fix(stats): optimize lifetime summary maintenance

- Recompute only affected anime after metadata changes
- Normalize fractional metrics across apply, rebuild, and delete
- Preserve transactions and recover from silent worker exits

src/core/services/immersion-tracker/__tests__/lifetime-delete.test.ts

@@ -10,7 +10,11 @@ import {
   linkVideoToAnimeRecord,
 } from '../storage.js';
 import { startSessionRecord } from '../session.js';
-import { rebuildLifetimeSummaries, repairLifetimeSummariesFromMedia } from '../lifetime.js';
+import {
+  applySessionLifetimeSummary,
+  rebuildLifetimeSummaries,
+  repairLifetimeSummariesFromMedia,
+} from '../lifetime.js';
 import { deleteMaintenanceBatch } from '../query-delete-maintenance.js';
 import { toDbTimestamp } from '../query-shared.js';
 
@@ -160,6 +164,123 @@ function snapshotAnime(db: DatabaseSync): unknown[] {
     .map((row) => cleanRow(row));
 }
 
+test('fractional lifetime metrics stay normalized across apply, rebuild, and delete', () => {
+  const db = createDb();
+  try {
+    const videoId = seedVideo(db, null, 'fractional-metrics');
+    const seedFractionalSession = (
+      startedAtMs: number,
+      metrics: { activeMs: number; cards: number; lines: number; tokens: number },
+    ) => {
+      const { state } = startSessionRecord(db, videoId, startedAtMs);
+      state.activeWatchedMs = metrics.activeMs;
+      state.cardsMined = metrics.cards;
+      state.linesSeen = metrics.lines;
+      state.tokensSeen = metrics.tokens;
+      const endedAtMs = startedAtMs + 2_000;
+      db.prepare(
+        `UPDATE imm_sessions SET
+           ended_at_ms = ?,
+           active_watched_ms = ?,
+           cards_mined = ?,
+           lines_seen = ?,
+           tokens_seen = ?
+         WHERE session_id = ?`,
+      ).run(
+        toDbTimestamp(endedAtMs),
+        metrics.activeMs,
+        metrics.cards,
+        metrics.lines,
+        metrics.tokens,
+        state.sessionId,
+      );
+      return { state, endedAtMs };
+    };
+    const readMediaMetrics = () =>
+      cleanRow<{
+        total_sessions: number;
+        total_active_ms: number;
+        total_cards: number;
+        total_lines_seen: number;
+        total_tokens_seen: number;
+      }>(
+        db
+          .prepare(
+            `SELECT total_sessions, total_active_ms, total_cards,
+                    total_lines_seen, total_tokens_seen
+             FROM imm_lifetime_media WHERE video_id = ?`,
+          )
+          .get(videoId),
+      );
+
+    const withoutTelemetry = seedFractionalSession(BASE_MS, {
+      activeMs: 1_234.9,
+      cards: 2.8,
+      lines: 3.7,
+      tokens: 4.6,
+    });
+    applySessionLifetimeSummary(db, withoutTelemetry.state, withoutTelemetry.endedAtMs);
+    assert.deepEqual(readMediaMetrics(), {
+      total_sessions: 1,
+      total_active_ms: 1_234,
+      total_cards: 2,
+      total_lines_seen: 3,
+      total_tokens_seen: 4,
+    });
+
+    const withTelemetry = seedFractionalSession(BASE_MS + DAY_MS, {
+      activeMs: 9_999.9,
+      cards: 9.9,
+      lines: 9.9,
+      tokens: 9.9,
+    });
+    db.prepare(
+      `INSERT INTO imm_session_telemetry (
+         session_id, sample_ms, active_watched_ms, cards_mined, lines_seen, tokens_seen
+       ) VALUES (?, ?, ?, ?, ?, ?)`,
+    ).run(withTelemetry.state.sessionId, withTelemetry.endedAtMs, 2_345.9, 5.8, 6.7, 7.6);
+    applySessionLifetimeSummary(db, withTelemetry.state, withTelemetry.endedAtMs);
+    assert.deepEqual(readMediaMetrics(), {
+      total_sessions: 2,
+      total_active_ms: 3_579,
+      total_cards: 7,
+      total_lines_seen: 9,
+      total_tokens_seen: 11,
+    });
+
+    deleteMaintenanceBatch(db, [{ kind: 'session', sessionId: withTelemetry.state.sessionId }]);
+    const retainedMetrics = {
+      total_sessions: 1,
+      total_active_ms: 1_234,
+      total_cards: 2,
+      total_lines_seen: 3,
+      total_tokens_seen: 4,
+    };
+    assert.deepEqual(readMediaMetrics(), retainedMetrics, 'delete subtracts floored telemetry');
+
+    rebuildLifetimeSummaries(db);
+    assert.deepEqual(
+      readMediaMetrics(),
+      retainedMetrics,
+      'rebuild floors session-row fallback values',
+    );
+
+    deleteMaintenanceBatch(db, [{ kind: 'session', sessionId: withoutTelemetry.state.sessionId }]);
+    assert.deepEqual(snapshotMedia(db), [], 'delete subtracts the normalized metrics exactly');
+    assert.deepEqual(snapshotGlobal(db), {
+      total_sessions: 0,
+      total_active_ms: 0,
+      total_cards: 0,
+      active_days: 0,
+      episodes_started: 0,
+      episodes_completed: 0,
+      anime_completed: 0,
+    });
+  } finally {
+    db.close();
+  }
+});
+
 test('incremental delete maintenance matches a full rebuild when no history is pruned', () => {
   const db = createDb();
   try {
@@ -387,3 +508,22 @@ test('repair preserves lifetime history from pruned sessions where a rebuild wou
     db.close();
   }
 });
+
+test('repair leaves a caller-owned transaction intact when its begin fails', () => {
+  const db = createDb();
+  try {
+    db.exec('BEGIN');
+    const animeId = seedAnime(db, 'Caller Transaction', null);
+
+    assert.throws(() => repairLifetimeSummariesFromMedia(db), /transaction/i);
+    assert.ok(
+      db.prepare('SELECT 1 FROM imm_anime WHERE anime_id = ?').get(animeId),
+      'the repair did not roll back the caller transaction',
+    );
+
+    db.exec('ROLLBACK');
+    assert.equal(db.prepare('SELECT 1 FROM imm_anime WHERE anime_id = ?').get(animeId), undefined);
+  } finally {
+    db.close();
+  }
+});

