Module rules: a native helper ships prebuilt, for Apple silicon and Windows

The machine running ProdDash is a packaged app or the Windows bundle plus
modules from the admin page's catalog. It has no compiler, and the catalog
delivers exactly the folder that is in the repo — so a module's native
program (audio capture, a decoder) ships already built, inside the module
folder, one file per platform: bin/<name>-macos-arm64 and
bin/<name>-win-x64.exe are required, Intel macOS optional, source and the
script that rebuilds every binary under native/.

The guide's rule 3 now says so, "The shape of a module" shows the layout,
and a new "Native helpers" section gives the contract: pick the binary by
platform at runtime, report the feature off when there is none — never
build, never search the machine, never ask the operator to install
anything — one command-line contract in any language per platform, bump
the version when a binary changes, keep them lean, sign the macOS one.
CLAUDE.md carries the one-line version. Rules only: no module changes here.

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

CLAUDE.md

@@ -28,7 +28,12 @@ title-bar controls). The rules that matter most:
   ship inside the module folder** (zero deps is the norm). **Everything the
   module does runs inside its server entry** — no helper scripts, companion
   programs or daemons the operator starts by hand; a listener or decoder is
-  started in `init()` and stopped in `stop()`. Declare `"proddash": ">=x.y.z"`
+  started in `init()` and stopped in `stop()`. **A native helper ships
+  prebuilt inside the module folder for Apple silicon macOS and 64-bit
+  Windows** (`bin/<name>-macos-arm64`, `bin/<name>-win-x64.exe`, source and
+  build script under `native/`); nothing is ever compiled on the machine
+  running ProdDash, and a missing binary means the feature reports itself
+  off, not a broken module. Declare `"proddash": ">=x.y.z"`
   and bump the module's `version` on every change.
 - Browsers never call upstream services directly; the module's server routes
   proxy everything (no CORS, secrets stay server-side).

README.md

@@ -325,8 +325,9 @@ below. Nothing is installed without someone clicking.
   session (Start ProdDash.command) and approve the one-time prompt; a server
   started over SSH or by bare launchd silently captures zeros. (Engine
   self-test: `node modules/propresenter-timers/ltc.selftest.js`.)
-- **PCO Plan** — Planning Center Services, as two tiles in the ＋ picker:
+- **PCO Plan** — Planning Center Services, as three tiles in the ＋ picker:
-  **Plan** (the order of service) and **Teams** (who is scheduled).
+  **Plan** (the order of service), **Teams** (who is scheduled) and **Song
+  Key** (the key of the item on screen).
 
   **Plan** shows every
   plan item with its scheduled start time, length, type, song key,
@@ -357,6 +358,16 @@ below. Nothing is installed without someone clicking.
   is switched off, or it has no host — nothing to turn off and nothing to
   explain.
 
+  **Song Key** is one value, as large as the tile allows: the key of the item
+  ProPresenter has live, with the song's name and the next key under it — both
+  switches, as is the colour. When the feed that picks the item is gone the key
+  stays up, faded, and the tile's dot says so rather than pretending to be
+  current.
+
+  Keys are written as notes wherever the module shows one: Planning Center's
+  `Bb` and `F#m` read as B♭ and F♯m, on the Plan tile's item badge and in the
+  Song Key tile alike.
+
   **Teams** shows the same plan's team and position assignments — each team
   as a band of its people, with their photo (fetched through ProdDash, never
   by the browser; initials when Planning Center has none) and a dot for

