One voice per listener, and the voice process stops stalling itself

Build 127. Reported from a live test: part of the translation came out in a
different voice on an Android phone, and iPhones were skipping and repeating.
Three investigations against the campus Mac's own log and transcript, one
test harness driving the voice process directly, and the answer is not what
it sounded like.

WHAT THE MACHINE DID. One voice process ran all afternoon. Every language
kept a single resident engine from its first sentence (14:54:26) to STOP
(15:23:18); 2,800 clips, 560 per language, every one filed under its own
language and spoken by its own bundle. No synthesis-side voice change was
possible with that configuration. What the log shows at the time of the
complaint instead:

  - Someone on the English stream heard the ROOM MICROPHONE for 21 s
    (15:09:10-32). English was the first button on every phone's list, forced
    there by the page whatever the operator had chosen (fixed in build 125).
  - A listener tapped Chinese at 15:11:17. The 121 MB zh model was fetched
    and unpacked THREE TIMES AT ONCE on the voice process's only thread.
    Every stream stalled for about a minute, 26 sentences were dropped across
    all five languages, and the catch-up rushed the Spanish voices to their
    +16% cap. Same voice, sounding wrong.

WHAT WAS WRONG, AND IS NOW FIXED.

The live path filed every engine as an "audition". speak() resolved the
language's default voice, which always has a bundle, and passed it as
`explicit`, so the key was 'audition:'+bundle for every ordinary sentence
while the preload warmed copies under the language name that no sentence
ever read. Five languages asked for nine engines against a cap of six; every
service's first sentence built its real engines on the spot (1.3-2 s); the
operator's voice save flushed nothing that mattered. Engines are now keyed
by bundle and shared by every language, variant and audition that uses one,
auditions take at most two slots of their own and can never evict a live
engine, and the cap is 8, sized to the largest campus from measurement
(~165 MB per engine once it has spoken, 1.3 GB for eight).

Voice installs ran on the thread that answers every sentence, and were not
de-duplicated. They now run in a worker thread (voice-install.js), one per
bundle however many ask, staged and renamed into place whole so a half-
written bundle can never pass isInstalled().

Listener rows are { code, count } and engine.js read { lang, n } in five
places, so the set of "languages someone is on" was always empty — and a late
sentence keeps speech only for those. Under load the app dropped EVERY
language's speech instead of only the unchosen ones. Late became silent.

HLS segment numbers restarted at 1 for every new stream object, under a
'max-age=60, immutable' header. A phone back from the lock screen could be
answered from its cache with the previous stream's audio under the new
number: an earlier sentence, replayed. Numbers are seeded from the clock.

In clips mode a clip still downloading when the listener switched language
landed and played in the voice they had left; the frame now carries its
language and voice and the page checks both when the bytes land. In stream
mode the old playlist stayed loaded through a switch and three things could
restart it; it is stopped, not paused. A listener's alternate voice no longer
loses a round trip to the default on the original-text toggle.

One genuine wrong-voice path, dormant today because natural voices are off on
this campus: a variant waiting on another variant's premium synthesis
inherited that variant's Piper FALLBACK, in that variant's bundle — spa_ES
received the byte-identical Mexican clip and its own voice never loaded. A
follower now shares a fallback only when it is its own voice.

An audition (the Voices card's play button) played on the system default
output, which on the campus Mac is the Dante card feeding the hardware
channels. It now plays on another output, or refuses and says why.

VERIFIED: a harness drives the voice process through the baseline, a batch
of four auditions during live sentences, a voices save mid-stream, and nine
live languages against the cache — every clip spoken by its own bundle, and
auditions of a live voice now cost 78-311 ms with nothing rebuilt.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

app/engine.js

@@ -190,9 +190,81 @@ const state = {
 
   /* health counters, reported to the operator page */
   degradedFinals: 0,         // finals that shipped with fewer languages (stale)
-  captionOnlyFinals: 0       // finals that shipped with no translations at all
+  captionOnlyFinals: 0,      // finals that shipped with no translations at all
+  captionOnlyAt: 0,          // when the last one happened
+  degradedAt: 0
 };
 
+/*
+ * THE SHAPE OF A LISTENER ROW. The server sends { code, count } — see
+ * listenerCounts() in server.js — and this file read { lang, n } in five
+ * places, so every set built from the rows was EMPTY: no language ever counted
+ * as being listened to. Mostly harmless, except in the one place it mattered.
+ * When a sentence arrives late, speech is kept only for the languages someone
+ * is actually on, and "someone is on" was never true for any of them — so
+ * under load the app dropped the speech of EVERY language, for everyone,
+ * instead of only the languages nobody had chosen. Late became silent.
+ * MEASURED on a campus Mac, 2026-10-15 15:11-15:12: 26 sentences dropped
+ * across five languages during a stall, every one of them with listeners
+ * present. Both spellings are read, so a server one build older or newer
+ * still counts.
+ */
+function rowLang(r)  { return r ? (r.code || r.lang || '') : ''; }
+function rowCount(r) { return r ? (Number(r.count != null ? r.count : r.n) || 0) : 0; }
+
+/*
+ * FOLLOW THE BOTTOM ONLY WHILE THE OPERATOR IS AT THE BOTTOM.
+ *
+ * Every one of these boxes used to end its update with
+ * `box.scrollTop = box.scrollHeight`, unconditionally. While the service is
+ * running that fires on every sentence, so scrolling back to re-read what was
+ * just said was impossible: the box yanked itself to the live edge a fraction
+ * of a second later, every time. Reported from the desk as "can't scroll on
+ * what's being said when it's live", which is exactly what it was.
+ *
+ * A box follows the live edge until the operator scrolls away from it, and
+ * starts following again when they come back to it. Nothing has to be pressed
+ * to get out, and nothing has to be pressed to get back in.
+ *
+ * The slack matters. A programmatic jump to the bottom also raises a scroll
+ * event, and it lands AT the bottom, so sticking survives its own scrolling.
+ * Sub-pixel layout and a growing last line can leave a couple of pixels
+ * behind, which with a zero threshold would unstick the box on its own output.
+ */
+/*
+ * Trimming the TOP of a box the operator is reading moves the text under
+ * their eyes — the other half of "it keeps jumping". While they are scrolled
+ * away the cap is suspended, so the lines they are looking at stay put; when
+ * they return to the live edge the backlog is trimmed in one go. The ceiling
+ * keeps a box that is left scrolled up all service from growing without end.
+ */
+function trimTop(box, cap) {
+  if (!box) return;
+  const held = box.dataset.stick === '0';
+  const limit = held ? cap * 6 : cap;
+  while (box.children.length > limit) box.removeChild(box.firstChild);
+}
+
+const STICK_SLACK_PX = 48;
+const stickWired = new WeakSet();
+
+function followBottom(box) {
+  if (!box) return;
+  if (!stickWired.has(box)) {
+    stickWired.add(box);
+    box.dataset.stick = '1';
+    box.addEventListener('scroll', () => {
+      const atBottom =
+        box.scrollHeight - box.scrollTop - box.clientHeight <= STICK_SLACK_PX;
+      box.dataset.stick = atBottom ? '1' : '0';
+    }, { passive: true });
+  }
+  /* Scrolled away: leave the view exactly where they put it. New content
+     grows BELOW the viewport, so not touching scrollTop is what holds the
+     reader's place — there is nothing else to do here. */
+  if (box.dataset.stick !== '0') box.scrollTop = box.scrollHeight;
+}
+
 // ────────────────────────────────────────────────────────── logging
 
 function log(msg, kind) {
@@ -206,8 +278,8 @@ function log(msg, kind) {
   if (kind) line.className = kind;
   line.textContent = new Date().toLocaleTimeString() + '  ' + msg;
   el.appendChild(line);
-  while (el.children.length > 200) el.removeChild(el.firstChild);
+  trimTop(el, 200);
-  el.scrollTop = el.scrollHeight;
+  followBottom(el);
 }
 
 function hero(stateName, title, body) {
@@ -891,12 +963,54 @@ async function respawnWorker(worker) {
         log('the speech model is too heavy for this machine — switching to ' +
             lighter.split('/').pop(), 'err');
       }
+      /*
+       * A LIGHTER MODEL GETS THE PREVIEW'S DTYPE, NOT THE BIG ONE'S.
+       *
+       * asrDtype is chosen for the accurate model and its weights are cached against
+       * it. Reusing it when stepping down asks for a variant that was never
+       * downloaded — and those weights live in the browser cache, with no network at
+       * a venue — so the step-down failed and the ladder could not move at all.
+       *
+       * MEASURED on a campus Mac: the cache held whisper-large-v3-turbo as
+       * encoder_model_q4f16.onnx (its asrDtype) and whisper-small as
+       * encoder_model_fp16.onnx (the preview's). Stepping down asked for
+       * whisper-small at q4f16, a file that is not there; it went to the network,
+       * failed, and logged "Unsupported model type: whisper" three times a minute
+       * for ever while the service sat dead.
+       *
+       * The preview runs whisper-small on exactly these settings every service, so
+       * they are the one combination this machine is known to be able to load.
+       */
+      const stepDtype = lighter
+        ? resolveDtype(cfg.asrFastDtype, { encoder_model: 'fp16', decoder_model_merged: 'q4' })
+        : resolveDtype(cfg.asrDtype, { encoder_model: 'fp16', decoder_model_merged: 'q4' });
       state.asrWorker = await loadWorkerWithFallback('speech', 'automatic-speech-recognition',
         state.asrModelInUse || cfg.asrModel,
-        resolveDtype(cfg.asrDtype, { encoder_model: 'fp16', decoder_model_merged: 'q4' }),
+        stepDtype,
         { encoder_model: 'q4', decoder_model_merged: 'q4' });
       log('speech model restarted' + (lighter ? ' on ' + lighter.split('/').pop() : ''), 'ok');
       state.slowRun = 0;
+      if (lighter) {
+        /*
+         * THROW AWAY THE BACKLOG THAT CAUSED THIS, AND LET THE NEW MODEL SETTLE.
+         *
+         * Swapping the model does nothing about the queue that triggered the swap.
+         * Those chunks are already past the caption-only cutoff, so they can no
+         * longer be translated in time and are worth nothing to the room — but the
+         * first of them gets handed to a model that has just loaded, takes the full
+         * worker timeout, and trips the absolute rule. MEASURED: a campus Mac fell
+         * large-v3-turbo -> small -> base in 34 seconds exactly that way, landing on
+         * a model SLOWER than the one it started from.
+         *
+         * So drop them, and refuse to step down again for a grace window, so the new
+         * model is judged on sentences it was actually given.
+         */
+        const dropped = queue.length;
+        queue.length = 0;
+        state.steppedDownAt = Date.now();
+        if (dropped) log('dropped ' + dropped + ' stale sentence' + (dropped === 1 ? '' : 's') +
+                         ' the old model never reached', 'warn');
+      }
     }
   } catch (err) {
     log('model restart failed: ' + err.message, 'err');
@@ -973,10 +1087,15 @@ function preloadNewVoices() {
   const want = state.targets.filter((l) =>
     state.spokenLanguages.indexOf(l) !== -1 && !preloadedVoices.has(l));
   if (!want.length) return;
-  want.forEach((l) => preloadedVoices.add(l));
   /* One at a time in the child anyway; cap the request so a burst of joins
-     cannot queue up a re-download marathon. */
+     cannot queue up a re-download marathon.
-  window.engineHost.ttsPreload(want.slice(0, 4));
+     Only what is SENT counts as warmed. Every wanted language used to be
+     marked and only the first four sent, so a fifth was never preloaded and
+     built its engine on its first sentence instead — por_PT, at all five
+     starts on the Mini on 2026-10-15. Six is the voice process's own cap. */
+  const batch = want.slice(0, 6);
+  batch.forEach((l) => preloadedVoices.add(l));
+  window.engineHost.ttsPreload(batch);
 }
 
