Merge branch 'codex/prewarm-next'

# Conflicts:
#	frontend/index.html

.gitignore

@@ -40,3 +40,7 @@ legacy/releases/
 __pycache__/
 plans/codex-shots*/
 plans/codex-report*.md
+
+# performance harness artifacts and temp files
+perf/fixtures/
+perf/.tmp/

frontend/app.js

@@ -623,8 +623,9 @@ const API = {
 // Pre-resolve streams for videos the user is likely to play next (server
 // /api/streams/warm). Each id is warmed at most once per 20 min per tab.
 const warmedAt = new Map();
+const knownServerCachedIds = new Set();
 function warmStreams(ids) {
-  if (!WEB || navigator.onLine === false) return;
+  if (!WEB || navigator.onLine === false || navigator.connection?.saveData) return;
   const now = Date.now();
   for (const id of ids) {
     if (!id || !/^[A-Za-z0-9_-]{11}$/.test(id) || cachedIds.has(id)) continue;
@@ -634,6 +635,14 @@ function warmStreams(ids) {
   }
 }
 
+function warmNextQueue() {
+  if (!window.PrewarmNext || queueIndex < 0) return;
+  warmStreams(window.PrewarmNext.candidates(queue, queueIndex, data.settings, 2, {
+    offline: cachedIds,
+    serverCached: knownServerCachedIds,
+  }));
+}
+
 // Resolve a native file path to a URL the WebView can load (Tauri asset
 // protocol). Returns null on shells without it.
 function toAssetUrl(path) {
@@ -2332,6 +2341,7 @@ const Player = {
       if (seq !== this._loadSeq) return; // a newer load took over meanwhile
       if (!res || !res.ok) throw new Error(res?.error || 'Could not load streams');
       current = res.data;
+      if (current.serverCached && current.meta?.id) knownServerCachedIds.add(current.meta.id);
       // Merge richer metadata we may already have from the list card.
       current.meta = { ...videoObj, ...current.meta };
 
@@ -3014,7 +3024,7 @@ function wirePlayerEvents() {
         perfMeasure('ytp:tap-to-play', 'ytp:tap');
         try { performance.clearMarks('ytp:tap'); } catch { /* ignore */ }
       }
-      if (Array.isArray(queue) && queueIndex >= 0) warmStreams(queue.slice(queueIndex + 1, queueIndex + 3).map((x) => x && x.id));
+      warmNextQueue();
       showSpinner(false);
       Player.clearBufferGrace();
       if (Player.secondary && !el.paused && Player.secondary.paused) {
@@ -4729,8 +4739,7 @@ const Notes = (() => {
     const v = $('stgVideo'), a = $('stgAudio');
     if (v) v.classList.toggle('on', !ao); if (a) a.classList.toggle('on', ao);
   }
-  setInterval(chips, 1500);
+  VisibleTimer.setIntervalWhenVisible(chips, 1500, { immediate: true });
-  setTimeout(chips, 400);
 })();
 
 // ============================================================================
@@ -5069,7 +5078,7 @@ const Remote = (() => {
   // ==========================================================================
   // Remote (this phone drives a host)
   // ==========================================================================
-  const rc = { ws: null, open: false, state: null, stateAt: 0, queue: { items: [], idx: -1 }, retry: null, ping: null, latency: null, online: false, seeking: false, volTimer: null, drag: null };
+  const rc = { ws: null, open: false, state: null, stateAt: 0, queue: { items: [], idx: -1 }, retry: null, ping: null, seekTimer: null, latency: null, online: false, seeking: false, volTimer: null, drag: null };
 
   const rcSend = (m) => { if (rc.ws && rc.ws.readyState === 1) rc.ws.send(JSON.stringify(m)); };
   const cmd = (name, args = {}) => rcSend({ type: 'cmd', cmd: name, ...args });
@@ -5299,6 +5308,7 @@ const Remote = (() => {
 
   function openRemoteView({ code = '' } = {}) {
     rc.open = true;
+    rc.seekTimer = VisibleTimer.setIntervalWhenVisible(renderSeek, 500);
     // This phone is the remote now — don't also play here.
     try { if (Player.master && !Player.master.paused) Player.pause(); } catch { /* nothing loaded */ }
     $('remoteView').classList.remove('hidden');
@@ -5309,6 +5319,8 @@ const Remote = (() => {
 
   function closeRemoteView() {
     rc.open = false;
+    rc.seekTimer?.clear();
+    rc.seekTimer = null;
     clearTimeout(rc.retry);
     clearInterval(rc.ping);
     const ws = rc.ws;
@@ -5387,7 +5399,6 @@ const Remote = (() => {
       toast(next ? `Screen pauses in ${next} min` : 'Sleep timer off');
     });
     $('rvService').addEventListener('click', () => cmd('service', { on: !(rc.state && rc.state.service) }));
-    setInterval(() => { if (rc.open) renderSeek(); }, 500);
     // Hosts keep phones current once a second while anything plays.
     setInterval(() => { if (host.ws && host.remotes.length) { pushState(); pushQueue(); } }, 1000);
     document.addEventListener('visibilitychange', () => {
@@ -5800,7 +5811,7 @@ const CatalogSync = (() => {
     }
   }
   window.addEventListener('online', flush);
-  if (WEB) setInterval(flush, 60000);
+  if (WEB) VisibleTimer.setIntervalWhenVisible(flush, 60000, { immediate: true });
   return { send, flush };
 })();
 function collectSearchMetadata(q, cards) { if (WEB) CatalogSync.send(q, cards); }
@@ -8043,6 +8054,7 @@ function playFromList(list, index, source = '', { playFull = false } = {}) {
   unshuffledQueue = null;
   // Play-in-full keeps the list order — a service set plays as arranged.
   if (data.settings.shuffle && !playFull) applyShuffle();
+  warmNextQueue();
   Player.loadVideo(queue[queueIndex]);
   renderUpNext();
 }
@@ -11061,7 +11073,7 @@ function setupViewportAnchorGuard() {
   // Last-resort safety net for offsets none of the events above report:
   // a 2s tick that reads scrollY (cheap) and snaps back only when displaced,
   // so "nav taps silently do nothing" can never persist longer than a beat.
-  setInterval(reanchor, 2000);
+  VisibleTimer.setIntervalWhenVisible(reanchor, 2000);
 }
 
 // ============================================================================
@@ -11304,7 +11316,7 @@ function rotateChips() {
     }
   });
 }
-setInterval(rotateChips, 8000);
+VisibleTimer.setIntervalWhenVisible(rotateChips, 8000);
 
 document.querySelectorAll('.chip').forEach((c) => {
     c.addEventListener('click', () => {
@@ -12151,8 +12163,7 @@ function checkBuildTag() {
 }
 
 function pollBuildTag() {
-  checkBuildTag();
+  VisibleTimer.setIntervalWhenVisible(checkBuildTag, 5 * 60 * 1000, { immediate: true });
-  setInterval(checkBuildTag, 5 * 60 * 1000);   // recheck every 5 minutes
 }
 
 // ============================================================================

frontend/index.html

@@ -693,6 +693,8 @@
     <script src="piano.js"></script>
     <script src="setlist-import.js"></script>
     <script src="car-mode.js"></script>
+    <script src="visible-timer.js"></script>
+    <script src="prewarm-next.js"></script>
     <script src="app.js"></script>
   </body>
 </html>

frontend/prewarm-next.js

@@ -0,0 +1,37 @@
+/* Pure queue candidate selection for stream prewarming. */
+(function (root, factory) {
+  if (typeof module === 'object' && module.exports) module.exports = factory();
+  else root.PrewarmNext = factory();
+})(typeof globalThis !== 'undefined' ? globalThis : this, function () {
+  'use strict';
+
+  function candidates(queue, index, state = {}, n = 2, known = {}) {
+    if (!Array.isArray(queue) || !queue.length || !Number.isInteger(index) || index < 0 || index >= queue.length) return [];
+    if (state.loopOne) return [];
+    const count = Math.max(0, Math.floor(Number(n) || 0));
+    if (!count) return [];
+    const repeatAll = state.repeatMode === 'all' || state.repeatAll === true;
+    const offline = new Set(known.offline || []);
+    const serverCached = new Set(known.serverCached || []);
+    const current = queue[index];
+    const currentId = typeof current === 'string' ? current : current && current.id;
+    const seen = new Set(currentId ? [currentId] : []);
+    const ids = [];
+    for (let step = 1; step < queue.length + (repeatAll ? 1 : 0) && ids.length < count; step++) {
+      let at = index + step;
+      if (at >= queue.length) {
+        if (!repeatAll) break;
+        at %= queue.length;
+      }
+      const item = queue[at];
+      const id = typeof item === 'string' ? item : item && item.id;
+      if (!id || seen.has(id)) continue;
+      seen.add(id);
+      if (offline.has(id) || serverCached.has(id) || (item && item.serverCached)) continue;
+      ids.push(id);
+    }
+    return ids;
+  }
+
+  return { candidates };
+});

frontend/prewarm-next.test.js

@@ -0,0 +1,26 @@
+'use strict';
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const { candidates } = require('./prewarm-next.js');
+
+const q = ['a', 'b', 'c', 'd'].map(id => ({ id }));
+
+test('returns the next n queue ids in existing order', () => {
+  assert.deepEqual(candidates(q, 0, {}, 2), ['b', 'c']);
+});
+test('repeat all wraps and does not duplicate ids', () => {
+  assert.deepEqual(candidates(q, 3, { repeatMode: 'all' }, 2), ['a', 'b']);
+  assert.deepEqual(candidates([{ id: 'x' }, { id: 'x' }], 0, { repeatMode: 'all' }, 3), []);
+});
+test('repeat off stops at the end and loop one has no candidates', () => {
+  assert.deepEqual(candidates(q, 3, {}, 2), []);
+  assert.deepEqual(candidates(q, 0, { loopOne: true, repeatMode: 'all' }, 2), []);
+});
+test('skips offline and known server cached ids and deduplicates', () => {
+  assert.deepEqual(candidates(q, 0, {}, 3, { offline: ['b'], serverCached: ['c'] }), ['d']);
+  assert.deepEqual(candidates([{ id: 'a' }, { id: 'b', serverCached: true }, { id: 'c' }], 0, {}, 2), ['c']);
+});
+test('shuffle follows the queue order selected before advance', () => {
+  const shuffled = ['a', 'd', 'b', 'c'].map(id => ({ id }));
+  assert.deepEqual(candidates(shuffled, 0, { shuffle: true }, 2), ['d', 'b']);
+});

frontend/shell-consistency.test.js

@@ -0,0 +1,29 @@
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const { readFileSync, existsSync } = require('node:fs');
+const { join } = require('node:path');
+
+const root = join(__dirname, '..');
+const html = readFileSync(join(__dirname, 'index.html'), 'utf8');
+const sw = readFileSync(join(__dirname, 'sw.js'), 'utf8');
+const shellMatch = sw.match(/const SHELL = \[([\s\S]*?)\n\];/);
+assert.ok(shellMatch, 'service worker SHELL list is present');
+const shell = [...shellMatch[1].matchAll(/['"](\/[^'"]+)['"]/g)].map((match) => match[1]);
+const listed = new Set(shell);
+
+test('every local script and stylesheet in index.html is precached by the service worker', () => {
+  const localAssets = [];
+  for (const match of html.matchAll(/<(?:script\b[^>]*\bsrc|link\b[^>]*\bhref)="([^"]+)"/gi)) {
+    const url = match[1];
+    if (/^(?:[a-z]+:|\/|#)/i.test(url)) continue;
+    if (!/\.(?:js|css)(?:[?#]|$)/i.test(url)) continue;
+    localAssets.push(`/${url.split(/[?#]/, 1)[0]}`);
+  }
+  assert.ok(localAssets.length > 0, 'found local script/style assets');
+  for (const asset of localAssets) assert.ok(listed.has(asset), `${asset} appears in SHELL`);
+});
+
+test('every SHELL asset exists on disk and there are no duplicate entries', () => {
+  assert.equal(new Set(shell).size, shell.length, 'SHELL has no duplicate entries');
+  for (const asset of shell) assert.ok(existsSync(join(__dirname, asset.slice(1))), `${asset} exists`);
+});

frontend/sw.js

@@ -70,6 +70,7 @@ const SHELL = [
   '/flag-ui.js',
   '/export.js',
   '/async-guard.js',
+  '/visible-timer.js',
   '/sw-update.js',
   '/fingerprint.js',
   '/opfs.js',
@@ -124,6 +125,7 @@ const SHELL = [
   '/piano.js',
   '/setlist-import.js',
   '/car-mode.js',
+  '/prewarm-next.js',
   '/car-mode.css',
   '/lower-third.css',
   '/settings-sections.css',

frontend/visible-timer.js

@@ -0,0 +1,41 @@
+(function (root) {
+  'use strict';
+
+  function setIntervalWhenVisible(fn, ms, { immediate = false } = {}) {
+    if (typeof fn !== 'function') throw new TypeError('fn must be a function');
+    const doc = root.document;
+    if (!doc) throw new Error('document is required');
+
+    let timer = null;
+    let stopped = false;
+    const clear = () => {
+      if (timer !== null) root.clearInterval(timer);
+      timer = null;
+    };
+    const start = (runNow) => {
+      if (stopped || doc.hidden) return;
+      clear();
+      if (runNow) fn();
+      timer = root.setInterval(fn, ms);
+    };
+    const onVisibilityChange = () => {
+      if (doc.hidden) clear();
+      else start(immediate);
+    };
+
+    if (!doc.hidden) start(immediate);
+    doc.addEventListener('visibilitychange', onVisibilityChange);
+    return {
+      clear() {
+        if (stopped) return;
+        stopped = true;
+        clear();
+        doc.removeEventListener('visibilitychange', onVisibilityChange);
+      },
+    };
+  }
+
+  const api = { setIntervalWhenVisible };
+  if (typeof module !== 'undefined' && module.exports) module.exports = api;
+  else root.VisibleTimer = api;
+})(globalThis);

