolveA(fqdn: String): String? = runCatching {
+        InetAddress.getAllByName(fqdn).firstOrNull { it is java.net.Inet4Address }?.hostAddress
+    }.getOrNull()
+}

echolot-app/core-probe/src/main/kotlin/app/echo_lot/probe/IcmpProbe.kt

@@ -0,0 +1,126 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.probe
+
+import android.content.Context
+import android.net.Network
+import android.system.Os
+import android.system.OsConstants
+import android.system.StructTimeval
+import app.echo_lot.measurement.Test
+import app.echo_lot.measurement.TestStatus
+import app.echo_lot.measurement.TestType
+import app.echo_lot.measurement.Tier
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.put
+import java.io.FileDescriptor
+import java.net.InetAddress
+import java.nio.ByteBuffer
+import java.util.Locale
+
+/**
+ * icmp.ping4 / icmp.ping6 via the unprivileged ICMP datagram socket, per active network
+ * (Network.bindSocket). Ported from the prober, which validated on real hardware that Android's
+ * open ping_group_range makes this work with no root — and that per-network binding turns a
+ * default-network v6 EAGAIN into topology evidence rather than a false failure.
+ */
+class IcmpProbe(
+    private val entries: List<NetworkInventory.Entry>,
+    private val v6: Boolean,
+    private val target: String = if (v6) "2606:4700:4700::1111" else "1.1.1.1",
+) : Probe {
+    override val type = if (v6) TestType.ICMP_PING6 else TestType.ICMP_PING4
+    override val tier = Tier.APP
+    // v6 on a v4-only network waits out a 3s timeout per network; v4 answers in ms.
+    override val estimatedMs = if (v6) 7_000L else 800L
+
+    override suspend fun run(ctx: Context, ids: ProbeIds): Test = withContext(Dispatchers.IO) {
+        val b = TestBuilder(type, tier, ids)
+        val perNetwork = LinkedHashMap<String, String>()
+        var anyOk = false
+        val rtts = ArrayList<Double>()
+
+        // Default network first, then each active network explicitly.
+        attempt(null).let { (ok, detail, rtt) ->
+            perNetwork["default"] = detail; if (ok) { anyOk = true; rtt?.let(rtts::add) }
+        }
+        for (e in entries) {
+            val label = "${e.model.transport.name.lowercase()}:${e.model.id}"
+            val (ok, detail, rtt) = attempt(e.handle)
+            perNetwork[label] = detail
+            if (ok) { anyOk = true; rtt?.let(rtts::add) }
+        }
+
+        val evidence: JsonObject = buildJsonObject {
+            put("target", target)
+            for ((k, v) in perNetwork) put(k, v)
+        }
+        val metrics: JsonObject = buildJsonObject {
+            put("networks_ok", rtts.size)
+            rtts.minOrNull()?.let { put("rtt_ms_min", round1(it)) }
+            if (rtts.isNotEmpty()) put("rtt_ms_avg", round1(rtts.average()))
+            rtts.maxOrNull()?.let { put("rtt_ms_max", round1(it)) }
+        }
+        val status = if (anyOk) TestStatus.OK else TestStatus.FAILED
+        b.build(status, evidence = evidence, metrics = metrics)
+    }
+
+    private data class Attempt(val ok: Boolean, val detail: String, val rttMs: Double?)
+
+    private fun attempt(network: Network?): Attempt {
+        var fd: FileDescriptor? = null
+        return try {
+            val proto = if (v6) OsConstants.IPPROTO_ICMPV6 else OsConstants.IPPROTO_ICMP
+            val family = if (v6) OsConstants.AF_INET6 else OsConstants.AF_INET
+            fd = Os.socket(family, OsConstants.SOCK_DGRAM, proto)
+            network?.bindSocket(fd)
+            Os.setsockoptTimeval(fd, OsConstants.SOL_SOCKET, OsConstants.SO_RCVTIMEO, StructTimeval.fromMillis(3000))
+            val addr = network?.getByName(target) ?: InetAddress.getByName(target)
+
+            val ident = (Os.getpid() and 0xFFFF)
+            val packet = buildEchoRequest(v6, ident.toShort(), 1)
+            val t0 = System.nanoTime()
+            Os.sendto(fd, packet, 0, packet.size, 0, addr, 0)
+            val buf = ByteBuffer.allocate(1500)
+            val received = Os.recvfrom(fd, buf, 0, null)
+            val rttMs = (System.nanoTime() - t0) / 1_000_000.0
+            val replyType = if (received > 0) buf.get(0).toInt() and 0xFF else -1
+            val ok = replyType == (if (v6) 129 else 0)
+            Attempt(ok, "reply type=$replyType rtt_ms=${"%.1f".format(Locale.ROOT, rttMs)} bytes=$received", if (ok) rttMs else null)
+        } catch (e: Throwable) {
+            Attempt(false, "error: ${e.message ?: e.javaClass.simpleName}", null)
+        } finally {
+            fd?.let { runCatching { Os.close(it) } }
+        }
+    }
+
+    private fun buildEchoRequest(v6: Boolean, ident: Short, seq: Short): ByteArray {
+        val type = if (v6) 128 else 8
+        val payload = "echolot".toByteArray()
+        val pkt = ByteBuffer.allocate(8 + payload.size)
+        pkt.put(type.toByte()); pkt.put(0); pkt.putShort(0)
+        pkt.putShort(ident); pkt.putShort(seq); pkt.put(payload)
+        val bytes = pkt.array()
+        if (!v6) {
+            val cs = checksum(bytes)
+            bytes[2] = (cs.toInt() shr 8).toByte(); bytes[3] = (cs.toInt() and 0xFF).toByte()
+        }
+        return bytes
+    }
+
+    private fun checksum(b: ByteArray): Short {
+        var sum = 0; var i = 0
+        while (i < b.size - 1) { sum += ((b[i].toInt() and 0xFF) shl 8) or (b[i + 1].toInt() and 0xFF); i += 2 }
+        if (i < b.size) sum += (b[i].toInt() and 0xFF) shl 8
+        while (sum shr 16 != 0) sum = (sum and 0xFFFF) + (sum shr 16)
+        return sum.inv().toShort()
+    }
+
+    private companion object {
+        fun round1(v: Double) = Math.round(v * 10.0) / 10.0
+    }
+}