 /* The translation model reports its download from the main process. */
@@ -987,7 +1106,10 @@ if (window.engineHost && window.engineHost.onTtsReady) {
     state.spokenDefaults = info.defaults || state.spokenDefaults || {};
     log('built-in voices ready — ' + state.spokenLanguages.length + ' languages', 'ok');
     /* Warm whatever people are already reading, so the first sentence of a
-       service is not the one that pays for the download. */
+       service is not the one that pays for the download. A voice process
+       that has just (re)started holds no engines, whatever this page warmed
+       in the last one — so forget that first. */
+    preloadedVoices.clear();
     preloadNewVoices();
   });
   window.engineHost.onTtsProgress((p) => log('voice ' + p.bundle + ': ' + p.status));
@@ -1681,9 +1803,9 @@ async function pumpPartial() {
      * still gets a preview.
      */
     const heard = (state.byLanguage || [])
-      .filter((r) => r && r.lang && r.lang !== state.source && (r.n || 0) > 0)
+      .filter((r) => r && rowLang(r) && rowLang(r) !== state.source && rowCount(r) > 0)
       .sort((a, b) => (b.n || 0) - (a.n || 0))
-      .map((r) => r.lang)
+      .map(rowLang)
       .filter((l) => state.targets.indexOf(l) !== -1);
     const want = (heard.length ? heard : orderedTargets()).slice(0, PARTIAL_MAX_LANGS);
     /* Never queue behind a finished sentence — a final in flight is worth more
@@ -1709,7 +1831,7 @@ async function pumpPartial() {
  */
 function orderedTargets() {
   const counts = {};
-  for (const row of state.byLanguage || []) counts[row.lang] = row.n || 1;
+  for (const row of state.byLanguage || []) counts[rowLang(row)] = rowCount(row) || 1;
   return state.targets
     .filter((t) => t !== state.source)
     .sort((a, b) => (counts[b] || 0) - (counts[a] || 0));
@@ -1849,15 +1971,33 @@ async function pump() {
       const sentences = collapseLoops(splitSentences(text));
 
       let targets = orderedTargets();
-      if (ageSec > 12) {
+      /*
+       * SKIPPING A TRANSLATION ONLY BUYS SOMETHING IF THERE IS A QUEUE TO DRAIN.
+       *
+       * Dropping the translations of stale audio is how the app catches up: the
+       * listener has moved on, so the work is wasted and the time is better spent on
+       * the sentences behind it. That reasoning needs a backlog. With nothing waiting
+       * behind it, skipping costs the room a sentence and saves nothing at all.
+       *
+       * MEASURED: a campus Mac took one 16 s stall — two Screen Sharing sessions
+       * competing for the machine — and skipped that sentence's translations with an
+       * EMPTY queue. The room lost a line of the sermon to a catch-up that had
+       * nothing to catch up on.
+       */
+      if (ageSec > 12 && queue.length > 0) {
         targets = [];
         state.captionOnlyFinals++;
-        log('audio ' + ageSec.toFixed(0) + 's stale — caption only, translations skipped', 'err');
+        state.captionOnlyAt = Date.now();
+        log('audio ' + ageSec.toFixed(0) + 's stale with ' + queue.length + ' waiting — ' +
+            'caption only, translations skipped', 'err');
+      } else if (ageSec > 12) {
+        /* Late, but nothing is behind it: say so, and translate it anyway. */
+        log('audio ' + ageSec.toFixed(0) + 's late, but nothing is queued — translating it anyway', 'warn');
       } else if (ageSec > 6) {
-        const listening = new Set((state.byLanguage || []).map((r) => r.lang));
+        const listening = new Set((state.byLanguage || []).map(rowLang));
         const before = targets.length;
         targets = targets.filter((t) => listening.has(t));
-        if (targets.length < before) state.degradedFinals++;
+        if (targets.length < before) { state.degradedFinals++; state.degradedAt = Date.now(); }
       }
 
       /* The segment's own loudness, measured once and shared by every sentence
@@ -1931,23 +2071,36 @@ async function pump() {
      * drains does not recover on its own.
      */
     /*
-     * 0.85 and a backlog of five, both measured rather than chosen.
+     * SLOWER THAN THE AUDIO IT COVERS, AND LANDING LATE.
      *
-     * The Mini's sentences ran 4.4 s against 4.5 s of audio — nominally FASTER
+     * This used to fire only past 8 s, on the reasoning that 8 s meant slower
-     * than real time, while the queue sat at 46 and the lag climbed past 150 s.
+     * than people talk. That held when a chunk could be 8 s long; chunks are
-     * Per-sentence time alone therefore misses it: the work outside this timer
+     * capped at HARD_CUT_MAX, 5.5 s, so a 4.4 s sentence is already losing and
-     * (segmenting, the preview model sharing the GPU, the scheduler) is enough
+     * never came near the old threshold.
-     * to lose on its own. The margin catches "near enough to real time to be
+     *
-     * losing"; the queue depth is the proof that it actually is, and keeps one
+     * Both numbers below were measured on a campus M4 Pro, and the second one
-     * slow sentence on a healthy machine from touching anything.
+     * only after a first attempt got it wrong. 0.85, because that Mac ran 4.4 s
+     * against 4.5 s of audio — nominally FASTER than real time while losing
+     * badly, since the work outside this timer (segmenting, the preview model
+     * sharing the GPU, the scheduler) loses on its own.
+     *
+     * The second test was a queue depth, and watching that Mac go red disproved
+     * it: the queue sat at 2-3 while the lag held at 15 s and the verdict was
+     * already red. A machine can be persistently late without ever stacking work
+     * up — it finishes each sentence just slightly too slowly, for ever. So the
+     * test is how far behind the speaker the sentence actually landed, which is
+     * what the operator is complaining about in the first place.
      */
-    const losingGround = jobAudioMs > 0 && took > jobAudioMs * 0.85 && queue.length >= 5;
+    /* A model that loaded seconds ago has not had a fair sentence yet. */
-    if (took > 8000 || losingGround) {
+    const settling = state.steppedDownAt && (Date.now() - state.steppedDownAt) < STEP_SETTLE_MS;
+    const behindMs = Date.now() - job.at;
+    const losingGround = jobAudioMs > 0 && took > jobAudioMs * 0.85 && behindMs > 8000;
+    if (!settling && (took > 8000 || losingGround)) {
       state.slowRun = (state.slowRun || 0) + 1;
       if (state.slowRun >= 3 && !respawning && lighterAsr(state.asrModelInUse || state.cfg.asrModel)) {
         state.slowRun = 0;
         log('transcription is slower than people are speaking (' + took + ' ms for ' +
-            Math.round(jobAudioMs) + ' ms of audio, ' + queue.length + ' waiting) — ' +
+            Math.round(jobAudioMs) + ' ms of audio, ' + Math.round(behindMs / 1000) + 's behind) — ' +
             'stepping down to a lighter model', 'err');
         respawnWorker(state.asrWorker);
       }
@@ -2041,7 +2194,7 @@ setInterval(() => {
 }, 30000);
 
 function translateSentence(cid, sentence, targets, gainDb, silent) {
-  const listening = new Set((state.byLanguage || []).map((r) => r.lang));
+  const listening = new Set((state.byLanguage || []).map(rowLang));
   for (const lang of targets) {
     if ((mtDepth[lang] || 0) > 6 && !listening.has(lang)) {
       state.degradedFinals++;
@@ -2396,8 +2549,8 @@ function monitorFinal(cid, text) {
   monRows.set(cid, el);
   /* Neither the map nor the box may grow for the length of a service. */
   while (monRows.size > 60) monRows.delete(monRows.keys().next().value);
-  while (box.children.length > 24) box.removeChild(box.firstChild);
+  trimTop(box, 24);
-  box.scrollTop = box.scrollHeight;
+  followBottom(box);
 }
 
 /*
@@ -2439,7 +2592,7 @@ function monitorTranslation(cid, lang, text) {
     row.classList.add('dropped');
   }
   const box = $('monitor');
-  if (box) box.scrollTop = box.scrollHeight;
+  followBottom(box);
 }
 
 /*
@@ -2459,6 +2612,11 @@ function monitorTranslation(cid, lang, text) {
  * It says it once per episode, and names both numbers so the operator can act
  * on it rather than go looking.
  */
+/* How long a freshly swapped speech model is left alone. Long enough to cover a
+   cold first inference, short enough that a genuinely hopeless model still falls
+   through the ladder within a sentence or two. */
+const STEP_SETTLE_MS = 20000;
+
 const DEAF_AFTER_MS = 90000;
 setInterval(() => {
   try {
@@ -2501,9 +2659,9 @@ function showMonitor(text, isPartial, langCount) {
     sub.textContent = langCount + ' language' + (langCount === 1 ? '' : 's') + ' · ' + state.lagMs + ' ms';
     el.appendChild(sub);
     box.appendChild(el);
-    while (box.children.length > 30) box.removeChild(box.firstChild);
+    trimTop(box, 30);
   }
-  box.scrollTop = box.scrollHeight;
+  followBottom(box);
 }
 
 // ────────────────────────────────────────────────────────── church server
@@ -2698,6 +2856,7 @@ function goLive(on) {
   state.live = on;
   if (on) {
     state.degradedFinals = 0; state.captionOnlyFinals = 0; state.fragmentFinals = 0;
+    state.captionOnlyAt = 0; state.degradedAt = 0;
     /* The watchdog measures from the start of the service, not from the last
        sentence of the previous one. */
     state.lastFinalAt = Date.now();
@@ -2772,6 +2931,10 @@ function reportStatus() {
       queue: queue.length,
       degradedFinals: state.degradedFinals,
       captionOnlyFinals: state.captionOnlyFinals,
+      /* WHEN, not just how many — the verdict needs to know whether this is
+         happening now or happened once an hour ago. */
+      captionOnlyAt: state.captionOnlyAt || 0,
+      degradedAt: state.degradedAt || 0,
       fragmentFinals: state.fragmentFinals || 0,
       cloud: state.cloudStats || null
     }
@@ -3423,14 +3586,50 @@ function shareChoice() {
   };
 }
 
-function shareBase() {
+/* This Mac on the church network. The operator page lives here and NOWHERE
+   else: it returns 404 to anything arriving through a proxy, by design. */
+function lanBase() {
   const c = shareChoice();
   if (!c || c.none) return '';
   return 'http://' + c.addr.address + ':' + state.local.port;
 }
 
+/*
+ * WHAT THE CONGREGATION OPENS.
+ *
+ * A church that has put this on a domain has said so in the operator page's
+ * Public address, and from that moment the LAN address is the wrong thing to
+ * print: it is not what is on the poster, not what the QR should encode, and
+ * not what someone off the building's wifi can reach. The app window went on
+ * showing the IP anyway, because this half of it never read that setting --
+ * the operator page honoured it and the main window did not, so the two
+ * disagreed about the one fact they both exist to display.
+ */
+function publicBaseConfigured() {
+  const u = opConfig && typeof opConfig.publicUrl === 'string' ? opConfig.publicUrl.trim() : '';
+  return u ? u.replace(/\/+$/, '') : '';
+}
+
+function shareBase() {
+  return publicBaseConfigured() || lanBase();
+}
+
 function renderQrWarning() {
   const el = $('qrWarn');
+  /*
+   * On a domain the warnings below are about an address nobody is being
+   * given any more. Saying "Wi-Fi is down, phones cannot reach the code"
+   * while the code points at a proxy would send the desk after the wrong
+   * thing entirely.
+   */
+  const pub = publicBaseConfigured();
+  if (pub) {
+    el.hidden = false;
+    el.textContent = 'The code points at ' + pub + ', set as the public address. ' +
+      'This Mac still has to be reachable from there; its own address is ' +
+      (lanBase() || 'unavailable') + '.';
+    return;
+  }
   const c = shareChoice();
   if (!c) { el.hidden = true; return; }
 
