test(multiple-subtitles): checkpoint native seek diagnostics [PKG-MULTI-SUB-05]

refactor/changes/2026-09-14-PKG-MULTI-SUB-05-seek-diagnostics.md

@@ -0,0 +1,63 @@
+# PKG-MULTI-SUB-05 checkpoint: source-seek diagnostics (not complete)
+
+Task11 is committed as318de37e8 and its commit audit passed. This checkpoint
+continues the reopened old-core source-seek issue without changing production
+code, declarations, dependencies or built artifacts.
+
+## Added evidence
+
+The optional diagnostics capture native events, public seek/fullscreen events,
+monotonic times, native position/duration/seeking, active cues and switch Promise
+settlement. Full mode forwards the original native currentTime/playbackRate
+accessors and records writes/stacks; events mode leaves those properties intact.
+Both modes are opt-in. Diagnostic side observers handle rejection while the
+original returned Promise still rejects for the test consumer.
+
+Initial WebKit serial3 and repeated9 cases pass their caption assertions. The
+repeated traces show all six old-core switches resolve while seeking=true;
+restoration seeked is delivered30..50ms later. The three candidate switches wait
+for restoration. No playback-rate assignment was observed in these source steps.
+The successful later user writes occurred after the prior native seeked event.
+
+The actual-main events-only matrix passes105 assertions, including explicitly
+labelled historical overlap/offset defect observations. It again shows early
+old-core settlement, including WebKit native seeked43/46ms later. This is not
+proof the previously missed seeks were repaired: observation may affect timing,
+and no failing native write trace was captured in those runs.
+
+The subsequent actual-main matrix with diagnostics disabled has62 passes and one
+failure on old5.3.0/WebKit. At failure, media time is0.0015139, the1..3-second cue
+is intact, active cues are empty, and the player is still alive. The candidate
+and other old-core cases pass in that run. This reproduces the same near-zero
+position category previously seen on old5.4.0; it does not implicate ASS conversion
+or prove the precise internal native overwrite sequence.
+
+## Separate restoration-event control
+
+`source-restoration.js` installs a native metadata listener before switchUrl.
+After the core's metadata handler, it waits for native seeked if seeking is active,
+and also waits for the original switch Promise. It cleans both listeners on
+completion or failure. There are no fixed delays, seek retries or source rewrites.
+It is enabled only with ARTPLAYER_SOURCE_RESTORE_EVENT=1; the default failing
+property-based path and existing immediate-call ordering probe remain available.
+
+With diagnostics disabled, the event control passes27 cases: three repetitions
+of three core inputs across three desktop engines using actual main artifacts.
+This supports independently verifying captions after native restoration. It is
+not proof of a production fix, or sufficient evidence to close the original
+immediate-seek failure. Do not make the normal path green by relabelling this
+control as the original public API behavior.
+
+Reports, input/artifact hashes, selected modes, timings and remaining failures are
+in [the checkpoint evidence](../baselines/multiple-subtitles-seek-diagnostics.json).
+The browser README documents flags. Explicit test/helper lint, CI50 and plan/risk
+checks pass. No source or package build was needed for these test-only additions.
+
+## Remaining work
+
+MULTI-SUB-SWITCH-01 stays open and task05 stays doing. The next diagnostic step is
+to capture the failed default path's restoration completion versus subsequent
+native seek without assuming that property polling equals event completion.
+Keep candidate public switch guarantees separate from immutable old-host defects;
+do not patch the shared media clock from the subtitle plugin. Broader historical
+profile/device acceptance and task06 distribution gates remain incomplete.

