fix(stats): preserve lifetime history across anime merges and moves

- Recompute anime aggregates from retained lifetime media summaries
- Prevent sequel title evidence and AniList conflicts from misattributing entries

src/core/services/__tests__/immersion-tracker-write-queue.test.ts

@@ -244,19 +244,18 @@ function queueTelemetry(tracker: TrackerInternals, linesSeen: number): void {
   });
 }
 
-function lifetimeForAnime(
-  db: DatabaseSync,
-  animeId: number,
-): { linesSeen: number; activeMs: number; cards: number } | null {
+/** The queued telemetry sample only exists in the database once the queue drained fully. */
+function latestTelemetryLinesSeen(db: DatabaseSync, sessionId: number): number | null {
   const row = db
     .prepare(
-      `SELECT total_lines_seen AS linesSeen, total_active_ms AS activeMs, total_cards AS cards
-       FROM imm_lifetime_anime WHERE anime_id = ?`,
+      `SELECT lines_seen AS linesSeen
+       FROM imm_session_telemetry
+       WHERE session_id = ?
+       ORDER BY sample_ms DESC, telemetry_id DESC
+       LIMIT 1`,
     )
-    .get(animeId) as { linesSeen: number; activeMs: number; cards: number } | undefined;
-  return row
-    ? { linesSeen: Number(row.linesSeen), activeMs: Number(row.activeMs), cards: Number(row.cards) }
-    : null;
+    .get(sessionId) as { linesSeen: number } | undefined;
+  return row ? Number(row.linesSeen) : null;
 }
 
 function countLinesForAnime(db: DatabaseSync, animeId: number): number {
@@ -267,12 +266,12 @@ function countLinesForAnime(db: DatabaseSync, animeId: number): number {
 }
 
 /**
- * Both entry points rebuild the lifetime summaries, which recompute from the
- * database. A single flushNow() only writes one batch off the front of the
- * queue, so anything past `batchSize` would still be unwritten when the rebuild
- * reads.
+ * Both entry points must see a settled database before changing episode
+ * ownership. A single flushNow() only writes one batch off the front of the
+ * queue, so anything past `batchSize` would still be unwritten when the merge
+ * repoints rows.
  */
-test('mergeAnime drains a queue larger than one batch before rebuilding summaries', async () => {
+test('mergeAnime drains a queue larger than one batch before repointing rows', async () => {
   const dbPath = makeDbPath();
   let tracker: ImmersionTrackerService | null = null;
 
@@ -289,19 +288,16 @@ test('mergeAnime drains a queue larger than one batch before rebuilding summarie
     await internals.mergeAnime(1, [2]);
 
     assert.equal(internals.queue.length, 0);
+    // Every queued line landed, attributed to the surviving entry.
     assert.equal(countLinesForAnime(internals.db, 1), 8);
-    // The surviving entry's summary was rebuilt from the fully drained queue.
-    const lifetime = lifetimeForAnime(internals.db, 1);
-    assert.equal(lifetime?.linesSeen, 8);
-    assert.equal(lifetime?.activeMs, 3500);
-    assert.equal(lifetime?.cards, 2);
+    assert.equal(latestTelemetryLinesSeen(internals.db, 1), 8);
   } finally {
     tracker?.destroy();
     cleanupDbPath(dbPath);
   }
 });
 
-test('moveVideoToAnime drains a queue larger than one batch before rebuilding summaries', async () => {
+test('moveVideoToAnime drains a queue larger than one batch before repointing rows', async () => {
   const dbPath = makeDbPath();
   let tracker: ImmersionTrackerService | null = null;
 
@@ -318,10 +314,7 @@ test('moveVideoToAnime drains a queue larger than one batch before rebuilding su
 
     assert.equal(internals.queue.length, 0);
     assert.equal(countLinesForAnime(internals.db, 1), 8);
-    const lifetime = lifetimeForAnime(internals.db, 1);
-    assert.equal(lifetime?.linesSeen, 8);
-    assert.equal(lifetime?.activeMs, 3500);
-    assert.equal(lifetime?.cards, 2);
+    assert.equal(latestTelemetryLinesSeen(internals.db, 1), 8);
   } finally {
     tracker?.destroy();
     cleanupDbPath(dbPath);

src/core/services/anilist/season-resolver.test.ts

@@ -156,7 +156,10 @@ test('season 1 resolves to the anchor without relation lookups', async () => {
   assert.deepEqual(relationLookups, []);
 });
 
