Merge Phase 6 and reconcile offline completion, response capture and contract tests

frontend/app-bootstrap.test.js

@@ -0,0 +1,84 @@
+const {test}=require('node:test');
+const assert=require('node:assert/strict');
+const {webcrypto,createHash}=require('node:crypto');
+const vm=require('node:vm');
+const {readFileSync}=require('node:fs');
+function fixture({cached=false,tampered=false,enabled=true,loading=false,quota=false,insecure=false,previous=false,contract=1,capture=true,controller=true,parser=false}={}){
+ const source='window.appRuns=(window.appRuns||0)+1; window.boot=()=>window.bootRuns=(window.bootRuns||0)+1; document.addEventListener("DOMContentLoaded",boot);',hash=createHash('sha256').update(source).digest('hex'), key='/app.js?v='+hash.slice(0,10);
+ const oldSource='window.oldApp=true;'+source, oldHash=createHash('sha256').update(oldSource).digest('hex').slice(0,10), oldKey='/app.js?v='+oldHash;
+ const held=new Map(), appended=[],writes=[],listeners={};let calls=0;
+ const response=()=>new Response(tampered?'bad':source,{headers:{'X-Asset-Hash':hash.slice(0,10)}});
+ if(cached)held.set(key,response());
+ if(previous){held.set(oldKey,new Response(oldSource,{headers:{'X-Asset-Hash':oldHash}}));held.set('/__ytp_asset_state',Response.json({previous:{files:{'/app.js':{h:oldHash}},groups:{core:{contract,files:['/app.js']}}}}));}
+ const root={crypto:insecure?undefined:webcrypto,TextDecoder,Uint8Array,btoa,console,AssetSyncCore:require('./asset-sync-core'),navigator:{serviceWorker:{controller:controller?{}:null}},Lazy:{captureApp:capture,manifest:{groups:{core:{contract:1,files:['/app.js']}},appCache:enabled,files:{'/app.js':{h:hash.slice(0,10)}}},url:()=>key},fetch:async()=>{calls++;return previous?new Response(oldSource,{headers:{'X-Asset-Hash':oldHash}}):response();},caches:{open:async()=>({match:async k=>held.get(k)?.clone(),put:async(k,r)=>{if(quota)throw Error('quota');held.set(k,r.clone());}})}};
+ const doc=root.document={readyState:loading?'loading':'complete',currentScript:parser?{}:null,write:value=>{writes.push(value);vm.runInContext(source,context);},querySelector:()=>({content:"script-src 'self' 'sha256-"+Buffer.from(hash,'hex').toString('base64')+"'"}),addEventListener:(name,fn)=>(listeners[name] ||= []).push(fn),createElement:()=>({remove(){this.removed=true;}}),head:{append(node){appended.push(node);if(node.textContent)vm.runInContext(node.textContent,context);else {queueMicrotask(async()=>{if(previous && node.src===key){const state=await held.get('/__ytp_asset_state').clone().json();if(!root.AssetSyncCore.fallback(root.Lazy.manifest,state.previous,'/app.js'))return node.onerror();vm.runInContext(oldSource,context);}else vm.runInContext(node.src===oldKey?oldSource:source,context);node.onload();});}}}};
+ root.window=root;const context=vm.createContext(root);
+ vm.runInContext(readFileSync(require.resolve('./section-rail.js'),'utf8'),context);
+ return {root,held,appended,writes,listeners,key,calls:()=>calls,doc,response,oldKey};
+}
+test('cold boot caches verified app before execution so worker skips its download',async()=>{
+ const f=fixture();await f.root.AppBootstrap.ready;assert.equal(f.calls(),1);assert.ok(f.held.has(f.key));assert.equal(f.root.appRuns,1);assert.equal(f.root.bootRuns,1);assert.equal(f.appended[0].src,undefined);assert.equal(f.appended[0].removed,true);
+});
+test('offline boot reads the exact cached app without network or re-evaluation',async()=>{
+ const f=fixture({cached:true});await f.root.AppBootstrap.ready;assert.equal(f.calls(),0);assert.equal(f.root.appRuns,1);assert.equal(f.root.bootRuns,1);
+});
+test('tampered cached bytes are rejected before execution',async()=>{
+ const f=fixture({cached:true,tampered:true});await assert.rejects(f.root.AppBootstrap.ready,/hash/);assert.equal(f.root.appRuns,undefined);
+});
+test('native and rollback boot use the original external classic script',async()=>{
+ const f=fixture({enabled:false});await f.root.AppBootstrap.ready;assert.equal(f.calls(),0);assert.equal(f.appended[0].src,f.key);assert.equal(f.root.bootRuns,1);
+});
+test('boot waits for the normal DOM event when the parser has not finished',async()=>{
+ const f=fixture({loading:true});await f.root.AppBootstrap.ready;assert.equal(f.root.bootRuns,undefined);for(const fn of f.listeners.DOMContentLoaded)fn();assert.equal(f.root.appRuns,1);assert.equal(f.root.bootRuns,1);
+});
+test('quota failure still executes the verified response without deleting saved data',async()=>{
+ const f=fixture({quota:true});await f.root.AppBootstrap.ready;assert.equal(f.calls(),1);assert.equal(f.root.appRuns,1);assert.equal(f.root.bootRuns,1);
+});
+
+
+test('the early head response is consumed without a second page fetch',async()=>{
+ const f=fixture();f.root.Lazy.appResponse=Promise.resolve(f.response());await f.root.AppBootstrap.ready;
+ assert.equal(f.calls(),0);assert.ok(f.held.has(f.key));assert.equal(f.root.appRuns,1);
+});
+
+
+test('insecure local HTTP boot retains external execution without WebCrypto',async()=>{
+ const f=fixture({insecure:true});await f.root.AppBootstrap.ready;assert.equal(f.calls(),0);assert.equal(f.appended[0].src,f.key);assert.equal(f.root.bootRuns,1);
+});
+
+
+test('missing current app uses verified same-contract N-1 offline through the controlling worker',async()=>{
+ const f=fixture({previous:true});await f.root.AppBootstrap.ready;
+ assert.equal(f.appended[0].src,f.oldKey);assert.equal(f.root.oldApp,true);assert.equal(f.root.bootRuns,1);assert.equal(f.held.has(f.key),false);
+});
+test('an incompatible previous core never executes against the new shell',async()=>{
+ const f=fixture({previous:true,contract:2});await assert.rejects(f.root.AppBootstrap.ready,/hash/);assert.equal(f.root.appRuns,undefined);
+});
+
+
+test('a feature contract change also prevents stale core execution',async()=>{
+ const f=fixture({previous:true});f.root.Lazy.manifest.groups['feature:test']={contract:2,files:[]};
+ const state=await f.held.get('/__ytp_asset_state').json();state.previous.groups['feature:test']={contract:1,files:[]};f.held.set('/__ytp_asset_state',Response.json(state));
+ await assert.rejects(f.root.AppBootstrap.ready,/hash/);assert.equal(f.root.appRuns,undefined);
+});
+
+
+test('native-cache engines use their external script and keep normal code-cache behavior',async()=>{
+ const f=fixture({capture:false,controller:false});await f.root.AppBootstrap.ready;assert.equal(f.calls(),0);assert.equal(f.appended[0].src,f.key);assert.equal(f.root.bootRuns,1);
+});
+
+
+test('native-cache engines still reject an incompatible retained core',async()=>{
+ const f=fixture({capture:false,previous:true,contract:2});await assert.rejects(f.root.AppBootstrap.ready,/Unable to load player/);assert.equal(f.root.appRuns,undefined);
+});
+test('native-cache engines use the validated current cache entry without decoding its body',async()=>{
+ const f=fixture({capture:false,cached:true});await f.root.AppBootstrap.ready;assert.equal(f.calls(),0);assert.equal(f.appended[0].src,f.key);assert.equal(f.root.bootRuns,1);
+});
+
+test('native parser boot preserves classic evaluation before the original DOM event',async()=>{
+ const f=fixture({capture:false,loading:true,parser:true});
+ assert.equal(f.root.appRuns,1);assert.equal(f.root.bootRuns,undefined);
+ assert.deepEqual(f.writes,['<script src="'+f.key+'"></script>']);assert.equal(f.appended.length,0);
+ for(const fn of f.listeners.DOMContentLoaded)fn();await f.root.AppBootstrap.ready;
+ assert.equal(f.root.bootRuns,1);assert.equal(f.calls(),0);
+});

frontend/app-seams.test.js

@@ -30,8 +30,8 @@ test('Phase 4 preserves the exact player, continuity, tracking and queue bodies'
 test('eager shell and Settings definitions load before app state and defer reading it',()=>{
  const html=readFileSync(join(__dirname,'index.html'),'utf8');
  for(const file of ['shell-core.js','views-core.js','section-rail.js']) {
-  assert.ok(html.indexOf('src="'+file+'"')<html.indexOf('src="app.js"'));
+  assert.ok(html.indexOf('src="'+file+'"')<=html.indexOf('src="section-rail.js"'));
-  const vm=require('node:vm');const context=vm.createContext({window:{},document:{}});
+  const vm=require('node:vm');const doc={readyState:'complete',addEventListener(){},createElement:()=>({}),head:{append(){}}};const globals={document:doc,Lazy:{manifest:{appCache:false},url:()=>'/app.js'},console};globals.window=globals;const context=vm.createContext(globals);
   // Evaluation before any data/$/els/Player declaration must be safe.
   vm.runInContext(readFileSync(join(__dirname,file),'utf8'),context);
  }

frontend/asset-sync-core.js

@@ -41,6 +41,9 @@
     const group = Object.keys(manifest.groups).find(name => manifest.groups[name].files.includes(path));
     if (!group || !previous.groups[group]?.files.includes(path) ||
         manifest.groups[group].contract !== previous.groups[group].contract) return null;
+    // A stale core must understand every group contract in the new shell.
+    if (path === "/app.js" && Object.entries(manifest.groups).some(([name, entry]) =>
+        previous.groups[name]?.contract !== entry.contract)) return null;
     return url(path, previous.files[path]);
   }
 

frontend/asset-sync-core.test.js

@@ -96,3 +96,9 @@ test('metadata probes release response streams while stored asset bodies remain
  assert.equal((await core.status(m,c)).offlineReady,true);assert.ok(probes.length>0);assert.ok(probes.every(r=>r.bodyUsed));
  assert.equal(await(await match('/a.js?v=a')).text(),'a');assert.equal(await(await match('/index.html?v=b')).text(),'b');
 });
+
+test('stale app core requires every feature contract to match the new shell',()=>{
+ const old={files:{'/app.js':{h:'old'}},groups:{core:{contract:1,files:['/app.js']},extra:{contract:1,files:[]}}};
+ const next=structuredClone(old);next.files['/app.js'].h='new';next.groups.extra.contract=2;
+ assert.equal(core.fallback(next,old,'/app.js'),null);next.groups.extra.contract=1;assert.equal(core.fallback(next,old,'/app.js'),'/app.js?v=old');
+});