refactor/plan.md

@@ -558,7 +558,7 @@
 - PKG-MULTI-SUB-04: [记录](baselines/multiple-subtitles-runtime-types.json) [记录](changes/2026-09-13-PKG-MULTI-SUB-04-runtime-types.md) [记录](baselines/multiple-subtitles-public-types.json) [记录](changes/2026-09-13-PKG-MULTI-SUB-04-public-types.md) [记录](type-compatibility-policy.md) [记录](baselines/multiple-subtitles-approved-types.json) [记录](changes/2026-09-13-PKG-MULTI-SUB-04-approved-types.md)
 - PKG-MULTI-SUB-07: [记录](baselines/multiple-subtitles-timestamps.json) [记录](changes/2026-09-13-PKG-MULTI-SUB-07-timestamps.md)
 - PKG-MULTI-SUB-08: [记录](changes/2026-09-14-PKG-MULTI-SUB-08-entities.md) [记录](baselines/multiple-subtitles-entities-validation.json)
-- PKG-MULTI-SUB-05: [记录](changes/2026-09-14-PKG-MULTI-SUB-05-combinations.md) [记录](baselines/multiple-subtitles-combinations-validation.json) [记录](baselines/multiple-subtitles-cores.json)
+- PKG-MULTI-SUB-05: [记录](changes/2026-09-14-PKG-MULTI-SUB-05-combinations.md) [记录](baselines/multiple-subtitles-combinations-validation.json) [记录](baselines/multiple-subtitles-cores.json) [记录](changes/2026-09-14-PKG-MULTI-SUB-05-seek-diagnostics.md) [记录](baselines/multiple-subtitles-seek-diagnostics.json)
 - PKG-JASSUB-01: [记录](baselines/jassub-release.json) [记录](baselines/jassub-vendor.json) [记录](baselines/jassub-font-metadata.json) [记录](baselines/jassub-contract.md) [记录](baselines/jassub-contract-validation.json) [记录](changes/2026-09-13-PKG-JASSUB-01-baseline.md) [记录](baselines/jassub-provenance.json) [记录](baselines/jassub-provenance-validation.json) [记录](changes/2026-09-14-PKG-JASSUB-01-provenance.md)
 - PKG-JASSUB-02: [记录](changes/2026-09-14-PKG-JASSUB-02-failure-baseline.md) [记录](baselines/jassub-failures-validation.json)
 - PKG-JASSUB-03: [记录](changes/2026-09-14-PKG-JASSUB-03-registration.md) [记录](baselines/jassub-registration-validation.json)

refactor/progress.md

@@ -1,5 +1,18 @@
 # 进度与证据
 
+## PKG-MULTI-SUB-05 切源时序诊断检查点（仍未完成）
+
+新增可选原生属性/事件跟踪和独立恢复事件等待对照。WebKit串行3项、重复9项及
+三引擎被动事件矩阵105项通过断言，但旧核心仍提前结算，WebKit恢复seeked晚30至50ms；
+候选核心会等待恢复。关闭诊断后63项中62通过，旧5.3.0/WebKit再次停在0.0015139秒，
+字幕cue仍完整；没有获得失败瞬间的原生写入轨迹，不能据带诊断的通过结果关闭风险。
+显式等待metadata后的原生恢复seeked对照27项通过，仅说明完成恢复后的字幕路径有效，
+不修改默认测试路径或旧公共API。即时调用探针、此前失败和MULTI-SUB-SWITCH-01保持open。
+见[检查点](changes/2026-09-14-PKG-MULTI-SUB-05-seek-diagnostics.md)和
+[证据](baselines/multiple-subtitles-seek-diagnostics.json)。本轮仅测试和文档修改，产物未变，
+脚本lint/CI50/计划风险检查通过；仍为179 done、17 doing、55 todo。task05/06未完成。
+保留原生失败时序定位入口；下一轮转回Auto Thumbnail剩余源码整理，再继续包级组合门槛。
+
 ## PKG-MULTI-SUB-11 旧发布核心 ASS 转换适配完成
 
