test(web): keep page timers running under the pinned fixture day

pinHostClock replaces Date.now in the Vitest worker, where Playwright's
server also runs. page.clock.setFixedTime therefore recorded the fixture
day, and after a navigation the page clock replayed the gap to the real
day. The resulting negative timer delay was truncated to a 32-bit integer
and, from 2026-10-15T13:45:20Z, became a delay of weeks that stopped every
page timer, failing the steering and seeded-history suites.

pinBrowserClock now replaces only the page's Date so it reads the fixture
day while native timers and animation frames keep their real schedule; a
regression test navigates twice with both clocks pinned.

apps/web/tests/markdown-images.e2e.ts

@@ -166,7 +166,6 @@ describe('web e2e: Markdown image rendering', () => {
   let browser: Browser
   let page: Page
   let tripwire: ReturnType<typeof watchConsole>
-  let unpinBrowserClock: (() => void) | undefined
   const mediaResponses = new Map<string, number>()
 
   beforeAll(async () => {
@@ -191,7 +190,7 @@ describe('web e2e: Markdown image rendering', () => {
       { createdAt: WEB_FIXTURE_TIME - 60_000 })
     browser = await chromium.launch()
     page = await newEnglishPage(browser)
-    unpinBrowserClock = await pinBrowserClock(page)
+    await pinBrowserClock(page)
     tripwire = watchConsole(page)
     page.on('response', (response) => {
       const url = new URL(response.url())
@@ -204,7 +203,6 @@ describe('web e2e: Markdown image rendering', () => {
   }, 120_000)
 
   afterAll(async () => {
-    unpinBrowserClock?.()
     await browser?.close()
     await scaffold?.close()
     if (imageOrigin !== undefined) await stopServer(imageOrigin.server)

apps/web/tests/message-actions.e2e.ts

@@ -191,7 +191,6 @@ describe('web e2e: message IconActions and clocks on settled history', () => {
   let browser: Browser
   let page: Page
   let tripwire: ReturnType<typeof watchConsole>
-  let unpinBrowserClock: (() => void) | undefined
 
   beforeAll(async () => {
     scaffold = await launchWebScaffold()
@@ -212,14 +211,13 @@ describe('web e2e: message IconActions and clocks on settled history', () => {
     await seedSession(scaffold, raw, SEED_ID, undefined, { createdAt: WEB_FIXTURE_TIME - 90_000 })
     browser = await chromium.launch()
     page = await newEnglishPage(browser)
-    unpinBrowserClock = await pinBrowserClock(page)
+    await pinBrowserClock(page)
     tripwire = watchConsole(page)
     await page.goto(scaffold.authenticatedUrl, { waitUntil: 'load' })
     await page.waitForSelector('[class*="frame"]', { timeout: 30_000 })
   }, 120_000)
 
   afterAll(async () => {
-    unpinBrowserClock?.()
     await browser?.close()
     await scaffold?.close()
   })

apps/web/tests/pinned-clock.e2e.ts

@@ -0,0 +1,38 @@
+/** Pinned Host and page calendars keep page timers on their real schedule across navigations. */
+import { chromium, type Browser } from 'playwright'
+import { afterAll, beforeAll, expect, it } from 'vitest'
+import { newEnglishPage, pinBrowserClock, pinHostClock, WEB_FIXTURE_TIME } from './support.ts'
+
+let browser: Browser | undefined
+let hostClock: ReturnType<typeof pinHostClock> | undefined
+
+beforeAll(async () => {
+  hostClock = pinHostClock()
+  browser = await chromium.launch()
+})
+
+afterAll(async () => {
+  try {
+    await browser?.close()
+  } finally {
+    hostClock?.mockRestore()
+  }
+})
+
+it('fires page timers after each navigation while reading the fixture day', async () => {
+  const page = await newEnglishPage(browser!)
+  await pinBrowserClock(page)
+  for (const body of ['<p>first document</p>', '<p>second document</p>']) {
+    await page.goto(`data:text/html,${encodeURIComponent(body)}`)
+    const fired = page.evaluate(() => Promise.all([
+      new Promise<void>((resolve) => { setTimeout(resolve, 0) }),
+      new Promise<void>((resolve) => { requestAnimationFrame(() => { resolve() }) }),
+    ]).then(() => 'fired' as const))
+    // The Node timer runs on the real clock, so it bounds a stalled page.
+    const stalled = new Promise<'stalled'>((resolve) => { setTimeout(() => { resolve('stalled') }, 5_000) })
+    expect(await Promise.race([fired, stalled])).toBe('fired')
+    const read = await page.evaluate(() => ({ now: Date.now(), constructed: new Date().getTime() }))
+    expect(Math.abs(read.now - WEB_FIXTURE_TIME)).toBeLessThan(120_000)
+    expect(Math.abs(read.constructed - WEB_FIXTURE_TIME)).toBeLessThan(120_000)
+  }
+})