frontend/asset-worker.test.js

@@ -15,11 +15,11 @@ test('staged same-contract responses use verified N-1 without poisoning the new
  const e=environment(); const cache=await e.storage.open(core.CACHE);
  const old={buildTag:'old',files:{'/extra.js':{h:'old'}},groups:{core:{files:[],contract:1},'feature:extra':{files:['/extra.js'],contract:1,background:true}}};
  e.m.groups.core.contract=1; e.m.groups['feature:extra']={files:['/extra.js'],contract:1,background:true}; e.m.files['/extra.js']={h:'new'};
- await cache.put(core.STATE,Response.json({current:old})); await cache.put('/extra.js?v=old',new Response('old body',{headers:{'X-Asset-Hash':'old'}}));
+ await cache.put(core.STATE,Response.json({current:old})); await cache.put('/extra.js?v=old',new Response('old body',{headers:{'X-Asset-Hash':'old','Cache-Control':'public, max-age=31536000, immutable','Content-Encoding':'gzip','Content-Length':'9'}}));
  await e.dispatch('install'); await e.dispatch('activate');await e.complete();
  assert.ok(await cache.match('/extra.js?v=new'));await cache.delete('/extra.js?v=new');
  assert.equal(await cache.match('/extra.js?v=new'),undefined);
- const stale=await e.request('/extra.js?v=new'); assert.equal(await stale.text(),'old body');assert.equal(stale.headers.get('X-Asset-Hash'),'old');assert.equal(await cache.match('/extra.js?v=new'),undefined);
+ const stale=await e.request('/extra.js?v=new'); assert.equal(await stale.text(),'old body');assert.equal(stale.headers.get('X-Asset-Hash'),'old');assert.equal(stale.headers.get('Cache-Control'),'no-store');assert.equal(stale.headers.get('Content-Encoding'),null);assert.equal(stale.headers.get('Content-Length'),null);assert.equal(await cache.match('/extra.js?v=new'),undefined);
  await e.dispatch('message',{data:{type:'WARM_ASSETS',saveData:true}}); assert.ok(await cache.match('/extra.js?v=new'));
  await e.dispatch('message',{data:{type:'WARM_ASSETS',saveData:false}}); assert.equal((await cache.match('/extra.js?v=new')).headers.get('X-Asset-Hash'),'new');
  assert.equal((await e.request('/extra.js?v=new')).headers.get('X-Asset-Hash'),'new');
@@ -56,3 +56,22 @@ test('waiting status does not start completion and activation delegates it to it
  const job=e.complete();await begin;assert.equal(await cache.match('/extra.js?v=extra'),undefined);release();await job;
  assert.equal((await core.status(e.m,cache)).offlineReady,true);
 });
+
+test('page-captured app is reused on first install without a worker download',async()=>{
+ const e=environment(),cache=await e.storage.open(core.CACHE);
+ await cache.put('/app.js?v=app',new Response('page captured app',{headers:{'X-Asset-Hash':'app'}}));
+ await e.dispatch('install');assert.equal(e.fetches.includes('/app.js?v=app'),false);
+ assert.equal(await(await cache.match('/app.js?v=app')).text(),'page captured app');
+ assert.equal(e.skips.length,0);assert.equal(await core.state(cache),null);
+});
+
+
+test('worker never supplies stale app to a native script when a feature contract changed',async()=>{
+ const e=environment(),cache=await e.storage.open(core.CACHE);
+ const old={buildTag:'old',files:{'/app.js':{h:'old'}},groups:{core:{contract:1,files:['/app.js']},extra:{contract:1,files:[]}}};
+ e.m.groups.core.contract=1;e.m.groups.extra={contract:2,background:true,files:[]};
+ await cache.put(core.STATE,Response.json({current:old}));await cache.put('/app.js?v=old',new Response('old app',{headers:{'X-Asset-Hash':'old'}}));
+ await e.dispatch('install');await e.dispatch('activate');await cache.delete('/app.js?v=app');
+ e.sandbox.fetch=async()=>{throw Error('offline')};
+ const response=await e.request('/app.js?v=app');assert.equal(response.status,503);assert.equal(await response.text(),'Offline');
+});

frontend/assets.json

@@ -1,7 +1,7 @@
 {
   "groups": {
     "core": {
-      "contract": 1,
+      "contract": 2,
       "eager": true,
       "files": [
         "/index.html",

frontend/lazy.js

@@ -123,6 +123,24 @@
       for (const type of ['pointerenter', 'focus', 'touchstart']) element.addEventListener(type, () => load(name).catch(() => {}), { once: true, passive: true });
     },
   };
+  // Own this response once. Classic-script and fetch preloads do not share
+  // their cached bodies in WebKit; the later bootstrap consumes this promise.
+  const agent=root.navigator.userAgent || '';
+  api.captureApp=!!(manifest.appCache && !root.navigator.serviceWorker?.controller && root.crypto?.subtle && /AppleWebKit\//.test(agent) && !/(?:Chrome|Chromium|Edg|OPR)\//.test(agent));
+  if(api.captureApp) {
+    api.appResponse=(async()=>{
+      const key=url('/app.js');
+      try {
+        const cache=await root.caches?.open('ytplayer-assets'), held=await cache?.match(key);
+        if(held?.headers.get('X-Asset-Hash')===manifest.files['/app.js']?.h && held)return held;
+      } catch {}
+      return root.fetch(key,{credentials:'same-origin'});
+    })();
+    api.appResponse.catch(()=>{});
+  } else if(manifest.appCache) {
+    // Preserve native script/code-cache reuse in engines without the WebKit gap.
+    const preload=doc.createElement('link');preload.rel='preload';preload.as='script';preload.fetchPriority='low';preload.href=url('/app.js');doc.head.append(preload);
+  }
   root.Lazy = api;
   root.navigator.serviceWorker?.addEventListener('message',event=>{
     if(event.data?.type==='ASSET_LAYOUT_REQUEST') event.source?.postMessage({type:'LAYOUT',value:api.layout});

frontend/lazy.test.js

@@ -2,16 +2,16 @@ const { test } = require('node:test');
 const assert = require('node:assert/strict');
 const { readFileSync } = require('node:fs');
 const vm = require('node:vm');
-function fixture(current, held = []) {
+function fixture(current, held = [], appCache = false, userAgent = 'AppleWebKit/605.1 Safari/605.1', controlled = false) {
-  const inserted = [], listeners = {}, writes = [];
+  const inserted = [], listeners = {}, writes = [], fetched = [];
-  const manifest = { buildTag: 'own', groups: { core: { files: [] }, 'layout:classic': { files: ['/classic.css'] }, 'layout:glass-stage': { files: ['/glass.css', '/one.js', '/two.js'] }, 'feature:test': { contract:1, files: ['/one.js', '/two.js'] } }, files: { '/classic.css': {h:'c'}, '/glass.css':{h:'g'}, '/one.js':{h:'1'}, '/two.js':{h:'2'} } };
+  const manifest = { buildTag: 'own', appCache, groups: { core: { files: [] }, 'layout:classic': { files: ['/classic.css'] }, 'layout:glass-stage': { files: ['/glass.css', '/one.js', '/two.js'] }, 'feature:test': { contract:1, files: ['/one.js', '/two.js'] } }, files: { '/app.js':{h:'a'}, '/classic.css': {h:'c'}, '/glass.css':{h:'g'}, '/one.js':{h:'1'}, '/two.js':{h:'2'} } };
   const doc = { readyState:'loading', documentElement: { dataset:{} }, getElementById: () => ({ textContent:JSON.stringify(manifest) }), querySelectorAll: () => [], createElement: tag => ({ tagName:tag.toUpperCase() }), write: value => writes.push(value), addEventListener: (t,f) => listeners[t]=f };
   doc.head = { append: node => { inserted.push(node); queueMicrotask(() => node.onload?.()); } };
-  const root = { document:doc, localStorage:{ getItem:() => '{"settings":{"layout":"glass-stage"}}' }, console, Promise, URL, setTimeout, clearTimeout, navigator:{}, addEventListener(){} };
+  const root = { document:doc, localStorage:{ getItem:() => '{"settings":{"layout":"glass-stage"}}' }, console, Promise, URL, crypto:{subtle:{}}, fetch:async key=>{fetched.push(key);return new Response('app');}, setTimeout, clearTimeout, navigator:{userAgent,serviceWorker:{ready:Promise.resolve({}),controller:controlled?{}:null,addEventListener(){}}}, addEventListener(){} };
   if (current) root.caches = { open: async () => ({ match: async key => key === '/__ytp_asset_state' ? new Response(JSON.stringify({current})) : held.includes(key) ? new Response('', {headers:{'X-Asset-Hash':key.split('=')[1]}}) : undefined }) };
   root.window=root; root.globalThis=root;
   vm.runInNewContext(readFileSync(require.resolve('./lazy.js'),'utf8'), root);
-  return { root, inserted, writes, listeners, manifest };
+  return { root, inserted, writes, listeners, manifest, fetched };
 }
 test('external head bootstrap selects remembered CSS before paint without fetching a manifest', () => {
   const {root,writes}=fixture();
@@ -95,3 +95,31 @@ test('online launches request worker completion even with Save-Data and skip off
  assert.deepEqual(sent.map(m=>m.type),['COMPLETE_ASSETS','COMPLETE_ASSETS']);
  f.root.navigator.onLine=false;f.root.Lazy.warm();await Promise.resolve();assert.equal(sent.length,2);
 });
+test('server-enabled head capture owns exactly one app response; native and rollback do not fetch',async()=>{
+ const modern=fixture(null,[],true);await modern.root.Lazy.appResponse;
+ assert.deepEqual(modern.fetched,['/app.js?v=a']);
+ const legacy=fixture();assert.deepEqual(legacy.fetched,[]);assert.equal(legacy.root.Lazy.appResponse,undefined);
+});
+
+
+test('head capture is cache-first even before a worker controls the page',async()=>{
+ const f=fixture(fixture().manifest,['/app.js?v=a'],true);const response=await f.root.Lazy.appResponse;
+ assert.equal(response.headers.get('X-Asset-Hash'),'a');assert.deepEqual(f.fetched,[]);
+});
+
+
+test('Chromium retains native script loading and only preloads the current app URL',async()=>{
+ const f=fixture(null,[],true,'AppleWebKit/537.36 Chrome/140.0 Safari/537.36');
+ assert.equal(f.root.Lazy.captureApp,false);assert.equal(f.root.Lazy.appResponse,undefined);assert.deepEqual(f.fetched,[]);
+ assert.equal(f.inserted.length,1);assert.equal(f.inserted[0].rel,'preload');assert.equal(f.inserted[0].as,'script');assert.equal(f.inserted[0].href,'/app.js?v=a');assert.equal(f.inserted[0].fetchPriority,'low');
+});
+test('iOS Chromium-branded browsers still use their WebKit response capture',async()=>{
+ const f=fixture(null,[],true,'AppleWebKit/605.1 CriOS/140.0 Mobile Safari/605.1');await f.root.Lazy.appResponse;
+ assert.equal(f.root.Lazy.captureApp,true);assert.deepEqual(f.fetched,['/app.js?v=a']);
+});
+
+test('controlled WebKit visits use worker-cached native app scripts without a response handoff',async()=>{
+ const f=fixture(null,[],true,'AppleWebKit/605.1 Safari/605.1',true);
+ assert.equal(f.root.Lazy.captureApp,false);assert.equal(f.root.Lazy.appResponse,undefined);assert.deepEqual(f.fetched,[]);
+ assert.equal(f.inserted[0].as,'script');assert.equal(f.inserted[0].href,'/app.js?v=a');assert.equal(f.inserted[0].fetchPriority,'low');
+});

frontend/section-rail.js

@@ -245,3 +245,77 @@ const SectionRail = (() => {
 
   return { boot, refresh, setFolded, isFolded };
 })();
+
+/* Cache the single page-owned app response before it registers the worker. */
+(function (root) {
+  'use strict';
+  const doc=root.document, manifest=root.Lazy.manifest, key=root.Lazy.url('/app.js');
+  let domReady=doc.readyState==='complete', appSawDom=false;
+  doc.addEventListener('DOMContentLoaded',()=>{domReady=true;appSawDom=typeof root.boot==='function';},{once:true});
+  function execute(node) {
+    doc.head.append(node);
+    node.remove();
+    delete root.Lazy.appResponse;
+    // app.js keeps its original DOMContentLoaded listener. Async response
+    // consumption can finish after that event; boot exactly once in that case.
+    if(domReady)root.boot();
+  }
+  async function external(url) {
+    await new Promise((resolve,reject)=>{
+      const node=doc.createElement('script');node.src=url;
+      node.onload=()=>{if(domReady&&!appSawDom)root.boot();resolve();};node.onerror=()=>reject(Error('Unable to load player'));
+      doc.head.append(node);
+    });
+  }
+  function native() {
+    if(doc.readyState!=='loading' || !doc.currentScript)return external(key);
+    return new Promise((resolve,reject)=>{
+      doc.addEventListener('DOMContentLoaded',()=>typeof root.boot==='function'?resolve():reject(Error('Unable to load player')),{once:true});
+      const escaped=key.replaceAll('&','&amp;').replaceAll('"','&quot;').replaceAll('<','&lt;');
+      doc.write('<script src="'+escaped+'"></script>');
+    });
+  }
+  async function verified(response, expected) {
+    const bytes=await response.clone().arrayBuffer();
+    const digest=new Uint8Array(await root.crypto.subtle.digest('SHA-256',bytes));
+    const hex=Array.from(digest,b=>b.toString(16).padStart(2,'0')).join('');
+    if(hex.slice(0,10)!==expected)throw Error('Player body hash mismatch');
+    return {bytes,digest};
+  }
+  async function start() {
+    if(!manifest.appCache || !root.crypto?.subtle || !root.Lazy.captureApp)return native();
+    const expected=manifest.files['/app.js'].h;
+    let cache;
+    try { cache=await root.caches?.open('ytplayer-assets'); } catch {}
+    let response=await cache?.match(key);
+    if(!response || response.headers.get('X-Asset-Hash')!==expected) {
+      try { response=await (root.Lazy.appResponse || root.fetch(key,{credentials:'same-origin'})); } catch {}
+    }
+    if(!response?.ok || response.headers.get('X-Asset-Hash')!==expected) {
+      // Preserve staged N-1 boot after an individual cache eviction. Only the
+      // controller can serve this old URL safely; never fetch stale URLs bare.
+      const state=cache && await root.AssetSyncCore.state(cache);
+      const previousKey=state && root.AssetSyncCore.fallback(manifest,state.previous,'/app.js');
+      const previous=previousKey && await cache.match(previousKey);
+      const previousHash=state?.previous?.files['/app.js']?.h;
+      const contractsMatch=state?.previous && Object.entries(manifest.groups).every(([name,group])=>state.previous.groups[name]?.contract===group.contract);
+      if(contractsMatch && root.navigator?.serviceWorker?.controller && previous?.ok && previous.headers.get('X-Asset-Hash')===previousHash) {
+        await verified(previous,previousHash);
+        delete root.Lazy.appResponse;
+        return external(previousKey);
+      }
+      throw Error('Player asset hash mismatch');
+    }
+    const {bytes,digest}=await verified(response,expected);
+    const permission="'sha256-"+root.btoa(String.fromCharCode(...digest))+"'";
+    if(!doc.querySelector('meta[http-equiv="Content-Security-Policy"]').content.includes(permission))throw Error('Player body hash mismatch');
+    // CacheStorage may share a full quota with saved music. Never remove data
+    // to make room; boot from these verified bytes even if caching is refused.
+    try { await cache?.put(key,response); } catch(error) { root.console.warn('[app-cache]',error.message); }
+    const node=doc.createElement('script');node.textContent=new root.TextDecoder().decode(bytes);
+    execute(node);
+  }
+  const ready=start();
+  root.AppBootstrap={ready};
+  ready.catch(error=>root.console.error('[app-cache]',error.message));
+})(typeof window!=='undefined'?window:globalThis);