@@ -3481,6 +3680,26 @@ function renderShare() {
   const list = state.local.addresses || [];
   const box = $('addrList');
   box.textContent = '';
+  /*
+   * WHICH INTERFACE THE QR USES IS A QUESTION ONLY A LAN SETUP HAS.
+   *
+   * These rows let the operator pick the address the code points at. Once a
+   * public address is configured the code points at the domain whatever they
+   * pick, so the list is a row of numbers that do nothing — and the one
+   * marked IN USE is not the address anyone is being given. Hide it.
+   */
+  const addrBox = $('addrList');
+  addrBox.hidden = !!publicBaseConfigured();
+  if (addrBox.hidden) {
+    /* Still draw the code itself — it is the only thing left in this panel. */
+    const only = shareBase();
+    $('qr').src = only
+      ? 'http://127.0.0.1:' + state.local.port + '/qr.svg?url=' + encodeURIComponent(only + '/')
+      : '';
+    renderQrWarning();
+    renderOperatorUrl();
+    return;
+  }
 
   /* Mark the row the QR is actually using, not the row that was saved — when
      a lease moves those are two different things and the saved one is gone. */
@@ -3522,8 +3741,40 @@ $('copyAddr').addEventListener('click', () => {
     .catch((err) => log('could not copy: ' + err.message, 'err'));
 });
 
-$('openPoster').addEventListener('click', () => {
+/*
-  window.open('http://127.0.0.1:' + state.local.port + '/poster', '_blank');
+ * The QR itself, saved as a file, because the poster people actually print
+ * is made in their own design tool. The built-in poster page is still there
+ * at /poster for anyone who wants it; it is just not what this button does.
+ */
+$('saveQr').addEventListener('click', async () => {
+  const base = shareBase();
+  if (!base) { log('no address to encode yet', 'err'); return; }
+  /*
+   * Fetch the code and hand the browser a BLOB rather than linking straight at
+   * the server. This window is served from the asset port and the QR comes off
+   * the congregation port, so a plain <a download> is CROSS-ORIGIN — the
+   * download attribute is ignored and the window navigates to the image
+   * instead. With no back button, no reload item and no address bar, that
+   * strands the operator on a full-screen QR with no way out; build 123 did
+   * exactly that to a booth Mac. A blob: URL is same-origin, so it downloads.
+   */
+  const url = 'http://127.0.0.1:' + state.local.port + '/qr.svg?url=' +
+              encodeURIComponent(base + '/');
+  try {
+    const r = await fetch(url, { cache: 'no-store' });
+    if (!r.ok) throw new Error('the server answered ' + r.status);
+    const href = URL.createObjectURL(await r.blob());
+    const a = document.createElement('a');
+    a.href = href;
+    a.download = 'church-translate-qr.svg';
+    document.body.appendChild(a);
+    a.click();
+    a.remove();
+    setTimeout(() => URL.revokeObjectURL(href), 10000);
+    log('saved the QR for ' + base + '/ to Downloads', 'ok');
+  } catch (err) {
+    log('could not save the QR: ' + err.message, 'err');
+  }
 });
 $('openOperator').addEventListener('click', () => {
   window.open('http://127.0.0.1:' + state.local.port + '/operator', '_blank');
@@ -3580,7 +3831,8 @@ function renderBuildTag() {
 }
 
 function renderOperatorUrl() {
-  const base = shareBase();
+  /* Deliberately lanBase, not shareBase: over a proxy /operator is a 404. */
+  const base = lanBase();
   $('opPageUrl').textContent = base ? base + '/operator' : 'no network';
 }
 
@@ -3883,6 +4135,7 @@ async function loadOperator() {
   try {
     const j = await opApi('/api/config');
     opConfig = j.config;
+    renderShare();   /* publicUrl may have just arrived */
     clearTimeout(opLoadTimer); opLoadTimer = null;   // it answered; stop retrying
     opRetryMs = 0;
     renderOpLanguages();
@@ -3937,6 +4190,7 @@ async function opSave(patch, okMsg) {
   try {
     const j = await opApi('/api/config', { method: 'POST', body: JSON.stringify(patch) });
     opConfig = j.config;
+    renderShare();   /* publicUrl may have just arrived */
     if (okMsg) log(okMsg, 'ok');
     return j;
   } catch (e) { log('could not save: ' + e.message, 'err'); throw e; }
@@ -4414,6 +4668,40 @@ function renderVoiceList() {
   }
 }
 
+/*
+ * WHERE AN AUDITION PLAYS: never on the card that feeds the room.
+ *
+ * An <audio> element with no sink plays on the system default output, and on
+ * the production Mini that IS the Dante Virtual Soundcard (system_profiler:
+ * "Default Output Device: Yes") — the same card that carries Spanish on its
+ * third channel (outputMap spa_Latn -> [2]). So ▶ there put the sample line
+ * onto the Dante network, service or no service. The phones were never
+ * exposed: an audition comes back to this page as bytes and never becomes a
+ * clip the server can see.
+ *
+ * Which of the card's channels it reached is Chromium's mono up-mix and the
+ * Dante routing, neither of which this page controls, so it does not try to
+ * pick a "safe" channel. It plays on another output, or not at all, and says
+ * why.
+ */
+async function auditionSink() {
+  const routedId = ($('outDevice') && $('outDevice').value) || '';
+  const routedLabel = (state.cfg && state.cfg.outputDeviceLabel) || '';
+  if (!routedId && !routedLabel) return '';           // no hardware output in use
+  const strip = (l) => String(l || '').toLowerCase().replace(/^default\s*-\s*/, '').trim();
+  let outs = [];
+  try {
+    outs = (await navigator.mediaDevices.enumerateDevices()).filter((d) => d.kind === 'audiooutput');
+  } catch (_) { /* refused below rather than guessed */ }
+  const card = strip(((outs.find((d) => d.deviceId === routedId) || {}).label) || routedLabel);
+  const isCard = (d) => (!!routedId && d.deviceId === routedId) || (!!card && strip(d.label) === card);
+  const def = outs.find((d) => d.deviceId === 'default');
+  if (def && !isCard(def)) return '';                 // the system default is somewhere else
+  const other = outs.find((d) => d.deviceId !== 'default' && d.deviceId !== 'communications' && !isCard(d));
+  if (other) return other.deviceId;
+  throw new Error('the only output here is the one feeding the hardware channels — auditions stay off it');
+}
+
 async function auditionVoice(lang, v, btn, msg) {
   if (auditionBusy) return;
   auditionBusy = true;
@@ -4438,9 +4726,14 @@ async function auditionVoice(lang, v, btn, msg) {
       msg.className = 'vmsg';
     }
     if (instruct) msg.textContent = 'with your direction…';
+    /* Where it will play is settled BEFORE the voice process builds anything:
+       an audition that cannot play should cost the service nothing. */
+    const sink = await auditionSink();
     const out = await window.engineHost.ttsAudition({ lang, voice: v, instruct });
     if (!auditionAudio) auditionAudio = new Audio();
     if (!out.wav) throw new Error('that voice produced no audio');
+    if (typeof auditionAudio.setSinkId === 'function') await auditionAudio.setSinkId(sink);
+    else if (sink) throw new Error('this build cannot keep auditions off the hardware output');
     auditionAudio.src = 'data:audio/wav;base64,' + out.wav;
     /* play() rejects on autoplay policy or a decode failure; either way the
        operator needs the reason, not a silent button. */

app/index.html

@@ -433,7 +433,7 @@
       <div id="addrList" class="addrlist"></div>
       <div class="railbtns">
         <button class="btn btn-primary" id="copyAddr">Copy address</button>
-        <button class="btn" id="openPoster">Printable poster</button>
+        <button class="btn" id="saveQr">Save QR image</button>
       </div>
 
       <h3 class="subhead">Operator page</h3>

app/main.js

@@ -662,6 +662,27 @@ function createWindow() {
              : '/index.html';
   win.loadURL(assetOrigin + page);
 
+  /*
+   * NOTHING replaces the app in this window. There is no back button, no
+   * reload item and no address bar, so a window that leaves the app page is a
+   * window the operator cannot get back from — which is precisely how build
+   * 123 stranded a booth Mac on a full-screen QR image. Our own pages still
+   * open as their OWN windows through setWindowOpenHandler below; this only
+   * refuses to replace the app itself, and sends anything external to the
+   * browser where it belongs.
+   */
+  win.webContents.on('will-navigate', (e, url) => {
+    if (url === assetOrigin + page) return;     /* reloading ourselves is fine */
+    e.preventDefault();
+    console.error('[main] refused to navigate the app window to ' + url);
+    let local = false;
+    try {
+      const u = new URL(url);
+      local = (u.hostname === '127.0.0.1' || u.hostname === 'localhost');
+    } catch (_) { local = false; }
+    if (!local) shell.openExternal(url).catch(() => {});
+  });
+
   win.webContents.on('did-finish-load', () => console.log('[main] page loaded'));
   win.webContents.on('did-fail-load', (_e, code, desc, url) =>
     console.error('[main] page FAILED to load: ' + code + ' ' + desc + ' ' + url));

app/package.json

@@ -2,7 +2,7 @@
   "name": "church-translate-engine",
   "productName": "Church Translate",
   "version": "3.23.2",
-  "buildNumber": 117,
+  "buildNumber": 127,
   "private": true,
   "description": "Live sermon translation — self-contained: captures audio, transcribes, translates, and serves the congregation page itself",
   "main": "main.js",
@@ -50,6 +50,7 @@
       "vendor/ort-wasm-simd-threaded.jsep.mjs",
       "server/**/*",
       "tts-service.js",
+      "voice-install.js",
       "kokoro-sidecar.js",
       "voices.js",
       "pt-variants.js",
@@ -106,7 +107,7 @@
       ]
     },
     "asar": false,
-    "buildVersion": "117",
+    "buildVersion": "127",
     "win": {
       "target": [
         {

app/server/live-audio.js

@@ -219,7 +219,21 @@ class LanguageStream {
     this.dropTimes = [];      // when, for a "recently" view on the operator page
     this.building = [];       // frames of the segment being filled
     this.segments = [];       // { seq, body, frames }
-    this.nextSeq = 1;
+    /*
+     * SEGMENT NUMBERS MUST NEVER REPEAT, and starting at 1 made them repeat.
+     * A stream object is built when a language's first listener arrives and
+     * dropped when the last one leaves, so within one service the same
+     * language can get a fresh stream several times — and a phone that came
+     * back from the lock screen, or a second listener, asked for
+     * spa_Latn/1.aac again. The segments are served 'max-age=60, immutable',
+     * which is the right header for a segment that is never reused and the
+     * wrong one for a number that is: for up to a minute the browser answered
+     * from its cache with the PREVIOUS stream's audio under the new number —
+     * a sentence from earlier in the sermon, replayed. Numbering from the
+     * clock makes every incarnation's numbers new; HLS only asks that they
+     * increase by one within a playlist, which they still do.
+     */
+    this.nextSeq = Date.now();
     this.timer = null;
     this.lastTick = 0;
     this.carry = 0;           // fractional frames owed from the last tick

app/server/public/listen.js

@@ -163,10 +163,21 @@
   function renderFeatured() {
     var wrap = $('featured');
     wrap.textContent = '';
+    /*
+     * THE OPERATOR'S LIST IS THE LIST. This used to unshift the source
+     * language in unconditionally, on the reasoning that plenty of people want
+     * the English captions for accessibility rather than translation — which
+     * is true, and still available, but it is not this code's call to make.
+     * The operator has a switch for every language including English, and for
+     * the source language alone that switch did nothing: English was put back
+     * on every render, so a desk that had deliberately turned it off still
+     * offered it as the first button on the page. A control that silently
+     * refuses is worse than no control.
+     *
+     * Wanting English captions is now one click in Settings, in the same list
+     * as every other language, and it stays where it is put.
+     */
     var list = (app.cfg.featured || []).slice();
-    /* The source language belongs in the list too — plenty of people want the
-       English captions for accessibility, not translation. */
-    if (list.indexOf(app.cfg.sourceLanguage) === -1) list.unshift(app.cfg.sourceLanguage);
     list.forEach(function (code) {
       var b = langButton(code);
       if (b) wrap.appendChild(b);
@@ -464,6 +475,7 @@
     drift: null,
     watchdog: null,       // catches engines that stall on HLS without erroring
     everPlayed: false,    // this engine has PROVEN it can play HLS
+    clipsForVoice: false, // on clips because of an alternate voice, not because HLS failed
     // clip-fallback state
     ctx: null,
     keepAlive: null,
@@ -508,7 +520,16 @@
     /* After any interruption the player resumes where it left off and stays
        behind live forever — no error, no stall, just permanently late. Every
        one of these events is a chance to catch back up. */
-    ['playing', 'stalled', 'waiting', 'canplay', 'loadedmetadata'].forEach(function (ev) {
+    /*
+     * 'stalled' and 'waiting' are deliberately NOT in this list. A seek on a
+     * live HLS stream makes the element re-buffer, which raises exactly those
+     * two events — so seeking from them is a loop that feeds itself: seek,
+     * stall, seek, stall. On Safari, where HLS is played natively and a seek
+     * lands on a segment boundary, each turn of that loop replays or skips
+     * part of a sentence. That is the "it repeats a bit two or three times
+     * then moves on" reported from iPhones.
+     */
+    ['playing', 'canplay', 'loadedmetadata'].forEach(function (ev) {
       a.addEventListener(ev, function () { seekLive(); });
     });
 