docs/MODULE-GUIDE.md

@@ -28,7 +28,10 @@ people running the booth depend on them.
    ProdDash. If your feature needs a listener, a decoder or a worker, your
    server entry owns it: start it in `init()`, stop it in `stop()`, report
    it in `health()`. A child process the module itself spawns and supervises
-   is fine; a program someone launches by hand is not.
+   is fine; a program someone launches by hand is not. **A native helper —
+   anything that is not JavaScript — ships prebuilt inside the module folder,
+   for Apple silicon macOS and 64-bit Windows; nothing is ever compiled on
+   the machine running ProdDash** (see "Native helpers" below).
 4. **Declare the ProdDash version you need** (`"proddash": ">=1.1.0"` in the
    manifest) and **bump your own `version`** whenever you change the module.
    The admin page refuses to install a module whose requirement the running
@@ -83,6 +86,10 @@ modules/<id>/
 ├── module.json      manifest (required)
 ├── client.js        ES module, client entry (required)
 ├── server.js        server entry (optional — only if you need server code)
+├── bin/             native helpers, prebuilt per platform (only if you need one)
+│   ├── <name>-macos-arm64
+│   └── <name>-win-x64.exe
+├── native/          their source and the script that builds every bin/ file
 └── ... assets       (css, images…) served statically at /modules/<id>/
 ```
 
@@ -97,6 +104,66 @@ the newer version runs. **Uninstall** in the admin page removes an installed
 module's files (a bundled one is hidden instead, since its folder belongs to
 the app); its settings are kept for a later reinstall.
 
+### Native helpers
+
+Some features need a program JavaScript cannot be: reading an audio input,
+decoding timecode, measuring sound. Rule 3 says the module owns that program;
+this section says how it ships: **already built, for every platform it runs
+on, inside the module folder.** The machine running ProdDash is a packaged
+app or the Windows bundle plus modules from the admin page's catalog. It has
+no compiler and never will — the catalog delivers exactly the folder that is
+in the repo, so the binaries live in git next to the code.
+
+- **Platforms.** Apple silicon macOS and 64-bit Windows are required. Intel
+  macOS is welcome but optional. One file per platform in `bin/`, named for
+  what it is:
+
+  | Platform | File |
+  | --- | --- |
+  | macOS, Apple silicon | `bin/<name>-macos-arm64` |
+  | Windows, 64-bit | `bin/<name>-win-x64.exe` |
+  | macOS, Intel (optional) | `bin/<name>-macos-x86_64` |
+
+- **Pick it at runtime, and cope without it.** Choose by `process.platform`
+  and `process.arch`; when there is no file for this machine, the feature
+  says so — in `health()` and in the tile's `setStatus` — and everything else
+  in the module keeps working. Never try to build it, never look for a copy
+  elsewhere on the machine, never tell the operator to install anything.
+
+  ```js
+  const HELPERS = {
+    darwin: { arm64: 'ltc-capture-macos-arm64', x64: 'ltc-capture-macos-x86_64' },
+    win32: { x64: 'ltc-capture-win-x64.exe' },
+  };
+  const name = HELPERS[process.platform]?.[process.arch];
+  const helper = name ? path.join(__dirname, 'bin', name) : '';
+  if (!helper || !fs.existsSync(helper)) {
+    // Timecode is off on this platform. Say it once, keep the clock running.
+  }
+  ```
+
+- **One contract, any language.** Every platform's binary speaks the same
+  command line and output format, so `server.js` has one code path. What is
+  behind it is your choice per platform — Swift against CoreAudio on macOS,
+  C#, C or Rust on Windows — the module does not care.
+- **Source and build beside it.** Keep the source under `native/` with one
+  script that produces every `bin/` file from a checkout, so any binary can be
+  rebuilt from what is committed. A helper that cannot be rebuilt does not
+  ship.
+- **Bump the module version whenever a binary changes**, like any other
+  file — that is how installs learn about it.
+- **Keep them lean.** Optimised builds, no debug symbols, a few megabytes at
+  most: the catalog fetches the whole repo as one archive, capped at 80 MB.
+- **Signing.** Apple silicon refuses unsigned code, so sign the macOS binary
+  — Developer ID when you have it, ad-hoc at least. Windows needs nothing:
+  files the app writes carry no download mark, so SmartScreen never sees
+  them. Permissions come from the launcher (see "Permissions macOS has to
+  grant"), not from the binary.
+
+A helper that ends up existing for one platform only is an exception made
+on purpose, not a default: say so in the module's README and in the health
+line, so a Windows booth knows why the feature is off.
+
 ## module.json
 
 ```json

modules/pco-plan/client.js

@@ -1,8 +1,8 @@
 /* PCO Plan — client part.
 
-   The module presents two tiles and this is the entry for both: the Teams
+   The module presents three tiles and this is the entry for all of them: the
-   tile (picker entry "teams") is built by teams-client.js, everything below
+   Teams tile (picker entry "teams") is built by teams-client.js and the Song
-   draws the Plan tile.
+   Key tile ("key") by key-client.js; everything below draws the Plan tile.
 