-test('season 2 preserves the anchor exact-title evidence through a sequel resolution', async () => {
+test('a sequel resolution is not certified by the anchor exact-title evidence', async () => {
+  // The anchor matched the search title exactly, but the hopped-to entry is a
+  // different inference (a split-cour chain can land one season short), so the
+  // sequel result must report its own title evidence, not the anchor's.
   const { execute } = createExecutor(OREGAIRU_SEARCH, OREGAIRU_RELATIONS);
   const result = await resolveAnilistSeasonMedia(
     { title: 'My Teen Romantic Comedy SNAFU', season: 2, episode: 1 },
@@ -165,6 +168,33 @@ test('season 2 preserves the anchor exact-title evidence through a sequel resolu
 
   assert.equal(result?.id, 20698);
   assert.equal(result?.via, 'sequel-chain');
+  assert.equal(result?.exactTitleMatch, false);
+});
+
+test('a sequel resolution whose own title matches the parsed title stays exact', async () => {
+  const anchor: AnilistSeasonMedia = {
+    id: 1,
+    episodes: 12,
+    format: 'TV',
+    title: { english: 'Show' },
+  };
+  const sequel: AnilistSeasonMedia = {
+    id: 2,
+    episodes: 12,
+    format: 'TV',
+    title: { english: 'Show 2nd Season' },
+  };
+  const { execute } = createExecutor([anchor], {
+    1: [{ relationType: 'SEQUEL', node: sequel }],
+  });
+
+  const result = await resolveAnilistSeasonMedia(
+    { title: 'Show 2nd Season', season: 2, episode: 1 },
+    { execute },
+  );
+
+  assert.equal(result?.id, 2);
+  assert.equal(result?.via, 'sequel-chain');
   assert.equal(result?.exactTitleMatch, true);
 });
 

src/core/services/anilist/season-resolver.ts

@@ -370,10 +370,20 @@ export async function resolveAnilistSeasonMedia(
     episode: season === null || season <= 1 ? input.episode : null,
   });
   if (!anchor) return null;
-  const exactTitleMatch = mediaTitles(anchor).includes(normalizeTitleIdentity(searchTitle));
+  // Certifies the media actually returned, never the anchor on its behalf: a
+  // sequel-chain hop can land one season short (split-cour entries) while the
+  // anchor title still matches perfectly, and that certainty must not carry
+  // over to the hopped-to entry.
+  const exactMatchFor = (candidate: AnilistSeasonMedia): boolean => {
+    const titles = mediaTitles(candidate);
+    return (
+      titles.includes(normalizeTitleIdentity(searchTitle)) ||
+      titles.includes(normalizeTitleIdentity(input.title))
+    );
+  };
 
   if (season === null || season <= 1) {
-    return toResolution(anchor, searchTitle, season, 'anchor', true, exactTitleMatch);
+    return toResolution(anchor, searchTitle, season, 'anchor', true, exactMatchFor(anchor));
   }
 
   let chainError: unknown = null;
@@ -387,7 +397,7 @@ export async function resolveAnilistSeasonMedia(
     deps.logInfo?.(
       `[anilist] season ${season} of "${searchTitle}" resolved via sequel chain: ${displayTitle(viaChain, searchTitle)} (${viaChain.id})`,
     );
-    return toResolution(viaChain, searchTitle, season, 'sequel-chain', true, exactTitleMatch);
+    return toResolution(viaChain, searchTitle, season, 'sequel-chain', true, exactMatchFor(viaChain));
   }
 
   const viaAirOrder = pickByAirOrder(anchor, season, media);
@@ -395,7 +405,14 @@ export async function resolveAnilistSeasonMedia(
     deps.logInfo?.(
       `[anilist] season ${season} of "${searchTitle}" resolved via air order: ${displayTitle(viaAirOrder, searchTitle)} (${viaAirOrder.id})`,
     );
-    return toResolution(viaAirOrder, searchTitle, season, 'air-order', true, exactTitleMatch);
+    return toResolution(
+      viaAirOrder,
+      searchTitle,
+      season,
+      'air-order',
+      true,
+      exactMatchFor(viaAirOrder),
+    );
   }
 
