engine: downstream MTU and downstream train in the measurement document

Three facts the client cannot produce alone, kept deliberately separate:
mtu.pmtud_down (largest datagram that arrives unfragmented — meaningful only
because the server sets DF), mtu.frag_delivery (whether larger ones arrive once
fragmentation is allowed), and train.udp_downstream (loss, reordering and
arrival spacing in the download direction, which a round trip cannot separate
from upstream loss).

ServerMeasurement now runs them on the same ProbeSession as the echo train. It
had to: a fresh session restarts client-side sequence numbers and the server's
anti-replay window discards the lot, so the re-primed source is never recorded
and every granted send goes to a socket that has already closed. That produced
four confidently-wrong FAILED tests and a RED verdict on a healthy network.

Live against fmr: path MTU 1500, fragments to 4000, 100/100 downstream, GREEN.

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

web/README.md

@@ -0,0 +1,74 @@
+# Echolot website (`web/`)
+
+Minimal single-page site for [echo-lot.app](https://echo-lot.app), served from Cloudflare
+Workers. Static files in `public/` are served straight from the edge; the tiny Worker in
+`src/index.js` only runs for paths that aren't files:
+
+| Path          | Behavior                                                                 |
+| ------------- | ------------------------------------------------------------------------ |
+| `/apk`        | 302 → newest `.apk` asset of the latest Gitea release (QR-code friendly) |
+| `/apk.sha256` | 302 → the matching `.sha256` asset                                       |
+| `/api/latest` | JSON `{version, published_at, apk, sha256}` — the homepage's version readout |
+| `/fdroid`, `/source` | 302 → the URLs configured in `wrangler.jsonc` vars               |
+
+The latest release is resolved from the Gitea API **at request time** (edge-cached 5 min), so
+publishing a release — `git tag v0.2.0 && git push origin v0.2.0`, which triggers
+`.gitea/workflows/release.yml` — is the only release step. The site never needs a redeploy for
+a new version, and empty/unreachable values fall back to the homepage instead of 404ing.
+
+Light/dark follows the OS (`prefers-color-scheme`), no toggle, no JS required for it. Colors
+come from the branding palette (teal = instrument, single amber point = finding).
+
+`public/assets/` (favicon, wordmark, social preview) are **copies** of `../assets/branding/` —
+that directory is the source of truth; re-copy after any branding change.
+
+## Deploy
+
+Everything is driven by [wrangler](https://developers.cloudflare.com/workers/wrangler/), config
+in `wrangler.jsonc`. No build step, no node_modules to commit.
+
+### One-time setup
+
+1. In the Cloudflare dashboard, add **echo-lot.app** as a zone (and point the domain's
+   nameservers at Cloudflare). The `routes` in `wrangler.jsonc` use `custom_domain: true`, so
+   wrangler creates the DNS records for `echo-lot.app` and `www` automatically on first deploy —
+   the zone just has to exist in the same account.
+2. Auth, either flavor:
+   - **Interactive:** `npx wrangler login` (opens the browser once, stores an OAuth token).
+   - **API token (also what CI uses):** dashboard → My Profile → API Tokens → create from the
+     **"Edit Cloudflare Workers"** template. Then:
+
+     ```
+     $env:CLOUDFLARE_API_TOKEN  = "..."   # PowerShell; export ... on POSIX
+     $env:CLOUDFLARE_ACCOUNT_ID = "..."   # dashboard → Workers & Pages, right sidebar
+     ```
+
+### Deploy
+
+```
+cd web
+npx wrangler@4 deploy
+```
+
+That's it — uploads `src/index.js` + the `public/` assets, wires the custom domains. Useful
+extras: `npx wrangler dev` (local preview at localhost:8787), `npx wrangler tail` (live logs),
+`npx wrangler versions list`.
+
+### CI deploy (Gitea Actions)
+
+`.gitea/workflows/deploy-site.yml` runs `wrangler deploy` on every push to `main`/`master` that
+touches `web/`. It stays inert until you add two repo secrets (Settings → Actions → Secrets):
+`CLOUDFLARE_API_TOKEN` and `CLOUDFLARE_ACCOUNT_ID` (same values as above).
+
+Cloudflare's raw REST API (`PUT /accounts/:id/workers/scripts/...`) exists, but the assets
+upload needs a manifest/session dance that wrangler already implements — use wrangler even in
+automation.
+
+## Config knobs (`wrangler.jsonc` → `vars`)
+
+- `GITEA_REPO_API` — Gitea repo API base; releases must be publicly readable.
+- `DOWNLOAD_URL` — manual `/apk` fallback while Gitea is unreachable.
+- `FDROID_URL` — set when the F-Droid listing exists; until then `/fdroid` loops home.
+- `SOURCE_URL` — public source mirror for the footer + `/source`.
+
+Vars are plain (non-secret) config; change + `wrangler deploy` to apply.