@@ -574,9 +595,13 @@
   /* Give up on streaming and use per-sentence clips. The clip path was already
      unlocked inside the tap precisely so this is possible after the gesture has
      been spent — otherwise a browser that lies about HLS would end up silent. */
-  function fallBackToClips() {
+  function fallBackToClips(forVoice) {
     if (srv.mode === 'clips') return;
     srv.mode = 'clips';
+    /* Remember WHY. Only a page that left the stream for an alternate voice
+       returns to it when the listener goes back to the default — see
+       applyVoiceMode(). */
+    srv.clipsForVoice = !!forVoice;
     stopStream();
     if (srv.keepAlive) srv.keepAlive.play().catch(function () {});
     try { console.warn('live stream unsupported here — using per-sentence clips'); } catch (_) {}
@@ -588,8 +613,28 @@
    * and 4s of tolerance plus a 5s check interval meant real drift could reach
    * nine seconds before anyone looked.
    */
-  var DRIFT_MAX = 1.5;
+  /*
-  var DRIFT_LAND = 0.6;
+   * DRIFT_LAND WAS 0.6 S, AND ONE SEGMENT IS 0.697 S.
+   *
+   * So the target sat INSIDE the newest segment — a point the player very
+   * often did not have yet. It would be dragged up to the edge, run out of
+   * audio, stall, and the stall would trigger another correction. A phone
+   * cannot hold a position closer to live than the segments arriving.
+   *
+   * Three segments back (~2.1 s) is what HLS players choose for themselves on
+   * a live playlist, and it is the smallest target with enough buffered audio
+   * to survive one late segment. The tolerance is wider than one segment too,
+   * so an ordinary arrival wobble is not read as drift.
+   *
+   * It costs about a second and a half of extra delay. A listener a second
+   * further behind is following the service; a listener whose audio keeps
+   * jumping backwards is not.
+   */
+  var DRIFT_MAX = 3.0;
+  var DRIFT_LAND = 2.1;
+  /* A correction needs time to settle before its own result is judged. */
+  var SEEK_COOLDOWN_MS = 5000;
+  var lastSeekAt = 0;
 
   /*
    * How far behind the live edge this listener is SUPPOSED to be.
@@ -616,6 +661,11 @@
       var want = driftTarget();
       var behind = (edge - a.currentTime) - want;   // + = too late, - = too early
       if (!force && Math.abs(behind) <= DRIFT_MAX) return;
+      /* One correction at a time. Without this, timeupdate (four times a
+         second) can fire a fresh seek while the last one is still buffering,
+         and the element never gets a chance to settle anywhere. */
+      if (!force && Date.now() - lastSeekAt < SEEK_COOLDOWN_MS) return;
+      lastSeekAt = Date.now();
       /*
        * Land just BEHIND the target, never on the edge. Seeking exactly to the
        * live edge leaves no buffered audio at all, so the phone stalls on the
@@ -823,14 +873,27 @@
    */
   function applyVoiceMode() {
     if (srv.voice) {
-      fallBackToClips();
+      fallBackToClips(true);
       return;
     }
     /* Back on the default: allow streaming again. fallBackToClips latches
        mode to 'clips' and maybeStartStream refuses to act on that, so the
        latch has to be released here or the listener stays on clips for the
        rest of the service. */
-    if (srv.mode === 'clips' && hlsSupported() && srv.unlocked && srv.serverHello) {
+    /*
+     * Only when the alternate is what put us on clips. Every engine reconnect
+     * sends every listener a 'voices' frame, and an engine that cannot play
+     * HLS used to be handed back to the stream by it — eight seconds of
+     * dropped clips until the watchdog demoted it again.
+     *
+     * And silence the alternate's clips that are still scheduled. Left to
+     * play out they overlapped the shared stream as it came up: the voice
+     * the listener left and the default together, for up to the six seconds
+     * the clip queue holds.
+     */
+    if (srv.mode === 'clips' && srv.clipsForVoice && hlsSupported() && srv.unlocked && srv.serverHello) {
+      stopClips();
+      srv.clipsForVoice = false;
       srv.mode = '';
       maybeStartStream();
     }
@@ -864,22 +927,52 @@
   function switchAudioLanguage(lang) {
     stopClips();                       // the old language stops NOW, mid-word
     if (srv.mode === 'stream' && srv.el) {
-      /* Pause the old stream; the new one starts when the server's hello
+      /*
-         confirms the new language's stream exists. */
+       * STOP the old stream, do not merely pause it; the new one starts when
-      try { srv.el.pause(); } catch (_) {}
+       * the server's hello confirms the new language's stream exists.
-      if (srv.retry) { clearTimeout(srv.retry); srv.retry = null; }
+       *
+       * Paused, the element still pointed at the OLD playlist until that
+       * hello, and three things restart a paused element without asking: the
+       * 8 s watchdog's retry (startStream(srv.lang, true), and srv.lang was
+       * still the old language), coming back from a locked screen
+       * (visibilitychange plays it), and the lock-screen play button. Each
+       * put the previous language's voice back in the listener's ear.
+       * stopStream() is what the back button already does, and the hello's
+       * maybeStartStream() brings the new language up from it.
+       */
+      stopStream();
     }
     setMediaSession();
   }
 
   // ------------------------------------------------- per-clip fallback path
 
+  /*
+   * Is this clip for the language AND voice this page is on right now?
+   *
+   * Asked twice — when the clip is announced and again when its bytes land —
+   * because the fetch and the decode take a few hundred milliseconds, and
+   * stopClips() can only silence what is already scheduled, not what is still
+   * downloading. A listener who switched language in that window heard the
+   * previous language's sentence AFTER the switch; for Spanish that is one
+   * sentence of the Mexican voice in a Spaniard's ear, or the reverse. The
+   * name carries the language (p<seq>-spa_ES.aac); the server also sends lang
+   * and voice in the frame, and a frame without them is judged on the name.
+   */
+  function clipIsOurs(frame) {
+    var lang = frame.lang || (String(frame.name).match(/-([a-z]{3}_[A-Za-z]+)\.aac$/) || [])[1];
+    if (lang !== app.lang) return false;
+    if ('voice' in frame && String(frame.voice || '') !== String(srv.voice || '')) return false;
+    return true;
+  }
+
   /* Fetch, decode and schedule one clip so it follows the previous one. Only
      used where native HLS is missing. */
   function playClip(frame) {
     var name = frame && frame.name;
     if (srv.mode === 'stream') return;      // the stream already carries it
     if (!tts.on || !srv.ctx || !name) return;
+    if (!clipIsOurs(frame)) return;
 
     fetch('/audio/' + encodeURIComponent(name))
       .then(function (r) { return r.ok ? r.arrayBuffer() : Promise.reject(new Error('missing')); })
@@ -891,6 +984,8 @@
       })
       .then(function (audio) {
         if (!tts.on || !srv.ctx) return;
+        /* Landed after a switch of language, voice or mode: not ours any more. */
+        if (srv.mode === 'stream' || !clipIsOurs(frame)) return;
         var src = srv.ctx.createBufferSource();
         src.buffer = audio;
         src.connect(srv.ctx.destination);
@@ -1379,7 +1474,11 @@
         }
         /* The playlist is guaranteed to exist from this moment — the server
            creates the stream when this listener registers. */
-        maybeStartStream();
+        /* Not for a listener on an alternate: the shared stream is the
+           operator's default voice, and starting it here played that voice
+           until the server's 'voices' reply moved the page to clips. */
+        if (srv.voice) fallBackToClips(true);
+        else maybeStartStream();
         /* The picker was rendered before this socket existed, when we still had
            to assume the device's own voice. Now we know better — re-render, or
            a listener keeps staring at a voice chooser that controls nothing. */

app/server/server.js

@@ -510,6 +510,11 @@ const ENGINE_STALE_MS = 12000;
  * A campus reported "constantly behind, in the red" and the cause took an
  * afternoon to find; it was eight languages on hardware tuned against one.
  */
+/* How long a stumble keeps colouring the verdict. Long enough that a real
+   problem stays visible while someone walks to the desk, short enough that a
+   one-off does not outlive the sentence after it. */
+const TROUBLE_WINDOW_MS = 120000;
+
 function loadNote() {
   const n = activeLanguages().length;
   if (n < 2) return '';
@@ -523,10 +528,27 @@ function healthVerdict(connected, stale) {
   if (stale)                    return { level: 'red',   detail: 'The translation app has stopped responding.' };
   if (!state.live)              return { level: 'green', detail: 'Ready.' };
   if (!es.modelsReady)          return { level: 'amber', detail: 'Models are still loading.' };
-  if ((es.lagMs || 0) > 12000 || (es.captionOnlyFinals || 0) > 0)
+  /*
+   * RECENTLY, not ever.
+   *
+   * captionOnlyFinals is a running total for the whole service, and testing it
+   * for "more than zero" meant a single stale sentence pinned the desk's light
+   * red until the next restart. MEASURED: a campus Mac took one 16 s stall at
+   * 14:25 — caused by two Screen Sharing sessions competing for the machine —
+   * recovered immediately to a 421 ms lag with an empty queue, and still showed
+   * red half an hour later. An operator who looks up and sees red wants to know
+   * what is wrong NOW; a light that cannot go back to green teaches them to
+   * ignore it.
+   *
+   * So the totals still travel, for the record and for the operator page, but
+   * the verdict asks when it last happened.
+   */
+  const recentCaptionOnly = es.captionOnlyAt && (Date.now() - es.captionOnlyAt) < TROUBLE_WINDOW_MS;
+  if ((es.lagMs || 0) > 12000 || recentCaptionOnly)
     return { level: 'red',
              detail: 'Falling badly behind — some sentences are captions only.' + loadNote() };
-  if ((es.lagMs || 0) > 6000 || (es.queue || 0) >= 2 || (es.degradedFinals || 0) > 0)
+  const recentDegraded = es.degradedAt && (Date.now() - es.degradedAt) < TROUBLE_WINDOW_MS;
+  if ((es.lagMs || 0) > 6000 || (es.queue || 0) >= 2 || recentDegraded)
     return { level: 'amber',
              detail: 'Running behind — idle languages may be trimmed to catch up.' + loadNote() };
   if (es.cloud && es.cloud.parked)
@@ -1741,12 +1763,20 @@ wss.on('connection', (ws, req) => {
         if (!m.voice) row.audio[m.lang] = m.name;
 