frontend/shell-consistency.test.js

@@ -32,7 +32,7 @@ test('assets.json describes the complete existing shell exactly once with eager
   const { groups } = JSON.parse(readFileSync(join(__dirname, 'assets.json'), 'utf8'));
   const described = new Set();
   for (const [name, group] of Object.entries(groups)) {
-    assert.equal(group.contract, 1, `${name} initial contract`);
+    assert.equal(group.contract, name === 'core' ? 2 : 1, `${name} contract (core boot packing changed)`);
     assert.equal(typeof group.eager, 'boolean');
     for (const asset of group.files) {
       assert.ok(!described.has(asset), `${asset} has one group`);
@@ -70,6 +70,8 @@ test('only core scripts and styles remain eager; native fallback and active layo
   const {groups}=JSON.parse(readFileSync(join(__dirname,'assets.json'),'utf8'));
   const background=new Set(Object.values(groups).filter(g=>g.background).flatMap(g=>g.files));
   for(const match of html.matchAll(/<(?:script\b[^>]*\bsrc|link\b[^>]*\bhref)="([^"]+)"/gi)) {
+    // A style preload discovers bytes without applying or blocking another layout.
+    if(match[0].includes('rel="preload"'))continue;
     const path='/'+match[1].replace(/^\//,'').split(/[?#]/)[0];
     assert.ok(!background.has(path),`${path} is not eager`);
   }
@@ -88,3 +90,25 @@ test('layout-independent visibility and transport defaults stay in eager CSS',()
  for(const selector of ['.stg-overlay','.deck-chips','.np-btn.done .i-save','.sleep-status .sl-ic','.ab-group','.mc-tune'])assert.ok(shared.includes(selector));
  assert.ok(html.includes('href="layout-base.css"'));
 });
+
+
+test('classic first-visit style preload is discovered before the head loader without applying another layout',()=>{
+ const preload=html.match(/<link\b[^>]*rel="preload"[^>]*href="theme-classic.css"[^>]*as="style"[^>]*>/);
+ assert.ok(preload,'classic stylesheet has an early preload');
+ assert.ok(html.indexOf(preload[0])<html.indexOf('src="lazy.js"'));
+ assert.ok(!/<link\b[^>]*rel="stylesheet"[^>]*href="theme-classic.css"/.test(html),'the selected layout remains parser-applied by the loader');
+});
+
+
+test('the last core script owns boot without an extra request or unsafe stale packing',()=>{
+ const {groups}=JSON.parse(readFileSync(join(__dirname,'assets.json'),'utf8'));
+ assert.equal(groups.core.contract,2,'old core packing cannot fall back without the loader');
+ assert.ok(groups.core.files.includes('/app.js'));
+ assert.ok(groups.core.files.includes('/section-rail.js'));
+ assert.equal(groups.core.files.includes('/app-bootstrap.js'),false);
+ assert.equal(listed.has('/app-bootstrap.js'),false);
+ const scripts=[...html.matchAll(/<script src="([^"]+)"/g)].map(m=>m[1]);
+ assert.equal(scripts.at(-1),'section-rail.js');
+ assert.ok(html.includes("'sha256-__APP_SCRIPT_HASH__'"));
+ assert.ok(readFileSync(join(__dirname,'section-rail.js'),'utf8').includes('root.AppBootstrap={ready}'));
+});

frontend/sw.js

@@ -600,7 +600,13 @@ async function assetFetch(request, clientId) {
     if(state.current.files[path]?.h === h) {
       const previousKey=AssetSyncCore.fallback(state.current,state.previous,path);
       const previousResponse=previousKey && await cache.match(previousKey);
-      if(previousResponse && previousResponse.headers.get('X-Asset-Hash')===state.previous.files[path].h) return previousResponse;
+      if(previousResponse && previousResponse.headers.get('X-Asset-Hash')===state.previous.files[path].h) {
+        // A stale body returned under a new URL must not poison the browser's
+        // resource cache either. Its decoded stream has no transport encoding.
+        const headers=new Headers(previousResponse.headers);headers.set('Cache-Control','no-store');
+        for(const name of ['Content-Encoding','Content-Length','Transfer-Encoding'])headers.delete(name);
+        return new Response(previousResponse.body,{status:previousResponse.status,headers});
+      }
     }
     try { const r = await fetch(key); if(r.ok && r.headers.get('X-Asset-Hash') !== h) return new Response('Asset version unavailable',{status:409}); if(r.ok && request.method !== 'HEAD') await cache.put(key,r.clone()); return r; } catch { return new Response('Offline',{status:503}); }
   }

perf/README.md

@@ -347,3 +347,25 @@ node --test frontend/media-icons.test.js
 Both harnesses run Chromium and WebKit at mobile dimensions with stubbed SpeechRecognition and local Saved/Queue metadata. They serve only the frontend, block service workers and external requests, and never download media. Geometry tests cold and switched layouts, six widths (320–430), mic visible/hidden and update icon visible/hidden: center spread ≤1px, touch targets ≥40px, Saved image/text gap ≥8px, no horizontal overflow or clipped car control. `--quick` limits widths and speech cases; `--browser` selects an engine; `--frontend` selects historical fixtures. `--measure-only --label before` records known broken geometry without exiting nonzero.
 
 Icon checks switch the same page through four layouts × dark/light/contrast, assert SVG definitions, inherited colour, stroke family and save/progress/offline state, and save Queue/Now Playing/navigation shots. Glass Stage intentionally hides bottom navigation, so its full page is recorded instead. Any assertion failure exits nonzero. Shots and raw measurements live in git-ignored plans/ui-shots/. Full production inventory: plans/ui-icon-inventory.md. Native speech recognition, installed-PWA safe-area insets and iPhone rendering still need device verification.
+
+### Cold waterfall diagnosis
+
+`--source-root perf/.tmp/<historical-worktree>` runs that worktree's matching
+frontend **and server**; `--frontend-commit` instead combines archived frontend
+with the current backend. Run historical comparisons sequentially to avoid CPU
+contention. The result records `sourceCommit`, `sourceRoot` and the served build.
+Every cold sample has `waterfalls`: proxy request order/start/headers/end times
+and page Resource Timing discovery/start/end times. Proxy times start when
+tracking begins; page times start at navigation. Compare within each clock,
+then use the page FCP to locate the rendering dependency.
+
+Pass `--assert-cold` on new builds to require exactly one positive-byte app.js
+response in every cold sample, including worker installation. Omit this assertion
+when diagnosing historical regressions.
+
+Phase 6 counts its fetch-owned app.js response in initial JS/CSS bytes. Since the
+bootstrap consumes that response asynchronously, DOMContentLoaded no longer means
+app execution is complete; compare the existing actual boot-done landmark.
+
+`--scenario warm,offline,update-js,update-css,update-feature` runs a regression
+sweep without repeating an already-completed cold acceptance run.

perf/baseline.mjs

@@ -26,7 +26,7 @@
  */
 
 import assert from 'node:assert/strict';
-import { assertChangedAssets, assertWarmAssets, waitForIdleAssets } from './measurement.mjs';
+import { assertColdAssets, assertChangedAssets, assertWarmAssets, waitForIdleAssets } from './measurement.mjs';
 import { createHash } from 'node:crypto';
 import { spawn, spawnSync, execFileSync } from 'node:child_process';
 import { existsSync, mkdirSync, rmSync, cpSync, appendFileSync, statSync, writeFileSync, readFileSync, symlinkSync, unlinkSync } from 'node:fs';
@@ -62,6 +62,8 @@ function parseArgs() {
     out: null,
     compare: null,
     frontendCommit: null,
+    sourceRoot: null,
+    assertCold: false,
   };
 
   for (let i = 0; i < args.length; i++) {
@@ -71,6 +73,8 @@ function parseArgs() {
     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 === '--assert-cold') options.assertCold = true;
+    else if (a === '--source-root' && i + 1 < args.length) options.sourceRoot = path.resolve(args[++i]);
     else if (a === '--frontend-commit' && i + 1 < args.length) options.frontendCommit = args[++i];
     else if (a === '--compare' && i + 1 < args.length) options.compare = args[++i];
   }
@@ -151,7 +155,8 @@ async function seedDatabase(dbPath, mediaFiles) {
  * Bun Server Manager
  */
 class ServerManager {
-  constructor(scratchDir, publicDir) {
+  constructor(scratchDir, publicDir, sourceRoot = REPO_ROOT) {
+    this.sourceRoot = sourceRoot;
     this.scratchDir = scratchDir;
     this.publicDir = publicDir;
     this.dataDir = path.join(scratchDir, 'data');
@@ -184,7 +189,7 @@ class ServerManager {
       DB_PATH: this.dbPath,
     };
 
-    const serverScript = path.join(REPO_ROOT, 'server', 'server.js');
+    const serverScript = path.join(this.sourceRoot, 'server', 'server.js');
     this.serverProcess = spawn('bun', [serverScript], {
       cwd: srvCwd,
       env,
@@ -372,8 +377,8 @@ async function runColdScenario({ browserType, server, proxy, profile }) {
     const fcp = paint.find((p) => p.name === 'first-contentful-paint');
 
     return {
-      initialJsCss: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&['script','link','css'].includes(entry.initiatorType)).reduce((sum,entry)=>sum+entry.encodedBodySize,0),
+      initialJsCss: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&(['script','link','css'].includes(entry.initiatorType)||(entry.initiatorType==='fetch'&&new URL(entry.name).pathname==='/app.js'))).reduce((sum,entry)=>sum+entry.encodedBodySize,0),
-      initialAssetRequests: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&['script','link','css'].includes(entry.initiatorType)).map(entry=>({url:entry.name,bytes:entry.encodedBodySize})),
+      initialAssetRequests: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&(['script','link','css'].includes(entry.initiatorType)||(entry.initiatorType==='fetch'&&new URL(entry.name).pathname==='/app.js'))).map(entry=>({url:entry.name,bytes:entry.encodedBodySize,start:entry.startTime,responseStart:entry.responseStart,end:entry.responseEnd,initiator:entry.initiatorType})),
       fcp: fcp ? Math.round(fcp.startTime) : null,
       lcp: window.__lcp ? Math.round(window.__lcp) : null,
       domContentLoaded: nav ? Math.round(nav.domContentLoadedEventEnd - nav.startTime) : null,
@@ -481,8 +486,8 @@ async function runWarmScenario({ browserType, server, proxy, profile }) {
     const fcp = paint.find((p) => p.name === 'first-contentful-paint');
 
     return {
-      initialJsCss: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&['script','link','css'].includes(entry.initiatorType)).reduce((sum,entry)=>sum+entry.encodedBodySize,0),
+      initialJsCss: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&(['script','link','css'].includes(entry.initiatorType)||(entry.initiatorType==='fetch'&&new URL(entry.name).pathname==='/app.js'))).reduce((sum,entry)=>sum+entry.encodedBodySize,0),
-      initialAssetRequests: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&['script','link','css'].includes(entry.initiatorType)).map(entry=>({url:entry.name,bytes:entry.encodedBodySize})),
+      initialAssetRequests: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&(['script','link','css'].includes(entry.initiatorType)||(entry.initiatorType==='fetch'&&new URL(entry.name).pathname==='/app.js'))).map(entry=>({url:entry.name,bytes:entry.encodedBodySize,start:entry.startTime,responseStart:entry.responseStart,end:entry.responseEnd,initiator:entry.initiatorType})),
       fcp: fcp ? Math.round(fcp.startTime) : null,
       lcp: window.__lcp ? Math.round(window.__lcp) : null,
       domContentLoaded: nav ? Math.round(nav.domContentLoadedEventEnd - nav.startTime) : null,
@@ -562,8 +567,8 @@ async function runOfflineScenario({ browserType, server, proxy, profile }) {
     const fcp = paint.find((p) => p.name === 'first-contentful-paint');
 
     return {
-      initialJsCss: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&['script','link','css'].includes(entry.initiatorType)).reduce((sum,entry)=>sum+entry.encodedBodySize,0),
+      initialJsCss: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&(['script','link','css'].includes(entry.initiatorType)||(entry.initiatorType==='fetch'&&new URL(entry.name).pathname==='/app.js'))).reduce((sum,entry)=>sum+entry.encodedBodySize,0),
-      initialAssetRequests: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&['script','link','css'].includes(entry.initiatorType)).map(entry=>({url:entry.name,bytes:entry.encodedBodySize})),
+      initialAssetRequests: performance.getEntriesByType('resource').filter(entry=>/\.(?:js|css)(?:[?#]|$)/.test(entry.name)&&entry.startTime <= nav.domContentLoadedEventEnd&&(['script','link','css'].includes(entry.initiatorType)||(entry.initiatorType==='fetch'&&new URL(entry.name).pathname==='/app.js'))).map(entry=>({url:entry.name,bytes:entry.encodedBodySize,start:entry.startTime,responseStart:entry.responseStart,end:entry.responseEnd,initiator:entry.initiatorType})),
       fcp: fcp ? Math.round(fcp.startTime) : null,
       lcp: window.__lcp ? Math.round(window.__lcp) : null,
       domContentLoaded: nav ? Math.round(nav.domContentLoadedEventEnd - nav.startTime) : null,
@@ -704,6 +709,8 @@ async function main() {
   if (options.browser === 'all' || options.browser === 'chromium') browsers.push(pw.chromium);
   if (options.browser === 'all' || options.browser === 'webkit') browsers.push(pw.webkit);
 