echolot-app/core-probe/src/main/kotlin/app/echo_lot/probe/LinkSnapshotProbe.kt

@@ -0,0 +1,47 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.probe
+
+import android.content.Context
+import app.echo_lot.measurement.Test
+import app.echo_lot.measurement.TestStatus
+import app.echo_lot.measurement.TestType
+import app.echo_lot.measurement.Tier
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.put
+import kotlinx.serialization.json.putJsonArray
+import kotlinx.serialization.json.addJsonObject
+
+/**
+ * link.snapshot: records every active network's LinkProperties as evidence. The full network
+ * models also feed the document's `networks[]` (see [NetworkInventory]); this test captures the
+ * count and a compact per-network summary so the snapshot is attributable in `tests[]`.
+ */
+class LinkSnapshotProbe(private val entries: List<NetworkInventory.Entry>) : Probe {
+    override val type = TestType.LINK_SNAPSHOT
+    override val tier = Tier.APP
+    override val estimatedMs = 200L // reads LinkProperties, no I/O
+
+    override suspend fun run(ctx: Context, ids: ProbeIds): Test {
+        val b = TestBuilder(type, tier, ids)
+        val evidence: JsonObject = buildJsonObject {
+            put("network_count", entries.size)
+            putJsonArray("networks") {
+                for (e in entries) addJsonObject {
+                    put("id", e.model.id)
+                    put("transport", e.model.transport.name.lowercase())
+                    put("interface", e.model.iface ?: "")
+                    put("mtu", e.model.link.mtu ?: 0)
+                    put("addresses", e.model.link.addresses.joinToString(", ") { "${it.addr}/${it.prefixLen}" })
+                    put("dns", (e.model.link.dns?.servers ?: emptyList()).joinToString(", "))
+                    put("nat64", e.model.link.dns?.nat64Prefix ?: "none")
+                }
+            }
+        }
+        val status = if (entries.isEmpty()) TestStatus.FAILED else TestStatus.OK
+        return b.build(status, evidence = evidence)
+    }
+}

echolot-app/core-probe/src/main/kotlin/app/echo_lot/probe/NetworkInventory.kt

@@ -0,0 +1,77 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app.echo_lot.probe
+
+import android.content.Context
+import android.net.ConnectivityManager
+import android.net.LinkProperties
+import android.net.NetworkCapabilities
+import app.echo_lot.measurement.Address
+import app.echo_lot.measurement.DnsConfig
+import app.echo_lot.measurement.Link
+import app.echo_lot.measurement.Route
+import app.echo_lot.measurement.Transport
+import app.echo_lot.measurement.Network as MNetwork
+
+/**
+ * Reads the app-tier snapshot of every active Android Network into measurement `networks[]`
+ * (measurement-schema.md §4). App tier fills what LinkProperties exposes; route proto and address
+ * lifetimes are Shizuku-tier and left absent (absence = "not observed"). Ported from the prober's
+ * LinkPropertiesProbe.
+ */
+object NetworkInventory {
+
+    /** One measurement Network per active Android Network, plus the Android Network handle so
+     *  server/ICMP probes can bind to it. */
+    data class Entry(val model: MNetwork, val handle: android.net.Network)
+
+    fun snapshot(ctx: Context): List<Entry> {
+        val cm = ctx.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+        val out = ArrayList<Entry>()
+        var idx = 0
+        for (net in cm.allNetworks) {
+            val caps = cm.getNetworkCapabilities(net) ?: continue
+            val lp = cm.getLinkProperties(net) ?: continue
+            out.add(Entry(model = toModel("net-${idx}", caps, lp), handle = net))
+            idx++
+        }
+        return out
+    }
+
+    private fun toModel(id: String, caps: NetworkCapabilities, lp: LinkProperties): MNetwork {
+        val transport = when {
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> Transport.WIFI
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> Transport.CELLULAR
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> Transport.ETHERNET
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_VPN) -> Transport.VPN
+            else -> Transport.OTHER
+        }
+        val addresses = lp.linkAddresses.map {
+            Address(
+                addr = it.address.hostAddress ?: it.address.toString(),
+                prefixLen = it.prefixLength,
+                scope = null,
+            )
+        }
+        val routes = lp.routes.map {
+            Route(
+                dst = it.destination.toString(),
+                gateway = it.gateway?.hostAddress,
+                iface = it.`interface`,
+            )
+        }
+        val nat64 = runCatching { lp.nat64Prefix?.toString() }.getOrNull()
+        val dns = DnsConfig(
+            servers = lp.dnsServers.mapNotNull { it.hostAddress },
+            privateDnsMode = if (lp.isPrivateDnsActive) "strict/opportunistic" else "off",
+            privateDnsHostname = lp.privateDnsServerName,
+            searchDomains = lp.domains?.split(",")?.map { it.trim() } ?: emptyList(),
+            nat64Prefix = nat64,
+        )
+        return MNetwork(
+            id = id, transport = transport, iface = lp.interfaceName,
+            link = Link(mtu = lp.mtu.takeIf { it > 0 }, addresses = addresses, routes = routes, dns = dns),
+        )
+    }
+}