         delayed((who) => {
-          const frame = JSON.stringify({
-            t: 'audio', id: row.id, name: m.name, seconds: m.seconds || 0
-          });
           /* Which voice this clip IS. '' is the operator's default, which is
              what a listener who never opened the chooser is on. */
           const clipVoice = String(m.voice || '');
+          /*
+           * The frame says which language and voice it carries, and the page
+           * checks both again when the clip's bytes land (clipIsOurs() in
+           * listen.js). The routing below is decided at SEND time; a listener
+           * who switches language or voice while a clip is still downloading
+           * would otherwise hear it after the switch, in the voice they left.
+           */
+          const frame = JSON.stringify({
+            t: 'audio', id: row.id, name: m.name, seconds: m.seconds || 0,
+            lang: m.lang, voice: clipVoice
+          });
           for (const [ws, meta] of state.listeners) {
             if (ws.readyState !== 1) continue;
             if (!who(meta)) continue;
@@ -2032,14 +2062,22 @@ wss.on('connection', (ws, req) => {
     if (m.t === 'lang') {
       const meta = state.listeners.get(ws);
       if (!meta) return;
-      meta.lang = String(m.lang || config.sourceLanguage);
+      const next = String(m.lang || config.sourceLanguage);
       /*
        * A voice belongs to a language. Carrying a Spanish speaker across to
        * Portuguese would ask the engine for a voice that language does not
        * have, so switching language always returns the listener to the
        * default and hands them the new language's options.
+       *
+       * Only a CHANGE of language, though. The page re-sends the language it
+       * is already on to have its captions re-rendered (the original-text
+       * toggle does exactly that), and resetting the voice there put a
+       * listener on an alternate back on the default for a round trip —
+       * until the page re-asserted its pick, they were sent the default
+       * voice's clips: one voice, then the other, then theirs again.
        */
-      meta.voice = '';
+      if (next !== meta.lang) meta.voice = '';
+      meta.lang = next;
       pushLanguagesToEngine();
       /*
        * builtInVoice MUST be here, not just on the first hello. The page does
@@ -2051,7 +2089,7 @@ wss.on('connection', (ws, req) => {
        */
       send(ws, { t: 'hello', live: state.live, lang: meta.lang, serviceName: config.serviceName, build: BUILD,
                  builtInVoice: Voices.hasVoice(meta.lang),
-                 voiceOptions: voiceOptionsFor(meta.lang), voice: '',
+                 voiceOptions: voiceOptionsFor(meta.lang), voice: meta.voice || '',
                  scrollback: scrollbackFor(meta.lang, meta.proxied) });
       broadcastOperators();
     }

app/tts-service.js

@@ -42,9 +42,6 @@ let VOICE_DIR = process.platform === 'win32'
   : path.join(os.homedir(), 'Library/Application Support/Church Translate Voices');
 let CLIP_DIR = path.join(os.tmpdir(), 'church-translate-audio');
 
-/* Loaded engines, one per language. Kept small: each costs ~330-400 MB of ONNX
-   arena regardless of the 63 MB model, so we do not hold voices nobody is
-   listening to. */
 /* What each voice says when auditioned — a real line of scripture, so the
    operator hears the voice on the material it will actually read. */
 const SAMPLE_TEXT = {
@@ -65,8 +62,25 @@ const SAMPLE_TEXT = {
   hat_Latn: 'Senyè a se gadò mwen, mwen p ap manke anyen.'
 };
 
-const loaded = new Map();
+/*
-const MAX_LOADED = 6;
+ * Loaded engines, ONE PER BUNDLE, shared by every language, variant and
+ * audition that speaks with it. Kept bounded, not small: MEASURED on an M2
+ * Max, an engine costs ~75 MB at construction and ~165 MB once it has spoken
+ * (8 engines, 1.3 GB after one sentence each), not the 330-400 MB this used
+ * to assume. The cap is sized to the largest campus — eight languages — so a
+ * live engine is never evicted to make room for another live one in normal
+ * service; below the cap an eviction means a reload of ~0.3-0.5 s on this
+ * process's only thread, in front of the next sentence, every time.
+ *
+ * `live` marks an engine a sentence or the preload asked for. Auditions keep
+ * to MAX_AUDITION slots of their own, always go first, and can never push a
+ * live engine out: with every slot speaking, an auditioned voice is built,
+ * played once and dropped. See engineFor() for why this is keyed by bundle.
+ */
+const loaded = new Map();          // 'bundle/model' -> { tts, usedAt, live }
+const installing = new Map();      // bundle -> Promise: one download, however many ask
+const MAX_LOADED = 8;
+const MAX_AUDITION = 2;
 
 /*
  * The operator's per-language voice choices, made by ear in the Voices
@@ -142,81 +156,120 @@ function isInstalled(v) {
  * 359 files, same total bytes — and it is now the same code on both platforms.
  */
 function installVoice(v) {
+  /*
+   * OFF THIS THREAD. The fetch, the bzip2 and the unpack all ran here, on the
+   * voice process's only thread, from inside engineFor() — so the first
+   * sentence of a language whose voice was not installed yet stalled every
+   * OTHER language's sentences for as long as the install took. MEASURED on a
+   * campus Mac, 2026-10-15 15:11: a listener tapped Chinese, the 121 MB zh
+   * model was fetched and unpacked three times at once on this thread, every
+   * stream stalled, 26 sentences were dropped and the catch-up rushed the
+   * Spanish voices to their +16% cap. The work now happens in a worker thread
+   * (voice-install.js); this thread only relays its progress and keeps
+   * speaking. The worker unpacks into a staging folder and renames it into
+   * place whole, so isInstalled() never sees a half-written bundle.
+   */
   return new Promise((resolve, reject) => {
-    fs.mkdirSync(VOICE_DIR, { recursive: true });
+    const fail = (why) => reject(new Error('could not install ' + v.bundle + ': ' + why));
-    const url = voices.bundleUrl(v.bundle);
-
     reply({ type: 'voiceProgress', bundle: v.bundle, status: 'downloading' });
-
+    let w;
-    (async () => {
+    try {
-      const res = await fetch(url, { redirect: 'follow' });
+      const { Worker } = require('worker_threads');
-      if (!res.ok) throw new Error('HTTP ' + res.status);
+      w = new Worker(path.join(__dirname, 'voice-install.js'), {
-      const body = Buffer.from(await res.arrayBuffer());
+        workerData: { url: voices.bundleUrl(v.bundle), voiceDir: VOICE_DIR, bundle: v.bundle }
-      /* A proxy or a captive portal returns an HTML error page with HTTP 200;
-         the bzip2 magic is the cheapest way to notice before unpacking it. */
-      if (body.length < 1024 || body.toString('latin1', 0, 3) !== 'BZh') {
-        throw new Error('that download was not a voice bundle');
-      }
-      reply({ type: 'voiceProgress', bundle: v.bundle, status: 'installing' });
-
-      const bunzip = require('unbzip2-stream');
-      const tar = require('tar-stream');
-      const { Readable } = require('stream');
-
-      await new Promise((res2, rej2) => {
-        const extract = tar.extract();
-        extract.on('entry', (header, stream, next) => {
-          /* Never write outside VOICE_DIR, whatever the archive claims. */
-          const dest = path.resolve(VOICE_DIR, header.name);
-          if (dest !== VOICE_DIR && !dest.startsWith(VOICE_DIR + path.sep)) {
-            stream.resume(); return next();
-          }
-          if (header.type === 'directory') {
-            fs.mkdirSync(dest, { recursive: true });
-            stream.resume(); return next();
-          }
-          fs.mkdirSync(path.dirname(dest), { recursive: true });
-          stream.pipe(fs.createWriteStream(dest)).on('finish', next).on('error', rej2);
       });
-        extract.on('finish', res2);
+    } catch (e) { return fail(e.message); }
-        extract.on('error', rej2);
+    let settled = false;
-        Readable.from(body).pipe(bunzip()).on('error', rej2).pipe(extract);
+    const done = (err) => { if (settled) return; settled = true; err ? fail(err) : resolve(); };
+    w.on('message', (m) => {
+      if (!m || !m.status) return;
+      if (m.status === 'error') { done(m.message || 'the installer failed'); return; }
+      reply({ type: 'voiceProgress', bundle: v.bundle, status: m.status });
+      if (m.status === 'ready') done();
     });
-
+    w.on('error', (e) => done((e && e.message) || String(e)));
-      reply({ type: 'voiceProgress', bundle: v.bundle, status: 'ready' });
+    w.on('exit', (code) => { if (!settled) done('the installer exited (' + code + ')'); });
-    })().then(resolve, (err) => reject(new Error('could not install ' + v.bundle + ': ' + err.message)));
   });
 }
 
-async function engineFor(lang, explicit) {
+/*
-  /* Auditions key the cache by bundle so trying five voices for one language
+ * The engine for one voice, built at most once however many ask for it.
-     does not evict the voice that language is actually using. */
+ *
-  const v = explicit || builtinVoiceFor(lang);
+ * KEYED BY BUNDLE — and the old keying is what put batches of four
-  const key = explicit ? "audition:" + v.bundle : lang;
+ * "audition:" loads in the production log with nobody at the Voices card.
-  if (loaded.has(key)) {
+ * Engines were keyed two ways: by language ('spa_Latn') for the preload, and
-    const e = loaded.get(key);
+ * 'audition:<bundle>' whenever a voice was passed in, which speak() did for
+ * EVERY ordinary sentence because the resolved default always has a bundle.
+ * So the live path was filed as an audition, every bundle was built at least
+ * twice (five languages asked for nine engines against a cap of six), the
+ * preload warmed copies no sentence ever read, and the first sentence of
+ * every service built the real ones on the spot. MEASURED on the Mini,
+ * 2026-10-15: the 14:26 service's first sentence was said at 14:54:26.291
+ * and its four engines were ready at 26.995, 27.309, 27.833 and 28.344 —
+ * ~0.3-0.5 s each on this process's only thread — while what got evicted
+ * was the startup preload's unused copies.
+ *
+ * The engine's config is a function of the bundle alone (voices.ttsConfig;
+ * speed, gain and sid are applied per sentence), so sharing is exact:
+ * spa_Latn and spa_MX read one es_MX-ald engine, and auditioning a voice that
+ * is already speaking reads the live engine instead of building a second.
+ */
+async function engineFor(v, live, who) {
+  if (!v || !v.bundle) throw new Error('no built-in voice' + (who ? ' for ' + who : ''));
+  const key = v.bundle + '/' + (v.model || '');
+
+  /*
+   * One download per bundle. A language joining mid-service is asked for by
+   * the preload AND by its first sentences at once, and each used to fetch
+   * and unpack the whole bundle itself — MEASURED on the Mini: pt_BR-jeff
+   * three times between 11:39:05 and 11:39:50, zh-ll three times between
+   * 15:11:17 and 15:12:16, two 'voice timed out' each time. The unpack is staged and
+   * renamed into place whole (voice-install.js), so isInstalled() stays false
+   * until the bundle is complete — but a second asker must still wait on the
+   * first install, not start its own.
+   */
+  if (!loaded.has(key) && (installing.has(v.bundle) || !isInstalled(v))) {
+    if (!installing.has(v.bundle)) {
+      installing.set(v.bundle, installVoice(v).finally(() => installing.delete(v.bundle)));
+    }
+    await installing.get(v.bundle);
+  }
+
+  /* Looked up again: whoever finished waiting first has built it. Nothing can
+     interleave from here to the set — construction is synchronous. */
+  let e = loaded.get(key);
+  if (!e) {
+    if (!sherpa) sherpa = require('sherpa-onnx-node');
+    e = { tts: new sherpa.OfflineTts(voices.ttsConfig(voicePath(v), v)), usedAt: 0, live: !!live };
+    if (makeRoom(!!live)) loaded.set(key, e);
+    log('voice ready: ' + v.bundle + (who ? ' for ' + who : '') +
+        (live ? '' : loaded.get(key) === e ? ' (audition)' : ' (audition, not kept: every slot is speaking)'));
+  }
   e.usedAt = Date.now();
+  /* An audition never demotes a live engine; a sentence promotes an auditioned one. */
+  if (live) e.live = true;
   return e.tts;
 }
 
