fix(subtitles): harden canonical cue recovery

- Avoid argument-count limits when reducing ASS event bounds
- Fall back from invalid canonical mining spans
- Share seek thresholds and reset timing at the exact boundary

src/core/services/subtitle-cue-parser.ts

@@ -380,14 +380,25 @@ function matchingAssAnimationEvents(options: {
     : [];
 }
 
+// Reductions rather than `Math.min(...events)`: one generated line can carry an
+// unbounded number of events, and spreading them all as arguments risks the engine's
+// argument-count limit.
+function earliestStartTime(events: readonly AnnotatedSubtitleCue[], seed = Infinity): number {
+  return events.reduce((earliest, event) => Math.min(earliest, event.startTime), seed);
+}
+
+function latestEndTime(events: readonly AnnotatedSubtitleCue[], seed = -Infinity): number {
+  return events.reduce((latest, event) => Math.max(latest, event.endTime), seed);
+}
+
 function includeCanonicalBoundaryEvents(options: {
   candidate: AnnotatedSubtitleCue;
   group: AssEventGroupIndex;
   animationEvents: readonly AnnotatedSubtitleCue[];
 }): AnnotatedSubtitleCue[] {
   const canonicalText = compactCueMatchText(options.candidate);
-  const startTime = Math.min(...options.animationEvents.map((event) => event.startTime));
+  const startTime = earliestStartTime(options.animationEvents);
-  const endTime = Math.max(...options.animationEvents.map((event) => event.endTime));
+  const endTime = latestEndTime(options.animationEvents);
   return eventsOverlappingWindow(
     options.group,
     startTime - CANONICAL_MATCH_MARGIN_SECONDS,
@@ -458,14 +469,8 @@ function recoverCanonicalAssEvents({
       animationEvents,
     });
     const generatedEvents = [...new Set([...animationEvents, ...boundaryEvents])];
-    const animationStartTime = Math.min(
+    const animationStartTime = earliestStartTime(generatedEvents, candidate.startTime);
-      candidate.startTime,
+    const animationEndTime = latestEndTime(generatedEvents, candidate.endTime);
-      ...generatedEvents.map((event) => event.startTime),
-    );
-    const animationEndTime = Math.max(
-      candidate.endTime,
-      ...generatedEvents.map((event) => event.endTime),
-    );
     const startTime = kind === 'comment' ? candidate.startTime : animationStartTime;
     const endTime = kind === 'comment' ? candidate.endTime : animationEndTime;
     const recoveredCue: AnnotatedSubtitleCue = {

src/main.ts

@@ -1825,12 +1825,21 @@ function captureCurrentPrimarySubtitleMiningContext(): SubtitleMiningContext | n
     currentTimeSec: Number(appState.mpvClient?.currentTimePos),
     cues: appState.activeParsedSubtitleCues,
   });
-  if (!canonical) {
+  // Same validity bar as the live capture path: an unusable canonical span must fall
+  // back rather than hand mining an empty line or an inverted range.
+  const canonicalText = canonical?.text.trim();
+  if (
+    !canonical ||
+    !canonicalText ||
+    !Number.isFinite(canonical.startTime) ||
+    !Number.isFinite(canonical.endTime) ||
+    canonical.endTime <= canonical.startTime
+  ) {
     return captureLiveSubtitleMiningContext(appState.mpvClient);
   }
   return {
     source: 'overlay',
-    text: canonical.text,
+    text: canonicalText,
     startTime: canonical.startTime,
     endTime: canonical.endTime,
     capturedAtMs: Date.now(),

src/main/runtime/anki-actions-main-deps.ts

@@ -1,13 +1,7 @@
-import type { createRefreshKnownWordCacheHandler } from './anki-actions';
+import type { createRefreshKnownWordCacheHandler, PrimarySubtitle } from './anki-actions';
 
 type RefreshKnownWordCacheMainDeps = Parameters<typeof createRefreshKnownWordCacheHandler>[0];
 