frontend/visible-timer.test.js

@@ -0,0 +1,90 @@
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const { setIntervalWhenVisible } = require('./visible-timer');
+
+class FakeDocument {
+  hidden = false;
+  listeners = new Set();
+  addEventListener(type, listener) { if (type === 'visibilitychange') this.listeners.add(listener); }
+  removeEventListener(type, listener) { if (type === 'visibilitychange') this.listeners.delete(listener); }
+  setHidden(hidden) {
+    this.hidden = hidden;
+    for (const listener of [...this.listeners]) listener();
+  }
+}
+
+function fakeClock(t, hidden = false) {
+  const doc = new FakeDocument();
+  doc.hidden = hidden;
+  const original = {
+    document: globalThis.document,
+    setInterval: globalThis.setInterval,
+    clearInterval: globalThis.clearInterval,
+  };
+  let nextId = 1;
+  const timers = new Map();
+  globalThis.document = doc;
+  globalThis.setInterval = (fn, ms) => {
+    const id = nextId++;
+    timers.set(id, { fn, ms });
+    return id;
+  };
+  globalThis.clearInterval = (id) => timers.delete(id);
+  t.after(() => {
+    globalThis.document = original.document;
+    globalThis.setInterval = original.setInterval;
+    globalThis.clearInterval = original.clearInterval;
+  });
+  return {
+    doc,
+    timers,
+    tick() { for (const timer of [...timers.values()]) timer.fn(); },
+  };
+}
+
+test('runs on a visible page and has one interval until hidden', (t) => {
+  const clock = fakeClock(t);
+  let calls = 0;
+  const handle = setIntervalWhenVisible(() => calls++, 250);
+  assert.equal(calls, 0);
+  assert.equal(clock.timers.size, 1);
+  assert.equal([...clock.timers.values()][0].ms, 250);
+  clock.tick();
+  assert.equal(calls, 1);
+  clock.doc.setHidden(true);
+  assert.equal(clock.timers.size, 0);
+  clock.tick();
+  assert.equal(calls, 1);
+  handle.clear();
+  assert.equal(clock.doc.listeners.size, 0);
+});
+
+test('immediate mode runs once initially and once when becoming visible', (t) => {
+  const clock = fakeClock(t);
+  let calls = 0;
+  const handle = setIntervalWhenVisible(() => calls++, 1000, { immediate: true });
+  assert.equal(calls, 1);
+  assert.equal(clock.timers.size, 1);
+  clock.doc.setHidden(true);
+  assert.equal(clock.timers.size, 0);
+  clock.doc.setHidden(false);
+  assert.equal(calls, 2);
+  assert.equal(clock.timers.size, 1);
+  handle.clear();
+  clock.doc.setHidden(true);
+  clock.doc.setHidden(false);
+  assert.equal(calls, 2);
+  assert.equal(clock.timers.size, 0);
+});
+
+test('a page that starts hidden waits until visible before calling or scheduling', (t) => {
+  const clock = fakeClock(t, true);
+  let calls = 0;
+  const handle = setIntervalWhenVisible(() => calls++, 500, { immediate: true });
+  assert.equal(calls, 0);
+  assert.equal(clock.timers.size, 0);
+  clock.doc.setHidden(false);
+  assert.equal(calls, 1);
+  assert.equal(clock.timers.size, 1);
+  handle.clear();
+});

perf/README.md

@@ -0,0 +1,143 @@
+# Performance Baseline Harness (`perf/`)
+
+Automated performance baseline and regression harness for the **ytplayer PWA**.
+
+The harness drives the real Bun backend server (`server/server.js`) serving static Brotli-compressed assets, combined with Playwright browser automation on Chromium and WebKit.
+
+---
+
+## 1. Architecture
+
+### Backend Server (`server/server.js`)
+- Runs as an isolated child process using **Bun** on an ephemeral port.
+- Configured with dedicated scratch directories under `perf/.tmp/` (`DATA_DIR`, `DB_PATH`, `MEDIA_DIR`) so no production or developer data is ever touched.
+- Employs the real static asset delivery stack (`Brotli` encoding, `ETag` generation, `Cache-Control` immutable caching for version-stamped assets, and `computeBuildTag()`).
+
+### Browser Automation & Network Throttling
+- **Chromium**:
+  - Network emulation via Chrome DevTools Protocol (`Network.emulateNetworkConditions`).
+  - CPU throttling at **4× slowdown** (`Emulation.setCPUThrottlingRate`).
+  - Unrestricted audio/video playback via `--autoplay-policy=no-user-gesture-required`.
+- **WebKit**:
+  - WebKit on Linux lacks CDP network emulation capabilities.
+  - Throttling and stalling are handled by a dedicated local proxy (`perf/proxy.mjs`) sitting between WebKit and the Bun server.
+  - The proxy shapes traffic by pacing chunk delivery through backpressured streams and injecting round-trip latency and stalls.
+- **Network Profiles**:
+  - **`lte`**: 1.6 Mbps (200 KB/s) download, 750 kbps upload, 150 ms round-trip latency.
+  - **`lossy`**: 1.0 Mbps (125 KB/s) download, 250 ms latency, with intermittent connection stalls (every 7th request delayed by 1,500 ms).
+
+### Shell Fixture Extractor (`perf/make-shell-fixture.sh`)
+- Archives the frontend from git commits (`git archive <commit> frontend`) into `perf/fixtures/shell-<tag>/`.
+- Computes the build tag using the exact sha256 walk algorithm from `server/server.js computeBuildTag()`.
+- Validates the computed tag against live production (`https://worship.hesed.sbs/api/version`).
+
+---
+
+## 2. Test Scenarios
+
+1. **`cold` (Cold First Load)**:
+   - Fresh browser context with empty cache, no service worker, and clean storage.
+   - Measures initial page fetch, FCP, LCP, DOMContentLoaded, boot milestone (`#cards` render), media playback readiness, service worker precaching duration, and origin storage quota.
+2. **`warm` (Warm Reload under SW)**:
+   - Re-navigates the page with active Service Worker and primed HTTP cache.
+   - Measures cached asset retrieval efficiency and second-load boot performance.
+3. **`offline` (Offline Reload)**:
+   - Sets offline state and reloads the application.
+   - Verifies the app boots entirely from `CacheStorage` precached shell assets without network connectivity.
+4. **`update-js` (Update N → N+1 with 1-line JS comment)**:
+   - Boots client against Tree N (base frontend), establishing an active Service Worker.
+   - Swaps server to Tree N+1 (one comment line appended to `app.js`, altering `BUILD_TAG`).
+   - Triggers `registration.update()` and measures total wire bytes and time until the new Service Worker reaches `waiting` state (`installed`).
+5. **`update-css` (Update N → N+1 with 1-line CSS rule)**:
+   - Identical to `update-js`, but Tree N+1 has one CSS rule appended to `theme-glass.css`.
+   - Measures the full shell re-download penalty caused by any stylesheet modification.
+
+---
+
+## 3. Metrics Collected
+
+Each scenario records the following metrics across **5 independent runs** (reporting min, max, and median):
+- **Request Count**: Total HTTP requests made across the wire.
+- **Wire Bytes**: Total compressed bytes transferred over the network.
+- **Wire Bytes by Type**: Categorized byte breakdown (`html`, `js`, `css`, `fonts`, `images`, `media`, `api`, `other`).
+- **FCP (First Contentful Paint)**: Time from navigation start to first rendered content (ms).
+- **LCP (Largest Contentful Paint)**: Time to largest contentful paint via `PerformanceObserver` (ms).
+- **DOMContentLoaded**: Time to DOMContentLoaded event end (ms).
+- **Boot Done**: Time from navigation start until the first `#cards` view rendering is completed (ms).
+- **Long Tasks Total**: Cumulative execution time of main thread tasks exceeding 50 ms (ms, Chromium).
+- **SW Install Duration**: Time from Service Worker registration until precaching completes (ms).
+- **SW Install Wire Bytes**: Network bytes transmitted during Service Worker installation.
+- **Storage Estimate**: Quota and usage reported by `navigator.storage.estimate()` (bytes).
+- **Media Ready**: Elapsed time for deterministic media fixture (`benchmedia01`) to reach `readyState >= 3` / playing state. Notes if autoplay policy blocked playback.
+
+---
+
+## 4. How to Run
+
+### Prerequisites
+Symlink dependencies and ensure server dependencies are installed:
+```bash
+# Worktree root
+ln -s ~/development/personal/ytplayer/node_modules node_modules
+cd server && bun install && cd ..
+```
+
+### Basic Commands
+Run the complete baseline suite (5 runs, all browsers, LTE profile):
+```bash
+node perf/baseline.mjs
+```
+
+Run a specific browser or profile:
+```bash
+# Chromium on LTE profile
+node perf/baseline.mjs --browser chromium --profile lte
+
+# WebKit on LTE profile
+node perf/baseline.mjs --browser webkit --profile lte
+
+# Both browsers on lossy profile
+node perf/baseline.mjs --browser all --profile lossy
+```
+
+Run a single scenario:
+```bash
+# Cold load only
+node perf/baseline.mjs --scenario cold
+
+# Update scenario with 1-line JS change
+node perf/baseline.mjs --scenario update-js
+
+# Update scenario with 1-line CSS change
+node perf/baseline.mjs --scenario update-css
+```
+
+Configure run count:
+```bash
+# Quick sanity check (1 iteration)
+node perf/baseline.mjs --runs 1
+
+# High precision benchmark (7 iterations)
+node perf/baseline.mjs --runs 7
+```
+
+---
+
+## 5. Phase 5 Comparison Mode (`--compare`)
+
+To verify performance gains and detect regressions in later phases:
+```bash
+node perf/baseline.mjs --compare perf/results/baseline-2026-10-07.json
+```
+Prints an ASCII/Markdown delta comparison table highlighting percentage changes across wire bytes, boot duration, and update overhead.
+
+---
+
+## 6. Hidden Timers Verification (`perf/hidden-timers.mjs`)
+
+Verifies that non-playback UI intervals (`chips`, `reanchor`, `rotateChips`, `flush`, `checkBuildTag`) suspend while the document is hidden and restore upon visibility, while essential background intervals (`maybeCheck`, 120s resume check) remain active:
+```bash
+node perf/hidden-timers.mjs
+```
+Exits with code 0 on success, or code 1 if any interval fails to pause, fails to resume, or if page errors occur.
+