   // The chain failed for transport reasons rather than because the season is absent;
@@ -407,5 +424,5 @@ export async function resolveAnilistSeasonMedia(
   deps.logInfo?.(
     `[anilist] could not resolve season ${season} of "${searchTitle}"; falling back to ${displayTitle(anchor, searchTitle)} (${anchor.id})`,
   );
-  return toResolution(anchor, searchTitle, season, 'anchor', false, exactTitleMatch);
+  return toResolution(anchor, searchTitle, season, 'anchor', false, exactMatchFor(anchor));
 }

src/core/services/immersion-tracker-service.ts

@@ -28,6 +28,7 @@ import {
 } from './immersion-tracker/storage';
 import {
   applySessionLifetimeSummary,
+  recomputeLifetimeAnimeAggregates,
   reconcileStaleActiveSessions,
   rebuildLifetimeSummaries as rebuildLifetimeSummaryTables,
   shouldBackfillLifetimeSummaries,
@@ -526,7 +527,7 @@ export class ImmersionTrackerService {
       this.logger.info(
         `Repaired season-scoped stats links on startup: scanned=${seasonRepair.scanned} movedVideos=${seasonRepair.movedVideos} deletedAnimeRows=${seasonRepair.deletedAnimeRows}`,
       );
-      rebuildLifetimeSummaryTables(this.db);
+      recomputeLifetimeAnimeAggregates(this.db);
     }
     if (shouldBackfillLifetimeSummaries(this.db)) {
       const result = rebuildLifetimeSummaryTables(this.db);
@@ -924,7 +925,7 @@ export class ImmersionTrackerService {
         animeId,
       );
     if (repair.movedVideos > 0 || repair.deletedAnimeRows > 0) {
-      rebuildLifetimeSummaryTables(this.db);
+      recomputeLifetimeAnimeAggregates(this.db);
     }
 
     // Update cover art for all videos in this anime
@@ -1372,7 +1373,7 @@ export class ImmersionTrackerService {
         metadataJson: candidate.metadataJson,
       });
     }
-    rebuildLifetimeSummaryTables(this.db);
+    recomputeLifetimeAnimeAggregates(this.db);
   }
 
   recordJellyfinPlaybackMetadata(metadata: JellyfinPlaybackMetadataInput): void {
@@ -1445,7 +1446,7 @@ export class ImmersionTrackerService {
       this.db.prepare('SELECT 1 FROM imm_lifetime_media WHERE video_id = ?').get(videoId),
     );
     if (hasLifetimeMedia || (previousLink && previousLink.animeId !== animeId)) {
-      rebuildLifetimeSummaryTables(this.db);
+      recomputeLifetimeAnimeAggregates(this.db);
     }
   }
 