    The server part reads Planning Center and (optionally) follows the
    ProPresenter module's live item; this tile only renders the plan it is
@@ -13,6 +13,8 @@
    the connection settings. */
 
 import createTeams from "./teams-client.js";
+import createKey from "./key-client.js";
+import { prettyKey } from "./key-notation.js";
 
 const REFRESH_SVG = '<svg viewBox="0 0 24 24" width="14" height="14" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round"><path d="M21 12a9 9 0 1 1-2.64-6.36"/><path d="M21 3v6h-6"/></svg>';
 
@@ -21,8 +23,9 @@ const MINUS_SVG = '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" st
 const PLUS_SVG = '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.4" stroke-linecap="round" aria-hidden="true"><path d="M12 5v14M5 12h14"/></svg>';
 
 export default function create({ root, moduleApi }) {
-  // Tiles added as "Teams" carry that variant and have their own settings.
+  // Each picker entry carries its variant and its own settings.
   if (moduleApi.variant === "teams") return createTeams({ root, moduleApi });
+  if (moduleApi.variant === "key") return createKey({ root, moduleApi });
   return createPlan({ root, moduleApi });
 }
 
@@ -367,7 +370,8 @@ function createPlan({ root, moduleApi }) {
       if (on('showKey') && item.keyName) {
         const key = document.createElement('span');
         key.className = 'pp-key';
-        key.textContent = item.keyName;
+        // B♭, F♯m — the same notation the Song Key tile uses.
+        key.textContent = prettyKey(item.keyName);
         titleLine.appendChild(key);
       }
       if (on('showNowIndicator')) {