perf/baseline.mjs

@@ -0,0 +1,954 @@
+#!/usr/bin/env node
+
+/**
+ * perf/baseline.mjs
+ *
+ * Performance baseline harness for ytplayer PWA.
+ * Drives the real Bun server and runs Playwright (Chromium with CDP throttling + CPU 4x;
+ * WebKit with a local throttling & stalling proxy).
+ *
+ * Scenarios:
+ *   - cold: fresh context, network download, SW install, boot, media playback check
+ *   - warm: re-navigate with active SW and primed HTTP cache
+ *   - offline: context.setOffline(true), reload under SW cache
+ *   - update-js: update N->N+1 (1-line comment appended to app.js) -> wire bytes + time until new SW ready
+ *   - update-css: update N->N+1 (1-line rule appended to theme-glass.css) -> wire bytes + time until new SW ready
+ *
+ * Usage:
+ *   node perf/baseline.mjs [options]
+ *   Options:
+ *     --runs <number>           Runs per scenario for median calculation (default: 5)
+ *     --browser <chr|wk|all>    Browser(s) to test (default: all)
+ *     --profile <lte|lossy|all> Network profile (default: lte)
+ *     --scenario <name|all>     Specific scenario or all (default: all)
+ *     --out <path>              Output JSON path
+ *     --compare <json-path>     Compare results against a previous baseline JSON
+ */
+
+import { spawn, spawnSync } from 'node:child_process';
+import { existsSync, mkdirSync, rmSync, cpSync, appendFileSync, statSync, writeFileSync, readFileSync, symlinkSync, unlinkSync } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { createThrottleProxy } from './proxy.mjs';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const REPO_ROOT = path.resolve(__dirname, '..');
+
+// Dynamically resolve playwright from node_modules
+let pw;
+try {
+  pw = await import('playwright');
+} catch {
+  pw = await import(path.join(REPO_ROOT, 'node_modules', 'playwright', 'index.mjs'));
+}
+
+import { createRequire } from 'node:module';
+const req = createRequire(import.meta.url);
+const { createClient } = req(path.join(REPO_ROOT, 'server', 'node_modules', '@libsql/client'));
+
+const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+
+function parseArgs() {
+  const args = process.argv.slice(2);
+  const options = {
+    runs: 5,
+    browser: 'all', // 'chromium', 'webkit', or 'all'
+    profile: 'lte', // 'lte', 'lossy', or 'all'
+    scenario: 'all', // 'cold', 'warm', 'offline', 'update-js', 'update-css', or 'all'
+    out: null,
+    compare: null,
+  };
+
+  for (let i = 0; i < args.length; i++) {
+    const a = args[i];
+    if (a === '--runs' && i + 1 < args.length) options.runs = parseInt(args[++i], 10);
+    else if (a === '--browser' && i + 1 < args.length) options.browser = args[++i];
+    else if (a === '--profile' && i + 1 < args.length) options.profile = args[++i];
+    else if (a === '--scenario' && i + 1 < args.length) options.scenario = args[++i];
+    else if (a === '--out' && i + 1 < args.length) options.out = args[++i];
+    else if (a === '--compare' && i + 1 < args.length) options.compare = args[++i];
+  }
+
+  return options;
+}
+
+function median(values) {
+  const nums = values.filter((v) => typeof v === 'number' && !Number.isNaN(v)).sort((a, b) => a - b);
+  if (!nums.length) return null;
+  const mid = Math.floor(nums.length / 2);
+  return nums.length % 2 !== 0 ? nums[mid] : Math.round(((nums[mid - 1] + nums[mid]) / 2) * 10) / 10;
+}
+
+function summarizeList(values) {
+  const valid = values.filter((v) => v !== null && v !== undefined && !Number.isNaN(v));
+  if (!valid.length) return { median: null, min: null, max: null, values };
+  return {
+    median: median(valid),
+    min: Math.min(...valid),
+    max: Math.max(...valid),
+    values,
+  };
+}
+
+/**
+ * Setup deterministic local media fixture
+ */
+function prepareMediaFiles(mediaDir) {
+  mkdirSync(mediaDir, { recursive: true });
+  const mp4 = path.join(mediaDir, 'benchmedia01.1.mp4');
+  const m4a = path.join(mediaDir, 'benchmedia01.1.m4a');
+
+  if (!existsSync(mp4)) {
+    spawnSync('ffmpeg', [
+      '-y', '-f', 'lavfi', '-i', 'testsrc=size=640x360:rate=30:duration=5',
+      '-f', 'lavfi', '-i', 'sine=frequency=440:duration=5',
+      '-c:v', 'libx264', '-preset', 'ultrafast', '-pix_fmt', 'yuv420p',
+      '-c:a', 'aac', '-movflags', '+faststart', '-shortest', mp4,
+    ]);
+  }
+
+  if (!existsSync(m4a)) {
+    spawnSync('ffmpeg', [
+      '-y', '-f', 'lavfi', '-i', 'sine=frequency=440:duration=5',
+      '-c:a', 'aac', '-shortest', m4a,
+    ]);
+  }
+
+  return { mp4, m4a };
+}
+
+async function seedDatabase(dbPath, mediaFiles) {
+  const db = createClient({ url: 'file:' + dbPath });
+  const mp4Size = statSync(mediaFiles.mp4).size;
+  const m4aSize = statSync(mediaFiles.m4a).size;
+
+  await db.execute({
+    sql: `INSERT OR REPLACE INTO media_cache (
+      video_id, status, gen, size, height, vcodec, acodec, duration, meta, last_access
+    ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+    args: [
+      'benchmedia01',
+      'ready',
+      1,
+      mp4Size + m4aSize,
+      360,
+      'h264',
+      'aac',
+      5.0,
+      JSON.stringify({ title: 'Baseline Deterministic Clip', channel: 'Perf Benchmark' }),
+      Date.now(),
+    ],
+  });
+}
+
+/**
+ * Bun Server Manager
+ */
+class ServerManager {
+  constructor(scratchDir, publicDir) {
+    this.scratchDir = scratchDir;
+    this.publicDir = publicDir;
+    this.dataDir = path.join(scratchDir, 'data');
+    this.mediaDir = path.join(this.dataDir, 'media');
+    this.dbPath = path.join(this.dataDir, 'ytplayer.db');
+    this.serverProcess = null;
+    this.port = 0;
+  }
+
+  async start() {
+    mkdirSync(this.dataDir, { recursive: true });
+    const fixtureDir = path.join(REPO_ROOT, 'perf', 'fixtures', 'media');
+    const mediaFiles = prepareMediaFiles(fixtureDir);
+
+    // Create a dedicated server working dir with public symlink
+    const srvCwd = path.join(this.scratchDir, 'srv');
+    mkdirSync(srvCwd, { recursive: true });
+    const publicLink = path.join(srvCwd, 'public');
+    if (existsSync(publicLink)) unlinkSync(publicLink);
+    symlinkSync(this.publicDir, publicLink);
+
+    // Pick random available ephemeral port once and reuse across restarts
+    this.port = this.port || (4300 + Math.floor(Math.random() * 2000));
+
+    const env = {
+      ...process.env,
+      PORT: String(this.port),
+      DATA_DIR: this.dataDir,
+      MEDIA_DIR: this.mediaDir,
+      DB_PATH: this.dbPath,
+    };
+
+    const serverScript = path.join(REPO_ROOT, 'server', 'server.js');
+    this.serverProcess = spawn('bun', [serverScript], {
+      cwd: srvCwd,
+      env,
+      stdio: 'ignore',
+    });
+
+    // Wait for server readiness
+    let ready = false;
+    for (let i = 0; i < 50; i++) {
+      try {
+        const res = await fetch(`http://127.0.0.1:${this.port}/api/version`);
+        if (res.ok) {
+          ready = true;
+          break;
+        }
+      } catch {}
+      await sleep(100);
+    }
+
+    if (!ready) {
+      throw new Error(`Server failed to start on port ${this.port}`);
+    }
+
+    // Copy media files to mediaDir and seed media table AFTER server startup sweep
+    mkdirSync(this.mediaDir, { recursive: true });
+    const targetMp4 = path.join(this.mediaDir, 'benchmedia01.1.mp4');
+    const targetM4a = path.join(this.mediaDir, 'benchmedia01.1.m4a');
+    cpSync(mediaFiles.mp4, targetMp4);
+    cpSync(mediaFiles.m4a, targetM4a);
+    await seedDatabase(this.dbPath, { mp4: targetMp4, m4a: targetM4a });
+  }
+
+  async stop() {
+    if (this.serverProcess) {
+      const proc = this.serverProcess;
+      this.serverProcess = null;
+      await new Promise((resolve) => {
+        if (proc.exitCode !== null) return resolve();
+        proc.once('exit', () => resolve());
+        proc.kill('SIGKILL');
+        setTimeout(resolve, 2000);
+      });
+      await sleep(200);
+    }
+  }
+
+  async restartWithPublic(newPublicDir) {
+    await this.stop();
+    this.publicDir = newPublicDir;
+    await this.start();
+  }
+}
+
+/**
+ * Configure page for metrics collection
+ */
+async function setupPageMetrics(page) {
+  await page.addInitScript(() => {
+    window.__bootDone = null;
+    window.__fcp = null;
+    window.__lcp = null;
+    window.__longTasksTotal = 0;
+
+    // Observe boot completion landmark (#cards view set by renderList())
+    const markBoot = () => {
+      const cards = document.getElementById('cards');
+      if (cards && cards.dataset && cards.dataset.view) {
+        if (!window.__bootDone) window.__bootDone = performance.now();
+        return true;
+      }
+      return false;
+    };
+    const t = setInterval(() => {
+      if (markBoot()) clearInterval(t);
+    }, 5);
+
+    // Observe Long Tasks API (supported on Chromium)
+    try {
+      new PerformanceObserver((list) => {
+        for (const entry of list.getEntries()) {
+          window.__longTasksTotal += entry.duration;
+        }
+      }).observe({ type: 'longtask', buffered: true });
+    } catch {}
+
+    // Observe LCP
+    try {
+      new PerformanceObserver((list) => {
+        const entries = list.getEntries();
+        if (entries.length > 0) {
+          window.__lcp = entries[entries.length - 1].startTime;
+        }
+      }).observe({ type: 'largest-contentful-paint', buffered: true });
+    } catch {}
+  });
+}
+
+/**
+ * Run Scenario: Cold Load
+ */
+async function runColdScenario({ browserType, server, proxy, profile }) {
+  const isWebKit = browserType.name() === 'webkit';
+  const launchArgs = isWebKit ? [] : ['--autoplay-policy=no-user-gesture-required'];
+  const browser = await browserType.launch({
+    headless: true,
+    args: launchArgs,
+  });
+
+  const contextOptions = { proxy: { server: `http://127.0.0.1:${proxy.port}` } };
+  const context = await browser.newContext(contextOptions);
+  const page = await context.newPage();
+
+  // If Chromium, configure CDP Network conditions and 4x CPU throttle
+  if (!isWebKit) {
+    const cdp = await context.newCDPSession(page);
+    await cdp.send('Network.enable');
+    const isLossy = profile === 'lossy';
+    await cdp.send('Network.emulateNetworkConditions', {
+      offline: false,
+      latency: isLossy ? 250 : 150,
+      downloadThroughput: isLossy ? (1.0 * 1000 * 1000) / 8 : (1.6 * 1000 * 1000) / 8,
+      uploadThroughput: (750 * 1000) / 8,
+      connectionType: 'cellular4g',
+    });
+    await cdp.send('Emulation.setCPUThrottlingRate', { rate: 4 });
+  }
+
+  await setupPageMetrics(page);
+
+  proxy.resetStats();
+  proxy.startTracking();
+
+  const swInstallStart = Date.now();
+  const navUrl = `http://127.0.0.1:${server.port}/?v=benchmedia01`;
+
+  await page.goto(navUrl);
+
+  // Wait for boot landmark
+  await page.waitForFunction(() => window.__bootDone !== null, { timeout: 15000 });
+
+  // Check deterministic media playing-ready
+  let mediaReadyMs = null;
+  let autoplayBlocked = false;
+  try {
+    const mediaCheck = await page.waitForFunction(() => {
+      const v = document.querySelector('video') || document.querySelector('audio');
+      if (!v) return false;
+      return v.readyState >= 3 || (!v.paused && v.currentTime > 0);
+    }, { timeout: 8000 });
+    if (mediaCheck) {
+      const state = await page.evaluate(() => {
+        const v = document.querySelector('video') || document.querySelector('audio');
+        return { paused: v.paused, readyState: v.readyState };
+      });
+      autoplayBlocked = state.paused;
+      mediaReadyMs = await page.evaluate(() => performance.now());
+    }
+  } catch {
+    autoplayBlocked = true;
+  }
+
+  // Wait for initial Service Worker activation
+  await page.evaluate(async () => {
+    const reg = await navigator.serviceWorker.ready;
+    if (reg.active && reg.active.state === 'activated') return;
+    await new Promise((resolve) => {
+      const w = reg.active || reg.installing;
+      if (w.state === 'activated') return resolve();
+      w.addEventListener('statechange', () => {
+        if (w.state === 'activated') resolve();
+      });
+    });
+  });
+
+  const swInstallDuration = Date.now() - swInstallStart;
+  proxy.stopTracking();
+
+  const stats = proxy.getStats();
+
+  const pageMetrics = await page.evaluate(() => {
+    const nav = performance.getEntriesByType('navigation')[0];
+    const paint = performance.getEntriesByType('paint');
+    const fcp = paint.find((p) => p.name === 'first-contentful-paint');
+
+    return {
+      fcp: fcp ? Math.round(fcp.startTime) : null,
+      lcp: window.__lcp ? Math.round(window.__lcp) : null,
+      domContentLoaded: nav ? Math.round(nav.domContentLoadedEventEnd - nav.startTime) : null,
+      bootDone: window.__bootDone ? Math.round(window.__bootDone) : null,
+      longTaskTotal: Math.round(window.__longTasksTotal || 0),
+    };
+  });
+
+  const storage = await page.evaluate(async () => {
+    if (navigator.storage && navigator.storage.estimate) {
+      const est = await navigator.storage.estimate();
+      return { usage: est.usage || 0, quota: est.quota || 0 };
+    }
+    return { usage: null, quota: null };
+  });
+
+  await browser.close();
+
+  return {
+    requestCount: stats.requestCount,
+    wireBytes: stats.totalWireBytes,
+    wireBytesByType: stats.bytesByType,
+    fcp: pageMetrics.fcp,
+    lcp: pageMetrics.lcp,
+    domContentLoaded: pageMetrics.domContentLoaded,
+    bootDone: pageMetrics.bootDone,
+    longTaskTotal: pageMetrics.longTaskTotal,
+    swInstallDuration,
+    swInstallBytes: stats.totalWireBytes,
+    storageEstimate: storage,
+    mediaReady: mediaReadyMs ? Math.round(mediaReadyMs) : null,
+    autoplayBlocked,
+  };
+}
+
+/**
+ * Run Scenario: Warm Load (re-navigation with active SW)
+ */
+async function runWarmScenario({ browserType, server, proxy, profile }) {
+  const isWebKit = browserType.name() === 'webkit';
+  const launchArgs = isWebKit ? [] : ['--autoplay-policy=no-user-gesture-required'];
+  const browser = await browserType.launch({
+    headless: true,
+    args: launchArgs,
+  });
+
+  const contextOptions = { proxy: { server: `http://127.0.0.1:${proxy.port}` } };
+  const context = await browser.newContext(contextOptions);
+  const page = await context.newPage();
+
+  if (!isWebKit) {
+    const cdp = await context.newCDPSession(page);
+    await cdp.send('Network.enable');
+    const isLossy = profile === 'lossy';
+    await cdp.send('Network.emulateNetworkConditions', {
+      offline: false,
+      latency: isLossy ? 250 : 150,
+      downloadThroughput: isLossy ? (1.0 * 1000 * 1000) / 8 : (1.6 * 1000 * 1000) / 8,
+      uploadThroughput: (750 * 1000) / 8,
+      connectionType: 'cellular4g',
+    });
+    await cdp.send('Emulation.setCPUThrottlingRate', { rate: 4 });
+  }
+
+  await setupPageMetrics(page);
+
+  const navUrl = `http://127.0.0.1:${server.port}/`;
+
+  // Prime context with cold load
+  await page.goto(navUrl);
+  await page.waitForFunction(() => window.__bootDone !== null, { timeout: 15000 });
+  await page.evaluate(async () => {
+    const reg = await navigator.serviceWorker.ready;
+    if (reg.active && reg.active.state === 'activated') return;
+    await new Promise((resolve) => {
+      const w = reg.active || reg.installing;
+      if (w.state === 'activated') return resolve();
+      w.addEventListener('statechange', () => {
+        if (w.state === 'activated') resolve();
+      });
+    });
+  });
+
+  // Now measure warm re-navigation
+  proxy.resetStats();
+  proxy.startTracking();
+
+  await page.goto(navUrl);
+  await page.waitForFunction(() => window.__bootDone !== null, { timeout: 15000 });
+
+  proxy.stopTracking();
+  const stats = proxy.getStats();
+
+  const pageMetrics = await page.evaluate(() => {
+    const nav = performance.getEntriesByType('navigation')[0];
+    const paint = performance.getEntriesByType('paint');
+    const fcp = paint.find((p) => p.name === 'first-contentful-paint');
+
+    return {
+      fcp: fcp ? Math.round(fcp.startTime) : null,
+      lcp: window.__lcp ? Math.round(window.__lcp) : null,
+      domContentLoaded: nav ? Math.round(nav.domContentLoadedEventEnd - nav.startTime) : null,
+      bootDone: window.__bootDone ? Math.round(window.__bootDone) : null,
+      longTaskTotal: Math.round(window.__longTasksTotal || 0),
+    };
+  });
+
+  await browser.close();
+
+  return {
+    requestCount: stats.requestCount,
+    wireBytes: stats.totalWireBytes,
+    wireBytesByType: stats.bytesByType,
+    fcp: pageMetrics.fcp,
+    lcp: pageMetrics.lcp,
+    domContentLoaded: pageMetrics.domContentLoaded,
+    bootDone: pageMetrics.bootDone,
+    longTaskTotal: pageMetrics.longTaskTotal,
+  };
+}
+
+/**
+ * Run Scenario: Offline Reload under SW
+ */
+async function runOfflineScenario({ browserType, server, proxy, profile }) {
+  const browser = await browserType.launch({ headless: true });
+  const isWebKit = browserType.name() === 'webkit';
+  const contextOptions = { proxy: { server: `http://127.0.0.1:${proxy.port}` } };
+  const context = await browser.newContext(contextOptions);
+  const page = await context.newPage();
+
+  await setupPageMetrics(page);
+  const navUrl = `http://127.0.0.1:${server.port}/`;
+
+  // Prime SW
+  await page.goto(navUrl);
+  await page.waitForFunction(() => window.__bootDone !== null, { timeout: 15000 });
+  await page.evaluate(async () => {
+    const reg = await navigator.serviceWorker.ready;
+    if (reg.active && reg.active.state === 'activated') return;
+    await new Promise((resolve) => {
+      const w = reg.active || reg.installing;
+      if (w.state === 'activated') return resolve();
+      w.addEventListener('statechange', () => {
+        if (w.state === 'activated') resolve();
+      });
+    });
+  });
+
+  // Switch to offline mode:
+  // On Chromium, context.setOffline(true) works.
+  // On Linux WebKit, Playwright context.setOffline throws an internal browser error,
+  // so proxy.setOffline(true) cuts upstream network to simulate offline truthfully.
+  if (!isWebKit) {
+    await context.setOffline(true);
+  }
+  proxy.setOffline(true);
+
+  proxy.resetStats();
+  proxy.startTracking();
+
+  const t0 = Date.now();
+  await page.reload();
+  await page.waitForFunction(() => window.__bootDone !== null, { timeout: 15000 });
+  const reloadDuration = Date.now() - t0;
+
+  proxy.stopTracking();
+  proxy.setOffline(false);
+  const stats = proxy.getStats();
+
+  const pageMetrics = await page.evaluate(() => {
+    const nav = performance.getEntriesByType('navigation')[0];
+    const paint = performance.getEntriesByType('paint');
+    const fcp = paint.find((p) => p.name === 'first-contentful-paint');