-  if (!v) throw new Error('no built-in voice for ' + lang);
+/*
-  if (!isInstalled(v)) await installVoice(v);
+ * Room for one more engine, or false when an audition should not take one.
-
+ * Least recently used goes first, as before — auditioned engines before live
-  if (!sherpa) sherpa = require('sherpa-onnx-node');
+ * ones, and a live engine only ever gives way to another live one.
-
+ */
-  const dir = voicePath(v);
+function makeRoom(live) {
-  const tts = new sherpa.OfflineTts(voices.ttsConfig(dir, v));
+  const stalest = (wantLive) => {
-
+    let k = null;
-  /* Evict the least recently used rather than growing without bound. */
+    for (const [key, x] of loaded) if (x.live === wantLive && (!k || x.usedAt < loaded.get(k).usedAt)) k = key;
-  if (loaded.size >= MAX_LOADED) {
+    return k;
-    let oldest = null;
+  };
-    for (const [k, e] of loaded) if (!oldest || e.usedAt < loaded.get(oldest).usedAt) oldest = k;
+  const evict = (k) => { log('evicted voice ' + k + (loaded.get(k).live ? '' : ' (audition)')); loaded.delete(k); };
-    if (oldest) { loaded.delete(oldest); log('evicted voice ' + oldest); }
+  const auditions = Array.from(loaded.values()).filter((x) => !x.live).length;
-  }
+  if (!live && auditions >= MAX_AUDITION) evict(stalest(false));
-
+  if (loaded.size < MAX_LOADED) return true;
-  loaded.set(key, { tts, usedAt: Date.now() });
+  const k = stalest(false) || (live ? stalest(true) : null);
-  log('voice ready: ' + key + ' (' + v.bundle + ')');
+  if (!k) return false;
-  return tts;
+  evict(k);
+  return true;
 }
 
 // ------------------------------------------------------------- cloud voices
@@ -928,6 +981,9 @@ async function speak(job) {
     text, Math.round((Number(job.gainDb) || 0) * 2) / 2, pinRate
   ].join('\u0001');
 
+  /* Set when the leader's result was a Piper fallback in ANOTHER variant's
+     voice — this job then speaks its own fallback, straight to Piper. */
+  let piperOnly = false;
   if (key) {
     const hit = synthCache.get(key);
     if (hit) {
@@ -941,8 +997,23 @@ async function speak(job) {
              counted as one; the key is deleted below so the NEXT utterance
              tries the natural voice again. */
           if (premiumPick && done.source !== premiumPick.provider) { cloudStats.fallback++; fallbackAt = Date.now(); }
+          /*
+           * ...but only a fallback in THIS language's own Piper voice. The key
+           * names the PREMIUM voice, and spa_Latn, spa_ES and spa_MX share it
+           * (KOKORO_LANG maps all three to 'e', both Portugueses to 'p'). Their
+           * Piper fallbacks they do not share: spa_ES falls back to davefx,
+           * spa_Latn to ald, por_PT to miro, por_Latn to jeff. Cloning the
+           * leader's fallback put the Mexican voice in the Castilian stream for
+           * that sentence — measured in a harness against this file: spa_ES's
+           * clip was the byte-identical ald file and davefx never even loaded.
+           * So the follower still skips the sidecar that just missed (the
+           * variants still switch together), but in its own voice.
+           */
+          if (done.source !== 'piper' || done.bundle === (voice.bundle || '')) {
             return cloneClip(done, job.lang, started);
           }
+          piperOnly = true;
+        }
       } catch (_) { /* the first caller failed — make our own */ }
     }
   }
@@ -956,7 +1027,7 @@ async function speak(job) {
      * alternate skips the premium path entirely — otherwise cloudSynth would
      * fall back to the operator's own pick and the page would lie.
      */
-    const cloudOut = (alt && alt.engine === 'builtin')
+    const cloudOut = (piperOnly || (alt && alt.engine === 'builtin'))
       ? null
       : await cloudSynth(job.lang, text, (alt && alt.engine !== 'builtin') ? alt : null, { speed: kokoroSpeed, deadline });
     if (cloudOut) {
@@ -984,13 +1055,16 @@ async function speak(job) {
         source: cloudOut.provider
       };
     }
-    if (!(alt && alt.engine === 'builtin') && cloudVoiceFor(job.lang)) {
+    /* A piperOnly job's fallback was already counted at the cache hit. */
+    if (!piperOnly && !(alt && alt.engine === 'builtin') && cloudVoiceFor(job.lang)) {
       cloudStats.fallback++;
       fallbackAt = Date.now();
       if (cloudStats.fallback === 1 || cloudStats.fallback % 10 === 0) pushStats('fallback');
     }
 
-    const tts = await engineFor(job.lang, voice.bundle ? voice : null);
+    /* Live: a sentence is speaking with this voice, so no audition may take
+       its engine. A listener's built-in alternate counts — someone is on it. */
+    const tts = await engineFor(voice.bundle ? voice : null, true, job.lang);
     if (!sherpa) sherpa = require('sherpa-onnx-node');
 
     /*
@@ -1067,6 +1141,9 @@ async function speak(job) {
     const seconds = secs;
     return {
       source: 'piper',
+      /* WHICH Piper voice spoke it. A follower may share a fallback only when
+         it is its own voice — see the cache hit above. */
+      bundle: voice.bundle || '',
       /* What the sentence ended on — the stream gives a full stop a full breath
          and a mid-thought fragment only a beat. */
       terminal: text.slice(-1),
@@ -1080,8 +1157,12 @@ async function speak(job) {
     };
   };
 
+  /* A piperOnly job is a fallback by construction. It must not stand in the
+     cache as a leader, or the next identical line would inherit the miss
+     without trying the natural voice — the chorus case below. */
+  const cacheKey = piperOnly ? null : key;
   const promise = produce();
-  if (key) synthCache.set(key, { promise, at: Date.now() });
+  if (cacheKey) synthCache.set(cacheKey, { promise, at: Date.now() });
   try {
     const out = await promise;
     /*
@@ -1091,10 +1172,10 @@ async function speak(job) {
      * miss would have re-created the very voice switch this file exists to
      * prevent (measured in the harness before shipping, not after).
      */
-    if (key && premiumPick && out && out.source !== premiumPick.provider) synthCache.delete(key);
+    if (cacheKey && premiumPick && out && out.source !== premiumPick.provider) synthCache.delete(cacheKey);
     return out;
   } catch (e) {
-    if (key) synthCache.delete(key);
+    if (cacheKey) synthCache.delete(cacheKey);
     throw e;
   }
 }
@@ -1187,11 +1268,15 @@ process.on('message', async (msg) => {
     if (msg.type === 'voices') {
       /* The operator changed a per-language voice choice. */
       voiceChoice = msg.choices || {};
-      /* Drop cached engines for languages whose choice changed, so the next
+      /*
-         sentence uses the new voice rather than the one already resident. */
+       * Nothing to drop. Engines are keyed by bundle, so a changed choice
-      for (const k of Array.from(loaded.keys())) {
+       * resolves to a different engine on the next sentence by itself, and
-        if (!String(k).startsWith("audition:")) loaded.delete(k);
+       * the one it replaced ages out like any other. The loop that was here
-      }
+       * only ever deleted the preload's per-language copies (the live path was
+       * filed under 'audition:'); under bundle keys it would delete the live
+       * engines too, and every "Use it" would make the next sentence rebuild
+       * every language's voice.
+       */
       reply({ type: 'voicesOk', count: Object.keys(voiceChoice).length });
       return;
     }
@@ -1222,7 +1307,9 @@ process.on('message', async (msg) => {
         } finally { voiceChoice = saved; }
       } else {
         if (!sherpa) sherpa = require('sherpa-onnx-node');
-        const tts = await engineFor(msg.lang, spec.bundle ? spec : null);
+        /* Not live: shares the engine when this voice is already speaking,
+           otherwise takes an audition slot — never a live one. */
+        const tts = await engineFor(spec.bundle ? spec : builtinVoiceFor(msg.lang), false, 'audition');
         const audio = tts.generate({ text, sid: spec.sid || 0, speed: spec.speed || 1.0 });
         if (spec.gain && spec.gain !== 1) {
           for (let i = 0; i < audio.samples.length; i++) {
@@ -1256,7 +1343,9 @@ process.on('message', async (msg) => {
       /* Warm the languages people are actually listening to, so the first
          sentence of a service is not the one that pays for the download. */
       for (const lang of msg.langs || []) {
-        try { await engineFor(lang); } catch (e) { log('preload failed for ' + lang + ': ' + e.message); }
+        /* Keyed exactly as speak() keys it, so this warms the engine the first
+           sentence will read, not a copy beside it. */
+        try { await engineFor(builtinVoiceFor(lang), true, lang); } catch (e) { log('preload failed for ' + lang + ': ' + e.message); }
       }
       reply({ type: 'preloaded', langs: msg.langs || [] });
       return;

app/voice-install.js

@@ -0,0 +1,78 @@
+/*
+ * voice-install.js — download and unpack ONE voice bundle, in a worker thread.
+ *
+ * This work used to run on the voice process's own event loop, from inside
+ * engineFor(), the moment a sentence arrived for a language whose voice was
+ * not installed. MEASURED on a campus Mac, 2026-10-15 15:11: a listener tapped
+ * Chinese, three parallel downloads and unpacks of the 121 MB zh model ran at
+ * once on the thread that has to answer every sentence, every other language
+ * stalled for about a minute, 26 sentences were dropped, and the catch-up
+ * pushed the Spanish voices to their +16% rush cap — reported from the pews
+ * as the voice "changing". bzip2 in pure JS is CPU work; it has no business on
+ * that thread.
+ *
+ * So the whole fetch-check-unpack now happens here, off the loop, and
+ * tts-service.js de-duplicates it per bundle. The archive is unpacked into a
+ * staging folder and renamed into place only when complete, so a half-written
+ * bundle can never pass isInstalled() and be handed to sherpa.
+ */
+'use strict';
+const { parentPort, workerData } = require('worker_threads');
+const fs = require('fs');
+const path = require('path');
+
+const { url, voiceDir, bundle } = workerData;
+
+(async () => {
+  fs.mkdirSync(voiceDir, { recursive: true });
+  const res = await fetch(url, { redirect: 'follow' });
+  if (!res.ok) throw new Error('HTTP ' + res.status);
+  const body = Buffer.from(await res.arrayBuffer());
+  /* A proxy or a captive portal returns an HTML error page with HTTP 200;
+     the bzip2 magic is the cheapest way to notice before unpacking it. */
+  if (body.length < 1024 || body.toString('latin1', 0, 3) !== 'BZh') {
+    throw new Error('that download was not a voice bundle');
+  }
+  parentPort.postMessage({ status: 'installing' });
+
+  const bunzip = require('unbzip2-stream');
+  const tar = require('tar-stream');
+  const { Readable } = require('stream');
+
+  const staging = path.join(voiceDir, '.installing-' + bundle + '-' + process.pid);
+  fs.rmSync(staging, { recursive: true, force: true });
+  fs.mkdirSync(staging, { recursive: true });
+
+  await new Promise((resolve, reject) => {
+    const extract = tar.extract();
+    extract.on('entry', (header, stream, next) => {
+      /* Never write outside the staging folder, whatever the archive claims. */
+      const dest = path.resolve(staging, header.name);
+      if (dest !== staging && !dest.startsWith(staging + path.sep)) {
+        stream.resume(); return next();
+      }
+      if (header.type === 'directory') {
+        fs.mkdirSync(dest, { recursive: true });
+        stream.resume(); return next();
+      }
+      fs.mkdirSync(path.dirname(dest), { recursive: true });
+      stream.pipe(fs.createWriteStream(dest)).on('finish', next).on('error', reject);
+    });
+    extract.on('finish', resolve);
+    extract.on('error', reject);
+    Readable.from(body).pipe(bunzip()).on('error', reject).pipe(extract);
+  });
+
+  /* The archive's top-level folder is the bundle name — that is what
+     voicePath() opens. Swap it into place in one rename. */
+  const unpacked = path.join(staging, bundle);
+  if (!fs.existsSync(unpacked)) throw new Error('the archive did not contain ' + bundle);
+  const final = path.join(voiceDir, bundle);
+  fs.rmSync(final, { recursive: true, force: true });
+  fs.renameSync(unpacked, final);
+  fs.rmSync(staging, { recursive: true, force: true });
+
+  parentPort.postMessage({ status: 'ready' });
+})().catch((err) => {
+  parentPort.postMessage({ status: 'error', message: (err && err.message) || String(err) });
+});

docs/PUBLIC-ACCESS.md

@@ -57,16 +57,45 @@ For a second campus, repeat with its own name — `translate-north`,
 
 ---
 
-## The other way: your existing nginx proxy
+## The other way: a name on your existing reverse proxy
 
-You already run a reverse proxy at `10.1.1.4` fronting `check.watersmedia.org`,
+You already run a reverse proxy on the NAS at `10.1.1.4` (Boba-Fett, Synology
-with split-horizon DNS. It can front this too, though it means the traffic goes
+DSM) fronting `check.watersmedia.org`. It can front this too, though it means
-through the NAS network to reach the booth Mac.
+the traffic goes through the NAS network to reach the booth Mac.
 