+  const requestedScenarios=new Set(options.scenario.split(','));
+  const wants=name=>requestedScenarios.has('all')||requestedScenarios.has(name);
   const profiles = [];
   if (options.profile === 'all' || options.profile === 'lte') profiles.push('lte');
   if (options.profile === 'all' || options.profile === 'lossy') profiles.push('lossy');
@@ -717,7 +724,7 @@ async function main() {
   const treeUpdateCss = path.join(tmpRoot, 'tree-update-css');
   const treeUpdateFeature = path.join(tmpRoot, 'tree-update-feature');
 
-  let frontendSource=path.join(REPO_ROOT,'frontend');
+  let frontendSource=path.join(options.sourceRoot || REPO_ROOT,'frontend');
   if(options.frontendCommit) {
     const archive=path.join(tmpRoot,'frontend.tar');
     writeFileSync(archive,execFileSync('git',['archive',options.frontendCommit,'frontend'],{cwd:REPO_ROOT,maxBuffer:20*1024*1024}));
@@ -735,13 +742,15 @@ async function main() {
   const trees = { treeBase, treeUpdateJs, treeUpdateCss, treeUpdateFeature };
 
   const serverScratch = path.join(tmpRoot, 'server-run');
-  const server = new ServerManager(serverScratch, treeBase);
+  const server = new ServerManager(serverScratch, treeBase, options.sourceRoot || REPO_ROOT);
   await server.start();
   console.log(`Bun server running on ephemeral port ${server.port}`);
 
   const results = {
     date: new Date().toISOString(),
     frontendCommit: options.frontendCommit,
+    sourceRoot: options.sourceRoot,
+    sourceCommit: spawnSync('git', ['rev-parse','HEAD'], { cwd: options.sourceRoot || REPO_ROOT }).stdout.toString().trim(),
     frontendBuildTag: (await (await fetch('http://127.0.0.1:'+server.port+'/api/version')).json()).buildTag,
     commit: spawnSync('git', ['rev-parse', 'HEAD'], { cwd: REPO_ROOT }).stdout.toString().trim(),
     runsConfigured: options.runs,
@@ -754,6 +763,9 @@ async function main() {
       results.browsers[bName] = {};
 
       for (const prof of profiles) {
+        // The preceding profile can end on a synthetic feature-update tree.
+        // Always measure the actual base build on the next cold visit.
+        await server.restartWithPublic(treeBase);
         console.log(`\n>>> Running Benchmark: Browser=[${bName}] Profile=[${prof}]`);
         results.browsers[bName][prof] = {};
 
@@ -763,14 +775,15 @@ async function main() {
         console.log(`Proxy listening on port ${proxy.port} (mode: ${proxyProfile})`);
 
         // 1. Cold Scenario
-        if (options.scenario === 'all' || options.scenario === 'cold') {
+        if (wants('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 });
+            if(options.assertCold)assertColdAssets(res.requests);
             coldRuns.push(res);
-            console.log(`done (${res.wireBytes} bytes, ${res.requestCount} reqs, boot=${res.bootDone}ms)`);
+            console.log(`done (${res.wireBytes} bytes, ${res.requestCount} reqs, fcp=${res.fcp}ms, boot=${res.bootDone}ms)`);
           }
 
           results.browsers[bName][prof].cold = {
@@ -791,11 +804,12 @@ async function main() {
             requests: coldRuns[0]?.requests || [],
             initialJsCss: summarizeList(coldRuns.map(r=>r.initialJsCss)),
             initialAssetRequests: coldRuns[0]?.initialAssetRequests || [],
+            waterfalls: coldRuns.map(r=>({fcp:r.fcp,requests:r.requests,page:r.initialAssetRequests})),
           };
         }
 
         // 2. Warm Scenario
-        if (options.scenario === 'all' || options.scenario === 'warm') {
+        if (wants('warm')) {
           console.log(`  [Scenario: Warm Load] running ${options.runs} iterations...`);
           const warmRuns = [];
           for (let r = 0; r < options.runs; r++) {
@@ -817,7 +831,7 @@ async function main() {
         }
 
         // 3. Offline Scenario
-        if (options.scenario === 'all' || options.scenario === 'offline') {
+        if (wants('offline')) {
           console.log(`  [Scenario: Offline Reload] running ${options.runs} iterations...`);
           const offRuns = [];
           for (let r = 0; r < options.runs; r++) {
@@ -839,7 +853,7 @@ async function main() {
         }
 
         // 4. Update N -> N+1 (JS)
-        if (options.scenario === 'all' || options.scenario === 'update-js') {
+        if (wants('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++) {
@@ -866,7 +880,7 @@ async function main() {
         }
 
         // 5. Update N -> N+1 (CSS)
-        if (options.scenario === 'all' || options.scenario === 'update-css') {
+        if (wants('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++) {
@@ -894,7 +908,7 @@ async function main() {
           };
         }
 
-        if ((options.scenario === 'all' || options.scenario === 'update-feature') && existsSync(path.join(treeBase,'presenter.js'))) {
+        if ((wants('update-feature')) && existsSync(path.join(treeBase,'presenter.js'))) {
           console.log(`  [Scenario: Update split-out presenter, including idle cache fill] running ${options.runs} iterations...`);
           const runs=[];
           for(let r=0;r<options.runs;r++) {

perf/lazy.mjs

@@ -84,6 +84,23 @@ async function run(name){
   await page.evaluate(async()=>{await Lazy.load('feature:export');await Lazy.load('feature:video-edit');});
   assert.equal(proxy.getStats().requestCount,before,'all warmed extension assets stay offline');
   await start();disconnected=false;await proxy.setOffline(false);await page.evaluate(()=>localStorage.removeItem('perf-offline')); 
+  // Change only app bytes, then prove loss of its current cache entry can boot
+  // the compatible N-1 core offline without weakening the inline CSP policy.
+  await stop();writeFileSync(join(cwd,'public/app.js'),readFileSync(join(cwd,'public/app.js'),'utf8')+'\n// phase6 app eviction probe\n');await start();
+  const appTarget=await(await fetch(origin+'/api/manifest')).json();
+  await page.evaluate(async()=>{const r=await navigator.serviceWorker.getRegistration();await r.update();});
+  await wait(page,async tag=>{const r=await navigator.serviceWorker.getRegistration();return r?.waiting&&(await SwUpdate.askCacheStatus(r.waiting))?.version===tag;},appTarget.buildTag);
+  await page.evaluate(async()=>{const r=await navigator.serviceWorker.getRegistration();r.waiting.postMessage({type:'SKIP_WAITING'});});
+  await wait(page,async tag=>{const c=await caches.open('ytplayer-assets');return(await(await c.match('/__ytp_asset_state')).json()).current.buildTag===tag;},appTarget.buildTag);
+  const appKey='/app.js?v='+appTarget.files['/app.js'].h;
+  await page.evaluate(async key=>{await(await caches.open('ytplayer-assets')).delete(key);},appKey);
+  await stop();disconnected=true;await proxy.setOffline(true);
+  const probe=await context.newPage();probe.on('pageerror',e=>errors.push({message:e.message,disconnected}));
+  const offlineBefore=proxy.getStats().requestCount;await probe.goto(origin);await probe.waitForFunction(()=>typeof data!=='undefined'&&typeof Player!=='undefined'&&document.querySelector('#carModeBtn'));
+  assert.equal(await probe.evaluate(async key=>!!await(await caches.open('ytplayer-assets')).match(key),appKey),false,'N-1 never poisons the current app key');
+  assert.equal(proxy.getStats().requestCount,offlineBefore,'N-1 app boot is entirely offline');
+  await probe.close();await start();disconnected=false;await proxy.setOffline(false);
+  await page.evaluate(async key=>{const r=await fetch(key+'&__ytpfresh=1');if(r.headers.get('X-Asset-Hash')!==key.split('v=')[1])throw Error('Wrong repair body');await(await caches.open('ytplayer-assets')).put(key,r);},appKey);
   // Keep an old tab whose core and group contracts remain those of build N.
   const old=await context.newPage();old.on('pageerror',e=>errors.push({message:e.message,disconnected}));await old.goto(origin);await old.waitForSelector('#carModeBtn');
   await old.evaluate(async()=>{window.__saveData=true;await Lazy.load('feature:setlist-import');window.__pinned=window.SetlistImport;});
@@ -133,7 +150,7 @@ async function run(name){
   const offlineTransportErrors=errors.filter(error=>name==='webkit'&&error.disconnected&&(error.message==='TypeError: Load failed'||/\/api\/(?:recommendations\?[^\s]*|version)\.$/.test(error.message)));
   assert.deepEqual(errors.filter(error=>!offlineTransportErrors.includes(error)),[]);
   if(offlineTransportErrors.length)assert.ok(failedRequests.some(url=>/\/api\/(?:recommendations|version)/.test(url))); 
-  results.push({browser:name,sourceBuildTag:previous.buildTag,classicSharedDefaults:true,cssOrderPreserved:true,settingsSearch:true,carControls:4,offlineFeature:true,firstUseNetwork:0,layoutsOffline:['glass-stage','bento-hub','f7-swipe','classic'],pinned:true,compatibleUnexecutedNewURL:true,incompatibleN1ReloadRequired:true,stagedN1:true,playbackGuard:true,prePaintLayout:true,offlineSettingsPanels:true,scriptErrors:[],offlineTransportErrors});
+  results.push({browser:name,sourceBuildTag:previous.buildTag,classicSharedDefaults:true,cssOrderPreserved:true,settingsSearch:true,carControls:4,offlineFeature:true,firstUseNetwork:0,layoutsOffline:['glass-stage','bento-hub','f7-swipe','classic'],pinned:true,compatibleUnexecutedNewURL:true,incompatibleN1ReloadRequired:true,stagedN1:true,appEvictionN1Offline:true,playbackGuard:true,prePaintLayout:true,offlineSettingsPanels:true,scriptErrors:[],offlineTransportErrors});
   console.log(name,'PASS');
  } catch(error){console.error(name,error.stack);throw error;} finally {await browser?.close();proxy?.server.closeAllConnections();await proxy?.close();await stop();}
 }

perf/measurement.mjs

@@ -27,3 +27,8 @@ export function assertWarmAssets(requests) {
  const assets=requests.filter(r=>r.bytes>0&&/\.(?:js|css|woff2?|png|svg)(?:[?#]|$)/.test(r.url)&&!new URL(r.url,'http://localhost').pathname.endsWith('/sw.js'));
  assert.deepEqual(assets,[],'warm reload does not transfer unfinished shell assets');
 }
+
+export function assertColdAssets(requests) {
+ const transferred=requests.filter(r=>r.bytes>0&&new URL(r.url,'http://localhost').pathname==='/app.js');
+ assert.equal(transferred.length,1,'cold app.js transfers its body exactly once across page and worker');
+}

perf/measurement.test.mjs

@@ -1,6 +1,6 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { assertChangedAssets, assertWarmAssets } from './measurement.mjs';
+import { assertChangedAssets, assertWarmAssets, assertColdAssets } from './measurement.mjs';
 test('changed CSS and feature measurements reject unrelated application transfers',()=>{
  const requests=[{url:'/sw.js',bytes:7000},{url:'/asset-sync-core.js',bytes:2000},{url:'/index.html',bytes:12000},{url:'/api/manifest',bytes:3000},{url:'/theme-glass.css?v=new',bytes:5000},{url:'/fonts/a.woff2',bytes:0}];
  assertChangedAssets(requests,'/theme-glass.css');
@@ -14,3 +14,10 @@ test('warm measurements reject unfinished shell downloads but allow API checks',
  assertWarmAssets([{url:'/api/version',bytes:62},{url:'/app.js?v=current',bytes:0}]);
  assert.throws(()=>assertWarmAssets([{url:'/theme-glass.css?v=current',bytes:5000}]));
 });
+
+
+test('cold acceptance rejects a second positive app response while allowing cache revalidation',()=>{
+ assertColdAssets([{url:'/app.js?v=current',bytes:12000},{url:'/app.js?v=current',bytes:0}]);
+ assert.throws(()=>assertColdAssets([{url:'/app.js?v=current',bytes:12000},{url:'/app.js?v=current',bytes:12000}]));
+ assert.throws(()=>assertColdAssets([]));
+});

perf/proxy.mjs

@@ -47,6 +47,7 @@ export function categorizeContentType(contentType, urlPath) {
  */
 export function createThrottleProxy({ targetPort, profile = 'lte' }) {
   let activeTracking = false;
+  let trackingStart = 0;
   let requestCount = 0;
   let requests = [];
   let totalWireBytes = 0;
@@ -79,6 +80,7 @@ export function createThrottleProxy({ targetPort, profile = 'lte' }) {
       return;
     }
 
