[playback] Harden service-worker rollout and rollback guardrails

README.md

@@ -356,6 +356,17 @@ This split is required for safe fast rollouts: HTML needs rapid update pickup,
 while fingerprinted static assets should remain aggressively cacheable for
 performance and cost control.
 
+
+#### Service worker rollback playbook
+
+If a deploy regresses playback and you suspect `sw.min.js`, use this rollback runbook:
+
+1. **Freeze impact**: redeploy the last known-good commit so clients fetch the previous worker script immediately.
+2. **Invalidate active workers**: from DevTools > Application > Service Workers, click **Unregister** for `sw.min.js` and hard reload once to verify playback without stale worker state.
+3. **Confirm claim flow**: in the browser console, confirm worker lifecycle messages (`BITVID_SW_LIFECYCLE`) appear and that requests to `/webtorrent/*` carry the `X-Bitvid-SW-Version` response header.
+4. **Check compatibility guardrails**: run `npm run lint:sw-compat` before shipping the fix. This fails deploys when service-worker runtime paths/scope changes are not accompanied by `_headers`, `index.html`, and `embed.html` updates in the same commit.
+5. **Redeploy + monitor**: publish the fix, then replay the URL-first fallback QA script in `docs/qa.md` and capture logs/screenshots in the PR.
+
 Inline styles are intentionally blocked. `npm run lint:inline-styles` scans HTML
 and scripts for `style=` attributes, `element.style`, or `style.cssText` usage
 and will fail CI until offending markup is moved into the shared CSS/token

_headers

@@ -18,6 +18,7 @@
 
 /sw.min.js
   Cache-Control: public, max-age=0, must-revalidate
+  X-Bitvid-SW-Version: bitvid-sw-2026-02-10
 
 /site.webmanifest
   Cache-Control: public, max-age=0, must-revalidate

embed.html

@@ -9,6 +9,7 @@
     <meta name="robots" content="noindex,follow" />
 
     <meta name="theme-color" content="var(--color-page)" />
+    <meta name="bitvid-sw-version" content="bitvid-sw-2026-02-10" />
     <script>
       (() => {
         try {

index.html

@@ -47,6 +47,7 @@
       hex values scattered across templates.
     -->
     <meta name="theme-color" content="var(--color-page)" />
+    <meta name="bitvid-sw-version" content="bitvid-sw-2026-02-10" />
     <script>
       (() => {
         try {

js/webtorrent.js

@@ -25,6 +25,22 @@ import { devLogger, userLogger } from "./utils/logger.js";
 import { emit } from "./embedDiagnostics.js";
 
 const DEFAULT_PROBE_TRACKERS = Object.freeze([...WSS_TRACKERS]);
+const SERVICE_WORKER_PATH = "/sw.min.js";
+const SERVICE_WORKER_SCOPE = "/";
+
+function compareServiceWorkerScripts(a = "", b = "") {
+  if (a === b) {
+    return true;
+  }
+
+  try {
+    const aUrl = new URL(a, window.location.origin);
+    const bUrl = new URL(b, window.location.origin);
+    return aUrl.pathname === bUrl.pathname;
+  } catch {
+    return false;
+  }
+}
 
 function normalizeTrackerList(trackers) {
   const normalized = [];
@@ -161,6 +177,7 @@ export class TorrentClient {
 
     // Timeout for SW operations
     this.TIMEOUT_DURATION = 60000;
+    this.swLifecycleListenerAttached = false;
   }
 
   ensureClientForProbe() {
@@ -467,6 +484,46 @@ export class TorrentClient {
     });
   }
 
+  attachServiceWorkerLifecycleListener() {
+    if (
+      this.swLifecycleListenerAttached ||
+      !("serviceWorker" in navigator) ||
+      !navigator.serviceWorker
+    ) {
+      return;
+    }
+
+    navigator.serviceWorker.addEventListener("message", (event) => {
+      const payload = event?.data;
+      if (payload?.type !== "BITVID_SW_LIFECYCLE") {
+        return;
+      }
+
+      this.log("[WebTorrent] Service worker lifecycle:", payload);
+    });
+    this.swLifecycleListenerAttached = true;
+  }
+
+  async activateWaitingWorker(registration) {
+    if (!registration?.waiting) {
+      return false;
+    }
+
+    const waitingWorker = registration.waiting;
+    const activeScript = registration.active?.scriptURL || "";
+    const waitingScript = waitingWorker.scriptURL || "";
+    if (compareServiceWorkerScripts(activeScript, waitingScript)) {
+      this.log("Activating waiting service worker", {
+        activeScript,
+        waitingScript,
+      });
+    }
+
+    waitingWorker.postMessage({ type: "SKIP_WAITING" });
+    await this.waitForActiveController(registration);
+    return true;
+  }
+
   /**
    * Ensure a live service worker is actively controlling the page before we
    * start WebTorrent streaming.
@@ -589,6 +646,8 @@ export class TorrentClient {
         throw new Error("Service Worker not supported or disabled");
       }
 