-Add a DNS record for `translate.watersmedia.org` — public to your WAN address,
+This is what North Attleboro runs as of 2026-10-15, in the **LAN-only** form:
-internal to `10.1.1.4` — and a server block. Copy the one that already serves
+`http://translate.watersmedia.org` works on the building's WiFi at both the
-the checklist app, change the name, and point it at the **booth Mac**, not the
+Apollo Beach and North Attleboro sites and nowhere else. Nothing was opened to
-NAS:
+the WAN. The pieces, with the exact scripts and a step-by-step runbook under
+[`examples/waters-church-na/`](examples/waters-church-na/README.md):
+
+| Piece | Where | What |
+| --- | --- | --- |
+| Local DNS | UniFi consoles at AB and NA (Settings → Policy Table → DNS) | A record `translate.watersmedia.org` → `10.1.1.4`, TTL 300, created with `unifi-dns-record.py` and a per-console Network API key |
+| Proxy rule | DSM → Control Panel → Login Portal → Advanced → Reverse Proxy | HTTP `translate.watersmedia.org:80` → HTTP `10.1.7.39:3100`, WebSocket headers, `X-Forwarded-Host: $http_host`, read timeout 3600 s |
+| HTTPS | `/usr/local/etc/nginx/sites-enabled/translate-redirect.conf` on the NAS | `https://` answers a 301 to `http://`; the name has no certificate, so browsers warn before the redirect |
+
+Both NAS pieces come from `boba-fett-translate-proxy.sh`, run as
+`ssh -t boba-fett sudo bash translate-proxy.sh` because DSM's reverse-proxy API
+is root-only. Going through DSM rather than a hand-edited nginx file means the
+rule shows up in the DSM UI and survives DSM updates. DSM adds `Host`,
+`X-Real-IP`, `X-Forwarded-For` and `X-Forwarded-Proto` on its own.
+
+Then: Operator page → **Public address** → `http://translate.watersmedia.org`
+(no trailing slash), so the QR code and poster use the name instead of the
+IP and port.
+
+To let people off-site use the same name later: add a public DNS record for
+`translate.watersmedia.org` pointing at the NA WAN address, get a certificate
+in DSM (Control Panel → Security → Certificate → Let's Encrypt), replace the
+redirect with an HTTPS rule to the same destination, and switch Public address
+to `https://`. The app behaves the same either way, including the `/operator`
+404 through a proxy.
+
+### If the proxy is plain nginx instead of DSM
+
+DSM writes most of this for you. On a hand-managed nginx the server block
+needs all of it:
 
 ```nginx
 server {
@@ -77,7 +106,7 @@ server {
     ssl_certificate_key /path/to/privkey.pem;
 
     location / {
-        proxy_pass http://10.6.3.222:3100;      # the booth Mac
+        proxy_pass http://10.1.7.39:3100;      # the booth Mac
 
         proxy_set_header Host              $host;
         proxy_set_header X-Real-IP         $remote_addr;
@@ -95,21 +124,36 @@ server {
         # the room reconnects at once.
         proxy_read_timeout  3600s;
         proxy_send_timeout  3600s;
+
+        # Live audio: do not hold HLS segments back.
+        proxy_buffering off;
     }
 }
 ```
 
-This has one real drawback the tunnel does not: the booth Mac needs a fixed
+Either way the booth Mac needs a fixed address or a DHCP reservation, or the
-address on the network, or the proxy breaks the next time DHCP moves it.
+proxy breaks the next time DHCP moves it.
 
 ---
 
 ## Checking it worked
 
 ```bash
-curl -s https://translate.watersmedia.org/healthz
+curl -s http://translate.watersmedia.org/healthz      # https:// once published
 ```
 
-Should return `{"ok":true,…}`. Then open the page on a phone **with WiFi turned
+Should return `{"ok":true,…}`, the same as `curl -s http://10.1.7.39:3100/healthz`.
-off** — that is the real test. If the page loads but captions never appear, the
+A proxy that passes the WebSocket answers `HTTP/1.1 101 Switching Protocols` to:
-WebSocket headers are missing.
+
+```bash
+curl -si -N -H 'Connection: Upgrade' -H 'Upgrade: websocket' \
+  -H 'Sec-WebSocket-Version: 13' -H 'Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==' \
+  http://translate.watersmedia.org/ws | head -1
+```
+
+Then open the page on a phone: for the LAN-only setup on the guest WiFi, for a
+published one **with WiFi turned off**. That is the real test. If the page loads
+but captions never appear, the WebSocket headers are missing. If phones on
+guest WiFi cannot connect at all, look at client isolation on that network
+before anything else. `/operator` returning 404 through the proxy is by design;
+staff use `http://10.1.7.39:3100/operator` on the LAN.

docs/examples/waters-church-na/README.md

@@ -0,0 +1,93 @@
+# translate.watersmedia.org — local DNS and reverse proxy
+
+Puts the Church Translate congregation page on a church hostname inside the
+Apollo Beach and North Attleboro networks. LAN only, plain HTTP, no WAN access.
+The app's own requirements are in [PUBLIC-ACCESS.md](../../PUBLIC-ACCESS.md). This
+was done on 2026-10-15 against app 3.23.2 build 121.
+
+| What | Value |
+| --- | --- |
+| App host | Translate Mac, North Attleboro LAN `10.1.7.39` |
+| App port | TCP 3100, plain HTTP + WebSocket on `/ws` (the only port to expose) |
+| Reverse proxy | Boba-Fett (Synology DSM 7.0.1), `10.1.1.4`, `ssh boba-fett` (port 202, user Michael) |
+| Hostname | `translate.watersmedia.org` |
+| Local DNS | A record on the AB and NA UDM Pro consoles → `10.1.1.4`, TTL 300 |
+| HTTPS | no certificate; `https://translate.watersmedia.org` answers 301 to `http://` |
+
+`curl -s http://10.1.7.39:3100/healthz` should return `{"ok":true,"live":true,...}`
+before anything below is tested.
+
+## 1. Local DNS on UniFi (AB and NA) — done 2026-10-15
+
+Each console has its own Network API key saved as
+`~/.config/unifi/<site>-network-api-key` (created in Settings → Control Plane →
+Integrations → Create API Key; all five sites are saved on Michael's Mac). The
+record was created with:
+
+```bash
+python3 docs/examples/waters-church-na/unifi-dns-record.py translate.watersmedia.org 10.1.1.4 --sites apollo-beach,north-attleboro
+```
+
+Resulting policy ids: AB `379f868d-a956-4ec1-acef-13557153ff3f`, NA
+`16bf7109-ec68-41f9-9c16-fa6a62471430`. Both gateways answer `10.1.1.4`.
+`--list` shows every DNS policy per console; `--dry-run` previews.
+
+Why Boba-Fett and not the Mac: the proxy owns the hostname so the port never
+appears in the URL, and AB clients reach `10.1.1.4` over the site-to-site link
+exactly as they already do for `chronicles-na.waterschurch.org`.
+
+## 2. Reverse proxy on Boba-Fett — done 2026-10-15
+
+[boba-fett-translate-proxy.sh](boba-fett-translate-proxy.sh) does the whole
+job and is idempotent. It was run on 2026-10-15; afterwards `/healthz`,
+`/api/languages`, the `/ws` upgrade (101) and the HTTPS 301 all checked out
+from both the AB and NA LANs, and `/operator` returned 404 as designed. A copy lives at `~/translate-proxy.sh` on Boba-Fett
+(Michael's home). DSM's reverse-proxy API and nginx reload both need root, and
+sudo there asks for Michael's password, so run it interactively:
+
+```bash
+ssh -t boba-fett sudo bash translate-proxy.sh
+```
+
+What it creates:
+
+| Piece | Where | Content |
+| --- | --- | --- |
+| DSM reverse proxy rule | Control Panel → Login Portal → Advanced → Reverse Proxy, "translate.watersmedia.org" | HTTP `translate.watersmedia.org:80` → HTTP `10.1.7.39:3100`; custom headers `Upgrade: $http_upgrade`, `Connection: $connection_upgrade` (WebSocket), `X-Forwarded-Host: $http_host`; read timeout 3600 s; HTTP/1.1 |
+| HTTPS redirect | `/usr/local/etc/nginx/sites-enabled/translate-redirect.conf` | `server { listen 443 ssl; server_name translate.watersmedia.org; return 301 http://translate.watersmedia.org$request_uri; }` |
+
+DSM already sends `Host`, `X-Real-IP`, `X-Forwarded-For` and
+`X-Forwarded-Proto` on every rule. The whole host lands on `/`, which the app
+requires. `/operator` returning 404 through the proxy is intended; staff use
+`http://10.1.7.39:3100/operator` on the LAN.
+
+To undo: delete the rule in the DSM Reverse Proxy list, remove the redirect
+file, and `sudo synosystemctl reload nginx`.
+
+Known limits:
+
+- The HTTPS redirect only runs after a TLS handshake with Boba-Fett's default
+  certificate, so a browser shows a certificate warning first. A trusted
+  certificate for this name would need DNS-01 validation against the
+  watersmedia.org zone (cPanel), which is not set up.
+- DSM's reverse proxy cannot turn `proxy_buffering` off. HLS segments under
+  `/live/` are small discrete files and the WebSocket is a tunnel after upgrade,
+  so the effect is minor; if audio lag is reported, that is the first thing to
+  revisit with a hand-written nginx include.
+
+## 3. After the proxy answers
+
+1. On the NA LAN open `http://10.1.7.39:3100/operator`, enter the operator PIN,
+   and set **Public address** to `http://translate.watersmedia.org` (no trailing
+   slash). Otherwise the QR code and poster keep advertising `10.1.7.39:3100`.
+2. Verify from a machine at AB and one at NA:
+
+```bash
+curl -s http://translate.watersmedia.org/healthz
+```
+
+   It must return the same JSON as the direct `10.1.7.39:3100` check.
+3. Open the page on a phone on guest wifi and confirm captions appear
+   (WebSocket) and spoken audio plays (`/live/`). If phones cannot connect at
+   all, look at client isolation on the guest network and the guest → `10.1.1.4`
+   firewall rule before anything else.