apps/web/tests/reference-composer.e2e.ts

@@ -142,7 +142,6 @@ describe.skipIf(MODE === 'record')('web e2e: file and session references through
   let browser: Browser
   let page: Page
   let tripwire: ReturnType<typeof watchConsole>
-  let unpinBrowserClock: (() => void) | undefined
 
   beforeAll(async () => {
     scaffold = await launchWebScaffold({})
@@ -151,7 +150,7 @@ describe.skipIf(MODE === 'record')('web e2e: file and session references through
     await seedSession(scaffold, targetSessionFixture(), TARGET_SESSION_ID, undefined, { createdAt: targetCreatedAt })
     browser = await chromium.launch()
     page = await newEnglishPage(browser)
-    unpinBrowserClock = await pinBrowserClock(page)
+    await pinBrowserClock(page)
     tripwire = watchConsole(page)
     // Fixture files land before the workspace connects so the Host's file
     // index never races their creation (the connect helper mkdirs the same
@@ -171,7 +170,6 @@ describe.skipIf(MODE === 'record')('web e2e: file and session references through
   }, 120_000)
 
   afterAll(async () => {
-    unpinBrowserClock?.()
     await browser?.close()
     await scaffold?.close()
   })

apps/web/tests/seeded-history.e2e.ts

@@ -230,7 +230,6 @@ describe('web e2e: seeded history renders through cold resume', () => {
   let seededThroughSeq = -1
   let openingWindow: unknown
   let hostClock: ReturnType<typeof pinHostClock> | undefined
-  let unpinBrowserClock: (() => void) | undefined
 
   beforeAll(async () => {
     // Seeded and later command timestamps share the renderer's fixture day across midnight.
@@ -271,7 +270,7 @@ describe('web e2e: seeded history renders through cold resume', () => {
     }
     browser = await chromium.launch()
     page = await newEnglishPage(browser)
-    if (MODE !== 'record') unpinBrowserClock = await pinBrowserClock(page)
+    if (MODE !== 'record') await pinBrowserClock(page)
     tripwire = watchConsole(page)
     if (MODE !== 'record') {
       // A one-message tail makes this short recording exercise the real Load earlier path.
@@ -303,7 +302,6 @@ describe('web e2e: seeded history renders through cold resume', () => {
       await browser?.close()
       await scaffold?.close()
     } finally {
-      unpinBrowserClock?.()
       hostClock?.mockRestore()
     }
   })

apps/web/tests/steering.e2e.ts

@@ -73,7 +73,6 @@ describe('web e2e: mid-turn steering lands durably and visibly', () => {
   let page: Page
   let tripwire: ReturnType<typeof watchConsole>
   let hostClock: MockInstance<typeof Date.now> | undefined
-  let unpinBrowserClock: (() => void) | undefined
   const sessionEvents: SessionEvent[] = []
 
   beforeAll(async () => {
@@ -87,7 +86,7 @@ describe('web e2e: mid-turn steering lands durably and visibly', () => {
     scaffold.ctx.on('session/event', (_session, event) => { sessionEvents.push(event) })
     browser = await chromium.launch()
     page = await newEnglishPage(browser)
-    unpinBrowserClock = await pinBrowserClock(page)
+    await pinBrowserClock(page)
     tripwire = watchConsole(page)
     await page.goto(scaffold.authenticatedUrl, { waitUntil: 'load' })
     await page.waitForSelector('[class*="frame"]', { timeout: 30_000 })
@@ -101,8 +100,7 @@ describe('web e2e: mid-turn steering lands durably and visibly', () => {
       await scaffold?.close()
     } finally {
       // A failing close (unconsumed fixture, mismatched snapshot) must not
-      // leave the pinned clocks running for the suites after this one.
-      unpinBrowserClock?.()
+      // leave the pinned Host clock running for the suites after this one.
       hostClock?.mockRestore()
     }
   })
@@ -396,7 +394,6 @@ describe('web e2e: empty-draft Cmd+Enter steers the whole queue', () => {
   let page: Page
   let tripwire: ReturnType<typeof watchConsole>
   let hostClock: MockInstance<typeof Date.now> | undefined
-  let unpinBrowserClock: (() => void) | undefined
   const sessionEvents: SessionEvent[] = []
 