web/public/assets/icon.svg

@@ -0,0 +1,24 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 96 96">
+  <defs>
+    <linearGradient id="tile" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0" stop-color="#0E2433"/>
+      <stop offset="1" stop-color="#071522"/>
+    </linearGradient>
+  </defs>
+  <rect width="96" height="96" rx="21" fill="url(#tile)"/>
+  <!-- the network, at rest -->
+  <g fill="#1E4A5C">
+    <circle cx="24" cy="24" r="2.6"/><circle cx="48" cy="24" r="2.6"/><circle cx="72" cy="24" r="2.6"/>
+    <circle cx="24" cy="48" r="2.6"/>                                <circle cx="72" cy="48" r="2.6"/>
+    <circle cx="24" cy="72" r="2.6"/><circle cx="48" cy="72" r="2.6"/><circle cx="72" cy="72" r="2.6"/>
+  </g>
+  <!-- one node, under examination -->
+  <circle cx="48" cy="48" r="8" fill="none" stroke="#FFB454" stroke-opacity="0.3" stroke-width="2"/>
+  <circle cx="48" cy="48" r="4.5" fill="#FFB454"/>
+  <g fill="none" stroke="#35E0C4" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M 33 41 V 33 H 41"/>
+    <path d="M 55 33 H 63 V 41"/>
+    <path d="M 63 55 V 63 H 55"/>
+    <path d="M 41 63 H 33 V 55"/>
+  </g>
+</svg>

web/public/assets/wordmark-on-dark.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="-10 -92 433 104">
+  <!-- "echolot" — hand-drawn monoline letterforms (no font dependency). For dark grounds. -->
+  <g fill="none" stroke="#E8F4F2" stroke-width="11" stroke-linecap="round">
+    <path d="M 0 -24 H 48"/>
+    <path d="M 48 -24 A 24 24 0 1 0 40.97 -7.03"/>
+    <path d="M 110.97 -40.97 A 24 24 0 1 0 110.97 -7.03"/>
+    <path d="M 140 -76 V 0"/>
+    <path d="M 140 -24 A 24 24 0 0 1 188 -24 L 188 0"/>
+    <circle cx="234" cy="-24" r="24"/>
+    <path d="M 280 -76 V 0"/>
+    <circle cx="326" cy="-24" r="24" stroke="#35E0C4"/>
+    <path d="M 372 -48 H 402"/>
+    <path d="M 387 -68 V 0"/>
+  </g>
+  <!-- the finding -->
+  <circle cx="326" cy="-24" r="6.5" fill="#FFB454"/>
+</svg>

web/public/assets/wordmark-on-light.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="-10 -92 433 104">
+  <!-- "echolot" — hand-drawn monoline letterforms (no font dependency). For light grounds. -->
+  <g fill="none" stroke="#1B3540" stroke-width="11" stroke-linecap="round">
+    <path d="M 0 -24 H 48"/>
+    <path d="M 48 -24 A 24 24 0 1 0 40.97 -7.03"/>
+    <path d="M 110.97 -40.97 A 24 24 0 1 0 110.97 -7.03"/>
+    <path d="M 140 -76 V 0"/>
+    <path d="M 140 -24 A 24 24 0 0 1 188 -24 L 188 0"/>
+    <circle cx="234" cy="-24" r="24"/>
+    <path d="M 280 -76 V 0"/>
+    <circle cx="326" cy="-24" r="24" stroke="#0E9384"/>
+    <path d="M 372 -48 H 402"/>
+    <path d="M 387 -68 V 0"/>
+  </g>
+  <!-- the finding -->
+  <circle cx="326" cy="-24" r="6.5" fill="#E08A1E"/>
+</svg>