src/core/services/immersion-tracker/__tests__/anime-merge.test.ts

@@ -72,7 +72,10 @@ interface EpisodeSeed {
   cards?: number;
 }
 
-/** One episode with one ended session, so lifetime rebuilds have something to sum. */
+/**
+ * One episode with one ended session, plus the imm_lifetime_media row the
+ * session would have left behind, so lifetime aggregates have something to sum.
+ */
 function insertEpisode(db: DatabaseSync, seed: EpisodeSeed): void {
   const activeMs = seed.activeMs ?? 1000;
   const cards = seed.cards ?? 1;
@@ -107,6 +110,18 @@ function insertEpisode(db: DatabaseSync, seed: EpisodeSeed): void {
     `INSERT INTO imm_subtitle_lines(session_id, video_id, anime_id, line_index, text, CREATED_DATE, LAST_UPDATE_DATE)
      VALUES (?, ?, ?, 1, ?, ?, ?)`,
   ).run(seed.videoId, seed.videoId, seed.animeId, `line ${seed.videoId}`, BASE_MS, BASE_MS);
+  db.prepare(
+    `INSERT INTO imm_lifetime_media(video_id, total_sessions, total_active_ms, total_cards, completed, first_watched_ms, last_watched_ms, CREATED_DATE, LAST_UPDATE_DATE)
+     VALUES (?, 1, ?, ?, 1, ?, ?, ?, ?)`,
+  ).run(
+    seed.videoId,
+    activeMs,
+    cards,
+    String(BASE_MS),
+    String(BASE_MS + activeMs),
+    BASE_MS,
+    BASE_MS,
+  );
 }
 
 function animeIds(db: DatabaseSync): number[] {
@@ -162,6 +177,49 @@ test('mergeAnimeRecords folds episodes, lines and lifetime totals into the targe
   });
 });
 
+test('merge and move preserve lifetime history whose raw sessions were pruned', () => {
+  withDb((db) => {
+    insertAnime(db, { animeId: 1, key: 'show', title: 'Show' });
+    insertAnime(db, { animeId: 2, key: 'show season 1', title: 'Show Season 1' });
+    insertAnime(db, { animeId: 3, key: 'other show', title: 'Other Show' });
+    insertEpisode(db, { videoId: 1, animeId: 1, activeMs: 1000, cards: 1 });
+    insertEpisode(db, { videoId: 2, animeId: 2, season: 1, activeMs: 2000, cards: 3 });
+    insertEpisode(db, { videoId: 3, animeId: 3, activeMs: 4000, cards: 5 });
+    // Retention pruned every raw session; only the lifetime summaries remain.
+    db.exec('DELETE FROM imm_sessions');
+    db.prepare(
+      `UPDATE imm_lifetime_global
+       SET total_sessions = 200, total_active_ms = 360000000, total_cards = 500, active_days = 90
+       WHERE global_id = 1`,
+    ).run();
+
+    mergeAnimeRecords(db, 1, [2]);
+    moveVideoToAnime(db, 3, 1);
+
+    const globalRow = db
+      .prepare(
+        `SELECT total_sessions AS sessions, total_active_ms AS activeMs, total_cards AS cards, active_days AS days
+         FROM imm_lifetime_global WHERE global_id = 1`,
+      )
+      .get() as { sessions: number; activeMs: number; cards: number; days: number };
+    assert.equal(globalRow.sessions, 200);
+    assert.equal(globalRow.activeMs, 360000000);
+    assert.equal(globalRow.cards, 500);
+    assert.equal(globalRow.days, 90);
+
+    const survivor = db
+      .prepare(
+        `SELECT total_active_ms AS activeMs, total_cards AS cards, episodes_started AS episodes
+         FROM imm_lifetime_anime WHERE anime_id = 1`,
+      )
+      .get() as { activeMs: number; cards: number; episodes: number };
+    assert.equal(survivor.activeMs, 7000);
+    assert.equal(survivor.cards, 9);
+    assert.equal(survivor.episodes, 3);
+    assert.equal(db.prepare('SELECT 1 FROM imm_lifetime_anime WHERE anime_id = 3').get(), undefined);
+  });
+});
+
 test('mergeAnimeRecords repoints subtitle lines recorded before the anime link landed', () => {
   withDb((db) => {
     insertAnime(db, { animeId: 1, key: 'show', title: 'Show' });
@@ -698,3 +756,33 @@ test('resolveAnimeAnilistConflict leaves an entry that already links elsewhere a
     assert.deepEqual(getAnimeMergeRecommendations(db), []);
   });
 });
+
+test('automatic AniList update onto an entry that already links elsewhere does not throw', () => {
+  withDb((db) => {
+    insertAnime(db, { animeId: 1, key: 'show', title: 'Show', anilistId: 163132 });
+    insertAnime(db, { animeId: 2, key: 'show s2', title: 'Show Season 2', anilistId: 999 });
+    insertEpisode(db, { videoId: 1, animeId: 1, season: 1 });
+    insertEpisode(db, { videoId: 2, animeId: 2, season: 2 });
+
+    // Entry 2 explicitly links to 999; a later video re-resolving to entry 1's
+    // id must be refused, not written over the UNIQUE anilist_id column.
+    updateAnimeAnilistInfo(db, 2, {
+      anilistId: 163132,
+      titleRomaji: 'Show',
+      titleEnglish: null,
+      titleNative: null,
+      episodesTotal: 12,
+      exactTitleMatch: true,
+    });
+
+    assert.deepEqual(animeIds(db), [1, 2]);
+    assert.equal(
+      (
+        db.prepare('SELECT anilist_id AS anilistId FROM imm_anime WHERE anime_id = 2').get() as {
+          anilistId: number;
+        }
+      ).anilistId,
+      999,
+    );
+  });
+});