modules/pco-plan/key-client.js

@@ -0,0 +1,181 @@
+/* PCO Plan — the Song Key tile.
+
+   One thing, big: the key of the plan item on screen. It reads the same
+   streamed state the Plan tile does, so it needs no connection of its own;
+   which item is current comes from the ProPresenter module, as ever. */
+
+import { parseKey, prettyKey } from "./key-notation.js";
+
+export default function createKey({ root, moduleApi }) {
+  let state = null;
+  let stream = null;
+  let feedOffline = false;
+
+  root.innerHTML = `
+    <div class="pk-wrap">
+      <div class="pk-key"></div>
+      <div class="pk-name"></div>
+      <div class="pk-next"></div>
+    </div>`;
+
+  const wrap = root.querySelector('.pk-wrap');
+  const keyEl = root.querySelector('.pk-key');
+  const nameEl = root.querySelector('.pk-name');
+  const nextEl = root.querySelector('.pk-next');
+
+  const cfg = () => moduleApi.instanceSettings || {};
+  const on = (key) => cfg()[key] !== false; // unset = shown
+
+  /* ── the item on screen, and the one after it ───────────────────── */
+
+  function items() {
+    return Array.isArray(state?.items) ? state.items : [];
+  }
+
+  function currentItem() {
+    const id = state?.live?.following ? state.live.currentItemId : '';
+    return id ? items().find((it) => it.id === id) || null : null;
+  }
+
+  /** The next item that actually has a key — a talk between two songs is skipped. */
+  function nextKeyed(after) {
+    const list = items();
+    const from = after ? list.findIndex((it) => it.id === after.id) + 1 : 0;
+    if (from <= 0) return null;
+    for (let i = from; i < list.length; i += 1) {
+      if (list[i].keyName) return list[i];
+    }
+    return null;
+  }
+
+  function titleOf(item) {
+    return item ? (item.song?.title || item.title || '') : '';
+  }
+
+  /* ── render ─────────────────────────────────────────────────────── */
+
+  function renderStatus() {
+    if (feedOffline) return moduleApi.setStatus('error', 'ProdDash server unreachable — reconnecting…');
+    if (!state) return moduleApi.setStatus('connecting', 'Connecting…');
+    if (!state.configured) return moduleApi.setStatus('error', 'No Planning Center credentials — add them in Admin');
+    if (!state.serviceTypeSet) return moduleApi.setStatus('error', 'No service type selected — pick one in Admin');
+    if (!state.reachable) {
+      return moduleApi.setStatus(state.lastFetched ? 'error' : 'connecting', state.lastError || 'Reading the plan…');
+    }
+    const item = currentItem();
+    if (!state.live?.following) return moduleApi.setStatus('ok', 'Not following ProPresenter — no item is current');
+    // The key on screen stays — the band still needs it — but a tile must
+    // never look confidently live while the feed that chose it is gone.
+    if (!state.live.available) {
+      return moduleApi.setStatus('error', `${state.live.reason || 'ProPresenter feed unavailable'} — showing the last item`);
+    }
+    if (!state.live.ppReachable) return moduleApi.setStatus('error', 'ProPresenter unreachable — showing the last item');
+    if (!item) return moduleApi.setStatus('ok', 'Waiting for an item to go live');
+    moduleApi.setStatus('ok', `${titleOf(item)}${item.keyName ? ` — ${prettyKey(item.keyName)}` : ' — no key in the plan'}`);
+  }
+
+  /**
+   * A key is a note, so it is worth setting properly: "Bb" and "F#m" read
+   * better with the accidental raised and the minor kept small.
+   */
+  function drawKey(text) {
+    keyEl.innerHTML = '';
+    const parts = parseKey(text);
+    if (!parts) {
+      keyEl.textContent = text;
+      return;
+    }
+    keyEl.appendChild(document.createTextNode(parts.note));
+    if (parts.accidental) {
+      const acc = document.createElement('span');
+      acc.className = 'pk-accidental';
+      acc.textContent = parts.accidental;
+      keyEl.appendChild(acc);
+    }
+    if (parts.quality) {
+      const tail = document.createElement('span');
+      tail.className = 'pk-quality';
+      tail.textContent = parts.quality;
+      keyEl.appendChild(tail);
+    }
+  }
+
+  function render() {
+    wrap.classList.toggle('is-offline', feedOffline);
+    const live = state?.live;
+    wrap.classList.toggle('is-stale', Boolean(live?.following && (!live.available || !live.ppReachable)));
+    const color = String(cfg().keyColor || '').trim();
+    wrap.style.setProperty('--pk-color', /^[#a-zA-Z0-9(),.%\s-]+$/.test(color) && color ? color : '#4ea1ff');
+    renderStatus();
+
+    const item = currentItem();
+    const key = item?.keyName || '';
+    wrap.classList.toggle('has-key', Boolean(key));
+
+    if (!state || !state.configured || !state.serviceTypeSet) {
+      drawKey('—');
+      nameEl.textContent = state ? 'Set up PCO Plan in Admin' : 'Connecting…';
+      nextEl.textContent = '';
+      return;
+    }
+    if (!item) {
+      drawKey('—');
+      nameEl.textContent = state.live?.following ? 'Nothing live' : 'Not following ProPresenter';
+      nextEl.textContent = '';
+      return;
+    }
+
+    drawKey(key || '—');
+    nameEl.textContent = on('showSongName') ? titleOf(item) : '';
+    nameEl.hidden = !nameEl.textContent;
+
+    const next = on('showNextKey') ? nextKeyed(item) : null;
+    nextEl.textContent = next ? `Next: ${prettyKey(next.keyName)} · ${titleOf(next)}` : '';
+    nextEl.hidden = !nextEl.textContent;
+  }
+
+  /* ── live feed ──────────────────────────────────────────────────── */
+
+  function accept(payload) {
+    if (!payload || typeof payload !== 'object' || !payload.state) return;
+    state = payload.state;
+    feedOffline = false;
+    render();
+  }
+
+  function connect() {
+    stream = moduleApi.sse('/stream', {
+      open() { feedOffline = false; render(); },
+      error() { feedOffline = true; render(); },
+      events: {
+        state(ev) {
+          try {
+            accept(JSON.parse(ev.data));
+          } catch { /* a bad frame is not fatal */ }
+        },
+      },
+    });
+  }
+
+  /* ── lifecycle ──────────────────────────────────────────────────── */
+
+  return {
+    start() {
+      moduleApi.setStatus('connecting', 'Connecting…');
+      moduleApi.fetch('/state')
+        .then((res) => (res.ok ? res.json() : null))
+        .then((body) => { if (body && !state) accept(body); })
+        .catch(() => { /* the stream will cover it */ });
+      connect();
+      render();
+    },
+    stop() {
+      stream?.close();
+      stream = null;
+      root.innerHTML = '';
+    },
+    onConfigChange() {
+      // Admin holds the connection only; the server re-inits and re-sends.
+    },
+  };
+}

