# Echolot — build status & next steps

Last updated: 2026-07-29.

## Decided
- Name **Echolot**; domain echo-lot.app; scheme `echolot://`; namespace `app.echo_lot.*`
  (hyphen→underscore; appIds/packages can't contain hyphens). Prober appId `app.echo_lot.prober`.
- Stack: native **Kotlin + Jetpack Compose**, no Flutter.
- Tiers: `app` (no root), **`shizuku` in v1** (wireless-ADB pairing), `root` future.
- **License (decided 2026-07-30):** all code **GPL-3.0-or-later**; the specs in `docs/` **CC-BY-4.0**.
  Rationale: the moat is the no-root platform research, which is trivially liftable into a
  proprietary repackage — copyleft is the only option that prevents that, and the F-Droid /
  network-engineer audience reads GPL as a trust signal rather than friction. The specs go
  permissive on purpose: a wire protocol only becomes a standard if anyone can implement it.
  **Not AGPL for the server** — the ASP loophole it closes is speculative here, while blanket
  corporate AGPL bans would hit exactly the enterprise network teams most likely to self-host.
  Sole copyright holder, so relicensing the server to AGPL later stays possible.
  Open: substitute a real legal copyright holder for "Echolot contributors" in the SPDX headers.

## Specs (in `docs/`, alongside this file)
- `feature-catalog-and-feasibility.md`, `measurement-schema.md`, `probe-protocol.md`. Considered draft-complete and reviewed by the user.

## Capability prober — DELIVERED (as zip, 2026-07-29)
Full Kotlin/Compose project scaffolded: `app.echo_lot.prober`, minSdk 26 / target+compile 35,
AGP 8.7.3, Kotlin 2.0.21, Compose BOM 2024.10, Shizuku api+provider 13.1.5, kotlinx-serialization.
Probes implemented: `link.snapshot`, `icmp.ping4/6` (unprivileged ICMP datagram), `sockopt.matrix`
(TTL/TOS/RECVERR/MTU_DISCOVER), `trace.errqueue_reachable`, `multinetwork.request_and_bind`,
`local.mdns_discover`, `peer.ble_advertise`, `shizuku.command_battery` (ip neigh / ip -6 route /
ip addr / ip monitor / dumpsys network_stack DHCP+IpClient / dumpsys wifi). JSON export via share
intent; results carry verdict + raw evidence.

Could NOT be compiled in the cloud sandbox: dl.google.com (Google Maven) and services.gradle.org
are proxy-blocked, and no device is reachable for on-device runs. Build + iterate locally
(Android Studio / Claude Code). Wrapper is pinned to Gradle 8.14.3.

## Website — `web/` (2026-07-30, LIVE at https://echo-lot.app)
Single-page site for echo-lot.app on Cloudflare Workers: static `public/` from the edge, a small
Worker for the stable short URLs (`/apk`, `/apk.sha256`, `/fdroid`, `/source`) and `/api/latest`.
Version info is resolved from the Gitea releases API at request time (edge-cached 5 min), so
tagging a release is the only publish step — the homepage shows the latest version/date/size via
progressive-enhancement JS and falls back to pre-release copy otherwise. Auto light/dark via
`prefers-color-scheme`: dark = sonar display, light = chart-recorder printout, same amber-accent
token system. Deploy: `npx wrangler deploy` from `web/`, or CI via
`.gitea/workflows/deploy-site.yml` (needs `CLOUDFLARE_API_TOKEN` + `CLOUDFLARE_ACCOUNT_ID`
secrets); full story in `web/README.md`. Branding applied (2026-07-30): real favicon/wordmark
copied into `web/public/assets/` (copies — `assets/branding/` is the source of truth), palette
switched to abyss/teal/amber with teal-as-instrument semantics, sonar-sweep hero replaced by a
Focus-lattice panel (rogue-DHCP finding vignette), tagline "measure, don't guess".