web/public/index.html

@@ -5,103 +5,124 @@
 <head>
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
-<title>Echolot — depth soundings for your local network</title>
+<title>Echolot — measure, don't guess</title>
 <meta name="description" content="Free Android app for detecting and debugging local network issues: rogue DHCP, broken IPv6 RAs, MTU black holes, multicast loss, lying DNS. No root required.">
 <meta property="og:title" content="Echolot">
-<meta property="og:description" content="Depth soundings for your local network. F/OSS Android network diagnostics — no root required.">
+<meta property="og:description" content="Measure, don't guess. F/OSS Android network diagnostics — no root required.">
 <meta property="og:url" content="https://echo-lot.app/">
-<link rel="icon" href="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32'%3E%3Crect width='32' height='32' fill='%23071A29'/%3E%3Cg fill='none' stroke='%23FFB454' stroke-width='2'%3E%3Ccircle cx='16' cy='16' r='3' fill='%23FFB454' stroke='none'/%3E%3Cpath d='M16 6a10 10 0 0 1 10 10'/%3E%3Cpath d='M16 1a15 15 0 0 1 15 15' opacity='.5'/%3E%3C/g%3E%3C/svg%3E">
+<meta property="og:image" content="https://echo-lot.app/assets/social-preview.png">
+<meta name="theme-color" media="(prefers-color-scheme: dark)" content="#071522">
+<meta name="theme-color" media="(prefers-color-scheme: light)" content="#F2F6F7">
+<link rel="icon" href="/assets/icon.svg" type="image/svg+xml">
+<link rel="icon" href="/assets/icon.png" type="image/png" sizes="512x512">
+<link rel="apple-touch-icon" href="/assets/icon.png">
 <style>
+  /* Branding: teal is always the instrument (links, brackets, controls);
+     the single amber point is the finding (the focused node, the version
+     readout). Dark = the instrument's own display; light = the same tokens
+     on paper. Palette from assets/branding/. */
   :root {
-    --depth-0:  #0B2437;   /* surface */
-    --depth-1:  #092031;   /* photic */
-    --depth-2:  #071A29;   /* mid */
-    --depth-3:  #051320;   /* floor */
-    --foam:     #DCE9F1;   /* primary text */
-    --slate:    #8AA5B8;   /* secondary text */
-    --grid:     #16374E;   /* hairlines, chart grid */
-    --ping:     #FFB454;   /* the one accent: sonar amber */
-    --ok:       #7BC98F;   /* verdict green, chips only */
+    color-scheme: dark;
+    --bg-0:   #0C2130;   /* top of page */
+    --bg-1:   #071522;   /* abyss — page floor, panel ground */
+    --tile:   #0E2433;   /* raised surfaces */
+    --foam:   #E8F4F2;   /* primary text */
+    --slate:  #7DA2AC;   /* secondary text */
+    --caption:#5E8B96;   /* mono captions, from the banner */
+    --grid:   #10303F;   /* hairlines */
+    --rest:   #1E4A5C;   /* the network, at rest */
+    --teal:   #35E0C4;   /* instrument */
+    --on-teal:#04212B;   /* text on teal */
+    --amber:  #FFB454;   /* the finding */
     --mono: "Cascadia Code", "SF Mono", Consolas, "Liberation Mono", Menlo, monospace;
     --sans: "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
   }
+  @media (prefers-color-scheme: light) {
+    :root {
+      color-scheme: light;
+      --bg-0:   #F2F6F7;
+      --bg-1:   #E4ECEF;
+      --tile:   #EBF1F3;
+      --foam:   #1B3540;   /* ink, from wordmark-on-light */
+      --slate:  #47656F;
+      --caption:#5E8B96;
+      --grid:   #C4D3D8;
+      --rest:   #9FB8C1;
+      --teal:   #0E9384;   /* instrument, printable contrast */
+      --on-teal:#F5FBFA;
+      --amber:  #C77413;   /* finding ink */
+    }
+  }
   * { box-sizing: border-box; margin: 0; }
   html { scroll-behavior: smooth; }
   body {
     font-family: var(--sans);
     color: var(--foam);
-    background: linear-gradient(var(--depth-0), var(--depth-1) 30%, var(--depth-2) 65%, var(--depth-3));
+    background: linear-gradient(var(--bg-0), var(--bg-1) 70%);
+    min-height: 100vh;
     line-height: 1.6;
     -webkit-font-smoothing: antialiased;
   }
-  a { color: var(--ping); text-decoration-thickness: 1px; text-underline-offset: 3px; }
+  a { color: var(--teal); text-decoration-thickness: 1px; text-underline-offset: 3px; }
   a:hover { text-decoration-thickness: 2px; }
-  :focus-visible { outline: 2px solid var(--ping); outline-offset: 3px; border-radius: 2px; }
+  :focus-visible { outline: 2px solid var(--teal); outline-offset: 3px; border-radius: 2px; }
 