   beforeAll(async () => {
@@ -416,7 +413,7 @@ describe('web e2e: empty-draft Cmd+Enter steers the whole queue', () => {
     scaffold.ctx.on('session/event', (_session, event) => { sessionEvents.push(event) })
     browser = await chromium.launch()
     page = await newEnglishPage(browser)
-    unpinBrowserClock = await pinBrowserClock(page)
+    await pinBrowserClock(page)
     tripwire = watchConsole(page)
     await page.goto(scaffold.authenticatedUrl, { waitUntil: 'load' })
     await page.waitForSelector('[class*="frame"]', { timeout: 30_000 })
@@ -431,7 +428,6 @@ describe('web e2e: empty-draft Cmd+Enter steers the whole queue', () => {
       await browser?.close()
       await scaffold?.close()
     } finally {
-      unpinBrowserClock?.()
       hostClock?.mockRestore()
     }
   })

apps/web/tests/support.ts

@@ -50,9 +50,6 @@ export const WEB_FIXTURE_TIME = Date.parse('2026-01-15T12:00:00+08:00')
  */
 export const PLUGIN_TOGGLE_SETTLE_MS = 10_000
 
-/** How often a pinned browser clock advances, in milliseconds. */
-const PINNED_CLOCK_STEP_MS = 250
-
 /**
  * Pin the Host clock to the shared fixture day for one scenario suite.
  *
@@ -74,31 +71,36 @@ export function pinHostClock(): MockInstance<typeof Date.now> {
 }
 
 /**
- * Pin a scenario page's clock to the shared fixture day, advancing with real
+ * Pin a scenario page's calendar to the shared fixture day, advancing with real
  * time. Pair it with {@link pinHostClock} for a scenario that stamps its own
  * message times, and with `seedSession`'s `createdAt` for a seeded one.
  *
- * The frozen instant is re-applied from the anchor on an interval rather than
- * left at one value, because product logic reads two `Date.now()` values to
- * decide a minimum display hold or a deadline window; a permanently frozen
- * clock stops supplying elapsed time, so a title that owes its golden settled
- * text keeps rendering its previous one. Both clocks therefore advance at the
- * real rate and stay within one step of each other.
- * @param page - page whose clock is pinned.
- * @returns the disposer that stops re-pinning; call it in teardown.
+ * Only the page's `Date` reads the fixture day; native timers and
+ * `requestAnimationFrame` keep their real scheduling. Playwright's
+ * `page.clock` is not used: its server records clock state with the Vitest
+ * worker's `Date.now`, which {@link pinHostClock} replaces, so after a
+ * navigation the page clock replays the gap between the real and fixture days
+ * and hands the resulting negative delay to native `setTimeout`. The browser
+ * truncates that delay to a 32-bit integer, and in about half of the dates the
+ * result is a positive delay of weeks that stops every page timer. The `Date`
+ * override is installed for every later document and on the current one, and
+ * stays until the page closes.
+ * @param page - page whose calendar is pinned.
  */
-export async function pinBrowserClock(page: Page): Promise<() => void> {
-  const startedAt = Date.now()
-  const step = async (): Promise<void> => {
-    try {
-      await page.clock.setFixedTime(WEB_FIXTURE_TIME + (Date.now() - startedAt))
-    } catch {
-      // The page closed under the interval; teardown owns the last word.
-    }
+export async function pinBrowserClock(page: Page): Promise<void> {
+  // The worker's `new Date()` keeps the real clock even when `Date.now` is pinned.
+  const offset = WEB_FIXTURE_TIME - new Date().getTime()
+  const install = (offset: number): void => {
+    const NativeDate = Date
+    const now = (): number => NativeDate.now() + offset
+    globalThis.Date = new Proxy(NativeDate, {
+      construct: (target, args, newTarget): Date => Reflect.construct(target, args.length === 0 ? [now()] : args, newTarget) as Date,
+      apply: () => new NativeDate(now()).toString(),
+      get: (target, property, receiver): unknown => property === 'now' ? now : Reflect.get(target, property, receiver),
+    })
   }
-  await step()
-  const timer = setInterval(() => { void step() }, PINNED_CLOCK_STEP_MS)
-  return () => { clearInterval(timer) }
+  await page.addInitScript(install, offset)
+  await page.evaluate(install, offset)
 }
 
 /**