modules/pco-plan/key-notation.js

@@ -0,0 +1,25 @@
+/* PCO Plan — how a song key is written.
+
+   Planning Center stores keys as typed: "Bb", "F#m", "Ab". Every tile in this
+   module shows them as notes instead — B♭, F♯m, A♭ — so the plan, the badge
+   on an item and the Song Key tile all agree. Shared rather than repeated
+   because the day one of them changes, they all should. */
+
+/** "F#m" → { note: 'F', accidental: '♯', quality: 'm' }; anything odd → null. */
+export function parseKey(raw) {
+  const match = /^([A-G])\s*([#b♯♭]?)\s*(.*)$/.exec(String(raw || '').trim());
+  if (!match) return null;
+  const [, note, accidental, quality] = match;
+  return {
+    note,
+    accidental: accidental === '#' ? '♯' : accidental === 'b' ? '♭' : accidental,
+    quality: quality.trim(),
+  };
+}
+
+/** The same thing as one string, for a badge or a caption. */
+export function prettyKey(raw) {
+  const parts = parseKey(raw);
+  if (!parts) return String(raw || '').trim();
+  return `${parts.note}${parts.accidental}${parts.quality}`;
+}

modules/pco-plan/module.json

@@ -1,9 +1,9 @@
 {
   "id": "pco-plan",
   "name": "PCO Plan",
-  "version": "1.8.0",
+  "version": "1.9.0",
   "proddash": ">=1.4.0",
-  "description": "Order of service and team assignments from Planning Center Services",
+  "description": "Order of service, team assignments and the song key from Planning Center Services",
   "provides": [
     "timers"
   ],
@@ -621,6 +621,36 @@
           "columns": 2
         }
       }
+    },
+    {
+      "id": "key",
+      "name": "Song Key",
+      "description": "The key of the item on screen, big",
+      "defaultSize": {
+        "w": 2,
+        "h": 2
+      },
+      "minSize": {
+        "w": 1,
+        "h": 1
+      },
+      "instanceSchema": {
+        "keyColor": {
+          "type": "color",
+          "label": "Key",
+          "default": "#4ea1ff"
+        },
+        "showSongName": {
+          "type": "boolean",
+          "label": "Song name",
+          "default": true
+        },
+        "showNextKey": {
+          "type": "boolean",
+          "label": "Next key",
+          "default": true
+        }
+      }
     }
   ]
 }

modules/pco-plan/style.css

@@ -206,7 +206,9 @@
 
 [data-module="pco-plan"] .pp-now-tag {
   display: none;
-  padding: 0.05em 0.45em;
+  /* Optically centred like the section chips: uppercase has no descenders,
+     so the capitals sat 0.59px low in the pill. */
+  padding: 0.018em 0.45em 0.082em;
   border-radius: 999px;
   background: var(--pp-current);
   color: var(--bg);
@@ -635,25 +637,110 @@
 
 [data-module="pco-plan"] .pp-abs-sec {
   flex: none;
-  padding: 0.1em 0.5em;
+  /* Uppercase text has no descenders, so the font's descent allowance below
-  border-radius: 999px;
+     the baseline leaves the caps sitting high in the box — measured at 0.9px
-  border: 1px solid var(--border);
+     too much headroom. The padding is a touch shallower on top and deeper
+     below to centre the letters themselves; in em, so it holds at any text
+     size. */
+  padding: 0.095em 0.55em 0.185em;
+  /* The same rounded square, tinted ground and transparent border the AbleSet
+     module gives its own section pills, so the two read as one family. */
+  border-radius: 0.35em;
+  border: 1px solid transparent;
+  background: color-mix(in srgb, var(--text) 8%, var(--panel));
   font-size: 0.72em;
   font-weight: 700;
   letter-spacing: 0.04em;
   text-transform: uppercase;
   white-space: nowrap;
   color: var(--muted);
-  transition: color 0.2s ease, border-color 0.2s ease;
+  transition: color 0.2s ease, border-color 0.2s ease, background 0.2s ease;
 }
 [data-module="pco-plan"] .pp-abs-sec.is-done { opacity: 0.45; }
 