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

@@ -8,6 +8,7 @@ export interface AnimeSeasonRepairSummary {
   repaired: number;
   movedVideos: number;
   deletedAnimeRows: number;
+  affectedAnimeIds: number[];
 }
 
 interface AnimeRow {
@@ -38,6 +39,7 @@ function emptySummary(scanned = 0): AnimeSeasonRepairSummary {
     repaired: 0,
     movedVideos: 0,
     deletedAnimeRows: 0,
+    affectedAnimeIds: [],
   };
 }
 
@@ -49,6 +51,7 @@ function mergeSummary(
   target.repaired += source.repaired;
   target.movedVideos += source.movedVideos;
   target.deletedAnimeRows += source.deletedAnimeRows;
+  target.affectedAnimeIds = [...new Set([...target.affectedAnimeIds, ...source.affectedAnimeIds])];
   return target;
 }
 
@@ -184,6 +187,7 @@ function redistributeAnimeRowByParsedSeasonsInTransaction(
 
   const videos = getParsedVideos(db, animeId);
   const summary = emptySummary(1);
+  summary.affectedAnimeIds.push(animeId);
   const updatedAt = toDbTimestamp(nowMs());
   const targetBySeason = new Map<number, number>();
 
@@ -233,6 +237,9 @@ function redistributeAnimeRowByParsedSeasonsInTransaction(
 
     if (videoUpdate.changes > 0 || lineUpdate.changes > 0) {
       summary.movedVideos += 1;
+      if (!summary.affectedAnimeIds.includes(targetAnimeId)) {
+        summary.affectedAnimeIds.push(targetAnimeId);
+      }
     }
   }
 

src/core/services/immersion-tracker/delete-maintenance-worker-runtime.test.ts

@@ -213,6 +213,27 @@ test('worker runtime falls back to the current thread when the worker crashes',
   assert.equal(warnings.length, 1);
 });
 