src/core/services/immersion-tracker/anime-merge.ts

@@ -1,5 +1,5 @@
 import type { DatabaseSync } from './sqlite';
-import { rebuildLifetimeSummariesInTransaction } from './lifetime';
+import { recomputeLifetimeAnimeAggregatesInTransaction } from './lifetime';
 import { toDbTimestamp } from './query-shared';
 import { nowMs } from './time';
 
@@ -151,8 +151,9 @@ function absorbAnimeMetadata(
  * is repointed, metadata the target is missing is inherited from the sources,
  * and the emptied source rows are deleted.
  *
- * Assumes the caller already holds a write transaction and rebuilds the
- * lifetime summaries afterwards; use {@link mergeAnimeRecords} otherwise.
+ * Assumes the caller already holds a write transaction and refreshes the
+ * per-anime lifetime aggregates afterwards; use {@link mergeAnimeRecords}
+ * otherwise.
  */
 export function mergeAnimeRecordsInTransaction(
   db: DatabaseSync,
@@ -237,7 +238,7 @@ export function mergeAnimeRecords(
   return runInTransaction(db, () => {
     const summary = mergeAnimeRecordsInTransaction(db, targetAnimeId, sourceAnimeIds);
     if (summary.mergedAnimeIds.length > 0) {
-      rebuildLifetimeSummariesInTransaction(db);
+      recomputeLifetimeAnimeAggregatesInTransaction(db);
     }
     return summary;
   });
@@ -286,7 +287,7 @@ export function moveVideoToAnime(
       removedPreviousAnime = true;
     }
 
-    rebuildLifetimeSummariesInTransaction(db);
+    recomputeLifetimeAnimeAggregatesInTransaction(db);
     return { targetAnimeId, previousAnimeId, removedPreviousAnime };
   });
 }

src/core/services/immersion-tracker/anime-season-repair.ts

@@ -380,8 +380,12 @@ export function resolveAnimeAnilistConflict(
       targetRow.anilist_id !== anilistId
     ) {
       // An automatic lookup disagreeing with an existing explicit link is a
-      // mis-resolution, not evidence that either row should move or merge.
-      return emptySummary(1);
+      // mis-resolution, not evidence that either row should move or merge. The
+      // colliding id must not be assigned either: another row owns it and
+      // imm_anime.anilist_id is UNIQUE.
+      const summary = emptySummary(1);
+      summary.anilistAssignmentBlocked = true;
+      return summary;
     }
     const isManual = options.survivor === 'target' || options.matchConfidence === 'manual';
     if (!isManual && hasDismissedAnimeMergeRecommendation(db, targetAnimeId, conflict.animeId)) {

src/core/services/immersion-tracker/lifetime.ts

@@ -708,6 +708,87 @@ export function rebuildLifetimeSummariesInTransaction(
   return rebuildLifetimeSummariesInternal(db, rebuiltAtMs);
 }
 
