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"
       ]
     },
     {