+test('worker runtime falls back when a worker exits cleanly without a response', async () => {
+  const { worker, listeners, terminationState } = createFakeWorker();
+  const fallbackTasks: unknown[] = [];
+  const runtime = new DeleteMaintenanceWorkerRuntime({
+    resolveWorkerPath: () => '/tmp/delete-worker.js',
+    createWorker: async () => worker,
+    executeFallback: (dbPath, task) => {
+      fallbackTasks.push({ dbPath, task });
+    },
+  });
+  const task = { kind: 'session' as const, sessionId: 1 };
+
+  const result = runtime.run('/tmp/test.sqlite', task);
+  await new Promise<void>((resolve) => setTimeout(resolve, 0));
+  listeners.get('exit')?.(0 as never);
+
+  await result;
+  assert.equal(terminationState.calls, 1);
+  assert.deepEqual(fallbackTasks, [{ dbPath: '/tmp/test.sqlite', task }]);
+});
+
 test('worker runtime surfaces a task failure without rerunning it', async () => {
   const { worker, listeners, terminationState } = createFakeWorker();
   const fallbackTasks: unknown[] = [];

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

@@ -21,10 +21,8 @@ interface AnimeRow {
 }
 
 function asPositiveNumber(value: number | null, fallback: number): number {
-  if (value === null || !Number.isFinite(value)) {
-    return fallback;
-  }
-  return Math.max(0, Math.floor(value));
+  const resolved = value !== null && Number.isFinite(value) ? value : fallback;
+  return Number.isFinite(resolved) ? Math.floor(Math.max(resolved, 0)) : 0;
 }
 
 interface ExistenceRow {
@@ -68,10 +66,10 @@ const RETAINED_SESSION_METRICS_CTE = `
       v.anime_id,
       s.started_at_ms,
       s.ended_at_ms,
-      MAX(COALESCE(t.active_watched_ms, s.active_watched_ms, 0), 0) AS active_ms,
-      MAX(COALESCE(t.cards_mined, s.cards_mined, 0), 0) AS cards_mined,
-      MAX(COALESCE(t.lines_seen, s.lines_seen, 0), 0) AS lines_seen,
-      MAX(COALESCE(t.tokens_seen, s.tokens_seen, 0), 0) AS tokens_seen,
+      CAST(MAX(COALESCE(t.active_watched_ms, s.active_watched_ms, 0), 0) AS INTEGER) AS active_ms,
+      CAST(MAX(COALESCE(t.cards_mined, s.cards_mined, 0), 0) AS INTEGER) AS cards_mined,
+      CAST(MAX(COALESCE(t.lines_seen, s.lines_seen, 0), 0) AS INTEGER) AS lines_seen,
+      CAST(MAX(COALESCE(t.tokens_seen, s.tokens_seen, 0), 0) AS INTEGER) AS tokens_seen,
       CASE WHEN v.watched > 0 THEN 1 ELSE 0 END AS completed
     FROM imm_sessions s
     JOIN imm_videos v
@@ -599,18 +597,10 @@ export function applySessionLifetimeSummary(
         .get(video.anime_id) as AnimeRow | null | undefined) ?? null)
     : null;
 