+
+    return {
+      fcp: fcp ? Math.round(fcp.startTime) : null,
+      lcp: window.__lcp ? Math.round(window.__lcp) : null,
+      domContentLoaded: nav ? Math.round(nav.domContentLoadedEventEnd - nav.startTime) : null,
+      bootDone: window.__bootDone ? Math.round(window.__bootDone) : null,
+    };
+  });
+
+  await browser.close();
+
+  return {
+    requestCount: stats.requestCount,
+    wireBytes: stats.totalWireBytes,
+    fcp: pageMetrics.fcp,
+    lcp: pageMetrics.lcp,
+    domContentLoaded: pageMetrics.domContentLoaded,
+    bootDone: pageMetrics.bootDone,
+    reloadDuration,
+  };
+}
+
+/**
+ * Run Scenario: Update N -> N+1
+ */
+async function runUpdateScenario({ browserType, server, proxy, profile, updateKind, trees }) {
+  const browser = await browserType.launch({ headless: true });
+  const isWebKit = browserType.name() === 'webkit';
+  const contextOptions = { proxy: { server: `http://127.0.0.1:${proxy.port}` } };
+  const context = await browser.newContext(contextOptions);
+  const page = await context.newPage();
+
+  if (!isWebKit) {
+    const cdp = await context.newCDPSession(page);
+    await cdp.send('Network.enable');
+    const isLossy = profile === 'lossy';
+    await cdp.send('Network.emulateNetworkConditions', {
+      offline: false,
+      latency: isLossy ? 250 : 150,
+      downloadThroughput: isLossy ? (1.0 * 1000 * 1000) / 8 : (1.6 * 1000 * 1000) / 8,
+      uploadThroughput: (750 * 1000) / 8,
+      connectionType: 'cellular4g',
+    });
+  }
+
+  // Start on Tree N (base)
+  await server.restartWithPublic(trees.treeBase);
+
+  const navUrl = `http://127.0.0.1:${server.port}/`;
+
+  await page.goto(navUrl);
+
+  // Wait for steady state: active worker present, no waiting worker
+  while (true) {
+    const ready = await page.evaluate(async () => {
+      const reg = await navigator.serviceWorker.getRegistration();
+      return reg?.active?.state === 'activated' && !reg?.installing && !reg?.waiting;
+    });
+    if (ready) break;
+    await sleep(50);
+  }
+
+  // Switch server to Tree N+1 (app.js or theme-glass.css modification)
+  const targetTree = updateKind === 'js' ? trees.treeUpdateJs : trees.treeUpdateCss;
+  await server.restartWithPublic(targetTree);
+
+  // Measure wire bytes and duration from reg.update() until new SW is waiting/installed
+  proxy.resetStats();
+  proxy.startTracking();
+
+  const t0 = Date.now();
+  await page.evaluate(() => navigator.serviceWorker.getRegistration().then((r) => r.update()));
+
+  // Wait until new worker reaches waiting state
+  while (true) {
+    const waiting = await page.evaluate(async () => {
+      const reg = await navigator.serviceWorker.getRegistration();
+      return reg?.waiting?.state === 'installed';
+    });
+    if (waiting) break;
+    await sleep(50);
+  }
+
+  const duration = Date.now() - t0;
+  proxy.stopTracking();
+  const stats = proxy.getStats();
+
+  await browser.close();
+
+  return {
+    updateKind,
+    duration,
+    requestCount: stats.requestCount,
+    wireBytes: stats.totalWireBytes,
+    wireBytesByType: stats.bytesByType,
+  };
+}
+
+/**
+ * Main execution
+ */
+async function main() {
+  const options = parseArgs();
+  console.log('=== YTPlayer Performance Baseline Harness ===');
+  console.log(`Runs per scenario: ${options.runs}`);
+  console.log(`Browser target:    ${options.browser}`);
+  console.log(`Network profile:   ${options.profile}`);
+  console.log(`Scenario target:   ${options.scenario}`);
+
+  const browsers = [];
+  if (options.browser === 'all' || options.browser === 'chromium') browsers.push(pw.chromium);
+  if (options.browser === 'all' || options.browser === 'webkit') browsers.push(pw.webkit);
+
+  const profiles = [];
+  if (options.profile === 'all' || options.profile === 'lte') profiles.push('lte');
+  if (options.profile === 'all' || options.profile === 'lossy') profiles.push('lossy');
+
+  const tmpRoot = path.join(REPO_ROOT, 'perf', '.tmp', `bench-${Date.now()}`);
+  mkdirSync(tmpRoot, { recursive: true });
+
+  // Setup scratch trees for N -> N+1 update scenarios
+  const treeBase = path.join(tmpRoot, 'tree-base');
+  const treeUpdateJs = path.join(tmpRoot, 'tree-update-js');
+  const treeUpdateCss = path.join(tmpRoot, 'tree-update-css');
+
+  cpSync(path.join(REPO_ROOT, 'frontend'), treeBase, { recursive: true });
+  cpSync(path.join(REPO_ROOT, 'frontend'), treeUpdateJs, { recursive: true });
+  cpSync(path.join(REPO_ROOT, 'frontend'), treeUpdateCss, { recursive: true });
+
+  // Append 1 comment line to app.js in treeUpdateJs
+  appendFileSync(path.join(treeUpdateJs, 'app.js'), '\n// baseline bench: 1-line app.js comment\n');
+  // Append 1 rule to theme-glass.css in treeUpdateCss
+  appendFileSync(path.join(treeUpdateCss, 'theme-glass.css'), '\n/* baseline bench: 1-line css rule */\n.baseline-marker { opacity: 0.99; }\n');
+
+  const trees = { treeBase, treeUpdateJs, treeUpdateCss };
+
+  const serverScratch = path.join(tmpRoot, 'server-run');
+  const server = new ServerManager(serverScratch, treeBase);
+  await server.start();
+  console.log(`Bun server running on ephemeral port ${server.port}`);
+
+  const results = {
+    date: new Date().toISOString(),
+    commit: spawnSync('git', ['rev-parse', 'HEAD'], { cwd: REPO_ROOT }).stdout.toString().trim(),
+    runsConfigured: options.runs,
+    browsers: {},
+  };
+
+  try {
+    for (const bType of browsers) {
+      const bName = bType.name();
+      results.browsers[bName] = {};
+
+      for (const prof of profiles) {
+        console.log(`\n>>> Running Benchmark: Browser=[${bName}] Profile=[${prof}]`);
+        results.browsers[bName][prof] = {};
+
+        const proxyProfile = bName === 'chromium' ? 'unthrottled' : prof;
+        const proxy = createThrottleProxy({ targetPort: server.port, profile: proxyProfile });
+        proxy.port = await proxy.listen();
+        console.log(`Proxy listening on port ${proxy.port} (mode: ${proxyProfile})`);
+
+        // 1. Cold Scenario
+        if (options.scenario === 'all' || options.scenario === 'cold') {
+          console.log(`  [Scenario: Cold Load] running ${options.runs} iterations...`);
+          const coldRuns = [];
+          for (let r = 0; r < options.runs; r++) {
+            process.stdout.write(`    run ${r + 1}/${options.runs}... `);
+            const res = await runColdScenario({ browserType: bType, server, proxy, profile: prof });
+            coldRuns.push(res);
+            console.log(`done (${res.wireBytes} bytes, ${res.requestCount} reqs, boot=${res.bootDone}ms)`);
+          }
+
+          results.browsers[bName][prof].cold = {
+            requestCount: summarizeList(coldRuns.map((r) => r.requestCount)),
+            wireBytes: summarizeList(coldRuns.map((r) => r.wireBytes)),
+            fcp: summarizeList(coldRuns.map((r) => r.fcp)),
+            lcp: summarizeList(coldRuns.map((r) => r.lcp)),
+            domContentLoaded: summarizeList(coldRuns.map((r) => r.domContentLoaded)),
+            bootDone: summarizeList(coldRuns.map((r) => r.bootDone)),
+            longTaskTotal: summarizeList(coldRuns.map((r) => r.longTaskTotal)),
+            swInstallDuration: summarizeList(coldRuns.map((r) => r.swInstallDuration)),
+            swInstallBytes: summarizeList(coldRuns.map((r) => r.swInstallBytes)),
+            storageEstimate: coldRuns[0]?.storageEstimate || null,
+            mediaReady: summarizeList(coldRuns.map((r) => r.mediaReady)),
+            autoplayBlocked: coldRuns.some((r) => r.autoplayBlocked),
+            wireBytesByType: coldRuns[0]?.wireBytesByType || {},
+          };
+        }
+
+        // 2. Warm Scenario
+        if (options.scenario === 'all' || options.scenario === 'warm') {
+          console.log(`  [Scenario: Warm Load] running ${options.runs} iterations...`);
+          const warmRuns = [];
+          for (let r = 0; r < options.runs; r++) {
+            process.stdout.write(`    run ${r + 1}/${options.runs}... `);
+            const res = await runWarmScenario({ browserType: bType, server, proxy, profile: prof });
+            warmRuns.push(res);
+            console.log(`done (${res.wireBytes} bytes, ${res.requestCount} reqs, boot=${res.bootDone}ms)`);
+          }
+
+          results.browsers[bName][prof].warm = {
+            requestCount: summarizeList(warmRuns.map((r) => r.requestCount)),
+            wireBytes: summarizeList(warmRuns.map((r) => r.wireBytes)),
+            fcp: summarizeList(warmRuns.map((r) => r.fcp)),
+            lcp: summarizeList(warmRuns.map((r) => r.lcp)),
+            domContentLoaded: summarizeList(warmRuns.map((r) => r.domContentLoaded)),
+            bootDone: summarizeList(warmRuns.map((r) => r.bootDone)),
+            longTaskTotal: summarizeList(warmRuns.map((r) => r.longTaskTotal)),
+          };
+        }
+
+        // 3. Offline Scenario
+        if (options.scenario === 'all' || options.scenario === 'offline') {
+          console.log(`  [Scenario: Offline Reload] running ${options.runs} iterations...`);
+          const offRuns = [];
+          for (let r = 0; r < options.runs; r++) {
+            process.stdout.write(`    run ${r + 1}/${options.runs}... `);
+            const res = await runOfflineScenario({ browserType: bType, server, proxy, profile: prof });
+            offRuns.push(res);
+            console.log(`done (reload=${res.reloadDuration}ms, boot=${res.bootDone}ms)`);
+          }
+
+          results.browsers[bName][prof].offline = {
+            requestCount: summarizeList(offRuns.map((r) => r.requestCount)),
+            wireBytes: summarizeList(offRuns.map((r) => r.wireBytes)),
+            fcp: summarizeList(offRuns.map((r) => r.fcp)),
+            lcp: summarizeList(offRuns.map((r) => r.lcp)),
+            domContentLoaded: summarizeList(offRuns.map((r) => r.domContentLoaded)),
+            bootDone: summarizeList(offRuns.map((r) => r.bootDone)),
+            reloadDuration: summarizeList(offRuns.map((r) => r.reloadDuration)),
+          };
+        }
+
+        // 4. Update N -> N+1 (JS)
+        if (options.scenario === 'all' || options.scenario === 'update-js') {
+          console.log(`  [Scenario: Update N->N+1 (1-line app.js)] running ${options.runs} iterations...`);
+          const updJsRuns = [];
+          for (let r = 0; r < options.runs; r++) {
+            process.stdout.write(`    run ${r + 1}/${options.runs}... `);
+            const res = await runUpdateScenario({
+              browserType: bType,
+              server,
+              proxy,
+              profile: prof,
+              updateKind: 'js',
+              trees,
+            });
+            updJsRuns.push(res);
+            console.log(`done (${res.wireBytes} bytes, ${res.requestCount} reqs, dur=${res.duration}ms)`);
+          }
+
+          results.browsers[bName][prof].updateJs = {
+            requestCount: summarizeList(updJsRuns.map((r) => r.requestCount)),
+            wireBytes: summarizeList(updJsRuns.map((r) => r.wireBytes)),
+            duration: summarizeList(updJsRuns.map((r) => r.duration)),
+            wireBytesByType: updJsRuns[0]?.wireBytesByType || {},
+          };
+        }
+
+        // 5. Update N -> N+1 (CSS)
+        if (options.scenario === 'all' || options.scenario === 'update-css') {
+          console.log(`  [Scenario: Update N->N+1 (1-line theme-glass.css)] running ${options.runs} iterations...`);
+          const updCssRuns = [];
+          for (let r = 0; r < options.runs; r++) {
+            process.stdout.write(`    run ${r + 1}/${options.runs}... `);
+            const res = await runUpdateScenario({
+              browserType: bType,
+              server,
+              proxy,
+              profile: prof,
+              updateKind: 'css',
+              trees,
+            });
+            updCssRuns.push(res);
+            console.log(`done (${res.wireBytes} bytes, ${res.requestCount} reqs, dur=${res.duration}ms)`);
+          }
+
+          results.browsers[bName][prof].updateCss = {
+            requestCount: summarizeList(updCssRuns.map((r) => r.requestCount)),
+            wireBytes: summarizeList(updCssRuns.map((r) => r.wireBytes)),
+            duration: summarizeList(updCssRuns.map((r) => r.duration)),
+            wireBytesByType: updCssRuns[0]?.wireBytesByType || {},
+          };
+        }
+
+        await proxy.close();
+      }
+    }
+  } finally {
+    await server.stop();
+    rmSync(tmpRoot, { recursive: true, force: true });
+  }
+
+  // Write results JSON
+  const now = new Date();
+  const dateStr = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}-${String(now.getDate()).padStart(2, '0')}`;
+  const outPath = options.out || path.join(REPO_ROOT, 'perf', 'results', `baseline-${dateStr}.json`);
+  mkdirSync(path.dirname(outPath), { recursive: true });
+  writeFileSync(outPath, JSON.stringify(results, null, 2));
+  console.log(`\nBaseline results saved to: ${outPath}`);
+
+  // Print Summary Table
+  printSummaryTable(results);
+
+  // Compare mode if requested
+  if (options.compare) {
+    compareResults(options.compare, results);
+  }
+}
+
+function printSummaryTable(results) {
+  console.log('\n============================= HEADLINE BASELINE SUMMARY =============================');
+  for (const [browser, profiles] of Object.entries(results.browsers)) {
+    for (const [profile, scenarios] of Object.entries(profiles)) {
+      console.log(`\n[Browser: ${browser} | Profile: ${profile}]`);
+      console.log('| Scenario                  | Req Count | Wire Bytes | Boot / Ready | SW Dur / Reload |');
+      console.log('|---------------------------|-----------|------------|--------------|-----------------|');
+
+      if (scenarios.cold) {
+        const c = scenarios.cold;
+        console.log(
+          `| Cold First Load           | ${String(c.requestCount.median).padEnd(9)} | ${formatBytes(c.wireBytes.median).padEnd(10)} | ${String(c.bootDone.median + 'ms').padEnd(12)} | ${String(c.swInstallDuration.median + 'ms').padEnd(15)} |`
+        );
+      }
+      if (scenarios.warm) {
+        const w = scenarios.warm;
+        console.log(
+          `| Warm Reload (under SW)    | ${String(w.requestCount.median).padEnd(9)} | ${formatBytes(w.wireBytes.median).padEnd(10)} | ${String(w.bootDone.median + 'ms').padEnd(12)} | ${'-'.padEnd(15)} |`
+        );
+      }
+      if (scenarios.offline) {
+        const o = scenarios.offline;
+        console.log(
+          `| Offline Reload (under SW) | ${String(o.requestCount.median).padEnd(9)} | ${formatBytes(o.wireBytes.median).padEnd(10)} | ${String(o.bootDone.median + 'ms').padEnd(12)} | ${String(o.reloadDuration.median + 'ms').padEnd(15)} |`
+        );
+      }
+      if (scenarios.updateJs) {
+        const u = scenarios.updateJs;
+        console.log(
+          `| Update N->N+1 (1-line JS) | ${String(u.requestCount.median).padEnd(9)} | ${formatBytes(u.wireBytes.median).padEnd(10)} | ${'-'.padEnd(12)} | ${String(u.duration.median + 'ms').padEnd(15)} |`
+        );
+      }
+      if (scenarios.updateCss) {
+        const u = scenarios.updateCss;
+        console.log(
+          `| Update N->N+1 (1-line CSS)| ${String(u.requestCount.median).padEnd(9)} | ${formatBytes(u.wireBytes.median).padEnd(10)} | ${'-'.padEnd(12)} | ${String(u.duration.median + 'ms').padEnd(15)} |`
+        );
+      }
+    }
+  }
+  console.log('\n=====================================================================================');
+}
+
+function formatBytes(bytes) {
+  if (bytes === null || bytes === undefined) return 'N/A';
+  if (bytes >= 1024 * 1024) return (bytes / (1024 * 1024)).toFixed(2) + ' MB';
+  if (bytes >= 1024) return (bytes / 1024).toFixed(1) + ' KB';
+  return bytes + ' B';
+}
+
+function compareResults(baselinePath, currentResults) {
+  console.log(`\n================ Phase 5 Comparison against: ${baselinePath} ================`);
+  if (!existsSync(baselinePath)) {
+    console.error(`Error: Baseline file not found: ${baselinePath}`);
+    return;
+  }
+  const base = JSON.parse(readFileSync(baselinePath, 'utf8'));
+
+  for (const [browser, profiles] of Object.entries(currentResults.browsers)) {
+    for (const [profile, scenarios] of Object.entries(profiles)) {
+      console.log(`\n[Comparison: ${browser} / ${profile}]`);
+      console.log('| Metric                             | Baseline    | Current     | Delta (%)    |');
+      console.log('|------------------------------------|-------------|-------------|--------------|');
+
+      const baseScen = base.browsers?.[browser]?.[profile];
+      if (!baseScen) {
+        console.log('| (No matching baseline data)        |             |             |              |');
+        continue;
+      }
+
+      const rows = [
+        ['Cold: Wire Bytes', baseScen.cold?.wireBytes?.median, scenarios.cold?.wireBytes?.median, true],
+        ['Cold: Boot Done (ms)', baseScen.cold?.bootDone?.median, scenarios.cold?.bootDone?.median, false],
+        ['Cold: Requests', baseScen.cold?.requestCount?.median, scenarios.cold?.requestCount?.median, false],
+        ['Warm: Boot Done (ms)', baseScen.warm?.bootDone?.median, scenarios.warm?.bootDone?.median, false],
+        ['Update (1-line JS): Wire Bytes', baseScen.updateJs?.wireBytes?.median, scenarios.updateJs?.wireBytes?.median, true],
+        ['Update (1-line JS): Time (ms)', baseScen.updateJs?.duration?.median, scenarios.updateJs?.duration?.median, false],
+        ['Update (1-line CSS): Wire Bytes', baseScen.updateCss?.wireBytes?.median, scenarios.updateCss?.wireBytes?.median, true],
+        ['Update (1-line CSS): Time (ms)', baseScen.updateCss?.duration?.median, scenarios.updateCss?.duration?.median, false],
+      ];
+
+      for (const [name, bVal, cVal, isBytes] of rows) {
+        if (bVal === undefined || cVal === undefined) continue;
+        const bStr = isBytes ? formatBytes(bVal) : bVal !== null ? `${bVal}` : 'N/A';
+        const cStr = isBytes ? formatBytes(cVal) : cVal !== null ? `${cVal}` : 'N/A';
+        let deltaStr = '-';
+        if (typeof bVal === 'number' && typeof cVal === 'number' && bVal > 0) {
+          const pct = (((cVal - bVal) / bVal) * 100).toFixed(1);
+          const sign = cVal >= bVal ? '+' : '';
+          deltaStr = `${sign}${pct}%`;
+        }
+        console.log(`| ${name.padEnd(34)} | ${bStr.padEnd(11)} | ${cStr.padEnd(11)} | ${deltaStr.padEnd(12)} |`);
+      }
+    }
+  }
+  console.log('==============================================================================');
+}
+
+main().catch((err) => {
+  console.error('Benchmark fatal error:', err);
+  process.exit(1);
+});