 实际5.1.2 tarball证明只有main转换器丢失模板换行，同版legacy与源码正确；新增

refactor/risks.json

@@ -2,7 +2,7 @@
   "schemaVersion": 1,
   "task": "BASE-07",
   "sourceCommit": "e01f39ff",
-  "updatedAt": "2026-09-14T05:41:02.580Z",
+  "updatedAt": "2026-09-14T06:00:35.506Z",
   "note": "Open means closure evidence is outstanding; source-observed and unverified are not reproduced runtime bugs. A source issue already mitigated in the workspace still requires candidate regression evidence. No accepted-with-scope item is implied by baseline task completion.",
   "items": [
     {
@@ -6034,7 +6034,7 @@
       "id": "MULTI-SUB-SWITCH-01",
       "title": "Intermittent WebKit core5.3.0 caption loss after selected-track source switch",
       "confirmation": "reproduced",
-      "workspaceState": "Reopened during task10: both source and actual-main matrices fail old5.4.0/WebKit caption after switch despite waiting seeking=false. Source failure native time0.001494, intact1..3 cue, active=[]; task09 attribution remains supported but the later-seek workaround is insufficient. Candidate core and old5.1 display regressions pass. Task05 must diagnose remaining old-host ordering, without hiding these failures.",
+      "workspaceState": "Still open after task11: property traces3+9 and passive105 cases pass while confirming early old-core settlement; default untraced63 has another near-zero seek miss on5.3.0/WebKit (time0.0015139, intact1..3 cue, no active cue). No failing native-write trace yet. Opt-in metadata/restoration-seeked control passes27 cases but is not a production/API fix; default and immediate-call probes remain unchanged. Candidate source guarantees pass. Task05 still owns remaining diagnosis and acceptance.",
       "compatibleResolution": "Classify the old-host source/native-seek race separately from caption rendering; preserve immediate-call probes, require candidate first seeks, and wait for real native source completion before independent caption-seek assertions.",
       "closureCriteria": "Root cause classified with targeted evidence, any required fix validated, and changed candidate/old-core combination rerun without hiding the original failure.",
       "status": "open",
@@ -6052,7 +6052,11 @@
         "refactor/baselines/multiple-subtitles-switch-validation.json",
         "test/browser/multiple-subtitles-switch.spec.js",
         "refactor/changes/2026-09-14-PKG-MULTI-SUB-10-legacy-captions.md",
-        "refactor/baselines/multiple-subtitles-legacy-validation.json"
+        "refactor/baselines/multiple-subtitles-legacy-validation.json",
+        "refactor/changes/2026-09-14-PKG-MULTI-SUB-05-seek-diagnostics.md",
+        "refactor/baselines/multiple-subtitles-seek-diagnostics.json",
+        "test/browser/source-seek-diagnostics.js",
+        "test/browser/source-restoration.js"
       ],
       "resolutionEvidence": [
         "refactor/changes/2026-09-14-PKG-MULTI-SUB-09-switch-order.md",

refactor/tasks.json

@@ -2417,7 +2417,9 @@
       "evidence": [
         "changes/2026-09-14-PKG-MULTI-SUB-05-combinations.md",
         "baselines/multiple-subtitles-combinations-validation.json",
-        "baselines/multiple-subtitles-cores.json"
+        "baselines/multiple-subtitles-cores.json",
+        "changes/2026-09-14-PKG-MULTI-SUB-05-seek-diagnostics.md",
+        "baselines/multiple-subtitles-seek-diagnostics.json"
       ]
     },
     {

test/browser/README.md

@@ -283,3 +283,21 @@ multiline text/HTML, overlapping translation, selection/reset and empty interval
 on5.1.2/5.1.7/5.3.0/5.4.0/candidate. The attachment records the unchanged original
 host converter output alongside actual native cues and browser/artifact hashes.
 It covers desktop video/track playback, not full ASS layout or physical devices.
+
+The multiple-subtitles combination suite has opt-in source-seek diagnostics:
+
+- `ARTPLAYER_SOURCE_SEEK_TRACE=events` records native and public events, clocks,
+  duration, active cues and switch settlement without replacing media properties.
+- `ARTPLAYER_SOURCE_SEEK_TRACE=1` additionally forwards native `currentTime` and
+  `playbackRate` accessors while recording writes/stacks. The page owns these
+  diagnostic listeners and descriptors; do not use this helper in production.
+- `ARTPLAYER_SOURCE_RESTORE_EVENT=1` selects a separate control that installs a
+  metadata listener before switching and, when restoration is seeking, waits for
+  its native seeked event as well as the original switch Promise. This tests caption
+  behavior after restoration; it does not repair the old public switch contract.
+
+With no flags, the original Promise plus seeking-property path remains unchanged.
+The immediate-call ordering probe also remains intact. Record the chosen flags
+alongside artifacts: diagnostic overhead may change an intermittent race, and
+passing the event control must not replace the original failure evidence. The
+combination attachment includes the selected modes and optional native trace.