-type PrimarySubtitle = {
-  text: string;
-  startTime: number;
-  endTime: number;
-};
-
 export function createBuildUpdateLastCardFromClipboardMainDepsHandler<TAnki>(deps: {
   getAnkiIntegration: () => TAnki;
   readClipboardText: () => string;

src/main/runtime/anki-actions.ts

@@ -2,7 +2,7 @@ type AnkiIntegrationLike = {
   refreshKnownWordCache: () => Promise<void>;
 };
 
-type PrimarySubtitle = {
+export type PrimarySubtitle = {
   text: string;
   startTime: number;
   endTime: number;

src/main/runtime/mpv-main-event-actions.ts

@@ -4,7 +4,8 @@ type AnilistPostWatchRunOptions = {
   watchedSeconds?: number;
 };
 
-const SEEK_LIKE_TIME_DELTA_SECONDS = 2.5;
+/** Jump size that marks a time-pos change as a seek rather than normal playback. */
+export const SEEK_LIKE_TIME_DELTA_SECONDS = 2.5;
 
 function isSeekLikeTimeChange(previousTime: number | null, nextTime: number): boolean {
   if (previousTime === null || !Number.isFinite(previousTime) || !Number.isFinite(nextTime)) {

src/main/runtime/mpv-main-event-main-deps.test.ts

@@ -486,6 +486,14 @@ test('canonical ASS cues replace live glyph spam for display, history, and immer
 
   assert.deepEqual(timing.slice(3), [{ text: '今　手にある物差しでは', start: 1.2, end: 3.8 }]);
   assert.equal(immersion.length, 3);
+
+  // A jump of exactly the seek threshold counts as a seek, matching the time-pos
+  // handler's own `>=` boundary.
+  handlers.onTimePosUpdate?.(4.5);
+  handlers.onTimePosUpdate?.(2);
+  handlers.recordSubtitleTiming('今', 0.8, 1.5);
+
+  assert.deepEqual(timing.slice(4), [{ text: '今　手にある物差しでは', start: 1.2, end: 3.8 }]);
 });
 
 test('subtitle-track changes stop stale canonical cues from substituting immediately', () => {

src/main/runtime/mpv-main-event-main-deps.ts

@@ -1,5 +1,6 @@
 import { createSubtitleLineDedupGate } from '../../core/services/subtitle-line-dedup-gate';
 import type { MergedToken, SubtitleCue, SubtitleData } from '../../types';
+import { SEEK_LIKE_TIME_DELTA_SECONDS } from './mpv-main-event-actions';
 import {
   resolveCanonicalPrimarySubtitle,
   resolvePrimarySubtitleText,
@@ -108,8 +109,6 @@ export function createBuildBindMpvMainEventHandlersMainDepsHandler(deps: {
   // Bumped on track/media changes so an immersion record whose tokenization resolves
   // after the change is dropped instead of landing in the next session.
   let subtitleSessionEpoch = 0;
-  // Matches the seek threshold used by the time-pos handler in mpv-main-event-actions.
-  const BACKWARD_SEEK_TIMING_RESET_SECONDS = 2.5;
   let lastTimePosForTimingReset: number | null = null;
   const canonicalCueKey = (cue: SubtitleCue): string =>
     `${cue.startTime}|${cue.endTime}|${cue.text}`;
@@ -326,7 +325,7 @@ export function createBuildBindMpvMainEventHandlersMainDepsHandler(deps: {
       if (
         Number.isFinite(time) &&
         lastTimePosForTimingReset !== null &&
-        time < lastTimePosForTimingReset - BACKWARD_SEEK_TIMING_RESET_SECONDS
+        time <= lastTimePosForTimingReset - SEEK_LIKE_TIME_DELTA_SECONDS
       ) {
         recordedTimingCanonicalKeys.clear();
       }