   .col { max-width: 46rem; margin: 0 auto; padding: 0 1.25rem; }
 
-  /* Depth ruler: fixed left margin scale, desktop only. Marks are set per-section
-     by scroll position purely decoratively — it is a ruler, not navigation. */
-  .ruler {
+  /* Graduated rule: the tick motif from the banner, vertical. Fixed left
+     margin, desktop only, purely decorative. */
+  .rule {
     position: fixed; top: 0; bottom: 0; left: 0; width: 3.5rem;
     border-right: 1px solid var(--grid);
-    font-family: var(--mono); font-size: .65rem; color: var(--slate);
     display: none;
   }
-  @media (min-width: 72rem) { .ruler { display: block; } }
-  .ruler span {
-    position: absolute; right: .5rem; transform: translateY(-50%);
-  }
-  .ruler span::after {
-    content: ""; position: absolute; right: -.55rem; top: 50%;
-    width: .35rem; height: 1px; background: var(--slate);
+  @media (min-width: 72rem) { .rule { display: block; } }
+  .rule::after {
+    content: ""; position: absolute; right: 0; top: 0; bottom: 0; width: .4rem;
+    background: repeating-linear-gradient(to bottom, var(--rest) 0 1.5px, transparent 1.5px 60px);
   }
 
   header.hero { padding: 4.5rem 0 3rem; }
-  .wordmark {
-    font-family: var(--mono); font-size: .8rem; letter-spacing: .35em;
-    text-transform: uppercase; color: var(--slate);
-  }
-  .wordmark b { color: var(--ping); font-weight: 600; }
+  .wordmark { display: block; height: 30px; width: auto; }
   h1 {
     font-size: clamp(1.9rem, 5vw, 3rem);
     font-weight: 650; letter-spacing: -.02em; line-height: 1.15;
-    margin: 1rem 0 .75rem; max-width: 30ch;
+    margin: 1.75rem 0 .75rem; max-width: 30ch;
   }
   .hero p.lede { color: var(--slate); max-width: 52ch; font-size: 1.05rem; }
   .hero p.lede strong { color: var(--foam); font-weight: 600; }
 