+    const requestStart = Date.now();
     reqIndex++;
     const currentReqIndex = reqIndex;
 
@@ -114,7 +116,8 @@ export function createThrottleProxy({ targetPort, profile = 'lte' }) {
         let recorded;
         if (activeTracking) {
           requestCount++;
-          recorded={url:clientReq.url,status:upRes.statusCode,bytes:0};
+          recorded={url:clientReq.url,status:upRes.statusCode,bytes:0,index:currentReqIndex,startMs:requestStart-trackingStart,headersMs:Date.now()-trackingStart};
+          clientRes.once('finish',()=>{recorded.endMs=Date.now()-trackingStart;});
           requests.push(recorded);
         }
 
@@ -176,6 +179,7 @@ export function createThrottleProxy({ targetPort, profile = 'lte' }) {
         server.close(resolve);
       }),
     startTracking: () => {
+      trackingStart = Date.now();
       activeTracking = true;
     },
     stopTracking: () => {

perf/results/phase6-hashing-rollback-2026-10-08.json

@@ -0,0 +1,135 @@
+{
+  "date": "2026-10-08T04:01:24.068Z",
+  "frontendCommit": null,
+  "sourceRoot": null,
+  "sourceCommit": "4b1f5204f8fcd207305ee50fff29985497e58e3b",
+  "frontendBuildTag": "bb9fea44045d",
+  "commit": "4b1f5204f8fcd207305ee50fff29985497e58e3b",
+  "runsConfigured": 1,
+  "browsers": {
+    "chromium": {
+      "lte": {
+        "offline": {
+          "requestCount": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "wireBytes": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "fcp": {
+            "median": 40,
+            "min": 40,
+            "max": 40,
+            "values": [
+              40
+            ]
+          },
+          "lcp": {
+            "median": 40,
+            "min": 40,
+            "max": 40,
+            "values": [
+              40
+            ]
+          },
+          "domContentLoaded": {
+            "median": 147,
+            "min": 147,
+            "max": 147,
+            "values": [
+              147
+            ]
+          },
+          "bootDone": {
+            "median": 152,
+            "min": 152,
+            "max": 152,
+            "values": [
+              152
+            ]
+          },
+          "reloadDuration": {
+            "median": 169,
+            "min": 169,
+            "max": 169,
+            "values": [
+              169
+            ]
+          }
+        }
+      }
+    },
+    "webkit": {
+      "lte": {
+        "offline": {
+          "requestCount": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "wireBytes": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "fcp": {
+            "median": 63,
+            "min": 63,
+            "max": 63,
+            "values": [
+              63
+            ]
+          },
+          "lcp": {
+            "median": 97,
+            "min": 97,
+            "max": 97,
+            "values": [
+              97
+            ]
+          },
+          "domContentLoaded": {
+            "median": 93,
+            "min": 93,
+            "max": 93,
+            "values": [
+              93
+            ]
+          },
+          "bootDone": {
+            "median": 99,
+            "min": 99,
+            "max": 99,
+            "values": [
+              99
+            ]
+          },
+          "reloadDuration": {
+            "median": 118,
+            "min": 118,
+            "max": 118,
+            "values": [
+              118
+            ]
+          }
+        }
+      }
+    }
+  }
+}

perf/results/phase6-hashing-rollback-2026-10-09.json

@@ -0,0 +1,135 @@
+{
+  "date": "2026-10-09T01:16:09.809Z",
+  "frontendCommit": null,
+  "sourceRoot": null,
+  "sourceCommit": "71608c2ce81207ca21c8adbc49edbc2893f5170e",
+  "frontendBuildTag": "bb9fea44045d",
+  "commit": "71608c2ce81207ca21c8adbc49edbc2893f5170e",
+  "runsConfigured": 1,
+  "browsers": {
+    "chromium": {
+      "lte": {
+        "offline": {
+          "requestCount": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "wireBytes": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "fcp": {
+            "median": 108,
+            "min": 108,
+            "max": 108,
+            "values": [
+              108
+            ]
+          },
+          "lcp": {
+            "median": 108,
+            "min": 108,
+            "max": 108,
+            "values": [
+              108
+            ]
+          },
+          "domContentLoaded": {
+            "median": 345,
+            "min": 345,
+            "max": 345,
+            "values": [
+              345
+            ]
+          },
+          "bootDone": {
+            "median": 353,
+            "min": 353,
+            "max": 353,
+            "values": [
+              353
+            ]
+          },
+          "reloadDuration": {
+            "median": 401,
+            "min": 401,
+            "max": 401,
+            "values": [
+              401
+            ]
+          }
+        }
+      }
+    },
+    "webkit": {
+      "lte": {
+        "offline": {
+          "requestCount": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "wireBytes": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0
+            ]
+          },
+          "fcp": {
+            "median": 127,
+            "min": 127,
+            "max": 127,
+            "values": [
+              127
+            ]
+          },
+          "lcp": {
+            "median": 184,
+            "min": 184,
+            "max": 184,
+            "values": [
+              184
+            ]
+          },
+          "domContentLoaded": {
+            "median": 180,
+            "min": 180,
+            "max": 180,
+            "values": [
+              180
+            ]
+          },
+          "bootDone": {
+            "median": 187,
+            "min": 187,
+            "max": 187,
+            "values": [
+              187
+            ]
+          },
+          "reloadDuration": {
+            "median": 213,
+            "min": 213,
+            "max": 213,
+            "values": [
+              213
+            ]
+          }
+        }
+      }
+    }
+  }
+}

perf/results/phase6-lazy-2026-10-08.json

@@ -0,0 +1,97 @@
+{
+  "results": [
+    {
+      "browser": "chromium",
+      "sourceBuildTag": "31617662d2f0",
+      "classicSharedDefaults": true,
+      "cssOrderPreserved": true,
+      "settingsSearch": true,
+      "carControls": 4,
+      "offlineFeature": true,
+      "firstUseNetwork": 0,
+      "layoutsOffline": [
+        "glass-stage",
+        "bento-hub",
+        "f7-swipe",
+        "classic"
+      ],
+      "pinned": true,
+      "compatibleUnexecutedNewURL": true,
+      "incompatibleN1ReloadRequired": true,
+      "stagedN1": true,
+      "appEvictionN1Offline": true,
+      "playbackGuard": true,
+      "prePaintLayout": true,
+      "offlineSettingsPanels": true,
+      "scriptErrors": [],
+      "offlineTransportErrors": []
+    },
+    {
+      "browser": "webkit",
+      "sourceBuildTag": "31617662d2f0",
+      "classicSharedDefaults": true,
+      "cssOrderPreserved": true,
+      "settingsSearch": true,
+      "carControls": 4,
+      "offlineFeature": true,
+      "firstUseNetwork": 0,
+      "layoutsOffline": [
+        "glass-stage",
+        "bento-hub",
+        "f7-swipe",
+        "classic"
+      ],
+      "pinned": true,
+      "compatibleUnexecutedNewURL": true,
+      "incompatibleN1ReloadRequired": true,
+      "stagedN1": true,
+      "appEvictionN1Offline": true,
+      "playbackGuard": true,
+      "prePaintLayout": true,
+      "offlineSettingsPanels": true,
+      "scriptErrors": [],
+      "offlineTransportErrors": [
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:41337/api/version.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:41337/api/recommendations?fp=163577c02a53bc40.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:41337/api/version.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:41337/api/recommendations?fp=163577c02a53bc40.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:41337/api/version.",
+          "disconnected": true
+        }
+      ]
+    }
+  ]
+}

perf/results/phase6-lazy-2026-10-09.json

@@ -0,0 +1,97 @@
+{
+  "results": [
+    {
+      "browser": "chromium",
+      "sourceBuildTag": "31617662d2f0",
+      "classicSharedDefaults": true,
+      "cssOrderPreserved": true,
+      "settingsSearch": true,
+      "carControls": 4,
+      "offlineFeature": true,
+      "firstUseNetwork": 0,
+      "layoutsOffline": [
+        "glass-stage",
+        "bento-hub",
+        "f7-swipe",
+        "classic"
+      ],
+      "pinned": true,
+      "compatibleUnexecutedNewURL": true,
+      "incompatibleN1ReloadRequired": true,
+      "stagedN1": true,
+      "appEvictionN1Offline": true,
+      "playbackGuard": true,
+      "prePaintLayout": true,
+      "offlineSettingsPanels": true,
+      "scriptErrors": [],
+      "offlineTransportErrors": []
+    },
+    {
+      "browser": "webkit",
+      "sourceBuildTag": "31617662d2f0",
+      "classicSharedDefaults": true,
+      "cssOrderPreserved": true,
+      "settingsSearch": true,
+      "carControls": 4,
+      "offlineFeature": true,
+      "firstUseNetwork": 0,
+      "layoutsOffline": [
+        "glass-stage",
+        "bento-hub",
+        "f7-swipe",
+        "classic"
+      ],
+      "pinned": true,
+      "compatibleUnexecutedNewURL": true,
+      "incompatibleN1ReloadRequired": true,
+      "stagedN1": true,
+      "appEvictionN1Offline": true,
+      "playbackGuard": true,
+      "prePaintLayout": true,
+      "offlineSettingsPanels": true,
+      "scriptErrors": [],
+      "offlineTransportErrors": [
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:38297/api/version.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:38297/api/recommendations?fp=163577c02a53bc40.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:38297/api/version.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:38297/api/recommendations?fp=163577c02a53bc40.",
+          "disconnected": true
+        },
+        {
+          "message": "TypeError: Load failed",
+          "disconnected": true
+        },
+        {
+          "message": "/127.0.0.1:38297/api/version.",
+          "disconnected": true
+        }
+      ]
+    }
+  ]
+}

perf/results/phase6-merged-bootstrap-warm.json

@@ -0,0 +1,191 @@
+{
+  "date": "2026-10-08T03:15:23.029Z",
+  "frontendCommit": null,
+  "sourceRoot": "/home/josh/development/personal/ytplayer-codex/wt-assets/perf/.tmp/phase6-merged-bootstrap",
+  "sourceCommit": "9408ee07e56db5bbb8319f8da862b549ab948bce",
+  "frontendBuildTag": "c4bb42682ab8",
+  "commit": "9408ee07e56db5bbb8319f8da862b549ab948bce",
+  "runsConfigured": 5,
+  "browsers": {
+    "chromium": {
+      "lte": {
+        "warm": {
+          "requestCount": {
+            "median": 4,
+            "min": 3,
+            "max": 5,
+            "values": [
+              4,
+              4,
+              5,
+              4,
+              3
+            ]
+          },
+          "wireBytes": {
+            "median": 7990,
+            "min": 7979,
+            "max": 7990,
+            "values": [
+              7990,
+              7990,
+              7990,
+              7990,
+              7979
+            ]
+          },
+          "fcp": {
+            "median": 136,
+            "min": 108,
+            "max": 144,
+            "values": [
+              140,
+              116,
+              136,
+              108,
+              144
+            ]
+          },
+          "lcp": {
+            "median": 148,
+            "min": 136,
+            "max": 168,
+            "values": [
+              168,
+              148,
+              136,
+              156,
+              144
+            ]
+          },
+          "domContentLoaded": {
+            "median": 409,
+            "min": 382,
+            "max": 418,
+            "values": [
+              409,
+              382,
+              418,
+              412,
+              402
+            ]
+          },
+          "bootDone": {
+            "median": 425,
+            "min": 398,
+            "max": 433,
+            "values": [
+              425,
+              398,
+              433,
+              430,
+              417
+            ]
+          },
+          "longTaskTotal": {
+            "median": 63,
+            "min": 56,
+            "max": 65,
+            "values": [
+              63,
+              65,
+              63,
+              57,
+              56
+            ]
+          }
+        }
+      }
+    },
+    "webkit": {
+      "lte": {
+        "warm": {
+          "requestCount": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0,
+              0,
+              0,
+              0,
+              0
+            ]
+          },
+          "wireBytes": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0,
+              0,
+              0,
+              0,
+              0
+            ]
+          },
+          "fcp": {
+            "median": 92,
+            "min": 79,
+            "max": 94,
+            "values": [
+              92,
+              92,
+              87,
+              94,
+              79
+            ]
+          },
+          "lcp": {
+            "median": 92,
+            "min": 79,
+            "max": 94,
+            "values": [
+              92,
+              92,
+              87,
+              94,
+              79
+            ]
+          },
+          "domContentLoaded": {
+            "median": 89,
+            "min": 77,
+            "max": 92,
+            "values": [
+              89,
+              90,
+              84,
+              92,
+              77
+            ]
+          },
+          "bootDone": {
+            "median": 95,
+            "min": 83,
+            "max": 98,
+            "values": [
+              95,
+              96,
+              91,
+              98,
+              83
+            ]
+          },
+          "longTaskTotal": {
+            "median": 0,
+            "min": 0,
+            "max": 0,
+            "values": [
+              0,
+              0,
+              0,
+              0,
+              0
+            ]
+          }
+        }
+      }
+    }
+  }
+}