 /* The section now playing fills left to right as it goes, like the row. */
+/* The section playing keeps its own ground and fills across it, so the
+   progress reads against the chip rather than against the row behind it. */
 [data-module="pco-plan"] .pp-abs-sec.is-now {
   color: var(--text);
   border-color: color-mix(in srgb, var(--pp-current) 60%, transparent);
   background:
     linear-gradient(90deg,
-      color-mix(in srgb, var(--pp-current) 40%, transparent) var(--pp-sec-fill, 0%),
+      color-mix(in srgb, var(--pp-current) 45%, var(--panel)) var(--pp-sec-fill, 0%),
-      transparent var(--pp-sec-fill, 0%));
+      color-mix(in srgb, var(--text) 8%, var(--panel)) var(--pp-sec-fill, 0%));
 }
+
+/* ── the Song Key tile ────────────────────────────────────────────────
+   One value, as large as the tile allows. Sizes come from the tile itself
+   (container units), like the AbleSet module's single readouts, so a small
+   tile and a wall-sized one both read properly. */
+
+[data-module="pco-plan"] .pk-wrap {
+  --pk-color: #4ea1ff;
+  position: absolute;
+  inset: 0;
+  container-type: size;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 0.2em;
+  padding: 4%;
+  text-align: center;
+  user-select: none;
+}
+
+[data-module="pco-plan"] .pk-key {
+  font-size: clamp(18px, 46cqmin, 260px);
+  font-weight: 800;
+  line-height: 1;
+  letter-spacing: -0.01em;
+  color: var(--muted);
+  white-space: nowrap;
+}
+[data-module="pco-plan"] .pk-wrap.has-key .pk-key { color: var(--pk-color); }
+
+/* A key is a note, but it has to read as one word at a glance from the back
+   of a room: the accidental and the quality sit on the same line as the
+   letter, only smaller. Raising the accidental looked like two stacked
+   characters at tile sizes. */
+[data-module="pco-plan"] .pk-accidental {
+  font-size: 0.68em;
+  margin-left: 0.01em;
+}
+[data-module="pco-plan"] .pk-quality {
+  font-size: 0.5em;
+  font-weight: 700;
+  margin-left: 0.05em;
+  opacity: 0.85;
+}
+
+[data-module="pco-plan"] .pk-name {
+  max-width: 100%;
+  font-size: clamp(9px, 9cqmin, 30px);
+  font-weight: 600;
+  line-height: 1.2;
+  color: var(--text);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+[data-module="pco-plan"] .pk-name[hidden] { display: none; }
+
+[data-module="pco-plan"] .pk-next {
+  max-width: 100%;
+  font-size: clamp(8px, 6.5cqmin, 20px);
+  font-weight: 600;
+  color: var(--muted);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+[data-module="pco-plan"] .pk-next[hidden] { display: none; }
+
+[data-module="pco-plan"] .pk-wrap.is-offline { opacity: 0.6; }
+/* The feed that picks the item is gone: the key stays readable, but faded,
+   so nobody trusts it as current without looking at the status dot. */
+[data-module="pco-plan"] .pk-wrap.is-stale .pk-key { opacity: 0.55; }
+[data-module="pco-plan"] .pk-wrap.is-stale .pk-name,
+[data-module="pco-plan"] .pk-wrap.is-stale .pk-next { opacity: 0.6; }

modules/spl-meter/module.json

@@ -1,7 +1,7 @@
 {
   "id": "spl-meter",
   "name": "SPL Meter",
-  "version": "0.4.1",
+  "version": "0.4.3",
   "proddash": ">=1.5.0",
   "description": "Calibrated sound level, Leq and RTA from an audio input on this machine",
   "permissions": [

modules/spl-meter/server.js

@@ -20,7 +20,7 @@
  */
 
 const path = require('path');
-const { createSplListener } = require('./spl-listener');
+const { createSplListener, ensureCaptureBinary } = require('./spl-listener');
 
 /** Reference level of a sound level calibrator. Effectively always 94 dB. */
 const CALIBRATOR_DB = 94;
@@ -114,11 +114,19 @@ module.exports = {
       error: '',
       streams: new Set(),
       silentSince: null,
+      toolMissing: '',
       listener: null,
       lastSent: '',
       pinger: null,
     };
 
+    // Before anything else: the device picker shells out to this tool, so a
+    // machine that installed the module from the catalog (source only — the
+    // binary is gitignored) needs the build kicked off here. Waiting for a
+    // listener would never happen: no tool means no device list, and no
+    // device means no listener.
+    state.toolMissing = ensureCaptureBinary({ moduleDir, log });
+
     if (!config.enabled) {
       state.error = 'Sound level measurement is off — turn it on in ProdDash settings';
       return { stop() { teardown(); }, health: () => ({ status: 'error', message: state.error }) };
@@ -177,6 +185,9 @@ module.exports = {
     return {
       stop() { teardown(); },
       health() {
+        if (state.toolMissing && !fsExists(path.join(moduleDir, 'spl-capture'))) {
+          return { status: 'error', message: state.toolMissing };
+        }
         if (state.error) return { status: 'error', message: state.error };
         if (!state.frame) return { status: 'connecting', message: 'waiting for the first reading' };
         const quiet = silentMs();
@@ -300,6 +311,13 @@ module.exports = {
       /** Device list for the admin page. Runs the capture tool's --list,
           which is the only thing that knows what CoreAudio can see. */
       'GET /devices': async (req, res) => {
+        const missing = ensureCaptureBinary({ moduleDir: __dirname, log });
+        if (missing) {
+          if (state) state.toolMissing = missing;
+          log(`device list unavailable — ${missing}`);
+          json(res, 200, { options: [] });
+          return;
+        }
         try {
           const devices = await listDevices();
           json(res, 200, {
@@ -438,6 +456,10 @@ function listDevices() {
   });
 }
 