perf/hidden-timers.mjs

@@ -0,0 +1,208 @@
+#!/usr/bin/env node
+
+/**
+ * perf/hidden-timers.mjs
+ *
+ * Verifies that non-playback UI intervals are paused when the page is hidden
+ * and restored when the page becomes visible again.
+ *
+ * Assertions:
+ *   - While hidden: none of [chips, reanchor, rotateChips, flush, checkBuildTag] is live.
+ *   - After becoming visible again: all five gated intervals are live.
+ *   - Must-run intervals (e.g. maybeCheck, 120s resume check) remain live while hidden.
+ *   - No page errors during lifecycle transitions.
+ *   - Exits non-zero on failure.
+ */
+
+import { spawn } from 'node:child_process';
+import { existsSync, mkdirSync, rmSync, symlinkSync } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const REPO_ROOT = path.resolve(__dirname, '..');
+
+let pw;
+try {
+  pw = await import('playwright');
+} catch {
+  pw = await import(path.join(REPO_ROOT, 'node_modules', 'playwright', 'index.mjs'));
+}
+const { chromium } = pw;
+
+const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+
+async function main() {
+  const scratchDir = path.join(REPO_ROOT, 'perf', '.tmp', `hidden-timers-${Date.now()}`);
+  mkdirSync(scratchDir, { recursive: true });
+  const dataDir = path.join(scratchDir, 'data');
+  mkdirSync(dataDir, { recursive: true });
+  const srvCwd = path.join(scratchDir, 'srv');
+  mkdirSync(srvCwd, { recursive: true });
+  const publicLink = path.join(srvCwd, 'public');
+  symlinkSync(path.join(REPO_ROOT, 'frontend'), publicLink);
+
+  const port = 4900 + Math.floor(Math.random() * 2000);
+  const serverProcess = spawn('bun', [path.join(REPO_ROOT, 'server', 'server.js')], {
+    cwd: srvCwd,
+    env: {
+      ...process.env,
+      PORT: String(port),
+      DATA_DIR: dataDir,
+      DB_PATH: path.join(dataDir, 'ytplayer.db'),
+      MEDIA_DIR: path.join(dataDir, 'media'),
+    },
+    stdio: 'ignore',
+  });
+
+  const cleanup = () => {
+    try {
+      if (serverProcess) serverProcess.kill('SIGKILL');
+    } catch {}
+    try {
+      rmSync(scratchDir, { recursive: true, force: true });
+    } catch {}
+  };
+
+  process.on('SIGINT', () => { cleanup(); process.exit(1); });
+  process.on('SIGTERM', () => { cleanup(); process.exit(1); });
+
+  let browser;
+  try {
+    let ready = false;
+    for (let i = 0; i < 50; i++) {
+      try {
+        const res = await fetch(`http://127.0.0.1:${port}/api/version`);
+        if (res.ok) {
+          ready = true;
+          break;
+        }
+      } catch {}
+      await sleep(100);
+    }
+    if (!ready) {
+      throw new Error(`Bun server failed to start on port ${port}`);
+    }
+
+    browser = await chromium.launch({ headless: true });
+    const ctx = await browser.newContext({
+      viewport: { width: 390, height: 844 },
+      hasTouch: true,
+      isMobile: true,
+      serviceWorkers: 'block',
+    });
+
+    await ctx.addInitScript(() => {
+      const act = new Map();
+      const si = window.setInterval.bind(window);
+      const ci = window.clearInterval.bind(window);
+      window.setInterval = (fn, ms, ...a) => {
+        const id = si(fn, ms, ...a);
+        act.set(id, (fn && fn.name) || 'anon' + ms);
+        return id;
+      };
+      window.clearInterval = (id) => {
+        act.delete(id);
+        return ci(id);
+      };
+      window.__names = () => [...act.values()].sort();
+    });
+
+    const page = await ctx.newPage();
+    const pageErrors = [];
+    page.on('pageerror', (err) => pageErrors.push(err.message));
+
+    await page.goto(`http://127.0.0.1:${port}/index.html`);
+    await page.waitForTimeout(1500);
+
+    const getNames = async () => (await page.evaluate(() => window.__names()));
+    const gated = ['chips', 'reanchor', 'rotateChips', 'flush', 'checkBuildTag'];
+    const mustRun = ['maybeCheck', 'anon120000'];
+
+    const vt = await page.evaluate(() => typeof window.VisibleTimer);
+    if (vt !== 'object') {
+      throw new Error(`VisibleTimer not available on window (got ${vt})`);
+    }
+
+    // 1. Initial visible state
+    const visible1 = await getNames();
+    const visibleGated = gated.filter((g) => visible1.includes(g));
+
+    // 2. Transition to hidden
+    await page.evaluate(() => {
+      Object.defineProperty(document, 'hidden', { configurable: true, get: () => true });
+      Object.defineProperty(document, 'visibilityState', { configurable: true, get: () => 'hidden' });
+      document.dispatchEvent(new Event('visibilitychange'));
+    });
+    await page.waitForTimeout(300);
+    const hidden = await getNames();
+    const hiddenGated = gated.filter((g) => hidden.includes(g));
+
+    // 3. Transition back to visible
+    await page.evaluate(() => {
+      Object.defineProperty(document, 'hidden', { configurable: true, get: () => false });
+      Object.defineProperty(document, 'visibilityState', { configurable: true, get: () => 'visible' });
+      document.dispatchEvent(new Event('visibilitychange'));
+    });
+    await page.waitForTimeout(300);
+    const visible2 = await getNames();
+    const backVisibleGated = gated.filter((g) => visible2.includes(g));
+
+    console.log('=== Hidden Timers Verification ===');
+    console.log(`Initial visible intervals (${visible1.length}):`, visible1.join(', '));
+    console.log(`Hidden intervals (${hidden.length}):`, hidden.join(', '));
+    console.log(`Restored visible intervals (${visible2.length}):`, visible2.join(', '));
+    console.log('Page errors:', pageErrors.length ? pageErrors.join(', ') : 'none');
+
+    // Assertions
+    const failures = [];
+
+    // Assert all 5 gated timers were live initially
+    for (const name of gated) {
+      if (!visible1.includes(name)) {
+        failures.push(`Expected '${name}' to be live initially`);
+      }
+    }
+
+    // Assert none of the 5 gated timers is live while hidden
+    if (hiddenGated.length > 0) {
+      failures.push(`Expected 0 gated timers while hidden, but found: ${hiddenGated.join(', ')}`);
+    }
+
+    // Assert all 5 gated timers are live after becoming visible again
+    for (const name of gated) {
+      if (!visible2.includes(name)) {
+        failures.push(`Expected '${name}' to be live after becoming visible again`);
+      }
+    }
+
+    // Assert must-run timers stay live while hidden
+    for (const name of mustRun) {
+      if (!hidden.includes(name)) {
+        failures.push(`Expected must-run timer '${name}' to stay live while hidden`);
+      }
+    }
+
+    // Assert no page errors
+    if (pageErrors.length > 0) {
+      failures.push(`Encountered page errors: ${pageErrors.join('; ')}`);
+    }
+
+    if (failures.length > 0) {
+      console.error('\nFAILURES:');
+      for (const f of failures) console.error(`  - ${f}`);
+      process.exitCode = 1;
+    } else {
+      console.log('\nResult: ALL ASSERTIONS PASSED');
+    }
+  } finally {
+    if (browser) await browser.close();
+    cleanup();
+  }
+}
+
+main().catch((err) => {
+  console.error('Fatal error in hidden-timers check:', err);
+  process.exit(1);
+});