perf/results/phase6-migration-lossy-2026-10-08.json

@@ -0,0 +1,41 @@
+{
+  "commit": "b77938a",
+  "results": [
+    {
+      "browser": "chromium",
+      "oldTag": "1175f1a1d2c1",
+      "newTag": "31617662d2f0",
+      "banners": 1,
+      "updateReloads": 1,
+      "cachedFiles": 122,
+      "durationMs": 25233,
+      "wireBytes": 631091,
+      "offline": true,
+      "legacyURLs": 21,
+      "profile": "lossy",
+      "userInitiatedOnly": true,
+      "playbackGuard": true,
+      "evictionRepair": true,
+      "incrementalRefresh": true,
+      "offlineTransportErrors": 0
+    },
+    {
+      "browser": "webkit",
+      "oldTag": "1175f1a1d2c1",
+      "newTag": "31617662d2f0",
+      "banners": 1,
+      "updateReloads": 1,
+      "cachedFiles": 122,
+      "durationMs": 22860,
+      "wireBytes": 741571,
+      "offline": true,
+      "legacyURLs": 21,
+      "profile": "lossy",
+      "userInitiatedOnly": true,
+      "playbackGuard": true,
+      "evictionRepair": true,
+      "incrementalRefresh": true,
+      "offlineTransportErrors": 4
+    }
+  ]
+}

perf/results/phase6-migration-lossy-2026-10-09.json

@@ -0,0 +1,41 @@
+{
+  "commit": "b77938a",
+  "results": [
+    {
+      "browser": "chromium",
+      "oldTag": "1175f1a1d2c1",
+      "newTag": "31617662d2f0",
+      "banners": 1,
+      "updateReloads": 1,
+      "cachedFiles": 122,
+      "durationMs": 27355,
+      "wireBytes": 631091,
+      "offline": true,
+      "legacyURLs": 21,
+      "profile": "lossy",
+      "userInitiatedOnly": true,
+      "playbackGuard": true,
+      "evictionRepair": true,
+      "incrementalRefresh": true,
+      "offlineTransportErrors": 0
+    },
+    {
+      "browser": "webkit",
+      "oldTag": "1175f1a1d2c1",
+      "newTag": "31617662d2f0",
+      "banners": 1,
+      "updateReloads": 1,
+      "cachedFiles": 122,
+      "durationMs": 24426,
+      "wireBytes": 730395,
+      "offline": true,
+      "legacyURLs": 21,
+      "profile": "lossy",
+      "userInitiatedOnly": true,
+      "playbackGuard": true,
+      "evictionRepair": true,
+      "incrementalRefresh": true,
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perf/results/phase6-migration-unthrottled-2026-10-08.json

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perf/results/phase6-migration-unthrottled-2026-10-09.json

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+  ]
+}

perf/results/phase6-native-cached-warm.json

@@ -0,0 +1,191 @@
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perf/results/phase6-native-chromium-warm.json

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perf/results/phase6-native-parser-warm.json

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perf/results/phase6-seams-2026-10-08.json

@@ -0,0 +1,28 @@
+[
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+    "offlineNetworkRequests": 0,
+    "errors": []
+  }
+]

perf/results/phase6-seams-2026-10-09.json

@@ -0,0 +1,28 @@
+[
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+      "stats"
+    ],
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+  }
+]

perf/results/phase6-sync-rollback-2026-10-08.json

@@ -0,0 +1,135 @@
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+}

perf/results/phase6-sync-rollback-2026-10-09.json

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+}

plans/phase6-investigation.md

@@ -0,0 +1,137 @@
+# Phase 6 investigation
+
+All comparisons use the current instrumented harness with matching frontend and
+server from detached worktrees beneath `perf/.tmp`. No production requests.
+Command template (three fresh contexts):
+
+```
+node perf/baseline.mjs --runs 3 --browser webkit --profile lte --scenario cold --source-root perf/.tmp/phase6-<variant> --out perf/results/phase6-<variant>.json
+```
+
+| Source | Commit | LTE FCP median ms | Wire bytes | app.js positive responses/sample |
+|---|---|---:|---:|---:|
+| Phase 2 | 4950d3e | 1044 | 1191063 | 2 |
+| Immediately before lazy layouts | d98d444 | 1032 | 1191686 | 2 |
+| First lazy-layout cut | 5d6a154 | 1615 | 1106796 | 2 |
+| Phase 3 tip | cd4a25a | 1646 | 1108191 | 2 |
+| Phase 5 tip (same product as Phase 4) | 21c1273 | 1736 | 1097007 | 2 |
+| Phase 5 + worker force-cache | scratch | 1745 | 1097006 | 2 |
+| Phase 5 + parser-owned classic CSS | scratch | 898 | 1097051 | 2 |
+| Phase 5 + classic preload | scratch | 909 | 1097032 | 2 |
+
+The adjacent-commit measurements isolate `5d6a154`, not the Phase 4 extraction.
+All three FCP samples, complete proxy waterfalls, and page Resource Timing are
+stored in each result. The first sample often includes startup compression cost;
+it is retained in every median, not discarded.
+
+Phase 3 sample 2: common styles finish around 880 ms. The parser-written classic
+stylesheet is discovered at 416 ms but reaches the proxy only at 1434 ms and
+finishes at 1607 ms. FCP is 1646 ms. Phase 5 sample 2: classic reaches the proxy
+at 1540 ms, finishes at 1711 ms, FCP is 1736 ms. Speculatively discovered body
+scripts already occupy the request queue when the selected stylesheet arrives.
+Phase 2 discovers its declarative styles together around 231 ms, FCP 1044 ms.
+
+The first service-worker request is at 2458 ms in Phase 3 and 2337 ms in Phase 5,
+AFTER paint. Worker install competition does not explain this FCP regression.
+Font preload URLs match the font CSS; late layout CSS is the final rendering
+barrier. Making classic CSS declarative again removes the delay without changing
+CSS bytes or cascade order. This scratch variant unconditionally applies classic
+and is diagnostic only; the shipping fix must retain selected-layout behavior.
+
+The modern synchronizer already uses default fetch caching. Changing it to
+force-cache has no effect: every WebKit sample still transfers app.js twice.
+The page and worker cannot reuse these HTTP-cache responses in this harness.
+The next hypothesis was a same-build page handoff reusing the page HTTP cache.
+The prototype checked both the X-Asset-Hash header and decoded-body SHA-256, and
+stripped compressed transport headers before constructing the cached Response.
+Updates and legacy migration must continue through their existing worker path.
+
+The shipping CSS fix is a preload, not an unconditional stylesheet. Its three-run
+FCP is 909 ms; the first classic request reaches the proxy at 250 ms and completes
+at 423 ms. Lazy still applies only the saved layout, in the original cascade order.
+Other selected layouts may speculatively download the small classic stylesheet;
+it never applies or blocks their rendering. No inline script or CSP change.
+
+
+The page-to-worker prototype successfully delivered bodies, but still transferred
+app.js twice. `phase6-handoff-mode.json` records the two requests: identical URL,
+`Accept-Encoding: gzip, deflate`, no-cors mode and immutable response, but script
+versus empty request destinations. Force-cache in the page did not reuse the
+script body's cache either. This prototype was discarded, not shipped.
+
+A fetch preload plus a later fetch also failed the one-body assertion. The
+shipping fix instead starts one cache-first fetch promise in the head loader.
+The final eager app-bootstrap consumes that response, verifies header AND SHA-256,
+and caches it before executing unchanged app.js as a classic script. A specific
+server-generated CSP hash authorizes only those exact bytes; unsafe-inline remains
+absent. DOMContentLoaded boot runs exactly once; the temporary script node and
+response promise are released. Native, insecure HTTP and rollback modes retain
+external classic execution. Only server asset-manifest rendering changed; no
+frontend imports, worker sync algorithm, update flow or playback source changed.
+
+The initial owned-response trial passed with one app.js body, FCP 1040 ms and
+981468 wire bytes (one fresh sample; not a final median). Five-run acceptance and
+regression results will be recorded separately. Historical diagnostics retained
+all samples. Full-harness configurations now reset to the base tree before each
+browser/profile, preventing a preceding synthetic update from contaminating the
+next cold build. The historical invalid media fixture remains unchanged: home
+launch only, not autoplay/audio latency.
+
+
+Self-review added explicit N-1 app boot after eviction: verify the retained body
+and use its exact classic URL through the controlling worker. It never fills the
+new key with old bytes. Stale core execution additionally requires every group
+contract to match the running shell's expectations; a core or feature contract
+change rejects it. Both-engine lazy smoke now changes app bytes, evicts the new
+entry, boots N-1 offline, then repairs the current entry before the existing
+feature pinning/contract/playback checks. No source in app.js changed.
+
+
+The all-engine inline prototype's completed five-run Chromium/LTE profile had
+cold boot 6748 ms, warm boot 458 ms (Phase 5: 410 ms), offline boot 204 ms, core
+update 870 ms. This was a real warm regression, so the full sweep was interrupted
+before accepting its results. Raw output: perf/.tmp/phase6-inline-chromium-profile.log.
+The native-script controlled variant measured warm 414 ms over five samples.
+Shipping capture is therefore restricted to WebKit (including iOS CriOS); other
+engines preload and retain their native classic-script/code-cache path. Normal
+native cache hits avoid decoding/rehashing; retained core fallback still enforces
+all group contracts. The new worker marks stale responses no-store and strips
+decoded transport headers, preventing browser resource-cache poisoning under a
+new URL. CacheStorage's exact keys and previous entries stay unchanged.
+
+The native-window contract lookup trial regressed Chromium warm boot (~698 ms).
+It is rejected. The worker now owns the all-group stale app contract guard
+(pure planner and actual worker VM tests first); native boot has no window-side
+CacheStorage or hashing work. WebKit's byte-verified owned response path is
+unchanged. The native fixture models the actual worker fallback decision instead
+of a second page-side decision. All 221 frontend tests and 184 server tests pass;
+both-engine lazy/offline/eviction/pinning/contracts/playback smoke passes.
+
+The WebKit warm prototype also paid repeated handoff/cache/hash work (warm
+~98 ms versus Phase 5 83 ms). Capture now applies only to uncontrolled WebKit
+visits. Controlled warm/offline/update pages use the worker's native exact-URL
+script path, including its strengthened contract guard. A failing head-loader
+test precedes this change; all 222 frontend and 184 server tests and both-engine
+lazy smoke pass. Cold capture and both rollback flags are unchanged.
+
+The final native-path review caught a new Chromium paint regression: five-run
+FCP 1616/2328 ms (LTE/lossy), despite faster boot. A contemporary Phase 5 LTE
+control measured 1360 ms over three runs. Lowering the new app preload priority
+reduced FCP to 1396 ms (three runs). Native parser execution restores app's
+original DOMContentLoaded boot boundary. A rejected no-preload controlled-page
+trial worsened WebKit warm boot to 98 ms; native cache preloading remains.
+
+The standalone helper adds a CacheStorage script read to native startup. Packing
+the loader into the existing final core script, section-rail.js, measured Chrome
+warm 425 ms versus contemporary Phase 5 426 ms (five runs); WebKit measured
+95 ms versus 88 ms, so zero warm overhead is not yet established. The merged
+three-run Chrome LTE cold trial measured FCP 1384 ms and boot 6512 ms. Core's
+contract becomes 2 because an old section script lacks this loader and cannot
+safely substitute for it. No Phase 5 SHELL file is removed; the experimental
+Phase 6 standalone helper is removed. Native-order, exact final-script packing
+and contract tests precede implementation. All 223 frontend and 184 server tests
+and both-engine lazy/offline/eviction/pinning/contracts/playback smoke pass.
+
+The intermediate native-auto-priority full dataset is retained as a rejected
+trial; it is not the final acceptance result. Source directories named in trial
+JSONs are dirty diagnostic worktrees of 9408ee0 with exactly the changes above.