test/browser/multiple-subtitles-combinations.spec.js

@@ -1,6 +1,9 @@
+import process from 'node:process'
 import { hash } from '../../refactor/scripts/releases.mjs'
 import { multipleSubtitlesCandidate, multipleSubtitlesHistorical } from '../helpers/multiple-subtitles.js'
 import { expect, test } from './fixtures.js'
+import { switchAfterNativeRestoration } from './source-restoration.js'
+import { installSeekDiagnostics } from './source-seek-diagnostics.js'
 
 const candidate = await multipleSubtitlesCandidate()
 const historical = (await multipleSubtitlesHistorical()).filter(item => /^published-.*-main$/.test(item.name))
@@ -15,7 +18,7 @@ test.afterEach(async ({ page }, testInfo) => {
       return null
     const track = art.template.$track?.track
     const read = cue => ({ start: cue.startTime, end: cue.endTime, text: cue.text })
-    return { destroyed: art.isDestroy, paused: art.video.paused, time: art.currentTime, offset: art.subtitleOffset, cues: Array.from(track?.cues || [], read), active: Array.from(track?.activeCues || [], read), displayed: art.template.$subtitle?.textContent }
+    return { destroyed: art.isDestroy, paused: art.video.paused, time: art.currentTime, seeking: art.video.seeking, duration: art.video.duration, readyState: art.video.readyState, offset: art.subtitleOffset, cues: Array.from(track?.cues || [], read), active: Array.from(track?.activeCues || [], read), displayed: art.template.$subtitle?.textContent, trace: window.sourceSeekTrace }
   })
   await testInfo.attach('multiple-combination-final-state', { contentType: 'application/json', body: JSON.stringify(state) })
 })
@@ -27,7 +30,9 @@ async function prepare(page, core, implementation, browser, testInfo) {
   await page.addScriptTag({ content: `(() => { const module = { exports: {} }; const exports = module.exports; ${implementation.code}; window.multipleFactory = module.exports.default || module.exports; })();` })
   await page.evaluate(() => window.createPlayer('/test/pattern.mp4'))
   await expect.poll(() => page.evaluate(() => window.art.isReady)).toBe(true)
-  await testInfo.attach('multiple-combination-inputs', { contentType: 'application/json', body: JSON.stringify({ core, plugin: implementation.name, pluginSha256: hash(implementation.code), browser: browser.version(), scope: 'Desktop engines; 5.3.0 is adjacent stable, not the unavailable 5.3.1 release; no minimum-version or physical-device claim' }) })
+  if (['1', 'events'].includes(process.env.ARTPLAYER_SOURCE_SEEK_TRACE))
+    await installSeekDiagnostics(page, process.env.ARTPLAYER_SOURCE_SEEK_TRACE === '1')
+  await testInfo.attach('multiple-combination-inputs', { contentType: 'application/json', body: JSON.stringify({ core, plugin: implementation.name, pluginSha256: hash(implementation.code), browser: browser.version(), traceMode: process.env.ARTPLAYER_SOURCE_SEEK_TRACE || 'off', sourceRestoration: process.env.ARTPLAYER_SOURCE_RESTORE_EVENT === '1' ? 'native-event-control' : 'promise-and-seeking-property', scope: 'Desktop engines; 5.3.0 is adjacent stable, not the unavailable 5.3.1 release; no minimum-version or physical-device claim' }) })
 }
 