+      this.attachServiceWorkerLifecycleListener();
+
       // Brave-specific logic: Brave Shields has a long-standing bug where
       // stale service worker registrations linger even after we ship fixes.
       // When that happens, the outdated worker keeps intercepting requests
@@ -617,11 +676,11 @@ export class TorrentClient {
         await new Promise((resolve) => setTimeout(resolve, 1000));
       }
 
-      this.log("Registering service worker at /sw.min.js...");
+      this.log(`Registering service worker at ${SERVICE_WORKER_PATH}...`);
       const registration = await navigator.serviceWorker.register(
-        "/sw.min.js",
+        SERVICE_WORKER_PATH,
         {
-          scope: "/",
+          scope: SERVICE_WORKER_SCOPE,
           updateViaCache: "none",
         }
       );
@@ -648,6 +707,9 @@ export class TorrentClient {
         });
       }
 
+      await registration.update();
+      await this.activateWaitingWorker(registration);
+
       await this.waitForServiceWorkerActivation(registration);
       this.log("Service worker activated");
 
@@ -675,8 +737,10 @@ export class TorrentClient {
       // newly installed worker claims the page before WebTorrent spins up.
       await this.waitForActiveController(registration);
 
-      // Force the SW to check for updates
-      registration.update();
+      // Force the SW to check for updates and immediately claim if a waiting
+      // worker appeared after activation.
+      await registration.update();
+      await this.activateWaitingWorker(registration);
       this.log("Service worker ready");
 
       return registration;

package.json

@@ -16,7 +16,7 @@
     "ci:beacon": "npm run build:beacon",
     "format": "prettier --cache --write css/tailwind.source.css css/tokens.css css/docs.css \"docs/**/*.html\" tailwind.config.cjs README.md CONTRIBUTING.md",
     "audit": "node scripts/daily-design-system-audit.mjs",
-    "lint": "npm run lint:css && npm run lint:hex && npm run lint:inline-styles && npm run lint:tokens && npm run lint:tailwind-brackets && npm run lint:tailwind-colors && npm run lint:file-size && npm run lint:innerhtml && npm run lint:assets",
+    "lint": "npm run lint:css && npm run lint:hex && npm run lint:inline-styles && npm run lint:tokens && npm run lint:tailwind-brackets && npm run lint:tailwind-colors && npm run lint:file-size && npm run lint:innerhtml && npm run lint:assets && npm run lint:sw-compat",
     "lint:file-size": "node scripts/check-file-size.mjs",
     "lint:innerhtml": "node scripts/check-innerhtml.mjs",
     "lint:css": "stylelint css/tailwind.source.css css/tokens.css css/docs.css",
@@ -38,7 +38,8 @@
     "test:unit:shard2": "cross-env UNIT_TEST_SHARD=2/3 node scripts/run-unit-tests.mjs",
     "test:unit:shard3": "cross-env UNIT_TEST_SHARD=3/3 node scripts/run-unit-tests.mjs",
     "telemetry:aggregate": "node scripts/agent/telemetry-aggregator.mjs",
-    "lint:assets": "node scripts/check-asset-references.mjs"
+    "lint:assets": "node scripts/check-asset-references.mjs",
+    "lint:sw-compat": "node scripts/check-sw-compat.mjs"
   },
   "devDependencies": {
     "@playwright/test": "^1.58.2",

scripts/build-dist.mjs

@@ -155,6 +155,14 @@ function rewriteEntryHtmlAssetPaths(manifest) {
 }
 
 function main() {
+  console.log('Validating service worker compatibility guard...');
+  try {
+    execSync('npm run lint:sw-compat', { stdio: 'inherit' });
+  } catch (error) {
+    console.error('Failed service worker compatibility guard.');
+    process.exit(1);
+  }
+
   console.log('Cleaning dist...');
   cleanDist();
 