-  /* Echogram: the signature. A chart-recorder trace of ping RTTs; the sweep
-     line is the sounder, the profile is the "seabed" the echoes draw. */
-  figure.echogram {
+  /* Focus panel: the signature, straight from the mark. The network at rest,
+     one node under examination — teal brackets are the instrument, the amber
+     point is the finding. */
+  figure.focus {
     margin: 2.5rem 0 0; border: 1px solid var(--grid); border-radius: 4px;
-    background:
-      repeating-linear-gradient(to right, transparent 0 39px, var(--grid) 39px 40px),
-      repeating-linear-gradient(to bottom, transparent 0 31px, var(--grid) 31px 32px),
-      var(--depth-3);
+    background: var(--tile);
     position: relative; overflow: hidden;
   }
-  .echogram svg { display: block; width: 100%; height: auto; }
-  .echogram figcaption {
+  .focus svg { display: block; width: 100%; height: auto; }
+  .focus .rest-node { fill: var(--rest); }
+  .focus .bracket   { fill: none; stroke: var(--teal); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
+  .focus .finding   { fill: var(--amber); }
+  .focus .halo      { fill: none; stroke: var(--amber); stroke-width: 2; opacity: .3; }
+  .focus .readout   { font-family: var(--mono); font-size: 11px; fill: var(--slate); }
+  .focus .readout .flag { fill: var(--amber); }
+  .focus .lead      { stroke: var(--grid); stroke-width: 1; }
+  .focus figcaption {
     position: absolute; top: .5rem; left: .75rem;
-    font-family: var(--mono); font-size: .65rem; color: var(--slate);
+    font-family: var(--mono); font-size: .65rem; color: var(--caption);
   }
-  .sweep {
-    position: absolute; top: 0; bottom: 0; width: 1px;
-    background: var(--ping); opacity: .8;
-    box-shadow: 0 0 8px var(--ping);
-    animation: sweep 7s linear infinite;
-  }
-  @keyframes sweep { from { left: 0; } to { left: 100%; } }
+  @keyframes examine { 0%, 100% { opacity: .3; } 50% { opacity: .1; } }
+  .focus .halo { animation: examine 3.2s ease-in-out infinite; }
   @media (prefers-reduced-motion: reduce) {
-    .sweep { animation: none; left: 62%; }
+    .focus .halo { animation: none; }
     html { scroll-behavior: auto; }
   }
 
   section { padding: 3.5rem 0 0; }
   .eyebrow {
     font-family: var(--mono); font-size: .7rem; letter-spacing: .25em;
-    text-transform: uppercase; color: var(--ping);
+    text-transform: uppercase; color: var(--teal);
   }
   h2 { font-size: 1.35rem; font-weight: 650; margin: .5rem 0 1rem; letter-spacing: -.01em; }
   section > .col > p { color: var(--slate); max-width: 58ch; }
@@ -129,21 +150,26 @@
     border: 1px solid var(--grid); border-radius: 3px; padding: .35rem .6rem;
     color: var(--slate);
   }
-  .tier b { color: var(--ok); font-weight: 600; }
+  .tier b { color: var(--teal); font-weight: 600; }
 
   /* Install */
-  .buttons { display: flex; gap: .75rem; flex-wrap: wrap; margin: 1.5rem 0 1rem; }
+  .release {
+    font-family: var(--mono); font-size: .8rem; color: var(--slate);
+    margin-top: 1.25rem;
+  }
+  .release b { color: var(--amber); font-weight: 600; }
+  .buttons { display: flex; gap: .75rem; flex-wrap: wrap; margin: 1rem 0 1rem; }
   .btn {
     display: inline-block; padding: .7rem 1.3rem; border-radius: 4px;
     font-weight: 600; text-decoration: none; font-size: .95rem;
   }
-  .btn.primary { background: var(--ping); color: var(--depth-3); }
+  .btn.primary { background: var(--teal); color: var(--on-teal); }
   .btn.primary:hover { filter: brightness(1.08); }
   .btn.ghost { border: 1px solid var(--grid); color: var(--foam); }
   .btn.ghost:hover { border-color: var(--slate); }
   .note {
     font-size: .85rem; color: var(--slate);
-    border-left: 2px solid var(--ping); padding-left: .9rem; max-width: 52ch;
+    border-left: 2px solid var(--teal); padding-left: .9rem; max-width: 52ch;
   }
   .checksum { font-family: var(--mono); font-size: .75rem; color: var(--slate); margin-top: 1rem; }
 
@@ -157,45 +183,51 @@
 </head>
 <body>
 
-<div class="ruler" aria-hidden="true">
-  <span style="top:6%">0 m</span>
-  <span style="top:28%">─ 20</span>
-  <span style="top:50%">─ 40</span>
-  <span style="top:72%">─ 60</span>
-  <span style="top:94%">─ 80</span>
-</div>
+<div class="rule" aria-hidden="true"></div>
 