+/**
+ * Re-derive every per-anime lifetime row from the per-video summaries after
+ * episodes changed owners (merge, move, season repair).
+ *
+ * Deliberately NOT a full rebuild: {@link rebuildLifetimeSummariesInTransaction}
+ * recomputes from raw sessions, which are pruned after the retention window, so
+ * it silently truncates lifetime history. `imm_lifetime_media` is keyed by
+ * video and survives repointing, so aggregating it preserves all-time totals;
+ * `imm_lifetime_global` only needs `anime_completed` refreshed because moving
+ * attribution between entries cannot change the global counters.
+ *
+ * Assumes the caller holds a write transaction; use
+ * {@link recomputeLifetimeAnimeAggregates} otherwise.
+ */
+export function recomputeLifetimeAnimeAggregatesInTransaction(db: DatabaseSync): void {
+  const updatedAt = toDbTimestamp(nowMs());
+  db.exec('DELETE FROM imm_lifetime_anime');
+  db.prepare(
+    `
+    INSERT INTO imm_lifetime_anime (
+      anime_id,
+      total_sessions,
+      total_active_ms,
+      total_cards,
+      total_lines_seen,
+      total_tokens_seen,
+      episodes_started,
+      episodes_completed,
+      first_watched_ms,
+      last_watched_ms,
+      CREATED_DATE,
+      LAST_UPDATE_DATE
+    )
+    SELECT
+      v.anime_id,
+      COALESCE(SUM(m.total_sessions), 0),
+      COALESCE(SUM(m.total_active_ms), 0),
+      COALESCE(SUM(m.total_cards), 0),
+      COALESCE(SUM(m.total_lines_seen), 0),
+      COALESCE(SUM(m.total_tokens_seen), 0),
+      COUNT(*),
+      COUNT(CASE WHEN m.completed > 0 THEN 1 END),
+      MIN(m.first_watched_ms),
+      MAX(m.last_watched_ms),
+      ?,
+      ?
+    FROM imm_lifetime_media m
+    JOIN imm_videos v ON v.video_id = m.video_id
+    WHERE v.anime_id IS NOT NULL
+    GROUP BY v.anime_id
+    `,
+  ).run(updatedAt, updatedAt);
+  db.prepare(
+    `
+    UPDATE imm_lifetime_global
+    SET
+      anime_completed = (
+        SELECT COUNT(*)
+        FROM imm_lifetime_anime la
+        JOIN imm_anime a ON a.anime_id = la.anime_id
+        WHERE a.episodes_total IS NOT NULL
+          AND a.episodes_total > 0
+          AND la.episodes_completed >= a.episodes_total
+      ),
+      LAST_UPDATE_DATE = ?
+    WHERE global_id = 1
+    `,
+  ).run(updatedAt);
+}
+
+export function recomputeLifetimeAnimeAggregates(db: DatabaseSync): void {
+  db.exec('BEGIN IMMEDIATE');
+  try {
+    recomputeLifetimeAnimeAggregatesInTransaction(db);
+    db.exec('COMMIT');
+  } catch (error) {
+    db.exec('ROLLBACK');
+    throw error;
+  }
+}
+
 export function reconcileStaleActiveSessions(db: DatabaseSync): number {
   const sessions = getRetainedStaleActiveSessions(db);
   if (sessions.length === 0) {

src/core/services/immersion-tracker/query-maintenance.ts

@@ -1,7 +1,10 @@
 import { createHash } from 'node:crypto';
 import type { DatabaseSync } from './sqlite';
 import { buildCoverBlobReference, normalizeCoverBlobBytes } from './storage';
-import { rebuildLifetimeSummaries, rebuildLifetimeSummariesInTransaction } from './lifetime';
+import {
+  recomputeLifetimeAnimeAggregates,
+  rebuildLifetimeSummariesInTransaction,
+} from './lifetime';
 import { getRollupGroupsForSessions, refreshRollupsForGroupsInTransaction } from './maintenance';
 import { nowMs } from './time';
 import { resolveAnimeAnilistConflict } from './anime-season-repair';
@@ -460,7 +463,7 @@ export function updateAnimeAnilistInfo(
     targetRow.anime_id,
   );
   if (repair.movedVideos > 0 || repair.deletedAnimeRows > 0) {
-    rebuildLifetimeSummaries(db);
+    recomputeLifetimeAnimeAggregates(db);
   }
 }