fix(subtitles): follow sub-delay in sidebar, navigation, and overlay matching

Anything comparing time-pos with parsed cues now converts through a
shared subtitle-clock helper: the sidebar highlight and click-to-seek,
the sub-seek cue sanitizer, overlay/primer line resolution, and the
replay pause point after sub-seek.

src/core/services/index.ts

@@ -22,7 +22,6 @@ export {
   handleMultiCopyDigit,
   markLastCardAsAudioCard,
   mineSentenceCard,
-  shiftSubtitleRangeToVideoClock,
   triggerFieldGrouping,
   updateLastCardFromClipboard,
 } from './mining';
@@ -56,6 +55,7 @@ export {
   subtitleCueListSeekTime,
   subtitleCueSeekTime,
 } from './subtitle-cue-navigation';
+export { shiftSubtitleRangeToVideoClock, toSubtitleClock, toVideoClock } from './subtitle-clock';
 export { createFrequencyDictionaryLookup } from './frequency-dictionary';
 export { createJlptVocabularyLookup } from './jlpt-vocab';
 export {

src/core/services/ipc.test.ts

@@ -89,6 +89,7 @@ function createSubtitleSidebarSnapshotFixture(): SubtitleSidebarSnapshot {
     cuesRevision: 1,
     cues: [],
     currentTimeSec: null,
+    subDelay: 0,
     currentSubtitle: { text: '', startTime: null, endTime: null },
     config: {
       enabled: false,

src/core/services/mining.ts

@@ -1,5 +1,6 @@
 import type { SubtitleTimingBlock } from '../../subtitle-timing-tracker';
 import type { SubtitleMiningContext } from '../../types/subtitle';
+import { shiftSubtitleRangeToVideoClock } from './subtitle-clock';
 
 interface SubtitleTimingTrackerLike {
   getRecentBlocks: (count: number) => string[];
@@ -56,21 +57,6 @@ export function handleMultiCopyDigit(
   }
 }
 
-/**
- * mpv's `sub-start`/`sub-end` and parsed cues carry the subtitle file's own timestamps,
- * but mpv plays each line `sub-delay` seconds later (z/x retiming). Media is cut from the
- * video, so subtitle timings move onto the video clock before they reach mining.
- */
-export function shiftSubtitleRangeToVideoClock<T extends { startTime: number; endTime: number }>(
-  range: T,
-  subDelay: number,
-): T {
-  if (!Number.isFinite(subDelay) || subDelay === 0) {
-    return range;
-  }
-  return { ...range, startTime: range.startTime + subDelay, endTime: range.endTime + subDelay };
-}
-
 /**
  * Snapshot the live mpv subtitle line and its timings as a mining context. Media
  * generation can run tens of seconds after the user mines (slow audio extraction),

src/core/services/mpv-protocol.test.ts

@@ -74,6 +74,7 @@ function createDeps(overrides: Partial<MpvProtocolHandleMessageDeps> = {}): {
       setCurrentSubEnd: () => {},
       getCurrentSubEnd: () => 0,
       setCurrentSubDelay: () => {},
+      getCurrentSubDelay: () => 0,
       emitMediaPathChange: (payload) => {
         state.mediaPath = payload.path;
       },
@@ -396,6 +397,21 @@ test('dispatchMpvProtocolMessage pauses on sub-end when pendingPauseAtSubEnd is
   });
 });
 
+test('dispatchMpvProtocolMessage pauses at the sub-delay retimed sub-end', async () => {
+  let pauseAtTime: number | null = null;
+  const { deps } = createDeps({
+    getPendingPauseAtSubEnd: () => true,
+    getCurrentSubDelay: () => 1.5,
+    setPauseAtTime: (next) => {
+      pauseAtTime = next;
+    },
+  });
+
+  await dispatchMpvProtocolMessage({ event: 'property-change', name: 'sub-end', data: 42 }, deps);
+
+  assert.equal(pauseAtTime, 43.5);
+});
+
 test('dispatchMpvProtocolMessage updates current time before emitting time-pos change', async () => {
   const calls: string[] = [];
   let currentTimePos = 0;

src/core/services/mpv-protocol.ts

@@ -1,6 +1,7 @@
 import { MpvSubtitleRenderMetrics } from '../../types';
 import { sanitizeMediaTitle } from '../../shared/media-identity';
 import { widenHalfwidthKana } from '../utils/halfwidth-kana';
+import { toVideoClock } from './subtitle-clock';
 
 export type MpvMessage = {
   event?: string;
@@ -65,6 +66,7 @@ export interface MpvProtocolHandleMessageDeps {
   setCurrentSubEnd: (value: number) => void;
   getCurrentSubEnd: () => number;
   setCurrentSubDelay: (value: number) => void;
+  getCurrentSubDelay: () => number;
   emitMediaPathChange: (payload: { path: string }) => void;
   emitMediaTitleChange: (payload: { title: string | null }) => void;
   emitTimePosChange: (payload: { time: number }) => void;
@@ -264,7 +266,8 @@ export async function dispatchMpvProtocolMessage(
       const subEnd = (msg.data as number) || 0;
       deps.setCurrentSubEnd(subEnd);
       if (deps.getPendingPauseAtSubEnd() && subEnd > 0) {
-        deps.setPauseAtTime(subEnd);
+        // `sub-end` is on the subtitle clock; the pause check compares it with `time-pos`.
+        deps.setPauseAtTime(toVideoClock(subEnd, deps.getCurrentSubDelay()));
         deps.setPendingPauseAtSubEnd(false);
         deps.sendCommand({ command: ['set_property', 'pause', false] });
       }