 <header class="hero">
   <div class="col">
-    <p class="wordmark"><b>●</b> echo·lot <span aria-hidden="true">/ˈɛçolo:t/ — echo sounder</span></p>
-    <h1>Depth soundings for your local network.</h1>
-    <p class="lede">An echo sounder maps the seabed by timing returns. <strong>Echolot</strong> does the
-    same to your network: free Android diagnostics for the layer where things actually break —
+    <picture>
+      <source srcset="/assets/wordmark-on-dark.svg" media="(prefers-color-scheme: dark)">
+      <img class="wordmark" src="/assets/wordmark-on-light.svg" alt="echolot" width="125" height="30">
+    </picture>
+    <h1>Measure, don't guess.</h1>
+    <p class="lede">Free Android diagnostics for the layer where networks actually break.
+    <strong>Echolot</strong> takes the failure you can feel and pins it to a fact you can show —
     <strong>no root required</strong>. Built for people who know what a neighbor table is.</p>
 
-    <figure class="echogram">
-      <figcaption>trace · icmp.ping4 · rtt ms ↓ / t →</figcaption>
-      <svg viewBox="0 0 720 190" role="img" aria-label="Chart-recorder style trace of ping round-trip times, drawn like a sonar seabed profile">
-        <!-- echo returns: the profile -->
-        <polyline fill="none" stroke="#FFB454" stroke-width="1.5" opacity=".9"
-          points="0,138 40,136 80,139 120,135 160,137 200,141 240,138 260,120 280,96 300,88 320,94 340,118 360,134 400,136 440,133 480,158 500,171 520,168 540,150 560,139 600,137 640,140 680,136 720,138"/>
-        <!-- second, fainter return (multipath) -->
-        <polyline fill="none" stroke="#FFB454" stroke-width="1" opacity=".25"
-          points="0,148 40,146 80,149 120,145 160,147 200,151 240,148 260,132 280,110 300,101 320,107 340,129 360,144 400,146 440,143 480,168 500,180 520,177 540,160 560,149 600,147 640,150 680,146 720,148"/>
-        <!-- dropped probes -->
-        <g fill="#8AA5B8" font-family="monospace" font-size="9">
-          <text x="497" y="30">×</text><text x="507" y="30">×</text>
-          <text x="288" y="30">▲ spike: wifi→cell handover</text>
+    <figure class="focus">
+      <figcaption>focus · dhcp.rogue_detect · tier:app</figcaption>
+      <svg viewBox="0 0 720 240" role="img" aria-label="A grid of network nodes at rest; one node is framed by viewfinder brackets, highlighted as a finding: two DHCP servers answered the same DISCOVER">
+        <!-- the network, at rest -->
+        <g class="rest-node">
+          <circle cx="120" cy="60" r="3"/><circle cx="240" cy="60" r="3"/><circle cx="360" cy="60" r="3"/><circle cx="480" cy="60" r="3"/><circle cx="600" cy="60" r="3"/>
+          <circle cx="120" cy="120" r="3"/><circle cx="480" cy="120" r="3"/><circle cx="600" cy="120" r="3"/>
+          <circle cx="120" cy="180" r="3"/><circle cx="240" cy="180" r="3"/><circle cx="360" cy="180" r="3"/><circle cx="480" cy="180" r="3"/><circle cx="600" cy="180" r="3"/>
+        </g>
+        <!-- one node, under examination -->
+        <circle class="halo" cx="240" cy="120" r="11"/>
+        <circle class="finding" cx="240" cy="120" r="5"/>
+        <g class="bracket">
+          <path d="M 222 111 V 102 H 231"/>
+          <path d="M 249 102 H 258 V 111"/>
+          <path d="M 258 129 V 138 H 249"/>
+          <path d="M 231 138 H 222 V 129"/>
+        </g>
+        <!-- the readout -->
+        <line class="lead" x1="262" y1="120" x2="296" y2="120"/>
+        <g class="readout">
+          <text x="304" y="112">DISCOVER → 2 OFFERs</text>
+          <text x="304" y="130">192.168.1.1 gw · <tspan class="flag">192.168.1.223 — who is this?</tspan></text>
         </g>
       </svg>
-      <div class="sweep" aria-hidden="true"></div>
     </figure>
   </div>
 </header>
 