-  const activeMs = telemetry
-    ? asPositiveNumber(telemetry.active_watched_ms, session.activeWatchedMs)
-    : session.activeWatchedMs;
-  const cardsMined = telemetry
-    ? asPositiveNumber(telemetry.cards_mined, session.cardsMined)
-    : session.cardsMined;
-  const linesSeen = telemetry
-    ? asPositiveNumber(telemetry.lines_seen, session.linesSeen)
-    : session.linesSeen;
-  const tokensSeen = telemetry
-    ? asPositiveNumber(telemetry.tokens_seen, session.tokensSeen)
-    : session.tokensSeen;
+  const activeMs = asPositiveNumber(telemetry?.active_watched_ms ?? null, session.activeWatchedMs);
+  const cardsMined = asPositiveNumber(telemetry?.cards_mined ?? null, session.cardsMined);
+  const linesSeen = asPositiveNumber(telemetry?.lines_seen ?? null, session.linesSeen);
+  const tokensSeen = asPositiveNumber(telemetry?.tokens_seen ?? null, session.tokensSeen);
   const watched = video?.watched ?? 0;
   const isFirstSessionForVideoRun =
     mediaLifetime === null &&
@@ -759,10 +749,10 @@ export function planLifetimeRemovals(
         SELECT
           s.video_id AS videoId,
           COUNT(*) AS sessions,
-          COALESCE(SUM(MAX(COALESCE(t.active_watched_ms, s.active_watched_ms, 0), 0)), 0) AS activeMs,
-          COALESCE(SUM(MAX(COALESCE(t.cards_mined, s.cards_mined, 0), 0)), 0) AS cards,
-          COALESCE(SUM(MAX(COALESCE(t.lines_seen, s.lines_seen, 0), 0)), 0) AS linesSeen,
-          COALESCE(SUM(MAX(COALESCE(t.tokens_seen, s.tokens_seen, 0), 0)), 0) AS tokensSeen
+          COALESCE(SUM(CAST(MAX(COALESCE(t.active_watched_ms, s.active_watched_ms, 0), 0) AS INTEGER)), 0) AS activeMs,
+          COALESCE(SUM(CAST(MAX(COALESCE(t.cards_mined, s.cards_mined, 0), 0) AS INTEGER)), 0) AS cards,
+          COALESCE(SUM(CAST(MAX(COALESCE(t.lines_seen, s.lines_seen, 0), 0) AS INTEGER)), 0) AS linesSeen,
+          COALESCE(SUM(CAST(MAX(COALESCE(t.tokens_seen, s.tokens_seen, 0), 0) AS INTEGER)), 0) AS tokensSeen
         FROM imm_sessions s
         JOIN imm_lifetime_applied_sessions a ON a.session_id = s.session_id
         LEFT JOIN imm_session_telemetry t
@@ -1132,17 +1122,20 @@ export interface LifetimeRepairSummary {
  * the full rebuild instead.
  */
 export function repairLifetimeSummariesFromMedia(db: DatabaseSync): LifetimeRepairSummary {
-  if (shouldBackfillLifetimeSummaries(db)) {
-    const rebuilt = rebuildLifetimeSummaries(db);
-    const animeRow = db
-      .prepare('SELECT COUNT(*) AS count FROM imm_lifetime_anime')
-      .get() as ExistenceRow;
-    return { recomputedAnime: Number(animeRow.count), repairedAtMs: rebuilt.rebuiltAtMs };
-  }
-
   const repairedAtMs = nowMs();
-  db.exec('BEGIN');
+  let transactionStarted = false;
   try {
+    db.exec('BEGIN IMMEDIATE');
+    transactionStarted = true;
+    if (shouldBackfillLifetimeSummaries(db)) {
+      const rebuilt = rebuildLifetimeSummariesInTransaction(db, repairedAtMs);
+      const animeRow = db
+        .prepare('SELECT COUNT(*) AS count FROM imm_lifetime_anime')
+        .get() as ExistenceRow;
+      db.exec('COMMIT');
+      return { recomputedAnime: Number(animeRow.count), repairedAtMs: rebuilt.rebuiltAtMs };
+    }
+
     const animeIds = new Set<number>();
     for (const row of db
       .prepare('SELECT DISTINCT anime_id AS animeId FROM imm_videos WHERE anime_id IS NOT NULL')
@@ -1160,7 +1153,7 @@ export function repairLifetimeSummariesFromMedia(db: DatabaseSync): LifetimeRepa
     db.exec('COMMIT');
     return { recomputedAnime: animeIds.size, repairedAtMs };
   } catch (error) {
-    db.exec('ROLLBACK');
+    if (transactionStarted) db.exec('ROLLBACK');
     throw error;
   }
 }

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

@@ -62,9 +62,9 @@ function selectIds(
 
 function mergeLexicalPlanEntries(
   target: LexicalRemovalPlan['words'],
+  byId: Map<number, LexicalRemovalPlan['words'][number]>,
   source: LexicalRemovalPlan['words'],
 ): void {
-  const byId = new Map(target.map((entry) => [entry.id, entry]));
   for (const entry of source) {
     const existing = byId.get(entry.id);
     if (!existing) {
@@ -90,9 +90,18 @@ function mergeLexicalPlanEntries(
   }
 }
 