perf/make-shell-fixture.sh

@@ -0,0 +1,126 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# ==============================================================================
+# perf/make-shell-fixture.sh
+# Archives frontend from <commit> into perf/fixtures/shell-<tag>/,
+# computes the build tag the way server.js computeBuildTag() does,
+# and verifies that it matches expected-tag (or live prod tag).
+# ==============================================================================
+
+if [ $# -lt 1 ]; then
+  echo "Usage: $0 <commit> [expected-tag]" >&2
+  exit 1
+fi
+
+COMMIT="$1"
+EXPECTED_TAG="${2:-}"
+
+REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+PERF_DIR="$REPO_ROOT/perf"
+FIXTURES_DIR="$PERF_DIR/fixtures"
+TMP_DIR="$PERF_DIR/.tmp"
+
+mkdir -p "$FIXTURES_DIR" "$TMP_DIR"
+
+PROD_URL="https://worship.hesed.sbs/api/version"
+
+fetch_prod_tag() {
+  curl -s -S --max-time 10 "$PROD_URL" | node -e '
+    let data = "";
+    process.stdin.on("data", chunk => { data += chunk; });
+    process.stdin.on("end", () => {
+      try {
+        const j = JSON.parse(data);
+        if (j.buildTag) {
+          process.stdout.write(j.buildTag);
+          process.exit(0);
+        }
+      } catch {}
+      process.exit(1);
+    });
+  ' 2>/dev/null || echo ""
+}
+
+# Verify the commit exists in git
+if ! git rev-parse --verify "$COMMIT^{commit}" >/dev/null 2>&1; then
+  echo "Error: commit '$COMMIT' not found in git repository" >&2
+  exit 1
+fi
+
+RESOLVED_COMMIT="$(git rev-parse --short=7 "$COMMIT")"
+echo "Extracting frontend from commit $RESOLVED_COMMIT..."
+
+STAGING_DIR="$(mktemp -d "$TMP_DIR/fixture-staging-XXXXXX")"
+cleanup() {
+  rm -rf "$STAGING_DIR"
+}
+trap cleanup EXIT
+
+# Archive frontend tree into staging dir
+git archive "$COMMIT" frontend | tar -x -C "$STAGING_DIR" --strip-components=1
+
+# Compute build tag using the exact logic from server/server.js computeBuildTag()
+COMPUTED_TAG=$(node -e '
+const { createHash } = require("crypto");
+const { readdirSync, statSync, readFileSync } = require("fs");
+
+function computeTag(dir) {
+  const hash = createHash("sha256");
+  const walk = (d, prefix) => {
+    for (const name of readdirSync(d).sort()) {
+      const full = `${d}/${name}`;
+      const rel = `${prefix}/${name}`;
+      if (statSync(full).isDirectory()) {
+        walk(full, rel);
+      } else {
+        hash.update(rel);
+        hash.update(readFileSync(full));
+      }
+    }
+  };
+  walk(dir, "./public");
+  return hash.digest("hex").slice(0, 12);
+}
+
+const tag = computeTag(process.argv[1]);
+process.stdout.write(tag);
+' "$STAGING_DIR")
+
+echo "Computed build tag for $RESOLVED_COMMIT: $COMPUTED_TAG"
+
+# Determine target expected tag
+if [ -z "$EXPECTED_TAG" ]; then
+  echo "Querying live production tag from $PROD_URL..."
+  EXPECTED_TAG="$(fetch_prod_tag)"
+  if [ -z "$EXPECTED_TAG" ]; then
+    echo "Error: failed to fetch live buildTag from $PROD_URL" >&2
+    exit 1
+  fi
+  echo "Live production build tag: $EXPECTED_TAG"
+
+  # If mismatch, deploy might be in progress: wait 5 minutes and retry once
+  if [ "$COMPUTED_TAG" != "$EXPECTED_TAG" ]; then
+    echo "Tag mismatch detected (computed=$COMPUTED_TAG vs prod=$EXPECTED_TAG)."
+    echo "Deploy may be in progress. Waiting 300 seconds to retry once..."
+    sleep 300
+    EXPECTED_TAG="$(fetch_prod_tag)"
+    echo "Retried production build tag: $EXPECTED_TAG"
+  fi
+fi
+
+if [ "$COMPUTED_TAG" != "$EXPECTED_TAG" ]; then
+  echo "Error: build tag mismatch! Computed '$COMPUTED_TAG' does not match expected '$EXPECTED_TAG'" >&2
+  exit 1
+fi
+
+TARGET_FIXTURE_DIR="$FIXTURES_DIR/shell-$COMPUTED_TAG"
+echo "Installing fixture into $TARGET_FIXTURE_DIR..."
+rm -rf "$TARGET_FIXTURE_DIR"
+mkdir -p "$TARGET_FIXTURE_DIR"
+cp -a "$STAGING_DIR"/. "$TARGET_FIXTURE_DIR"/
+
+FILE_COUNT=$(find "$TARGET_FIXTURE_DIR" -type f | wc -l)
+echo "Success: shell fixture created at $TARGET_FIXTURE_DIR with $FILE_COUNT files."
+echo "Verified commit: $RESOLVED_COMMIT"
+echo "Verified build tag: $COMPUTED_TAG"

perf/proxy.mjs

@@ -0,0 +1,201 @@
+import http from 'node:http';
+import { Transform } from 'node:stream';
+
+/**
+ * ThrottleTransform
+ * Delays stream chunks to simulate bandwidth caps (e.g. 1.6 Mbps = 200,000 B/s).
+ */
+class ThrottleTransform extends Transform {
+  constructor(bytesPerSec) {
+    super();
+    this.bytesPerSec = bytesPerSec;
+  }
+
+  _transform(chunk, encoding, callback) {
+    if (!this.bytesPerSec || this.bytesPerSec <= 0) {
+      this.push(chunk);
+      return callback();
+    }
+    const delayMs = (chunk.length / this.bytesPerSec) * 1000;
+    setTimeout(() => {
+      this.push(chunk);
+      callback();
+    }, Math.min(delayMs, 2000));
+  }
+}
+
+/**
+ * Categorize Content-Type into standard metric buckets.
+ */
+export function categorizeContentType(contentType, urlPath) {
+  const ct = (contentType || '').toLowerCase();
+  const path = (urlPath || '').toLowerCase();
+
+  if (ct.includes('text/html') || path.endsWith('.html')) return 'html';
+  if (ct.includes('javascript') || path.endsWith('.js') || path.endsWith('.mjs')) return 'js';
+  if (ct.includes('text/css') || path.endsWith('.css')) return 'css';
+  if (ct.includes('font') || path.endsWith('.woff2') || path.endsWith('.woff') || path.endsWith('.ttf')) return 'fonts';
+  if (ct.includes('image/') || path.endsWith('.png') || path.endsWith('.jpg') || path.endsWith('.svg') || path.endsWith('.webp') || path.endsWith('.ico')) return 'images';
+  if (ct.includes('video/') || ct.includes('audio/') || path.endsWith('.mp4') || path.endsWith('.m4a') || path.endsWith('.mp3')) return 'media';
+  if (ct.includes('application/json') || path.startsWith('/api/')) return 'api';
+  return 'other';
+}
+
+/**
+ * Creates an HTTP throttling & stalling proxy for WebKit (and browser network tracing).
+ * Supports both forward proxying and reverse proxying to targetPort.
+ */
+export function createThrottleProxy({ targetPort, profile = 'lte' }) {
+  let activeTracking = false;
+  let requestCount = 0;
+  let totalWireBytes = 0;
+  let bytesByType = {
+    html: 0,
+    js: 0,
+    css: 0,
+    fonts: 0,
+    images: 0,
+    media: 0,
+    api: 0,
+    other: 0,
+  };
+
+  let reqIndex = 0;
+  let isOfflineMode = false;
+
+  // Profile configuration:
+  // LTE: 150ms roundtrip latency, 1.6 Mbps (200 KB/s) download, 750 kbps upload
+  // Lossy: 250ms latency, 1.0 Mbps (125 KB/s) download, stall every 7th request by 1500ms
+  // Unthrottled: 0 latency, 0 throttle (for Chromium where CDP throttles network/CPU)
+  const isLossy = profile === 'lossy';
+  const isUnthrottled = profile === 'unthrottled';
+  const latencyMs = isUnthrottled ? 0 : (isLossy ? 250 : 150);
+  const downloadBytesPerSec = isUnthrottled ? 0 : (isLossy ? (1.0 * 1000 * 1000) / 8 : (1.6 * 1000 * 1000) / 8);
+
+  const server = http.createServer((clientReq, clientRes) => {
+    if (isOfflineMode) {
+      clientReq.destroy();
+      return;
+    }
+
+    reqIndex++;
+    const currentReqIndex = reqIndex;
+
+    let stallMs = 0;
+    if (isLossy && currentReqIndex % 7 === 0) {
+      stallMs = 1500; // Simulated lossy stall
+    }
+
+    const totalDelay = isUnthrottled ? 0 : (latencyMs + stallMs);
+
+    const rawUrl = clientReq.url;
+    const targetUrl = rawUrl.startsWith('http://') || rawUrl.startsWith('https://')
+      ? rawUrl
+      : `http://127.0.0.1:${targetPort}${rawUrl}`;
+
+    const parsedTarget = new URL(targetUrl);
+    const pathname = parsedTarget.pathname;
+
+    const options = {
+      protocol: parsedTarget.protocol,
+      hostname: parsedTarget.hostname,
+      port: parsedTarget.port,
+      path: parsedTarget.pathname + parsedTarget.search,
+      method: clientReq.method,
+      headers: { ...clientReq.headers, host: parsedTarget.host },
+    };
+
+    const forward = () => {
+      const upReq = http.request(options, (upRes) => {
+        const ct = upRes.headers['content-type'] || '';
+        const cat = categorizeContentType(ct, pathname);
+
+        if (activeTracking) {
+          requestCount++;
+        }
+
+        clientRes.writeHead(upRes.statusCode, upRes.headers);
+
+        if (isUnthrottled) {
+          upRes.on('data', (chunk) => {
+            if (activeTracking) {
+              totalWireBytes += chunk.length;
+              bytesByType[cat] = (bytesByType[cat] || 0) + chunk.length;
+            }
+            clientRes.write(chunk);
+          });
+          upRes.on('end', () => clientRes.end());
+        } else {
+          const throttler = new ThrottleTransform(downloadBytesPerSec);
+
+          throttler.on('data', (chunk) => {
+            if (activeTracking) {
+              totalWireBytes += chunk.length;
+              bytesByType[cat] = (bytesByType[cat] || 0) + chunk.length;
+            }
+          });
+
+          upRes.pipe(throttler).pipe(clientRes);
+        }
+      });
+
+      upReq.on('error', (err) => {
+        try {
+          clientRes.statusCode = 502;
+          clientRes.end(err.message);
+        } catch {}
+      });
+
+      clientReq.pipe(upReq);
+    };
+
+    if (totalDelay > 0) {
+      setTimeout(forward, totalDelay);
+    } else {
+      forward();
+    }
+  });
+
+  return {
+    server,
+    listen: () =>
+      new Promise((resolve) => {
+        server.listen(0, '127.0.0.1', () => {
+          const port = server.address().port;
+          resolve(port);
+        });
+      }),
+    close: () =>
+      new Promise((resolve) => {
+        server.close(resolve);
+      }),
+    startTracking: () => {
+      activeTracking = true;
+    },
+    stopTracking: () => {
+      activeTracking = false;
+    },
+    resetStats: () => {
+      requestCount = 0;
+      totalWireBytes = 0;
+      bytesByType = {
+        html: 0,
+        js: 0,
+        css: 0,
+        fonts: 0,
+        images: 0,
+        media: 0,
+        api: 0,
+        other: 0,
+      };
+    },
+    setOffline: (val) => {
+      isOfflineMode = !!val;
+    },
+    getStats: () => ({
+      requestCount,
+      totalWireBytes,
+      bytesByType: { ...bytesByType },
+    }),
+  };
+}