 <section id="what">
   <div class="col">
-    <p class="eyebrow">What it sounds out</p>
+    <p class="eyebrow">What it measures</p>
     <h2>Signal bars lie. Timings don't.</h2>
     <p>Most wifi apps show you signal strength and call it a diagnosis. The failures that ruin
     home and office networks live deeper: a second DHCP server nobody admits to, IPv6 router
@@ -234,15 +266,16 @@
   <div class="col">
     <p class="eyebrow">Install</p>
     <h2>Get Echolot</h2>
+    <p class="release" id="release" hidden></p>
     <div class="buttons">
-      <a class="btn primary" href="/apk">Download APK</a>
+      <a class="btn primary" id="dl-btn" href="/apk">Download APK</a>
       <a class="btn ghost" href="/fdroid">F-Droid</a>
     </div>
-    <p class="note"><strong>Pre-release.</strong> The capability prober is running on real
-    hardware; the production app is under construction. These links go live with the first
-    release — until then they loop back here. No mailing list, no tracker: check back, or watch
-    the <a href="/source">repository</a>.</p>
-    <p class="checksum">releases will ship with sha256sums + a signing key you can pin</p>
+    <p class="note" id="prerelease-note"><strong>Pre-release.</strong> The capability prober is
+    running on real hardware; the production app is under construction. These links go live with
+    the first release — until then they loop back here. No mailing list, no tracker: check back,
+    or watch the <a href="/source">repository</a>.</p>
+    <p class="checksum" id="checksum">releases will ship with sha256sums + a signing key you can pin</p>
   </div>
 </section>
 
@@ -253,5 +286,41 @@
   </div>
 </footer>
 
+<script>
+// Release readout: asks this site's own Worker (/api/latest, which proxies the
+// Gitea "latest release" API, edge-cached). Progressive enhancement — with no
+// JS, no network, or no release yet, the static pre-release copy above stands.
+(async () => {
+  let rel;
+  try {
+    const res = await fetch("/api/latest");
+    if (!res.ok) return;
+    rel = await res.json();
+  } catch { return; }
+  if (!rel || !rel.available) return;
+
+  const line = document.getElementById("release");
+  const ver = document.createElement("b");
+  ver.textContent = rel.version;
+  line.append("» latest ", ver);
+  const date = (rel.published_at || "").slice(0, 10);
+  if (date) line.append(" · " + date);
+  if (rel.apk && rel.apk.size) {
+    line.append(" · " + (rel.apk.size / 1048576).toFixed(1) + " MiB");
+  }
+  line.hidden = false;
+
+  document.getElementById("prerelease-note").hidden = true;
+  if (rel.sha256) {
+    const c = document.getElementById("checksum");
+    c.textContent = "";
+    const a = document.createElement("a");
+    a.href = "/apk.sha256";
+    a.textContent = "sha256";
+    c.append(a, " · verify before you sideload");
+  }
+})();
+</script>
+
 </body>
 </html>

web/src/index.js

@@ -3,28 +3,32 @@
 
 // Everything under public/ is served straight from the edge without invoking
 // this Worker. The Worker exists for the short stable URLs (/apk, /fdroid,
-// /source) — short enough for a QR code — and to resolve "/apk" to the newest
-// release asset at request time, so tagging a release in Gitea is the only
-// publish step. No site redeploy, no URL to update.
+// /source) — short enough for a QR code — and for /api/latest, which the
+// homepage uses to show the current version. Both resolve the newest release
+// from the Gitea API at request time, so tagging a release in Gitea is the
+// only publish step. No site redeploy, no URL to update.
 
 const STATIC_ROUTES = {
   "/fdroid": "FDROID_URL",
   "/source": "SOURCE_URL",
 };
 