## Branding — `assets/branding/` (2026-07-30)
Identity chosen: the **Focus** mark — a quiet lattice of nodes with exactly one under examination
(amber) inside teal viewfinder brackets. Tone is surgical measurement, not scanning (sonar-sweep
visuals and the "sound out your network" tagline were explicitly rejected); tagline is
**"measure, don't guess"**. Palette: abyss `#071522`, tile `#0E2433`, instrument teal `#35E0C4`,
finding amber `#FFB454`, foam `#E8F4F2` — teal is always the instrument, the single amber point is
the finding. The wordmark is hand-drawn monoline SVG paths (zero font dependency); the second "o"
is the signature teal ring + amber ping. Assets: `icon.svg` (+ `icon.png` 512² — Gitea avatars reject SVG), `icon-adaptive-{foreground,background}.svg`
(108dp adaptive-icon layers, art inside the 66dp safe circle), `wordmark-on-{dark,light}.svg`,
`banner.svg` (1200×300, wired into the repo README), `social-preview.svg`/`.png` (1280×640, for the
Gitea/GitHub social-preview slot). The website's placeholder favicon/wordmark can now be replaced
from these.

## First device report — OnePlus 15, Android 16/SDK 36 (2026-07-30)
Archived at `echolot-prober/reports/CPH2747-android16-sdk36.json`. Collection workflow that works:
deploy over (wireless) adb, but the **user** starts the run and exports the JSON manually — probe
runs reliably kill the adb-over-wifi session (multinetwork/multicast churn the link adb rides on).

OS findings:
- `link.snapshot`, `icmp.ping4` (38 ms), `sockopt.matrix` 4/4, `peer.ble_advertise`: SUPPORTED.
- **`trace.errqueue_reachable` SUPPORTED** — full Os-API errqueue path exists on Android 16;
  the C-over-JNI shim (next-steps #2) may be unnecessary on modern devices. Still needs a real
  errqueue round-trip test, and older devices may differ.
- `icmp.ping6` EAGAIN — topology, not capability: wifi was v4-only, v6 only on cellular, socket
  used the default network. Probe should bind per-network (also covers the ping4 case properly).
- `shizuku.command_battery` SUPPORTED, shell(2000): real `ip -6 route` RA data (lifetimes,
  per-table), `ip monitor` NEIGH events, wifi dump with full DhcpResults. Vendor formats look
  parseable.
- `local.mdns_discover`: lock acquired, discovery ran, 0 services in the 4 s window — needs a
  longer window / known-good reference network before calling it more than formally SUPPORTED.

Prober bugs the run exposed (all fixed same day):
- rotation wiped results + cancelled runs → state moved to a ViewModel;
- `multinetwork.request_and_bind` ERROR → missing `CHANGE_NETWORK_STATE` in the manifest;
- `rtt_ms: "38,1"` → device locale leaked into report numbers, now `Locale.ROOT`;
- 3/7 Shizuku commands `SHIZUKU_BIND_TIMEOUT` → bind/unbind-per-command raced Shizuku; now one
  bind per battery (`execBatch`).
Run 2 (same device, fixed APK — `…-run2.json`) confirmed all three fixes:
- `multinetwork.request_and_bind` **SUPPORTED** — wifi + cellular acquired and bound concurrently
  (downKbps 39094 / 13231); requesting cellular even brought up a second, dual-stack PDN
  (`rmnet_data2`, private v4 /30 + carrier-NAT DNS) next to the IPv6-only default PDN — exactly
  the per-network behavior the production app needs.
- Shizuku battery **7/7** in 2.9 s (was 4/7 in 34 s): full ARP/NDP neighbor table, `ip addr`,
  IpClient ProvisioningConfiguration incl. SSID/BSSID and APF caps (v6000, 4096 B).
- `rtt_ms: "32.0"` — locale fix holds.
Still open (probe improvements, not blockers): ping6 should bind per-network (still EAGAIN via
v4-only default wifi); mDNS window too short to see real services (0 found on a network that has
them); `ip monitor` 2 s window caught nothing on a quiet net — consider longer/event-triggered
capture; IP_MTU read via getsockoptInt reflection unavailable — reader belongs in the errqueue
shim if that lands.

## Go server skeleton — `server/` (2026-07-30)
Pure-Go stdlib implementation of the spec's core: control plane (enroll with single-use tokens,
profile with SPKI pin, sessions with the §2.4 HKDF key schedule) + UDP data plane (ELT1 header,
HMAC gate, 1024-wide anti-replay, ECHO_RESP with observation block, TIMESYNC, §3.4
anti-amplification). Wire format covered by `go test` (roundtrip, replay/bad-HMAC/unknown-prefix
silent drops); full enroll→profile→session flow smoke-tested live. Two run modes: **container**
(autodetected via /.dockerenv etc. or `--docker`; config from `ECHOLOT_*` env; distroless image,
`network_mode: host` required — Docker NAT would falsify the observed sources the protocol
measures) and **native** (`--install-systemd`/`--uninstall-systemd`, opt-in `--self-update`
against a Gitea releases API). CI: `.gitea/workflows/build-server.yml` — tests on push;
`server-v*` tags push the image to the Gitea registry + attach linux amd64/arm64 binaries that
self-update consumes. Not yet: TCP/TLS echo, STUN, canary DNS, actions, observations API,
real admin UI, self-update signature verification.