+function fsExists(p) {
+  try { return require('fs').existsSync(p); } catch { return false; }
+}
+
 function json(res, code, body) {
   const text = JSON.stringify(body);
   res.writeHead(code, {

modules/spl-meter/spl-listener.js

@@ -17,7 +17,8 @@
  * module's ltc-capture. It normally arrives already built — compiled beside
  * the app, or copied from any Mac of the same architecture. When it is
  * missing this will build it, but in the background and never on the event
- * loop: see ensureBinary for what that cost the first time it was wrong.
+ * loop, and from module scope so the device picker can trigger it too — see
+ * ensureCaptureBinary for what both of those cost the first time round.
  *
  * The same macOS gotcha applies as for LTC, and is worth repeating because
  * it costs an afternoon every time: a ProdDash launched over SSH or from a
@@ -30,6 +31,74 @@ const path = require('path');
 const fs = require('fs');
 const { spawn } = require('child_process');
 
+const BUILD_HELP = 'Sound level capture tool missing — build it on any Apple Silicon Mac with '
+  + '`swiftc -O -o modules/spl-meter/spl-capture modules/spl-meter/spl-capture.swift` '
+  + 'and copy it next to spl-capture.swift';
+const BUILDING = 'Building the capture tool — this takes a minute or two';
+
+/**
+ * Build the capture tool if it is missing, WITHOUT blocking, and shared by
+ * everything that needs it.
+ *
+ * This lives at module scope rather than inside a listener because of a trap
+ * the first version walked into: the admin page's device picker runs the tool
+ * with --list, but the build only ran when a listener started, and a listener
+ * only starts once a device has been picked. On a machine that got the module
+ * from the catalog — source only, the binary being gitignored — the picker
+ * was empty, and nothing would ever fill it.
+ *
+ * It also must never block. It was a spawnSync once, copied from the LTC
+ * listener where the source is a third the size and builds in seconds. Here
+ * it took nearly two minutes on the production Mac and held the Node event
+ * loop for all of it, freezing every other module, then did it again on the
+ * next retry.
+ *
+ * The binary should normally already be there: built beside the app, or
+ * copied from any Mac of the same architecture. This is the fallback.
+ *
+ * @returns {string} '' when the tool is ready, otherwise what to say.
+ */
+let building = false;
+let buildFailed = false;
+
+function ensureCaptureBinary({ moduleDir, log, onReady }) {
+  const bin = path.join(moduleDir, 'spl-capture');
+  if (fs.existsSync(bin)) return '';
+  const src = bin + '.swift';
+  if (!fs.existsSync(src)) return 'spl-capture.swift is missing from the module folder';
+  if (building) return BUILDING;
+  if (buildFailed) return BUILD_HELP;
+
+  building = true;
+  log('spl-capture binary missing — building it in the background');
+  const build = spawn('swiftc', ['-O', '-o', bin, src], { stdio: ['ignore', 'ignore', 'pipe'] });
+  let buildErr = '';
+  build.stderr.setEncoding('utf8');
+  build.stderr.on('data', (t) => { buildErr = (buildErr + t).slice(-800); });
+  const giveUp = setTimeout(() => {
+    try { build.kill('SIGKILL'); } catch { /* already gone */ }
+  }, 300000);
+  build.on('error', (err) => {
+    clearTimeout(giveUp);
+    building = false; buildFailed = true;
+    log(`swiftc could not be run: ${err.message}`);
+  });
+  build.on('exit', (code) => {
+    clearTimeout(giveUp);
+    building = false;
+    if (code === 0 && fs.existsSync(bin)) {
+      log('spl-capture built');
+      buildFailed = false;
+      if (typeof onReady === 'function') onReady();
+      return;
+    }
+    buildFailed = true;
+    log(`spl-capture build failed (exit ${code})`
+      + (buildErr ? `: ${buildErr.trim().split('\n').pop()}` : ''));
+  });
+  return BUILDING;
+}
+
 const RESTART_MS = 5000;
 /** An immediate exit is config-shaped (bad device, channel out of range) —
     retrying every 5 s would only fill the log with the same sentence. */
@@ -53,64 +122,13 @@ function createSplListener(opts) {
   let stallTimer = null;
   let startedAt = 0;
   let meta = null;
-  let building = false;
-  let buildFailed = false;
   let lastFrameWall = 0;
 