 async function seek(page, time) {
@@ -94,7 +99,22 @@ for (const core of cores.filter(core => !['published-5.1.2', 'published-5.1.7'].
     await page.evaluate(() => window.art.plugins.multipleSubtitles.tracks(['b']))
     await expect(page.locator('.art-subtitle-a')).toHaveCount(0)
     await expect(page.locator('.art-subtitle-b')).toHaveText('Translation')
-    await page.evaluate(() => window.art.switchUrl('/test/pattern.mp4?subtitles-combination'))
+    if (process.env.ARTPLAYER_SOURCE_RESTORE_EVENT === '1') {
+      await switchAfterNativeRestoration(page, '/test/pattern.mp4?subtitles-combination')
+    }
+    else {
+      await page.evaluate(() => {
+        window.recordSourceSeek?.('before-switch')
+        const pending = window.art.switchUrl('/test/pattern.mp4?subtitles-combination')
+        if (window.recordSourceSeek) {
+          void pending.then(
+            () => window.recordSourceSeek('switch-resolved'),
+            error => window.recordSourceSeek('switch-rejected', String(error)),
+          )
+        }
+        return pending
+      })
+    }
     // Old core promises can settle during their native restoration seek.
     // The immediate-seek path is retained separately in multiple-subtitles-switch.spec.js.
     await expect.poll(() => page.evaluate(() => window.art.video.seeking)).toBe(false)

test/browser/source-restoration.js

@@ -0,0 +1,31 @@
+export async function switchAfterNativeRestoration(page, url) {
+  await page.evaluate((url) => {
+    const art = window.art
+    if (url === art.url)
+      return art.switchUrl(url)
+    const video = art.video
+    let resolveRestored
+    const restored = new Promise((resolve) => {
+      resolveRestored = resolve
+    })
+    const onSeeked = () => resolveRestored()
+    const onMetadata = () => {
+      if (video.seeking)
+        video.addEventListener('seeked', onSeeked, { once: true })
+      else
+        resolveRestored()
+    }
+    const cleanup = () => {
+      video.removeEventListener('loadedmetadata', onMetadata)
+      video.removeEventListener('seeked', onSeeked)
+    }
+    video.addEventListener('loadedmetadata', onMetadata, { once: true })
+    try {
+      return Promise.all([art.switchUrl(url), restored]).then(() => undefined).finally(cleanup)
+    }
+    catch (error) {
+      cleanup()
+      throw error
+    }
+  }, url)
+}

test/browser/source-seek-diagnostics.js

@@ -0,0 +1,27 @@
+export async function installSeekDiagnostics(page, properties = true) {
+  await page.evaluate((properties) => {
+    const art = window.art
+    const video = art.video
+    window.sourceSeekTrace = []
+    const state = () => ({ clock: performance.now(), time: video.currentTime, duration: video.duration, seeking: video.seeking, paused: video.paused, rate: video.playbackRate, readyState: video.readyState, source: video.currentSrc, active: Array.from(art.template.$track.track.activeCues || [], cue => cue.text) })
+    const record = (event, detail) => window.sourceSeekTrace.push({ event, detail, ...state() })
+    for (const property of properties ? ['currentTime', 'playbackRate'] : []) {
+      const descriptor = Object.getOwnPropertyDescriptor(HTMLMediaElement.prototype, property)
+      Object.defineProperty(video, property, {
+        configurable: true,
+        get() { return descriptor.get.call(this) },
+        set(value) {
+          record(`before:${property}`, { value, stack: new Error('Native media property write').stack })
+          descriptor.set.call(this, value)
+          record(`after:${property}`, { value })
+        },
+      })
+    }
+    for (const event of ['loadstart', 'loadedmetadata', 'loadeddata', 'canplay', 'seeking', 'seeked', 'emptied', 'pause', 'ratechange', 'timeupdate'])
+      video.addEventListener(event, () => record(`native:${event}`))
+    for (const event of ['restart', 'seek', 'fullscreen'])
+      art.on(event, (...values) => record(`art:${event}`, values))
+    window.recordSourceSeek = record
+    record('installed')
+  }, properties)
+}