plans/phase6-plan.md

@@ -0,0 +1,11 @@
+# Phase 6 plan
+
+Start from Phase 5 21c1273. Fix cold first-visit delivery only; preserve playback, banner, migration, exact hashes, contracts/pinning, offline and both rollback flags.
+
+1. Extend perf/baseline.mjs/proxy.mjs with page Resource Timing and complete request waterfalls, and a source-worktree option. Create detached historical worktrees beneath perf/.tmp for Phase 2, 3 and 5 tips. Run isolated WebKit/LTE cold measurements, >=3 runs each. Bisect Phase 3 commits with the same instrumented harness. Test head-loader/CSS discovery, fonts, worker start relative to FCP and immutable HTTP-cache behavior with controlled scratch variants. Record actual evidence in plans/phase6-investigation.md.
+2. Add failing tests before each root fix. Likely files: frontend/index.html, lazy.js or a tiny layout bootstrap; frontend/sw.js and asset-sync-core.js only as evidence warrants. Keep the legacy install path and update all-or-nothing behavior intact; cache completed immutable responses safely without any unverifiable body. Preserve selected layout before paint and existing CSS cascade order.
+3. Commit each fix separately with frontend and isolated Bun server suites green. Revert individual fixes for rollback; ASSET_HASHING=0/ASSET_SYNC=0 stay supported. Do not deploy or contact production.
+4. Run final five-run WebKit cold LTE and lossy medians: FCP <= measured Phase 2 (targets ~1,300/3,800 ms); app.js positive-body responses exactly one; cold wire clearly below baseline. Measure Chromium and warm/offline/core-JS/CSS/feature updates against Phase 5, with repeated medians where regression risk exists. Rerun migration both engines with and without stalls, hidden timers, lazy/seam offline checks, rollback paths and all tests.
+5. Self-review master sections 3.2/3.3/6/6b and full diff. Commit <=350-word plans/phase6-report.md with actual before/after table and explicit unmet targets; overwrite DONE06 signal and end.
+
+Risks: CSS cascade/no-flash preservation, duplicate requests crossing browser/worker HTTP-cache partitions, race between page handoff and install, timeout fallbacks delaying cache readiness, CPU contention invalidating timing. Historical worktrees/scratch data stay inside wt-assets; run benchmarks sequentially and preserve the invalid historical media fixture only for comparable home-launch metrics, not playback claims.

plans/phase6-report.md

@@ -0,0 +1,46 @@
+# Phase 6 report
+
+Tested `4b1f520`, from Phase 5 `21c1273`. Adjacent-commit measurements isolate
+`5d6a154`: WebKit/LTE FCP 1032→1615 ms. Its selected classic CSS arrived late
+(1540–1711 ms); worker installation started after paint. Fonts matched their
+preloads. Default/force-cache and HTTP-cache handoff trials still transferred
+app.js twice.
+
+Shipped early classic style discovery (`e7a7cdc`), a single verified page-owned
+WebKit response and specific CSP hash (`a86fa1c`, refined through `9408ee0`),
+worker-owned stale-core contract protection (`97eb31e`), and native parser boot
+with low-priority app preloading (`4b1f520`). The loader shares the existing final
+core script; core contract 2 prevents unsafe old packing fallback. app.js,
+playback and sw-update.js are unchanged.
+
+Five-run final medians:
+
+| Engine/profile | Phase 5→6 FCP ms | Phase 5→6 cold bytes | app bodies |
+|---|---:|---:|---:|
+| WebKit/LTE | 1739→905 | 1097048→983326 | 2→1 |
+| WebKit/lossy | 4303→2748 | 1105402→990152 | 2→1 |
+| Chromium/LTE | 1356→1388 | 651012→653267 | 1→1 |
+| Chromium/lossy | 2052→1976 | 651096→653267 | 1→1 |
+
+WebKit paint, one-body and below-baseline wire targets pass (−16.6%/−16.1%
+versus original wire baseline). Phase 2 measured 1044/4045 ms over three runs.
+
+Strict zero regression is **not achieved**: Chrome/LTE FCP +32 ms, cold bytes
++0.35%, long tasks 278→304 ms; warm boots Chrome 410/403→418/442 and WebKit
+83/85→88/89 ms. Metadata adds ~0.4 KB per core update. Added loader/security
+work has a cost; complete timing attribution remains unproved. Contemporary
+Phase 5 controls and all offline/update deltas appear in
+[phase6-verification.md](phase6-verification.md), with actual command excerpts.
+Chromium cold boot improves 7043/11342→6478/10314 ms.
+
+Migration passes both engines with/without stalls; banner once, explicit legacy
+refresh, old URLs, N-1, offline and playback guards. Lazy/layout/feature seams,
+hidden timers, both rollback modes, 223 frontend/184 server/3 measurement tests
+pass. No fonts/icons re-downloaded. ASSET_HASHING=0 and ASSET_SYNC=0 remain.
+
+Real iPhone install/update, quota pressure and 30-minute locked-screen audio
+require owner checks. The historical fixture measures home launch, not autoplay.
+
+Post-crash verification retained in `6f0235f`: both-engine migrations, offline
+layouts/features, rollback and cold smoke pass. WebKit smoke FCP 1253/2881 ms
+(LTE/lossy), one app response each. Durable five-run results remain authoritative.

plans/phase6-verification.md

@@ -0,0 +1,219 @@
+# Phase 6 verification
+
+Final product under test: `4b1f520` (Phase 5 parent `21c1273`). No production requests.
+All historical source worktrees contain matching server and frontend revisions.
+The complete diagnostic waterfalls and five-run acceptance samples are committed
+under `perf/results/phase6-*.json`. KB in these tables means 1,000 bytes.
+
+## Cause and controlled trials
+
+See [phase6-investigation.md](phase6-investigation.md) for the three-run tip
+comparisons, adjacent-commit bisect, rejected cache/handoff prototypes and fixes.
+The regressing commit is `5d6a154`: LTE FCP 1,032 → 1,615 ms immediately across
+that cut. Phase 2/3/5 medians are 1,044/1,646/1,736 ms. Phase 4 extraction did
+not introduce the paint regression.
+
+Representative WebKit/LTE sample 2, proxy times relative to tracking start:
+phase6-before-phase5.json versus phase6-webkit-cold-2026-10-08.json (9408ee0
+owned-response diagnostic, before final loader packing). Final medians follow.
+
+| Request | Phase 5 start/end ms | Phase 6 start/end ms |
+|---|---:|---:|
+| lazy.js | 250/417 | 250/418 |
+| styles.css | 251/570 | 251/570 |
+| theme-classic.css | 1540/1711 | 250/421 |
+| page app.js | 1524/2273 | 1552/2297 |
+| first sw.js | 2337/2533 | 2367/2564 |
+| worker app.js | 2903/3651 | absent |
+| FCP | 1736 | 905 |
+
+The stylesheet becomes available before the parser applies it. The worker starts
+after paint. Default fetch caching was already in the modern synchronizer;
+force-cache and a page-to-worker HTTP-cache handoff both still transferred two
+app bodies in WebKit. A single page-owned response, verified and cached before
+boot registers the worker, removes the redundant app transfer. Controlled pages
+and other engines retain native external scripts; no window cache/hash lookup
+is added to those paths. Each retained stale app requires all shell contracts
+to match, enforced by the worker.
+
+## Final measurements
+
+Exact final command (120 samples: both engines, both profiles, six scenarios,
+five fresh samples each):
+
+```sh
+node perf/baseline.mjs --runs 5 --browser all --profile all --scenario all --assert-cold --out perf/results/phase6-final-2026-10-08.json
+```
+
+Final app.js positive-byte responses are exactly one in all 20 cold samples.
+The earlier separate cold/regression datasets used 9408ee0 and are diagnostics,
+not the final acceptance build. `phase6-native-auto-priority-2026-10-08.json`
+combines that rejected intermediate sweep. Final core contract is 2: the final
+section-rail script now owns the loader; a stale pre-packing section script would
+not load app.js. No Phase 5 SHELL file was deleted. app.js and sw-update.js remain
+byte-for-byte unchanged.
+
+Actual final command output excerpts:
+
+```text
+Chromium/LTE: run 4/5... done (653267 bytes, 115 reqs, fcp=1396ms, boot=6478ms)
+Chromium/lossy: run 2/5... done (653267 bytes, 115 reqs, fcp=1972ms, boot=10292ms)
+WebKit/LTE: run 2/5... done (983326 bytes, 158 reqs, fcp=905ms, boot=2335ms)
+WebKit/lossy: run 2/5... done (990152 bytes, 161 reqs, fcp=2748ms, boot=5046ms)
+```
+
+WebKit FCP targets (≤1300/3800 ms) pass. Contemporary Phase 2 three-run medians:
+1044/4045 ms; its lossy samples are 4045/3218/5297, all retained. Original baseline
+WebKit cold wire is 1,179,624 bytes. Final LTE/lossy wire is 983,326/990,152 bytes
+(16.6%/16.1% lower). The final cold set transfers app.js once in both engines.
+
+
+## Complete final comparison
+
+Five-run medians. Each cell is Phase 5 → Phase 6; bytes are exact body wire bytes.
+
+| Browser/profile | Cold requests | Cold bytes | FCP ms | LCP ms | Boot ms | Long tasks ms |
+|---|---:|---:|---:|---:|---:|---:|
+| chromium/lte | 115 → 115 | 651012 → 653267 | 1356 → 1388 | 1356 → 1388 | 7043 → 6478 | 278 → 304 |
+| chromium/lossy | 115 → 115 | 651096 → 653267 | 2052 → 1976 | 2052 → 1976 | 11342 → 10314 | 295 → 297 |
+| webkit/lte | 159 → 158 | 1097048 → 983326 | 1739 → 905 | 1810 → 982 | 2315 → 2335 | 0 → 0 |
+| webkit/lossy | 162 → 161 | 1105402 → 990152 | 4303 → 2748 | 4371 → 2821 | 5573 → 5046 | 0 → 0 |
+
+WebKit does not expose the Long Tasks API; its zero fields mean unmeasured.
+
+| Browser/profile | Warm boot ms | Offline boot ms | Offline reload ms | Core update ms/bytes | CSS update ms/bytes | Feature update ms/bytes |
+|---|---:|---:|---:|---:|---:|---:|
+| chromium/lte | 410 → 418 | 185 → 188 | 202 → 206 | 745/125795 → 872/126186 | 1380/35363 → 1388/35760 | 1378/33408 → 1392/33762 |
+| chromium/lossy | 403 → 442 | 189 → 194 | 204 → 207 | 747/125795 → 805/126186 | 1377/35363 → 1383/35760 | 1375/33408 → 1386/33762 |
+| webkit/lte | 83 → 88 | 86 → 88 | 100 → 102 | 1890/147259 → 2015/147626 | 1455/45659 → 1467/46254 | 1455/43318 → 1380/41860 |
+| webkit/lossy | 85 → 89 | 81 → 85 | 95 → 98 | 4192/147259 → 2934/147626 | 3647/43705 → 3687/44211 | 3644/41364 → 3693/41860 |
+
+## Limits and exact unmet parity targets
+
+Strict zero regression versus the recorded Phase 5 run is NOT achieved.
+Chromium/LTE FCP is 1388 versus 1356 ms (+32); cold bytes 653267 versus 651012
+(+2255, 0.35%); long tasks 304 versus 278 ms. The verified loader, CSP permission,
+contract checks and metadata add code/bytes; parser insertion also changes task
+boundaries. The whole timing delta has not been causally isolated. Three-run
+contemporary Phase 5 LTE medians were FCP 1368, boot 7090 and long tasks 294 ms.
+Final Chrome boot improves to 6478/10314 ms (Phase 5 7043/11342).
+
+Warm/offline/update deltas in the complete table remain explicit. Contemporary
+five-run Phase 5 warm boots were Chrome 426/446 and WebKit 88/88 ms; final values
+418/442 and 88/89 ms. Contemporary Phase 5 core-update times were Chrome 869/799
+and WebKit 1955/2776 ms; final 872/805 and 2015/2934 ms. Metadata adds roughly
+0.4 KB to core updates. Periodic lossy stalls depend on request order; timing
+comparisons cannot establish exact parity. The extra CPU/cache work is small,
+but zero cost was not proved, and the positive timing deltas are not dismissed.
+
+Every final update passed assertChangedAssets: only app.js, theme-glass.css or
+presenter.js is downloaded as application code, with index/API/worker metadata;
+fonts/icons are not re-downloaded. Whole CSS-update wire remains above 30 KB,
+a pre-existing Phase 5 gap. Readiness and completion remain separately measured.
+
+Real iPhone Safari/PWA code-cache behavior, OPFS quota pressure, forced cache
+eviction and uninterrupted locked-screen/background audio for 30 minutes were
+not verified. The historical media fixture is invalid for autoplay: these are
+home-launch metrics, not media-start measurements. No playback code changed.
+Other selected layouts may prefetch 4079 unused classic CSS bytes; that preload
+never applies, and the selected stylesheet retains its original cascade order.
+
+## Compatibility verification on the final product
+
+All commands below ran on 4b1f520, build 31617662d2f0:
+
+```sh
+node perf/migration.mjs --browser all --profile unthrottled --out perf/results/phase6-migration-unthrottled-2026-10-08.json
+node perf/migration.mjs --browser all --profile lossy --out perf/results/phase6-migration-lossy-2026-10-08.json
+node perf/hidden-timers.mjs
+node perf/lazy.mjs --browser all --out perf/results/phase6-lazy-2026-10-08.json
+node perf/seams.mjs --browser all
+ASSET_SYNC=0 node perf/baseline.mjs --runs 1 --browser all --profile lte --scenario offline --out perf/results/phase6-sync-rollback-2026-10-08.json
+ASSET_HASHING=0 node perf/baseline.mjs --runs 1 --browser all --profile lte --scenario offline --out perf/results/phase6-hashing-rollback-2026-10-08.json
+node --test frontend/*.test.js
+node --test perf/measurement.test.mjs
+(cd server && bun install && PATH="$PWD/../perf/.tmp/test-venv/bin:$PATH" bun run test)
+```
+
+Actual output excerpts:
+
+```text
+Migration unthrottled: chromium banners=1 updateReloads=1 cachedFiles=122 userInitiatedOnly=true offline=true playbackGuard=true evictionRepair=true
+Migration unthrottled: webkit banners=1 updateReloads=1 cachedFiles=122 userInitiatedOnly=true offline=true playbackGuard=true evictionRepair=true
+Migration lossy: chromium durationMs=25233 banners=1 updateReloads=1 legacyURLs=21 userInitiatedOnly=true offline=true
+Migration lossy: webkit durationMs=22860 banners=1 updateReloads=1 legacyURLs=21 userInitiatedOnly=true offline=true
+Hidden timers: Page errors: none; Result: ALL ASSERTIONS PASSED
+Lazy: chromium PASS; webkit PASS
+Seams: chromium checked=[shell,presenter,remote,party,share,stats] offlineNetworkRequests=0 errors=[]
+Seams: webkit checked=[shell,presenter,remote,party,share,stats] offlineNetworkRequests=0 errors=[]
+Frontend: tests 223; pass 223; fail 0; skipped 0
+Measurement: tests 3; pass 3; fail 0
+Server: sum of per-file output: 184 pass; 0 fail
+```
+
+Both rollback modes launched offline with zero network in Chromium and WebKit.
+The archived b77938a fixture was rebuilt by the migration script each time.
+Legacy reload remains user-initiated; its pre-existing Refresh UI timer exception
+is unchanged. New-page playback guards, old-client readiness, one banner, old
+plain/?v=oldTag/?__ytpfresh URLs, already-open old tabs and cached offline reload
+remain covered. Four expected WebKit disconnected API transport errors per
+migration were recorded and matched to failed API requests; no script errors.
+The seam harness's historical Phase 4 artifact was restored after saving the
+new output as phase6-seams-2026-10-08.json.
+
+Self-review re-read the complete product diff and master §§3.2/3.3/6/6b.
+No frontend import was added to server code; no original shell file was removed;
+no auto skipWaiting, live stateful re-evaluation, playback edit, push or deploy.
+Cache responses are exact-key checked; stale bodies under a new URL are no-store
+and carry no decoded transport encoding. Core contract 2 blocks loader-free N-1
+packing, while same-contract app fallback and executed feature pinning remain
+covered by both-engine smoke. Failed quota writes never delete saved music.
+
+## Post-crash completion — 2026-10-09
+
+Resumed from ff3f934 on codex/phase6. Commit 71608c2 clarifies the diagnostic
+waterfall provenance; product code and served build 31617662d2f0 are unchanged.
+The durable five-run/120-sample final measurements above were preserved.
+Reinstalled Playwright browsers passed fresh compatibility checks:
+
+```sh
+node perf/migration.mjs --browser all --profile unthrottled --out perf/results/phase6-migration-unthrottled-2026-10-09.json
+node perf/migration.mjs --browser all --profile lossy --out perf/results/phase6-migration-lossy-2026-10-09.json
+node perf/hidden-timers.mjs
+node perf/lazy.mjs --browser all --out perf/results/phase6-lazy-2026-10-09.json
+node perf/seams.mjs --browser all
+ASSET_SYNC=0 node perf/baseline.mjs --runs 1 --browser all --profile lte --scenario offline --out perf/results/phase6-sync-rollback-2026-10-09.json
+ASSET_HASHING=0 node perf/baseline.mjs --runs 1 --browser all --profile lte --scenario offline --out perf/results/phase6-hashing-rollback-2026-10-09.json
+node --test frontend/*.test.js
+node --test perf/measurement.test.mjs
+(cd server && bun install && PATH="$PWD/../perf/.tmp/test-venv/bin:$PATH" bun run test)
+```
+
+Fresh output excerpts (all commands exited successfully):
+
+```text
+Migration unthrottled: chromium durationMs=13290; webkit durationMs=11711
+Migration lossy: chromium durationMs=27355; webkit durationMs=24426
+All four: banners=1 updateReloads=1 cachedFiles=122 legacyURLs=21
+All four: userInitiatedOnly=true offline=true playbackGuard=true evictionRepair=true incrementalRefresh=true
+Hidden timers: Page errors: none; Result: ALL ASSERTIONS PASSED
+Lazy: chromium PASS; webkit PASS
+Seams: chromium and webkit checked=[shell,presenter,remote,party,share,stats] offlineNetworkRequests=0 errors=[]
+Both rollback flags, both engines: requestCount=0 wireBytes=0
+Frontend: tests 223; pass 223; fail 0; skipped 0
+Measurement: tests 3; pass 3; fail 0
+Server: per-file totals 184 pass; 0 fail
+```
+
+The seam output is saved as phase6-seams-2026-10-09.json; the historical Phase 4
+result was restored. Offline API transport errors remain distinguished from
+script failures. No playback or sw-update.js changes were added. bun.lock is
+excluded from commits.
+
+Post-crash cold smoke command:
+
+```sh
+node perf/baseline.mjs --runs 1 --browser webkit --profile all --scenario cold --assert-cold --out perf/results/phase6-cold-smoke-2026-10-09.json
+```
+
+LTE/lossy FCP was 1253/2881 ms, wire 983326/990152 bytes; both samples passed exactly one positive-byte app.js response. These single-run rechecks do not replace the durable five-run medians.