-  const BUILD_HELP = 'Sound level capture tool missing — build it on any Apple Silicon Mac with '
+  /** '' when the tool is ready, otherwise what to say about it. */
-    + '`swiftc -O -o modules/spl-meter/spl-capture modules/spl-meter/spl-capture.swift` '
-    + 'and copy it next to spl-capture.swift';
-
-  /**
-   * Build the capture tool if it is missing, WITHOUT blocking.
-   *
-   * This used to be a spawnSync, copied from the LTC listener where the
-   * source is a third the size and builds in a few seconds. Here it took
-   * nearly two minutes on the production Mac and froze the entire ProdDash
-   * server for every second of it — one module's optional helper took the
-   * whole dashboard down, then did it again on every retry. Nothing that
-   * runs while a service might be on is allowed to hold the event loop.
-   *
-   * The build is a fallback for a module installed from the catalog on a
-   * machine with a Swift toolchain. The normal path is a binary built
-   * alongside the app, or copied from any same-architecture Mac.
-   *
-   * @returns {string} '' when the binary is ready, otherwise what to say.
-   */
   function ensureBinary() {
-    if (fs.existsSync(bin)) return '';
+    return ensureCaptureBinary({ moduleDir, log, onReady() {
-    const src = bin + '.swift';
-    if (!fs.existsSync(src)) return 'spl-capture.swift is missing from the module folder';
-    if (building) return 'Building the capture tool — this takes a minute or two';
-    if (buildFailed) return BUILD_HELP;
-
-    building = true;
-    log('spl-capture binary missing — building it in the background');
-    const build = spawn('swiftc', ['-O', '-o', bin, src], { stdio: ['ignore', 'ignore', 'pipe'] });
-    let buildErr = '';
-    build.stderr.setEncoding('utf8');
-    build.stderr.on('data', (t) => { buildErr = (buildErr + t).slice(-800); });
-    const giveUp = setTimeout(() => {
-      try { build.kill('SIGKILL'); } catch { /* already gone */ }
-    }, 300000);
-    build.on('error', (err) => {
-      clearTimeout(giveUp);
-      building = false; buildFailed = true;
-      log(`swiftc could not be run: ${err.message}`);
-    });
-    build.on('exit', (code) => {
-      clearTimeout(giveUp);
-      building = false;
-      if (code === 0 && fs.existsSync(bin)) {
-        log('spl-capture built');
-        buildFailed = false;
       if (!stopped) { clearTimeout(restartTimer); restartTimer = null; start(); }
-        return;
+    } });
-      }
-      buildFailed = true;
-      log(`spl-capture build failed (exit ${code})` + (buildErr ? `: ${buildErr.trim().split('\n').pop()}` : ''));
-    });
-    return 'Building the capture tool — this takes a minute or two';
   }
 
   function scheduleRestart(ms) {
@@ -135,9 +153,13 @@ function createSplListener(opts) {
     const missing = ensureBinary();
     if (missing) {
       onUpdate({ error: missing });
-      // A build in flight calls start() itself when it lands; anything else
+      // onReady is only the FAST path (a successful build restarts us at
-      // is config-shaped and should back off hard rather than spin.
+      // once). The slow retry must stay armed regardless: a failed build
-      if (!building) scheduleRestart(BAD_CONFIG_RETRY_MS);
+      // never calls back, and a binary can also arrive from outside — scp'd
+      // in on a machine whose toolchain can't build (AB's broken CLT).
+      // Waiting on onReady alone deadlocked exactly that way in the Timers
+      // module: "building…" forever, with a working binary on disk.
+      scheduleRestart(BAD_CONFIG_RETRY_MS);
       return;
     }
 
@@ -236,4 +258,4 @@ function createSplListener(opts) {
   };
 }
 
-module.exports = { createSplListener };
+module.exports = { createSplListener, ensureCaptureBinary };