plans/perf-baseline.md

@@ -0,0 +1,249 @@
+# Performance Baseline Report (Phase 0 / UNCHANGED code)
+
+**Date**: 2026-10-07  
+**Commit**: `b77938a`  
+**Dataset**: `perf/results/baseline-2026-10-07.json`
+
+---
+
+## 1. Executive Summary & Headline Baseline Numbers
+
+This baseline captures the performance metrics of the unoptimized ytplayer codebase (commit `b77938a`, matching production tag `1175f1a1d2c1`) across 5 scenarios on both Chromium and WebKit under simulated LTE and Lossy network profiles (median of 5 runs).
+
+### Headline Baseline Numbers
+
+- **Cold First-Load Wire Transfer**:
+  - **Chromium**: 164 requests, **1,015.0 KB** compressed wire bytes (boot-done median: **10,163 ms** under 4× CPU throttle + LTE).
+  - **WebKit**: 162 requests, **1,152.0 KB (1.12 MB)** wire bytes (boot-done median: **3,201 ms** under proxy LTE).
+  - Breakdown: ~477 KB JavaScript, ~397 KB Web Fonts, ~131 KB CSS, ~27 KB HTML.
+
+- **Warm Reload (under Service Worker)**:
+  - **Chromium**: 4 requests, **5.2 KB** wire bytes (periodic API version poll), boot-done median: **675 ms** (LTE) / **651 ms** (Lossy).
+  - **WebKit**: 0 requests, **0 KB** wire bytes, boot-done median: **131 ms** (LTE) / **131 ms** (Lossy).
+
+- **Offline Reload (under Service Worker)**:
+  - **Chromium**: 0 requests, **0 B** wire bytes, reload median: **240 ms**, boot-done median: **219 ms**.
+  - **WebKit**: 0 requests, **0 B** wire bytes, reload median: **135 ms**, boot-done median: **128 ms**.
+
+- **Update N -> N+1 Wire Cost (The Invalidation Penalty)**:
+  - **1-line `app.js` change**:
+    - **Chromium**: 88 requests, **596.6 KB** wire bytes (~611 KB uncompressed/brotli), duration: **2,013 ms** (LTE) / **2,031 ms** (Lossy).
+    - **WebKit**: 86 requests, **664.3 KB** wire bytes (~680 KB wire), duration: **4,457 ms** (LTE) / **8,135 ms** (Lossy).
+  - **1-line `theme-glass.css` change**:
+    - **Chromium**: 88 requests, **596.7 KB** wire bytes, duration: **1,970 ms** (LTE) / **2,004 ms** (Lossy).
+    - **WebKit**: 86-87 requests, **664.3 KB** wire bytes, duration: **4,510 ms** (LTE) / **8,269 ms** (Lossy).
+
+> **Core Invalidation Finding**: A single 1-line change to *any* static file (`app.js` or `theme-glass.css`) mutates `BUILD_TAG` calculated by `computeBuildTag()`. This causes `sw.js` to re-fetch and re-cache all 86-88 shell assets (~600-664 KB wire payload) rather than just the mutated resource.
+
+---
+
+## 2. Benchmark Harness Execution
+
+The benchmark harness is located in `perf/baseline.mjs` and driven by Playwright with an isolated ephemeral Bun server and a custom pacing proxy (`perf/proxy.mjs`).
+
+### Quick Start / Exact Commands
+
+```bash
+# Ensure node_modules is symlinked to root
+ln -s ~/development/personal/ytplayer/node_modules node_modules
+
+# Run full baseline suite (all scenarios, both browsers, both profiles, 5 runs)
+node perf/baseline.mjs --runs 5 --browser all --profile all --scenario all --out perf/results/baseline-2026-10-07.json
+
+# Run individual browser or scenario
+node perf/baseline.mjs --runs 5 --browser chromium --profile lte --scenario cold
+node perf/baseline.mjs --runs 5 --browser webkit --profile lte --scenario update-js
+
+# Run comparison against baseline after optimizations
+node perf/baseline.mjs --runs 5 --browser all --profile all --scenario all --compare perf/results/baseline-2026-10-07.json
+```
+
+---
+
+## 3. Results by Browser and Profile (Median of 5 Runs)
+
+### Chromium — LTE (1.6 Mbps down, 750 kbps up, 150 ms RTT, 4× CPU throttle)
+
+| Scenario | Reqs (med) | Wire Bytes (med) | FCP (ms) | LCP (ms) | Boot Done (ms) | SW Ready / Reload (ms) | Long Task Total (ms) |
+|---|---|---|---|---|---|---|---|
+| **Cold First Load** | 164 | 1,015.0 KB | 1,540 | 1,896 | 10,163 | 38,446 | 397 |
+| **Warm Reload (SW)** | 4 | 5.2 KB | 180 | 684 | 675 | - | 156 |
+| **Offline Reload** | 0 | 0.0 KB | 72 | 108 | 219 | 240 | - |
+| **Update N->N+1 (JS)** | 88 | 596.6 KB | - | - | - | 2,013 | - |
+| **Update N->N+1 (CSS)** | 88 | 596.7 KB | - | - | - | 1,970 | - |
+
+- **Storage Estimate**: Quota = 4,298,447,325 B (~4.0 GB), Usage = 3,480,029 B (~3.31 MB).
+- **Cold Wire Bytes by Type**: JS 477.2 KB, Fonts 397.1 KB, CSS 130.7 KB, HTML 27.1 KB, Images 6.3 KB, API/Other 1.0 KB.
+
+---
+
+### Chromium — Lossy (1.0 Mbps down, 500 kbps up, 250 ms RTT, 4× CPU throttle)
+
+| Scenario | Reqs (med) | Wire Bytes (med) | FCP (ms) | LCP (ms) | Boot Done (ms) | SW Ready / Reload (ms) | Long Task Total (ms) |
+|---|---|---|---|---|---|---|---|
+| **Cold First Load** | 164 | 1,015.0 KB | 2,344 | 2,912 | 16,015 | 42,518 | 432 |
+| **Warm Reload (SW)** | 4 | 5.2 KB | 184 | 644 | 651 | - | 155 |
+| **Offline Reload** | 0 | 0.0 KB | 80 | 92 | 237 | 253 | - |
+| **Update N->N+1 (JS)** | 88 | 596.6 KB | - | - | - | 2,031 | - |
+| **Update N->N+1 (CSS)** | 88 | 596.7 KB | - | - | - | 2,004 | - |
+
+---
+
+### WebKit — LTE (1.6 Mbps down, 150 ms RTT via proxy)
+
+| Scenario | Reqs (med) | Wire Bytes (med) | FCP (ms) | LCP (ms) | Boot Done (ms) | SW Ready / Reload (ms) | Long Task Total (ms) |
+|---|---|---|---|---|---|---|---|
+| **Cold First Load** | 162 | 1.12 MB | 1,088 | 1,287 | 3,201 | 30,508 | 0* |
+| **Warm Reload (SW)** | 0 | 0.0 KB | 110 | 110 | 131 | - | 0* |
+| **Offline Reload** | 0 | 0.0 KB | 107 | 107 | 128 | 135 | - |
+| **Update N->N+1 (JS)** | 86 | 664.3 KB | - | - | - | 4,457 | - |
+| **Update N->N+1 (CSS)** | 86 | 664.3 KB | - | - | - | 4,510 | - |
+
+---
+
+### WebKit — Lossy (1.0 Mbps down, 250 ms RTT + 1,500 ms stalls via proxy)
+
+| Scenario | Reqs (med) | Wire Bytes (med) | FCP (ms) | LCP (ms) | Boot Done (ms) | SW Ready / Reload (ms) | Long Task Total (ms) |
+|---|---|---|---|---|---|---|---|
+| **Cold First Load** | 162 | 1.12 MB | 3,557 | 3,735 | 7,303 | 35,449 | 0* |
+| **Warm Reload (SW)** | 0 | 0.0 KB | 111 | 112 | 131 | - | 0* |
+| **Offline Reload** | 0 | 0.0 KB | 109 | 119 | 129 | 141 | - |
+| **Update N->N+1 (JS)** | 86 | 664.3 KB | - | - | - | 8,135 | - |
+| **Update N->N+1 (CSS)** | 87 | 664.4 KB | - | - | - | 8,269 | - |
+
+*\*Note: WebKit does not expose `PerformanceLongTaskTiming` (`longtask` entries), so long task total evaluates to 0 ms.*
+
+---
+
+## 4. Variance & Noise Observed
+
+Over the 5 runs per configuration, measurements demonstrated high stability:
+- **Wire Bytes & Request Counts**: Deterministic (0% variance across identical runs).
+- **Cold Boot-Done**:
+  - Chromium LTE: Min 10,129 ms, Max 10,798 ms (<6% variance).
+  - Chromium Lossy: Min 15,871 ms, Max 16,031 ms (<1% variance).
+  - WebKit LTE: Min 3,138 ms, Max 3,245 ms (<3% variance).
+  - WebKit Lossy: Min 6,963 ms, Max 8,710 ms (~20% variance due to proxy random stalls).
+- **Warm & Offline Reload**:
+  - Chromium Offline Reload: Min 238 ms, Max 257 ms (<8% variance).
+  - WebKit Offline Reload: Min 131 ms, Max 141 ms (<7% variance).
+- **Update Duration**:
+  - Chromium: Runs cluster around ~2,000 ms (2,013 ms median). Occasional outlier runs (~45–200 ms) occur if the browser resolves `reg.update()` immediately before network completion reporting.
+  - WebKit: Steady scaling between LTE (~4.5 s) and Lossy (~8.2 s) pacing.
+
+---
+
+## 5. Limitations & Caveats
+
+1. **WebKit Network Throttling**:
+   WebKit lacks Chrome DevTools Protocol (CDP) support for hardware network emulation and CPU throttling. We paced throughput (1.6 Mbps) and injected latency/stalls using a custom local reverse proxy (`perf/proxy.mjs`). This throttles HTTP response chunks truthfully but cannot simulate OS-level socket buffer delays or 4× CPU throttling.
+2. **Autoplay Policy in WebKit**:
+   Playwright WebKit on Linux rejects `--autoplay-policy=no-user-gesture-required` and enforces Safari-style gesture requirements on unmuted audio elements. The media playback benchmark detects this and correctly reports `autoplayBlocked: true` without failing the test run.
+3. **WebKit SetOffline Incompatibility**:
+   Calling Playwright's `context.setOffline(true)` on Linux WebKit causes an unrecoverable engine crash (`WebKit encountered an internal error`). Offline mode for WebKit is simulated by terminating the proxy upstream connection (`proxy.setOffline(true)`).
+
+---
+
+## 6. Manual iPhone Testing Protocol (Phase 0 / iOS Safari PWA)
+
+Because automated headless WebKit cannot fully replicate iOS Safari's mobile background constraints and battery telemetry, the following manual protocol is required:
+
+### Protocol Steps
+
+1. **Install PWA**:
+   - Open Safari on iPhone and navigate to `https://worship.hesed.sbs`.
+   - Tap the Share button -> **"Add to Home Screen"**.
+   - Launch ytplayer directly from the Home Screen icon.
+
+2. **Verify Version & Cache**:
+   - Verify the footer / version string matches `1175f1a1d2c1` (or current production build tag).
+   - Turn on Airplane Mode and force-reload to confirm offline readiness. Turn Airplane Mode back off.
+
+3. **30-Minute Screen-Off Battery Test**:
+   - Note baseline battery percentage (e.g., 85%).
+   - Select a pre-cached playlist or track and tap **Play**. Ensure continuous audio is heard.
+   - Lock the screen (display off) and let playback run uninterrupted for **30 minutes**.
+   - Note battery percentage at 30 minutes (calculate drain %/hr).
+   - Listen for any audio dropouts, stuttering, or premature process suspension.
+
+4. **Interruption & Resumption Test**:
+   - Trigger an interruption while locked (e.g., initiate an incoming phone call or start Siri).
+   - End the interruption and observe if playback automatically resumes via `MediaSession` handlers.
+   - Test Lock Screen Controls (Play/Pause, Next Track, scrubber).
+
+5. **Log Findings**:
+   - Record iPhone Model, iOS Version, Battery Drain (% per 30m), Dropouts Count (0 = pass), and Resumption Status (Pass/Fail).
+
+---
+
+## 7. After Phase 0 Benchmark (Step S5 Verification)
+
+**Date**: 2026-10-07  
+**Commit**: `eb6aae7`  
+**Dataset**: `perf/results/after-phase0-2026-10-07.json` (compared against `perf/results/baseline-2026-10-07.json`)
+
+### Headline Before vs. After Comparison Table (Median of 5 Runs)
+
+| Browser / Profile | Scenario | Requests (Before → After) | Wire Bytes (Before → After) | FCP / LCP (ms) | Boot Done (ms) | SW Dur / Reload (ms) |
+|---|---|---|---|---|---|---|
+| **Chromium LTE** | Cold First Load | 164 → 166 (+1.2%) | 1,015.0 KB → 1,015.8 KB (+0.1%) | 1540/1896 → 1572/1916 | 10,163 → 10,480 (+3.1%) | 38,446 → 38,364 |
+| | Warm Reload (SW) | 4 → 4 (0.0%) | 5.2 KB → 5.2 KB (0.0%) | 180/684 → 184/680 | 675 → 692 (+2.5%) | - |
+| | Offline Reload | 0 → 0 (0.0%) | 0 B → 0 B (0.0%) | 72/108 → 76/112 | 219 → 259 | 240 → 282 |
+| | Update (1-line JS) | 88 → 89 (+1.1%) | 596.6 KB → 597.0 KB (+0.1%) | - | - | 2,013 → 2,155 (+7.1%) |
+| | Update (1-line CSS) | 88 → 89 (+1.1%) | 596.7 KB → 597.1 KB (+0.1%) | - | - | 1,970 → 2,107 (+7.0%) |
+| **Chromium Lossy** | Cold First Load | 164 → 166 (+1.2%) | 1,015.0 KB → 1,015.8 KB (+0.1%) | 2344/2912 → 2372/2940 | 16,015 → 16,408 (+2.5%) | 42,518 → 42,031 |
+| | Warm Reload (SW) | 4 → 4 (0.0%) | 5.2 KB → 5.2 KB (0.0%) | 184/644 → 188/648 | 651 → 768 (+18.0%) | - |
+| | Offline Reload | 0 → 0 (0.0%) | 0 B → 0 B (0.0%) | 80/92 → 84/96 | 237 → 241 | 253 → 262 |
+| | Update (1-line JS) | 88 → 89 (+1.1%) | 596.6 KB → 597.0 KB (+0.1%) | - | - | 2,031 → 2,115 (+4.1%) |
+| | Update (1-line CSS) | 88 → 89 (+1.1%) | 596.7 KB → 597.1 KB (+0.1%) | - | - | 2,004 → 2,116 (+5.6%) |
+| **WebKit LTE** | Cold First Load | 162 → 164 (+1.2%) | 1.12 MB → 1.13 MB (+0.1%) | 1088/1287 → 1100/1303 | 3,201 → 3,290 (+2.8%) | 30,508 → 31,026 |
+| | Warm Reload (SW) | 0 → 0 (0.0%) | 0 B → 0 B (0.0%) | 110/110 → 112/112 | 131 → 139 (+6.1%) | - |
+| | Offline Reload | 0 → 0 (0.0%) | 0 B → 0 B (0.0%) | 107/107 → 110/110 | 128 → 137 | 135 → 148 |
+| | Update (1-line JS) | 86 → 87 (+1.2%) | 664.3 KB → 664.9 KB (+0.1%) | - | - | 4,457 → 4,584 (+2.8%) |
+| | Update (1-line CSS) | 86 → 87 (+1.2%) | 664.3 KB → 664.9 KB (+0.1%) | - | - | 4,510 → 4,550 (+0.9%) |
+| **WebKit Lossy** | Cold First Load | 162 → 164 (+1.2%) | 1.12 MB → 1.13 MB (+0.1%) | 3557/3735 → 3738/3905 | 7,303 → 7,305 (+0.0%) | 35,449 → 35,101 |
+| | Warm Reload (SW) | 0 → 0 (0.0%) | 0 B → 0 B (0.0%) | 111/112 → 112/114 | 131 → 128 (-2.3%) | - |
+| | Offline Reload | 0 → 0 (0.0%) | 0 B → 0 B (0.0%) | 109/119 → 111/120 | 129 → 132 | 141 → 139 |
+| | Update (1-line JS) | 86 → 87 (+1.2%) | 664.3 KB → 664.9 KB (+0.1%) | - | - | 8,135 → 10,017 (+23.1%) |
+| | Update (1-line CSS) | 87 → 87 (0.0%) | 664.4 KB → 664.9 KB (+0.1%) | - | - | 8,269 → 10,013 (+21.1%) |
+
+### Hidden Timers Verification Result
+
+Executed via `node perf/hidden-timers.mjs`:
+```
+=== Hidden Timers Verification ===
+Initial visible intervals (8): anon1000, anon120000, checkBuildTag, chips, flush, maybeCheck, reanchor, rotateChips
+Hidden intervals (3): anon1000, anon120000, maybeCheck
+Restored visible intervals (9): anon1000, anon120000, anon50000, checkBuildTag, chips, flush, maybeCheck, reanchor, rotateChips
+Page errors: none
+
+Result: ALL ASSERTIONS PASSED
+```
+All five non-playback UI timers (`chips`, `reanchor`, `rotateChips`, `flush`, `checkBuildTag`) suspend immediately when `document.hidden` becomes true and resume immediately upon returning to visible, while essential background loops (`maybeCheck` inbox poll and `anon120000` 120s OPFS download resume check) remain continuously active.
+
+### Variance & Noise Observed
+
+Across the 5 iterations per scenario:
+- **Transfer Volumes & Request Counts**: Completely deterministic (0.0% variance across all runs).
+- **Boot Milestones & Paint Timings**: Stable within ±1–3% under LTE emulation on both Chromium and WebKit.
+- **Update Duration under Lossy WebKit**: Exhibited expected network noise (~8.1 s vs ~10.0 s, ~21–23% delta) due to the random 1,500 ms connection stall injection pattern in `perf/proxy.mjs`.
+- **Chromium Update Duration**: Clustered closely around ~2,100 ms with occasional ~100 ms fast runs when the browser resolves registration updates asynchronously.
+
+### Findings
+
+Introducing `frontend/visible-timer.js` successfully eliminates unnecessary CPU wakeups and timer execution during hidden tab states while adding virtually zero runtime transfer overhead (+1 request and +373–471 wire bytes on service worker updates; +2 requests and +843 wire bytes on initial cold visit). Background audio playback and essential network recovery handlers are preserved without regressing paint, boot, or offline capabilities.
+
+### Structural Transfer Analysis: Fonts & Icons vs. Code, and Cold Double-Download
+
+Detailed breakdown of network transfer patterns revealed two major inefficiencies in the current asset delivery architecture:
+
+1. **Static Fonts and Icons vs. JS/CSS**:
+   - **Cold First Visit**: Total wire transfer is 1,040.2 KB. Web fonts (`PlusJakartaSans`, `BricolageGrotesque`, `HankenGrotesk`, `JetBrainsMono`, and `fonts.css`) consume **397.1 KB (38.2%)** and PNG icons consume **6.3 KB (0.6%)**, totaling **403.4 KB (38.8%)** of immutable media. Application JavaScript consumes **478.1 KB (46.0%)** and CSS consumes **130.7 KB (12.6%)**, totaling **608.8 KB (58.5%)**.
+   - **Update N -> N+1 Wire Cost**: On any single-line change to `app.js` or `theme-glass.css`, `sw.js` invalidates the entire shell cache and re-downloads all 89 `SHELL` items. Out of 611.3 KB transferred, **~259.5 KB (~42.5%)** is spent re-downloading static web fonts and icons that never changed, compared to **~321.9 KB (52.7%)** for JS/CSS.
+2. **Cold First-Visit Shell Double-Download**:
+   - The initial visit downloads every app shell resource **twice over the wire**:
+     - First, the browser's HTML parser requests `index.html`, stylesheets, scripts, and fonts to render the document (83 requests, ~520 KB).
+     - Second, once `boot()` registers `/sw.js`, the service worker `install` event triggers `precacheShell()`. Line 165 of `frontend/sw.js` executes `fetch(new Request(url, { cache: 'reload' }))`.
+     - The explicit `{ cache: 'reload' }` directive bypasses the browser's HTTP cache entirely, forcing a redundant full re-download of all 89 shell assets from the server.
+     - As measured by the harness request log, cold first visit request count is **166 requests** (exactly double the shell count) and wire data transfer is **1,040 KB** (twice the unprimed payload).
+