-// Resolve the newest APK from the Gitea "latest release" API. Cached at the
-// edge for 5 minutes so a release becomes visible quickly, while Gitea sees
-// at most one API hit per POP per 5 min regardless of download traffic.
-async function latestApkUrl(env) {
+// Fetch the Gitea "latest release" object. Cached at the edge for 5 minutes so
+// a new release becomes visible quickly, while Gitea sees at most one API hit
+// per POP per 5 min regardless of traffic. Returns null on any failure —
+// callers degrade to fallbacks rather than surfacing errors.
+async function latestRelease(env) {
   if (!env.GITEA_REPO_API) return null;
   const res = await fetch(`${env.GITEA_REPO_API}/releases/latest`, {
     headers: { Accept: "application/json", "User-Agent": "echolot-site" },
     cf: { cacheTtl: 300, cacheEverything: true },
   });
   if (!res.ok) return null;
-  const rel = await res.json();
-  const apk = rel.assets?.find((a) => a.name?.endsWith(".apk"));
-  return apk?.browser_download_url ?? null;
+  return res.json();
+}
+
+function asset(rel, suffix) {
+  return rel?.assets?.find((a) => a.name?.endsWith(suffix)) ?? null;
 }
 
 function redirect(location) {
@@ -38,21 +42,50 @@ function redirect(location) {
   });
 }
 
+function json(body, maxAge) {
+  return new Response(JSON.stringify(body), {
+    headers: {
+      "Content-Type": "application/json",
+      "Cache-Control": `public, max-age=${maxAge}`,
+    },
+  });
+}
+
 export default {
   async fetch(request, env) {
     const { pathname } = new URL(request.url);
     const path = pathname.replace(/\/$/, "");
     const fallback = new URL("/#install", request.url).toString();
 
-    if (path === "/apk" || path === "/download") {
-      // Order: live Gitea release → manual override → install section.
+    if (path === "/apk" || path === "/download" || path === "/apk.sha256") {
+      const suffix = path === "/apk.sha256" ? ".sha256" : ".apk";
       let target = null;
       try {
-        target = await latestApkUrl(env);
+        target = asset(await latestRelease(env), suffix)?.browser_download_url;
       } catch {
         // Gitea unreachable — fall through rather than 500 on a download link.
       }
-      return redirect(target || env.DOWNLOAD_URL || fallback);
+      const override = suffix === ".apk" ? env.DOWNLOAD_URL : null;
+      return redirect(target || override || fallback);
+    }
+
+    if (path === "/api/latest") {
+      let rel = null;
+      try {
+        rel = await latestRelease(env);
+      } catch {}
+      const apk = asset(rel, ".apk");
+      if (!rel || !apk) return json({ available: false }, 60);
+      return json(
+        {
+          available: true,
+          version: rel.tag_name,
+          published_at: rel.published_at,
+          apk: { name: apk.name, size: apk.size, url: apk.browser_download_url },
+          sha256: Boolean(asset(rel, ".sha256")),
+        },
+        300,
+      );
     }
 
     const varName = STATIC_ROUTES[path];

web/wrangler.jsonc

@@ -22,14 +22,14 @@
   // its route fall back to the homepage's install section, so nothing 404s
   // before the first release exists.
   "vars": {
-    // Gitea repo API base, e.g. "https://git.example.net/api/v1/repos/mram/echolot".
-    // The repo (or at least its releases) must be publicly readable.
-    "GITEA_REPO_API": "",
-    // Manual override / fallback while GITEA_REPO_API is unset or unreachable.
+    // Gitea repo API base. The repo (or at least its releases) must be
+    // publicly readable for /apk and /api/latest to resolve.
+    "GITEA_REPO_API": "https://git.rambossek.at/api/v1/repos/EchoLot/echolot",
+    // Manual override / fallback while GITEA_REPO_API is unreachable.
     "DOWNLOAD_URL": "",
     // F-Droid listing, once it exists: https://f-droid.org/packages/app.echo_lot.app/
     "FDROID_URL": "",
     // Public source URL, the footer + /source target.
-    "SOURCE_URL": ""
+    "SOURCE_URL": "https://git.rambossek.at/EchoLot/echolot"
   }
 }