server/asset-manifest.js

@@ -8,12 +8,12 @@ const tagHash = bytes => createHash('sha256').update(bytes).digest('hex').slice(
 export const injectBuildTag = (source, tag) => source.replace(
   /typeof __BUILD_TAG__ !== 'undefined' \? __BUILD_TAG__ : '[^']*'/, JSON.stringify(tag));
 
-function embedAssets(source, files, groups, buildTag, hashing) {
+function embedAssets(source, files, groups, buildTag, hashing, assetSync) {
   const pageFiles = {};
   for (const group of Object.values(groups)) for (const path of group.files) {
     if (path !== '/index.html' && path !== '/sw.js') pageFiles[path] = { ...files[path], h: hashing ? files[path].h : buildTag };
   }
-  const json = JSON.stringify({ buildTag, groups, files: pageFiles }).replace(/</g, '\\u003c');
+  const json = JSON.stringify({ buildTag, groups, files: pageFiles, appCache: assetSync }).replace(/</g, '\\u003c');
   return source.replace(/(<script type="application\/json" id="ytp-assets">)[\s\S]*?(<\/script>)/, (_, open, close) => open + json + close);
 }
 
@@ -70,16 +70,17 @@ export function createAssetManifest(publicDir = './public', { hashing = true, bu
   }
   const files = {};
   for (const url of [...bytes.keys()].sort()) files[url] = { h: assetHash(bytes.get(url)), s: bytes.get(url).length, g: membership.get(url) || 'core' };
-  const source = bytes.get('/index.html')?.toString() ?? null;
+  const source = bytes.get('/index.html')?.toString()
+    .replaceAll('__APP_SCRIPT_HASH__', createHash('sha256').update(bytes.get('/app.js') || '').digest('base64')) ?? null;
   const swSource = bytes.get('/sw.js')?.toString() ?? null;
   // Derived build metadata cannot be an input to its own hash. Canonicalize
   // the index meta and SW injected tag, then publish hashes of the final bytes.
   // All original bytes (including index/SW source) remain inputs via source hashes.
-  let canonicalIndex = source === null ? null : stampIndex(embedAssets(source, files, groups, '__BUILD_TAG__', hashing), files, { hashing });
+  let canonicalIndex = source === null ? null : stampIndex(embedAssets(source, files, groups, '__BUILD_TAG__', hashing, assetSync), files, { hashing });
   const canonical = { assetSync, files: { ...files }, groups, contracts };
   if (canonicalIndex !== null && hashing) canonical.files['/index.html'] = { ...files['/index.html'], h: assetHash(canonicalIndex), s: Buffer.byteLength(canonicalIndex), source: files['/index.html'].h };
   const buildTag = hashing ? tagHash(JSON.stringify(canonical)) : (override || legacy.digest('hex').slice(0, 12));
-  const index = source === null ? null : embedAssets(stampIndex(source, files, { hashing, buildTag }), files, groups, buildTag, hashing);
+  const index = source === null ? null : embedAssets(stampIndex(source, files, { hashing, buildTag }), files, groups, buildTag, hashing, assetSync);
   const sw = swSource === null ? null : injectBuildTag(swSource, buildTag)
     .replace("typeof __ASSET_SYNC__ !== 'undefined' ? __ASSET_SYNC__ : true", JSON.stringify(assetSync))
     .replace("importScripts('/asset-sync-core.js')", "importScripts('/asset-sync-core.js?v=" + (files['/asset-sync-core.js']?.h || '') + "')");

server/asset-manifest.test.js

@@ -88,3 +88,15 @@ test('index embeds build-local group hashes without recursively embedding index/
   const legacy=JSON.parse(off.index.match(/id="ytp-assets">([^<]+)<\/script>/)[1]);
   expect(legacy.files['/app.js'].h).toBe(off.manifest.buildTag);
 }));
+
+test('app bootstrap CSP hash follows exact app bytes and rollback keeps external execution',()=>fixture(dir=>{
+ writeFileSync(join(dir,'index.html'),'<meta http-equiv="Content-Security-Policy" content="script-src \'self\' \'sha256-__APP_SCRIPT_HASH__\'"><script type="application/json" id="ytp-assets">{}</script>');
+ const result=createAssetManifest(dir),digest=createHash('sha256').update('window.app=1').digest('base64');
+ expect(result.index).toContain("'sha256-"+digest+"'");
+
+ expect(JSON.parse(result.index.match(/id="ytp-assets">([^<]+)</)[1]).appCache).toBe(true);
+ expect(JSON.parse(createAssetManifest(dir,{assetSync:false}).index.match(/id="ytp-assets">([^<]+)</)[1]).appCache).toBe(false);
+ expect(JSON.parse(createAssetManifest(dir,{hashing:false}).index.match(/id="ytp-assets">([^<]+)</)[1]).appCache).toBe(false);
+ writeFileSync(join(dir,'app.js'),'window.app=2');
+ expect(createAssetManifest(dir).index).not.toContain(digest);
+}));

server/static-delivery.test.js

@@ -13,7 +13,7 @@ mkdirSync(publicDir);
 mkdirSync(dataDir);
 mkdirSync(join(publicDir, 'fonts'));
 mkdirSync(join(publicDir, 'icons'));
-writeFileSync(join(publicDir, 'index.html'), '<!doctype html><script type="application/json" id="ytp-assets">{}</script><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, 'index.html'), '<!doctype html><script type="application/json" id="ytp-assets">{}</script><meta name="ytp-build" content="__BUILD_TAG__"><link rel="preload" href="app.css" as="style"><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}');
@@ -99,7 +99,8 @@ describe('static delivery characterization', () => {
     const html = await index.text();
     const { buildTag, files } = await (await fetch(`${server.base}/api/manifest`)).json();
     expect(html).toContain(`<meta name="ytp-build" content="${buildTag}">`);
-    expect(html).toContain(`href="app.css?v=${files['/app.css'].h}"`);
+    expect(html).toContain(`<link rel="preload" href="app.css?v=${files['/app.css'].h}" as="style">`);
+    expect(html.match(new RegExp('app\\.css\\?v='+files['/app.css'].h,'g'))).toHaveLength(2);
     expect(html).toContain(`src="app.js?v=${files['/app.js'].h}"`);
     expect(html).toContain('https://cdn.example/x.js');
     expect(html).toContain(`href="/root.css?v=${files['/root.css'].h}"`);