docs/examples/waters-church-na/boba-fett-translate-proxy.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+# translate.watersmedia.org on Boba-Fett (Synology DSM 7.0.1).
+#
+# 1. Creates the DSM reverse-proxy rule  http://translate.watersmedia.org:80
+#    -> http://10.1.7.39:3100 (Church Translate) with WebSocket headers,
+#    X-Forwarded-Host, and a 3600 s read timeout, through DSM's own API so it
+#    shows up in Control Panel -> Login Portal -> Advanced -> Reverse Proxy.
+# 2. Adds an nginx server block that answers https://translate.watersmedia.org
+#    with a 301 to the http:// address (the name is LAN-only and has no
+#    certificate, so browsers warn before the redirect; that is expected).
+# 3. Tests the nginx config, reloads it, and prints a local check.
+#
+# Idempotent: re-running skips the rule if it exists and rewrites the redirect.
+# Run on Boba-Fett as root:   sudo bash ~/translate-proxy.sh
+set -euo pipefail
+
+NAME=translate.watersmedia.org
+BACKEND_IP=10.1.7.39
+BACKEND_PORT=3100
+RP_JSON=/usr/syno/etc/www/ReverseProxy.json
+REDIRECT_CONF=/usr/local/etc/nginx/sites-enabled/translate-redirect.conf
+
+if [ "$(id -u)" != 0 ]; then
+  echo "Run with sudo: sudo bash $0" >&2
+  exit 1
+fi
+
+echo "== 1. DSM reverse proxy rule for $NAME"
+if grep -q "\"fqdn\" : \"$NAME\"" "$RP_JSON"; then
+  echo "   rule already present in $RP_JSON, skipping create"
+else
+  # $http_upgrade etc. are nginx variables and must reach DSM literally.
+  ENTRY='{"description":"translate.watersmedia.org","frontend":{"acl":null,"fqdn":"translate.watersmedia.org","https":{"hsts":false},"port":80,"protocol":0},"backend":{"fqdn":"10.1.7.39","port":3100,"protocol":0},"customize_headers":[{"name":"Upgrade","value":"$http_upgrade"},{"name":"Connection","value":"$connection_upgrade"},{"name":"X-Forwarded-Host","value":"$http_host"}],"proxy_connect_timeout":60,"proxy_read_timeout":3600,"proxy_send_timeout":60,"proxy_http_version":1,"proxy_intercept_errors":false}'
+  OUT=$(/usr/syno/bin/synowebapi --exec api=SYNO.Core.AppPortal.ReverseProxy method=create version=1 entry="$ENTRY" 2>&1 || true)
+  echo "   $OUT"
+  if ! echo "$OUT" | grep -q '"success" *: *true'; then
+    echo "   synowebapi did not report success; stopping before the redirect." >&2
+    exit 1
+  fi
+fi
+
+echo "== 2. HTTPS -> HTTP redirect block"
+cat > "$REDIRECT_CONF" <<'EOF'
+# translate.watersmedia.org is served over plain HTTP on the LAN (no certificate).
+# Anyone who types https:// is sent to the http:// address. Added 2026-10-15.
+server {
+    listen 443 ssl;
+    server_name translate.watersmedia.org;
+    return 301 http://translate.watersmedia.org$request_uri;
+}
+EOF
+echo "   wrote $REDIRECT_CONF"
+
+echo "== 3. nginx test + reload"
+/usr/bin/nginx -t
+/usr/syno/bin/synosystemctl reload nginx 2>/dev/null || /usr/bin/nginx -s reload
+echo "   reloaded"
+
+echo "== 4. Local checks from Boba-Fett"
+echo -n "   http  /healthz : "
+curl -s -m 5 --resolve "$NAME:80:127.0.0.1" "http://$NAME/healthz"; echo
+echo -n "   https /        : "
+curl -sk -m 5 -o /dev/null -w '%{http_code} -> %{redirect_url}\n' --resolve "$NAME:443:127.0.0.1" "https://$NAME/"
+echo "done"

docs/examples/waters-church-na/unifi-dns-record.py

@@ -0,0 +1,211 @@
+#!/usr/bin/env python3
+"""Create or update a local DNS A record on every Waters Church UniFi console.
+
+Usage:
+    docs/examples/waters-church-na/unifi-dns-record.py repo.watersmedia.org 10.3.8.90
+    docs/examples/waters-church-na/unifi-dns-record.py repo.watersmedia.org 10.3.8.90 --sites apollo-beach,norwood
+    docs/examples/waters-church-na/unifi-dns-record.py repo.watersmedia.org 10.3.8.90 --dry-run
+    docs/examples/waters-church-na/unifi-dns-record.py --list                # show every DNS policy per site
+
+Each console needs its own Network API key (Site Manager keys from api.ui.com are
+rejected locally). Create one per console in the UniFi UI:
+    Settings -> Control Plane -> Integrations -> Create API Key
+and save it, one line, mode 600, as:
+    ~/.config/unifi/<site>-network-api-key
+where <site> is one of the names in SITES below.
+
+The script talks to the console's Network Integration API
+(/proxy/network/integration/v1/sites/{siteId}/dns/policies) over the LAN /
+site-to-site links, so it must run from inside the church network. Gateways use
+self-signed certificates, so certificate verification is disabled for them.
+Keys are read from disk and sent only in the X-API-KEY header; they are never
+printed.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import shutil
+import ssl
+import subprocess
+import sys
+import urllib.error
+import urllib.parse
+import urllib.request
+
+# Console name -> gateway LAN address (UDM Pro at each site, 2026-10).
+SITES = {
+    "apollo-beach": "10.3.0.1",
+    "north-attleboro": "10.1.0.1",
+    "woonsocket": "10.2.0.1",
+    "norwood": "10.4.0.1",
+    "southcoast": "10.5.0.1",
+}
+
+KEY_DIR = os.path.expanduser("~/.config/unifi")
+TIMEOUT = 15
+
+
+class ApiError(RuntimeError):
+    pass
+
+
+class Console:
+    def __init__(self, name: str, gateway: str):
+        self.name = name
+        self.gateway = gateway
+        self.base = f"https://{gateway}/proxy/network/integration/v1"
+        self.key_path = os.path.join(KEY_DIR, f"{name}-network-api-key")
+        self.key = self._load_key()
+        self.ctx = ssl.create_default_context()
+        self.ctx.check_hostname = False
+        self.ctx.verify_mode = ssl.CERT_NONE
+
+    def _load_key(self) -> str | None:
+        try:
+            with open(self.key_path) as fh:
+                key = fh.read().strip()
+        except FileNotFoundError:
+            return None
+        return key or None
+
+    def request(self, method: str, path: str, body: dict | None = None, query: dict | None = None):
+        url = self.base + path
+        if query:
+            url += "?" + urllib.parse.urlencode(query)
+        data = json.dumps(body).encode() if body is not None else None
+        req = urllib.request.Request(url, data=data, method=method)
+        req.add_header("X-API-KEY", self.key or "")
+        req.add_header("Accept", "application/json")
+        if data is not None:
+            req.add_header("Content-Type", "application/json")
+        try:
+            with urllib.request.urlopen(req, timeout=TIMEOUT, context=self.ctx) as resp:
+                raw = resp.read()
+                return json.loads(raw) if raw else None
+        except urllib.error.HTTPError as e:
+            detail = e.read().decode(errors="replace")[:300]
+            raise ApiError(f"{method} {path} -> HTTP {e.code}: {detail}") from None
+        except (urllib.error.URLError, TimeoutError, OSError) as e:
+            raise ApiError(f"{method} {path} -> {e}") from None
+
+    def site_id(self) -> str:
+        sites = self.request("GET", "/sites").get("data", [])
+        if not sites:
+            raise ApiError("console reports no sites")
+        for s in sites:
+            if s.get("internalReference") == "default" or s.get("name") == "default":
+                return s["id"]
+        return sites[0]["id"]
+
+    def dns_policies(self, site_id: str) -> list[dict]:
+        out: list[dict] = []
+        offset, limit = 0, 100
+        while True:
+            page = self.request("GET", f"/sites/{site_id}/dns/policies", query={"offset": offset, "limit": limit})
+            data = page.get("data", [])
+            out.extend(data)
+            total = page.get("totalCount")
+            offset += len(data)
+            if not data or (total is not None and offset >= total) or len(data) < limit:
+                return out
+
+    def ensure_a_record(self, site_id: str, fqdn: str, ipv4: str, ttl: int | None, dry_run: bool) -> str:
+        existing = [p for p in self.dns_policies(site_id) if p.get("domain", "").lower() == fqdn.lower()]
+        a_records = [p for p in existing if p.get("type") == "A_RECORD"]
+        other = [p for p in existing if p.get("type") != "A_RECORD"]
+        if other:
+            kinds = ", ".join(sorted({p.get("type", "?") for p in other}))
+            return f"SKIPPED: {fqdn} already has a non-A policy here ({kinds}); fix by hand"
+        if len(a_records) > 1:
+            return f"SKIPPED: {len(a_records)} A records already exist for {fqdn}; fix by hand"
+
+        body = {"type": "A_RECORD", "enabled": True, "domain": fqdn, "ipv4Address": ipv4}
+        if ttl:
+            body["ttlSeconds"] = ttl
+
+        if a_records:
+            cur = a_records[0]
+            same = cur.get("ipv4Address") == ipv4 and cur.get("enabled", True) and (ttl is None or cur.get("ttlSeconds") == ttl)
+            if same:
+                return f"unchanged: {fqdn} -> {ipv4} already present (id {cur.get('id')})"
+            if dry_run:
+                return f"would UPDATE {fqdn}: {cur.get('ipv4Address')} -> {ipv4} (id {cur.get('id')})"
+            self.request("PUT", f"/sites/{site_id}/dns/policies/{cur['id']}", body=body)
+            return f"UPDATED {fqdn}: {cur.get('ipv4Address')} -> {ipv4}"
+
+        if dry_run:
+            return f"would CREATE {fqdn} -> {ipv4}"
+        created = self.request("POST", f"/sites/{site_id}/dns/policies", body=body)
+        return f"CREATED {fqdn} -> {ipv4} (id {created.get('id') if isinstance(created, dict) else '?'})"
+
+
+def resolve_via(gateway: str, fqdn: str) -> str:
+    """Ask the gateway's resolver directly; returns the answer or a short status."""
+    dig = shutil.which("dig")
+    if not dig:
+        return "(dig not installed)"
+    try:
+        res = subprocess.run([dig, "+short", "+time=3", "+tries=1", f"@{gateway}", fqdn, "A"],
+                             capture_output=True, text=True, timeout=10)
+    except subprocess.TimeoutExpired:
+        return "(timeout)"
+    answer = res.stdout.strip().replace("\n", " ")
+    return answer or "(no answer)"
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
+    ap.add_argument("fqdn", nargs="?", help="host name, e.g. repo.watersmedia.org")
+    ap.add_argument("ipv4", nargs="?", help="IPv4 address the name should resolve to")
+    ap.add_argument("--sites", default=",".join(SITES), help="comma-separated subset of: " + ", ".join(SITES))
+    ap.add_argument("--ttl", type=int, default=300, help="TTL in seconds (default 300; the API rejects a null TTL)")
+    ap.add_argument("--dry-run", action="store_true", help="show what would change without writing")
+    ap.add_argument("--list", action="store_true", help="print every DNS policy on each console and exit")
+    ap.add_argument("--no-verify", action="store_true", help="skip the dig check after writing")
+    args = ap.parse_args()
+
+    if not args.list and (not args.fqdn or not args.ipv4):
+        ap.error("fqdn and ipv4 are required unless --list is given")
+
+    names = [s.strip() for s in args.sites.split(",") if s.strip()]
+    unknown = [n for n in names if n not in SITES]
+    if unknown:
+        ap.error(f"unknown site(s): {', '.join(unknown)}")
+
+    failures = 0
+    for name in names:
+        console = Console(name, SITES[name])
+        label = f"{name:16s} {console.gateway:10s}"
+        if not console.key:
+            print(f"{label} NO KEY: save the console's API key to {console.key_path}")
+            failures += 1
+            continue
+        try:
+            site_id = console.site_id()
+            if args.list:
+                policies = console.dns_policies(site_id)
+                print(f"{label} {len(policies)} DNS policies")
+                for p in sorted(policies, key=lambda p: p.get("domain", "")):
+                    target = p.get("ipv4Address") or p.get("ipv6Address") or p.get("targetDomain") or p.get("text") or ""
+                    flag = "" if p.get("enabled", True) else " (disabled)"
+                    print(f"    {p.get('type', '?'):12s} {p.get('domain', ''):40s} -> {target}{flag}")
+                continue
+            result = console.ensure_a_record(site_id, args.fqdn, args.ipv4, args.ttl, args.dry_run)
+            line = f"{label} {result}"
+            if not args.dry_run and not args.no_verify and not result.startswith("SKIPPED"):
+                line += f" | dig @{console.gateway}: {resolve_via(console.gateway, args.fqdn)}"
+            print(line)
+            if result.startswith("SKIPPED"):
+                failures += 1
+        except ApiError as e:
+            print(f"{label} FAILED: {e}")
+            failures += 1
+
+    return 1 if failures else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())