scripts/check-sw-compat.mjs

@@ -0,0 +1,90 @@
+import { execSync } from 'node:child_process';
+
+const ENTRY_HTML_FILES = ['index.html', 'embed.html'];
+const REQUIRED_COMPANION_FILES = ['_headers', ...ENTRY_HTML_FILES];
+const CRITICAL_FILES = ['sw.min.js', 'js/webtorrent.js'];
+const CRITICAL_PATH_PATTERNS = [
+  '/webtorrent/',
+  '/sw.min.js',
+  'scope: "/"',
+  'scope:"/"',
+  'SERVICE_WORKER_PATH',
+  'SERVICE_WORKER_SCOPE'
+];
+
+function getChangedFilesAgainstHeadParent() {
+  const hasHeadParent = execSync('git rev-parse --verify --quiet HEAD^', {
+    encoding: 'utf8',
+    stdio: ['ignore', 'pipe', 'ignore']
+  }).trim();
+
+  if (!hasHeadParent) {
+    return [];
+  }
+
+  const output = execSync('git diff-tree --no-commit-id --name-only -r HEAD', {
+    encoding: 'utf8'
+  }).trim();
+
+  if (!output) {
+    return [];
+  }
+
+  return output.split('\n').map((value) => value.trim()).filter(Boolean);
+}
+
+function getCriticalPathDiff() {
+  const output = execSync(
+    `git diff --unified=0 HEAD^ HEAD -- ${CRITICAL_FILES.join(' ')}`,
+    { encoding: 'utf8' }
+  );
+  return output
+    .split('\n')
+    .map((line) => line.trim())
+    .filter((line) => (line.startsWith('+') || line.startsWith('-')) && !line.startsWith('+++') && !line.startsWith('---'));
+}
+
+function hasCriticalPathChange(diffLines) {
+  return diffLines.some((line) =>
+    CRITICAL_PATH_PATTERNS.some((pattern) => line.includes(pattern))
+  );
+}
+
+function main() {
+  const changedFiles = getChangedFilesAgainstHeadParent();
+  if (!changedFiles.length) {
+    console.log('[sw-compat] No commit delta found; skipping compatibility check.');
+    return;
+  }
+
+  const touchedCriticalFile = changedFiles.some((file) => CRITICAL_FILES.includes(file));
+  if (!touchedCriticalFile) {
+    console.log('[sw-compat] No service worker files changed; compatibility check passed.');
+    return;
+  }
+
+  const diffLines = getCriticalPathDiff();
+  const criticalPathChanged = hasCriticalPathChange(diffLines);
+  if (!criticalPathChanged) {
+    console.log('[sw-compat] Service worker changes did not alter critical runtime paths.');
+    return;
+  }
+
+  const missingCompanionFiles = REQUIRED_COMPANION_FILES.filter(
+    (file) => !changedFiles.includes(file)
+  );
+
+  if (missingCompanionFiles.length > 0) {
+    const messageLines = [
+      '[sw-compat] Detected service worker scope/runtime path changes.',
+      '[sw-compat] Update deployment compatibility files in the same commit:',
+      ...missingCompanionFiles.map((file) => `  - ${file}`),
+      '[sw-compat] Required companion files: _headers, index.html, embed.html'
+    ];
+    throw new Error(messageLines.join('\n'));
+  }
+
+  console.log('[sw-compat] Critical service worker path updates include required companion files.');
+}
+
+main();

sw.min.js

@@ -1,8 +1,29 @@
 (() => {
   "use strict";
 
+  const SW_VERSION = "bitvid-sw-2026-02-10";
+  const SW_METADATA = Object.freeze({
+    version: SW_VERSION,
+    runtimePathPrefix: "/webtorrent/",
+  });
+
   let cancelled = false;
 
+  function broadcastLifecycle(eventType, details = {}) {
+    return clients
+      .matchAll({ type: "window", includeUncontrolled: true })
+      .then((windowClients) => {
+        windowClients.forEach((client) => {
+          client.postMessage({
+            type: "BITVID_SW_LIFECYCLE",
+            eventType,
+            metadata: SW_METADATA,
+            ...details,
+          });
+        });
+      });
+  }
+
   // Handle messages from clients
   self.addEventListener("message", (event) => {
     if (event.data && event.data.type === "SKIP_WAITING") {
@@ -22,7 +43,7 @@
 
   // Immediately install and skip waiting
   self.addEventListener("install", (event) => {
-    self.skipWaiting();
+    event.waitUntil(Promise.all([self.skipWaiting(), broadcastLifecycle("install")]));
   });
 
   // Claim clients on activation and clear caches
@@ -31,6 +52,9 @@
       Promise.all([
         clients.claim(),
         self.skipWaiting(),
+        broadcastLifecycle("activate", {
+          scope: self.registration?.scope || null,
+        }),
         caches
           .keys()
           .then((cacheNames) =>
@@ -115,6 +139,7 @@
         );
         responseHeaders.set("Pragma", "no-cache");
         responseHeaders.set("Expires", "0");
+        responseHeaders.set("X-Bitvid-SW-Version", SW_VERSION);
 
         // 3e) If the response is not a streaming request, return it directly
         if (clientResponse.body !== "STREAM") {