src/core/services/mpv.ts

@@ -464,6 +464,7 @@ export class MpvIpcClient implements MpvClient {
       setCurrentSubDelay: (value: number) => {
         this.currentSubDelay = value;
       },
+      getCurrentSubDelay: () => this.currentSubDelay,
       emitMediaPathChange: (payload) => {
         this.emit('media-path-change', payload);
       },

src/core/services/subtitle-clock.ts

@@ -0,0 +1,32 @@
+/**
+ * mpv's `sub-start`/`sub-end` and parsed cues carry the subtitle file's own timestamps
+ * (the subtitle clock), but mpv plays each line `sub-delay` seconds later (z/x retiming,
+ * `sub-step`). Playback position, seeks, and media cuts are on the video clock, so any
+ * value crossing between the two converts here.
+ */
+
+function finiteDelay(subDelay: number): number {
+  return Number.isFinite(subDelay) ? subDelay : 0;
+}
+
+/** Playback position (`time-pos`) on the subtitle clock, comparable with cue times. */
+export function toSubtitleClock(videoTimeSec: number, subDelay: number): number {
+  return videoTimeSec - finiteDelay(subDelay);
+}
+
+/** Subtitle-clock seconds on the video clock, for seeks. */
+export function toVideoClock(subtitleTimeSec: number, subDelay: number): number {
+  return subtitleTimeSec + finiteDelay(subDelay);
+}
+
+/** A subtitle-clock range on the video clock, for mining and media generation. */
+export function shiftSubtitleRangeToVideoClock<T extends { startTime: number; endTime: number }>(
+  range: T,
+  subDelay: number,
+): T {
+  const delay = finiteDelay(subDelay);
+  if (delay === 0) {
+    return range;
+  }
+  return { ...range, startTime: range.startTime + delay, endTime: range.endTime + delay };
+}

src/core/services/subtitle-cue-navigation.test.ts

@@ -26,7 +26,7 @@ test('next subtitle navigation skips generated ASS events and seeks to the next
     },
   ];
 
-  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 10.2), [
+  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 10.2, 0), [
     'seek',
     13.08,
     'absolute+exact',
@@ -41,7 +41,7 @@ test('next subtitle navigation treats simultaneous sanitized cues as one line bo
     { startTime: 13.02, endTime: 16, text: 'Next English' },
   ];
 
-  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 10.1), [
+  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 10.1, 0), [
     'seek',
     13.08,
     'absolute+exact',
@@ -55,7 +55,7 @@ test('next subtitle navigation advances past the latest overlapping lyric', () =
     { startTime: 16, endTime: 19, text: 'next lyric' },
   ];
 
-  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 13.2), [
+  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 13.2, 0), [
     'seek',
     16.08,
     'absolute+exact',
@@ -68,7 +68,7 @@ test('previous subtitle navigation leaves the current cue and seeks to the prior
     { startTime: 13, endTime: 16, text: 'current line' },
   ];
 
-  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', -1], cues, 14.5), [
+  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', -1], cues, 14.5, 0), [
     'seek',
     10.08,
     'absolute+exact',
@@ -78,8 +78,22 @@ test('previous subtitle navigation leaves the current cue and seeks to the prior
 test('subtitle navigation falls back when no sanitized destination exists', () => {
   const cues = [{ startTime: 10, endTime: 13, text: 'only line' }];
 
-  assert.equal(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 10.2), null);
-  assert.equal(resolveSanitizedSubtitleSeekCommand(['seek', 5], cues, 10.2), null);
+  assert.equal(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 10.2, 0), null);
+  assert.equal(resolveSanitizedSubtitleSeekCommand(['seek', 5], cues, 10.2, 0), null);
+});
+
+test('subtitle cue navigation finds and seeks cues on the sub-delay retimed timeline', () => {
+  const cues = [
+    { startTime: 10, endTime: 13, text: 'one' },
+    { startTime: 13, endTime: 16, text: 'two' },
+  ];
+
+  // At 14.5 with a 2s delay, mpv is showing "one" (12-15 on the video clock).
+  assert.deepEqual(resolveSanitizedSubtitleSeekCommand(['sub-seek', 1], cues, 14.5, 2), [
+    'seek',
+    15.08,
+    'absolute+exact',
+  ]);
 });
 
 test('sidebar cue seeks share the boundary-safe sanitized cue timestamp', () => {

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

@@ -1,3 +1,4 @@
+import { toSubtitleClock, toVideoClock } from './subtitle-clock';
 import type { SubtitleCue } from './subtitle-cue-parser';
 
 const CUE_START_GROUP_TOLERANCE_SECONDS = 0.05;
@@ -80,8 +81,10 @@ export function subtitleCueListSeekTime(
 export function resolveSanitizedSubtitleSeekCommand(
   command: readonly (string | number)[],
   cues: readonly SubtitleCue[],
-  currentTimeSec: number,
+  videoTimeSec: number,
+  subDelay: number,
 ): (string | number)[] | null {
+  const currentTimeSec = toSubtitleClock(videoTimeSec, subDelay);
   if (
     command.length < 2 ||
     command[0] !== 'sub-seek' ||
@@ -124,5 +127,5 @@ export function resolveSanitizedSubtitleSeekCommand(
   if (!destination) {
     return null;
   }
-  return ['seek', subtitleCueSeekTime(destination.cue), 'absolute+exact'];
+  return ['seek', toVideoClock(subtitleCueSeekTime(destination.cue), subDelay), 'absolute+exact'];
 }