-function mergeLexicalPlans(target: LexicalRemovalPlan, source: LexicalRemovalPlan): void {
-  mergeLexicalPlanEntries(target.words, source.words);
-  mergeLexicalPlanEntries(target.kanji, source.kanji);
+interface LexicalPlanEntryMaps {
+  words: Map<number, LexicalRemovalPlan['words'][number]>;
+  kanji: Map<number, LexicalRemovalPlan['kanji'][number]>;
+}
+
+function mergeLexicalPlans(
+  target: LexicalRemovalPlan,
+  byId: LexicalPlanEntryMaps,
+  source: LexicalRemovalPlan,
+): void {
+  mergeLexicalPlanEntries(target.words, byId.words, source.words);
+  mergeLexicalPlanEntries(target.kanji, byId.kanji, source.kanji);
 }
 
 /**
@@ -108,11 +117,15 @@ function planLexicalRemovalsForDelete(
   videoIds: number[],
 ): LexicalRemovalPlan {
   const combined: LexicalRemovalPlan = { words: [], kanji: [] };
+  const byId: LexicalPlanEntryMaps = {
+    words: new Map(),
+    kanji: new Map(),
+  };
   forEachIdChunk(sessionIdsOnSurvivingVideos, (chunk) => {
-    mergeLexicalPlans(combined, planLexicalRemovalsForSessions(db, chunk));
+    mergeLexicalPlans(combined, byId, planLexicalRemovalsForSessions(db, chunk));
   });
   forEachIdChunk(videoIds, (chunk) => {
-    mergeLexicalPlans(combined, planLexicalRemovalsForVideos(db, chunk));
+    mergeLexicalPlans(combined, byId, planLexicalRemovalsForVideos(db, chunk));
   });
   return combined;
 }

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

@@ -1,7 +1,12 @@
 import { createHash } from 'node:crypto';
 import type { DatabaseSync } from './sqlite';
 import { buildCoverBlobReference, normalizeCoverBlobBytes } from './storage';
-import { repairLifetimeSummariesFromMedia } from './lifetime';
+import {
+  recomputeLifetimeAnimeFromMedia,
+  recomputeLifetimeGlobalFromSummaries,
+  repairLifetimeSummariesFromMedia,
+  shouldBackfillLifetimeSummaries,
+} from './lifetime';
 import { nowMs } from './time';
 import { resolveAnimeAnilistConflict } from './anime-season-repair';
 import { deleteMaintenanceBatch } from './query-delete-maintenance';
@@ -421,7 +426,7 @@ export function updateAnimeAnilistInfo(
   } | null;
   if (!row?.anime_id) return;
 
-  resolveAnimeAnilistConflict(db, row.anime_id, info.anilistId);
+  const conflictRepair = resolveAnimeAnilistConflict(db, row.anime_id, info.anilistId);
   const targetRow = db
     .prepare('SELECT anime_id FROM imm_videos WHERE video_id = ?')
     .get(videoId) as {
@@ -450,10 +455,15 @@ export function updateAnimeAnilistInfo(
     toDbTimestamp(nowMs()),
     targetRow.anime_id,
   );
-  // Moves change which anime owns the media rows, and an episodes_total change
-  // can flip anime_completed even without a move — both are derivable from the
-  // summary tables, so a full (retention-lossy) rebuild is never needed here.
-  repairLifetimeSummariesFromMedia(db);
+  if (shouldBackfillLifetimeSummaries(db)) {
+    repairLifetimeSummariesFromMedia(db);
+  } else {
+    const affectedAnimeIds = new Set(conflictRepair.affectedAnimeIds);
+    affectedAnimeIds.add(row.anime_id);
+    affectedAnimeIds.add(targetRow.anime_id);
+    recomputeLifetimeAnimeFromMedia(db, [...affectedAnimeIds]);
+    recomputeLifetimeGlobalFromSummaries(db);
+  }
 }
 
 export function markVideoWatched(db: DatabaseSync, videoId: number, watched: boolean): void {