Prober build numbering: ascending `versionCode` shown on screen + as `proberBuild` in the JSON
report; current deployed build = **3**. Bump on every deployed change.

## Build-2 reports: OnePlus 15 (A16) + Lenovo TB330FU (A15) — 2026-07-30
Archived as `…-build2.json` in `echolot-prober/reports/`. The findings:
- **`traceroute.udp4` SUPPORTED on BOTH devices** (SDK 35 + 36): 6 real hops via pure-Kotlin
  `Os.recvmsg(MSG_ERRQUEUE)` in ~250 ms, identical paths (A1 → Cloudflare). **The C-over-JNI
  errqueue shim is dead** for Android 15+; keep it in mind only if pre-15 devices matter.
- Per-network ICMP works as designed: phone ping6 = "cellular only, default has no v6 path"
  (SUPPORTED with topology evidence instead of the old bare ERROR); per-network RTTs
  (wifi 20 ms vs cellular 201 ms on v4).
- **Network finding (dogfood!): hudeWLAN advertises a v6 default route via RA but hands out no
  global v6 address** — both devices have only link-local + a ::/0 route on wifi. That's a
  half-broken IPv6 config on the LAN, exactly the class of issue the product should flag.
- mDNS: meta-query returns 0 on BOTH devices (NsdManager limitation, now confirmed twice);
  concrete `_http._tcp` finds 4 real services (3× "Magic 2 LAN", EPSON WF-7840) on both.
  Production inventory must enumerate concrete types, not trust the meta-query.
- Tablet Shizuku: binder alive, permission granted, but UserService bind timed out (0/7) —
  first-spawn dex extraction on slow storage suspected; build 3 raises the bind window to
  25 s + one retry. Phone stays 7/7 with rich neighbor/RA/DHCP evidence.
  **Build-3 verdict: not timing.** Both 25 s attempts timed out (50 s total) — the UserService
  spawn genuinely fails on the Lenovo/A15. Build 4 adds a reflection fallback to the legacy
  `Shizuku.newProcess` remote-process API when the bind fails; `exec_path` in the evidence says
  which path ran. Whatever the outcome, core-shizuku must not assume UserService works
  everywhere. (Phone build 3: still 7/7; `ip_monitor` now catches provoked NEIGH
  PROBE→REACHABLE transitions, and a mid-path router dropping one TTL round showed the "*"
  hop path works in traceroute.udp4.)

  **Build-4 verdict (`…-build4.json`): the fallback WORKS.** Tablet Shizuku now SUPPORTED via
  `exec_path: newProcess fallback` — 6/7 commands with real data (full neighbor table, per-netId
  v6 route tables, Lenovo's IpClient dump — a distinctly different format from OnePlus's, i.e.
  the per-vendor parser sample we wanted). **core-shizuku design consequence: dual-path executor
  is mandatory** — UserService where it binds, newProcess where it doesn't; both confirmed live
  on real hardware. Known rough edges: `ip monitor` times out under newProcess (subshell trick
  doesn't survive that path); the 2×25 s bind wait before falling back is worth shortening once
  a device is known-bad. Tablet UserService root cause still open — multi-user (3 users) is the
  prime suspect; Shizuku app is current (13.6.0), so the stale-app theory is dead.
- `ip_monitor` returned no events this run even with the provoked gateway ping (gateway was
  already REACHABLE, so no NEIGH transition happened). Evidence-dependent, not a bug.

## Next steps
1. Build locally, run on several physical devices (varied Android versions/vendors), collect the
   JSON reports — especially the real per-device Shizuku dump formats.
2. If `trace.errqueue_reachable` = PARTIAL, add a C-over-JNI errqueue shim (`recvmsg`+cmsg parse)
   as a `:native` module and a real `traceroute.udp4` probe.
3. Start the Go server skeleton (enrollment + profile + sessions + UDP echo with observation
   blocks + canary-DNS reference records) per probe-protocol.md.
4. Fold confirmed capabilities into the production `core-probe` / `core-shizuku` modules.