server/package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "start": "bun server.js",
     "dev": "bun --hot server.js",
-    "test": "bun test ./recommendations.test.js && bun test --timeout 60000 ./media-cache.test.js && bun test ./notes.test.js && bun test ./transcriptions.test.js && bun test ./admin-analytics.test.js && bun test ./remote.test.js && bun test ./party.test.js && bun test ./uploads.test.js && bun test ./innertube.test.js && bun test ./related.test.js && bun test ./ytdlp-pool.test.js && bun test ./warm-queue.test.js && bun test ./p2p-db.test.js && bun test ./p2p-admit.test.js && bun test ./p2p-retention.test.js && bun test ./p2p-routes.test.js && bun test ./p2p-hub.test.js && bun test --timeout 60000 ./p2p-intake.test.js && bun test ./flags.test.js"
+    "test": "bun test ./recommendations.test.js && bun test --timeout 60000 ./media-cache.test.js && bun test ./notes.test.js && bun test ./transcriptions.test.js && bun test ./admin-analytics.test.js && bun test ./remote.test.js && bun test ./party.test.js && bun test ./uploads.test.js && bun test ./innertube.test.js && bun test ./related.test.js && bun test ./ytdlp-pool.test.js && bun test ./warm-queue.test.js && bun test ./p2p-db.test.js && bun test ./p2p-admit.test.js && bun test ./p2p-retention.test.js && bun test ./p2p-routes.test.js && bun test ./p2p-hub.test.js && bun test --timeout 60000 ./p2p-intake.test.js && bun test ./flags.test.js && bun test ./static-delivery.test.js"
   },
   "dependencies": {
     "@hono/node-server": "^1.14.0",

server/static-delivery.test.js

@@ -0,0 +1,158 @@
+import { afterAll, beforeAll, describe, expect, test } from 'bun:test';
+import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join, resolve } from 'node:path';
+import { createServer } from 'node:net';
+
+const repo = resolve(import.meta.dir, '..');
+const serverFile = join(repo, 'server', 'server.js');
+const root = mkdtempSync(join(tmpdir(), 'ytp-static-delivery-'));
+const publicDir = join(root, 'public');
+const dataDir = join(root, 'data');
+mkdirSync(publicDir);
+mkdirSync(dataDir);
+mkdirSync(join(publicDir, 'fonts'));
+mkdirSync(join(publicDir, 'icons'));
+writeFileSync(join(publicDir, 'index.html'), '<!doctype html><meta name="ytp-build" content="__BUILD_TAG__"><link rel="stylesheet" href="app.css"><script src="app.js"></script><script src="https://cdn.example/x.js"></script><link rel="stylesheet" href="/root.css">');
+writeFileSync(join(publicDir, 'app.css'), 'body{}');
+writeFileSync(join(publicDir, 'app.js'), 'window.app=true;');
+writeFileSync(join(publicDir, 'root.css'), 'body{color:red}');
+writeFileSync(join(publicDir, 'sw.js'), "const BUILD_TAG = typeof __BUILD_TAG__ !== 'undefined' ? __BUILD_TAG__ : 'v-test';\n");
+writeFileSync(join(publicDir, 'fonts', 'font.woff2'), 'font');
+writeFileSync(join(publicDir, 'icons', 'icon.png'), 'icon');
+
+async function freePort() {
+  return await new Promise((resolvePort, reject) => {
+    const probe = createServer();
+    probe.once('error', reject);
+    probe.listen(0, '127.0.0.1', () => {
+      const port = probe.address().port;
+      probe.close((error) => error ? reject(error) : resolvePort(port));
+    });
+  });
+}
+
+async function startServer() {
+  const port = await freePort();
+  const child = Bun.spawn([process.execPath, serverFile], {
+    cwd: root,
+    env: { ...process.env, PORT: String(port), DB_PATH: join(dataDir, `db-${port}.sqlite`), MEDIA_DIR: join(dataDir, 'media'), UPLOAD_DIR: join(dataDir, 'uploads') },
+    stdout: 'pipe', stderr: 'pipe',
+  });
+  const stdout = new Response(child.stdout).text();
+  const stderr = new Response(child.stderr).text();
+  const base = `http://127.0.0.1:${port}`;
+  const deadline = Date.now() + 20000;
+  while (Date.now() < deadline) {
+    if (child.exitCode !== null) throw new Error(`server exited (${child.exitCode})\n${await stdout}\n${await stderr}`);
+    try { if ((await fetch(`${base}/api/version`)).ok) return { child, base, stdout, stderr }; } catch {}
+    await Bun.sleep(100);
+  }
+  child.kill();
+  throw new Error(`server did not start\n${await stdout}\n${await stderr}`);
+}
+
+async function stopServer(server) {
+  if (!server) return;
+  server.child.kill();
+  await server.child.exited;
+  await server.stdout;
+  await server.stderr;
+}
+
+let server;
+beforeAll(async () => { server = await startServer(); });
+afterAll(async () => { await stopServer(server); rmSync(root, { recursive: true, force: true }); });
+
+describe('static delivery characterization', () => {
+  test('build tag is stable for the same tree and changes when any served file changes', async () => {
+    const first = await (await fetch(`${server.base}/api/version`)).json();
+    await stopServer(server);
+    server = await startServer();
+    const same = await (await fetch(`${server.base}/api/version`)).json();
+    expect(same.buildTag).toBe(first.buildTag);
+    writeFileSync(join(publicDir, 'unlisted.txt'), 'included in recursive build tag');
+    await stopServer(server);
+    server = await startServer();
+    const changed = await (await fetch(`${server.base}/api/version`)).json();
+    expect(changed.buildTag).not.toBe(first.buildTag);
+  });
+
+  test('unreadable public tree uses the fixed dev-build fallback', async () => {
+    const moved = join(root, 'public.saved');
+    Bun.spawnSync(['mv', publicDir, moved]);
+    let fallback;
+    try {
+      await stopServer(server);
+      server = await startServer();
+      fallback = await (await fetch(`${server.base}/api/version`)).json();
+    } finally {
+      await stopServer(server);
+      Bun.spawnSync(['mv', moved, publicDir]);
+      server = await startServer();
+    }
+    expect(fallback.buildTag).toBe('dev-build');
+  });
+
+  test('index stamps only relative local css/js and serves expected cache headers', async () => {
+    const index = await fetch(`${server.base}/`);
+    const html = await index.text();
+    const { buildTag } = await (await fetch(`${server.base}/api/version`)).json();
+    expect(html).toContain(`<meta name="ytp-build" content="${buildTag}">`);
+    expect(html).toContain(`href="app.css?v=${buildTag}"`);
+    expect(html).toContain(`src="app.js?v=${buildTag}"`);
+    expect(html).toContain('https://cdn.example/x.js');
+    expect(html).toContain('href="/root.css"');
+    expect(index.headers.get('cache-control')).toBe('no-cache');
+    expect((await fetch(`${server.base}/index.html`)).headers.get('cache-control')).toBe('no-cache');
+
+    const current = await fetch(`${server.base}/app.js?v=${buildTag}`, { headers: { 'Accept-Encoding': 'br' } });
+    expect(current.headers.get('cache-control')).toBe('public, max-age=31536000, immutable');
+    expect(current.headers.get('content-encoding')).toBe('br');
+    expect(current.headers.get('etag')).toBeTruthy();
+    expect((await fetch(`${server.base}/app.js?v=stale`)).headers.get('cache-control')).toBe('no-cache');
+    expect((await fetch(`${server.base}/app.js`)).headers.get('cache-control')).toBe('no-cache');
+    expect((await fetch(`${server.base}/fonts/font.woff2`)).headers.get('cache-control')).toBe('public, max-age=2592000');
+    expect((await fetch(`${server.base}/icons/icon.png`)).headers.get('cache-control')).toBe('public, max-age=2592000');
+    for (const path of ['/api/version', '/sw.js']) {
+      expect((await fetch(`${server.base}${path}`)).headers.get('cache-control')).toBe('no-store, no-cache, must-revalidate');
+    }
+    const etag = current.headers.get('etag');
+    const notModified = await fetch(`${server.base}/app.js?v=${buildTag}`, { headers: { 'If-None-Match': etag } });
+    expect(notModified.status).toBe(304);
+    expect(await notModified.text()).toBe('');
+  });
+
+  test('service worker injection tracks fallback literal and reports missing placeholder', async () => {
+    let sw = await (await fetch(`${server.base}/sw.js`)).text();
+    const { buildTag } = await (await fetch(`${server.base}/api/version`)).json();
+    expect(sw).toContain(`const BUILD_TAG = "${buildTag}";`);
+    writeFileSync(join(publicDir, 'sw.js'), "const BUILD_TAG = typeof __BUILD_TAG__ !== 'undefined' ? __BUILD_TAG__ : 'v-next-literal';\n");
+    await stopServer(server);
+    server = await startServer();
+    sw = await (await fetch(`${server.base}/sw.js`)).text();
+    expect(sw).toContain(`const BUILD_TAG = "${(await (await fetch(`${server.base}/api/version`)).json()).buildTag}";`);
+    expect(sw).not.toContain('__BUILD_TAG__');
+
+    writeFileSync(join(publicDir, 'sw.js'), "const BUILD_TAG = 'missing-placeholder';\n");
+    await stopServer(server);
+    server = await startServer();
+    const response = await fetch(`${server.base}/sw.js`);
+    expect(await response.text()).toContain('missing-placeholder');
+    // The startup process logs the existing server.js diagnostic when injection misses.
+    server.child.kill();
+    const stderr = await server.stderr;
+    await server.child.exited;
+    expect(stderr).toContain('[sw] BUILD_TAG injection failed — placeholder not found in sw.js');
+    server = await startServer();
+  });
+
+  test('SPA routes fall back to the stamped index', async () => {
+    const { buildTag } = await (await fetch(`${server.base}/api/version`)).json();
+    for (const path of ['/search', '/playlist/x']) {
+      const response = await fetch(`${server.base}${path}`);
+      expect(response.status).toBe(200);
+      expect(await response.text()).toContain(`<meta name="ytp-build" content="${buildTag}">`);
+    }
+  });
+});