diff --git a/changes/stats-vocabulary-summary-totals.md b/changes/stats-vocabulary-summary-totals.md
index fe3a24ae..af8f4023 100644
--- a/changes/stats-vocabulary-summary-totals.md
+++ b/changes/stats-vocabulary-summary-totals.md
@@ -2,5 +2,5 @@ type: fixed
 area: stats
 
 - Fixed Vocabulary totals and charts counting only the first browsing page instead of all tracked vocabulary, without delaying the rest of the page.
-- New-word history now uses permanent daily lexical rollups, backfilled in the background and repaired when tracked material is removed or reprocessed.
+- New-word history now uses permanent daily lexical rollups, backfilled in the background and repaired when tracked material is removed or reprocessed; playback writes queue safely during the one-time rebuild and resume afterward.
 - Calendar-day chart labels now preserve the recorded local date in time zones west of UTC.
diff --git a/src/core/services/immersion-tracker-service.test.ts b/src/core/services/immersion-tracker-service.test.ts
index a8c55b1a..6e4e6a68 100644
--- a/src/core/services/immersion-tracker-service.test.ts
+++ b/src/core/services/immersion-tracker-service.test.ts
@@ -609,6 +609,99 @@ test('tracker starts the injected lexical rollup backfill when it is pending', a
   }
 });
 
+test('tracker queues playback writes until lexical rollup backfill settles', async () => {
+  const dbPath = makeDbPath();
+  let tracker: ImmersionTrackerService | null = null;
+  let startBackfill = (): void => {};
+  let releaseBackfill = (): void => {};
+  let markBackfillStarted = (): void => {};
+  const backfillStartGate = new Promise<void>((resolve) => {
+    startBackfill = resolve;
+  });
+  const heldBackfill = new Promise<void>((resolve) => {
+    releaseBackfill = resolve;
+  });
+  const backfillStarted = new Promise<void>((resolve) => {
+    markBackfillStarted = resolve;
+  });
+
+  try {
+    const setupDb = new Database(dbPath);
+    const { ensureSchema } = await import('./immersion-tracker/storage');
+    ensureSchema(setupDb);
+    setupDb
+      .prepare(
+        `UPDATE imm_rollup_state SET state_value = '0' WHERE state_key = 'lexical_daily_rollups_ready'`,
+      )
+      .run();
+    setupDb.close();
+
+    const Ctor = await loadTrackerCtor();
+    tracker = new Ctor(
+      { dbPath },
+      {
+        runLexicalRollupBackfillTask: async (workerDbPath) => {
+          await backfillStartGate;
+          const workerDb = new Database(workerDbPath);
+          try {
+            workerDb.exec('BEGIN IMMEDIATE');
+            markBackfillStarted();
+            await heldBackfill;
+            workerDb.exec('COMMIT');
+          } catch (error) {
+            try {
+              workerDb.exec('ROLLBACK');
+            } catch {
+              // Preserve the original worker failure.
+            }
+            throw error;
+          } finally {
+            workerDb.close();
+          }
+        },
+      },
+    );
+    tracker.handleMediaChange('https://example.com/backfill-test.mp4', 'Backfill Test');
+    startBackfill();
+    await backfillStarted;
+    tracker.recordCardsMined(1);
+
+    const privateApi = tracker as unknown as {
+      db: DatabaseSync;
+      queue: unknown[];
+      flushNow: () => void;
+      writeLock: { locked: boolean };
+    };
+    assert.equal(privateApi.writeLock.locked, true);
+    privateApi.flushNow();
+
+    assert.ok(privateApi.queue.length > 0);
+    assert.equal(
+      (
+        privateApi.db.prepare('SELECT COUNT(*) AS total FROM imm_session_events').get() as {
+          total: number;
+        }
+      ).total,
+      0,
+    );
+
+    releaseBackfill();
+    await waitForCondition(() => privateApi.queue.length === 0);
+    assert.equal(
+      (
+        privateApi.db.prepare('SELECT COUNT(*) AS total FROM imm_session_events').get() as {
+          total: number;
+        }
+      ).total,
+      1,
+    );
+  } finally {
+    releaseBackfill();
+    tracker?.destroy();
+    cleanupDbPath(dbPath);
+  }
+});
+
 test('startup backfills lifetime summaries when retained sessions exist but summary tables are empty', async () => {
   const dbPath = makeDbPath();
   let tracker: ImmersionTrackerService | null = null;
diff --git a/src/core/services/immersion-tracker-service.ts b/src/core/services/immersion-tracker-service.ts
index 56f53277..0cca853c 100644
--- a/src/core/services/immersion-tracker-service.ts
+++ b/src/core/services/immersion-tracker-service.ts
@@ -413,7 +413,10 @@ export class ImmersionTrackerService {
   private readonly monthlyRollupRetentionMs: number;
   private readonly vacuumIntervalMs: number;
   private readonly dbPath: string;
-  private readonly writeLock = { locked: false };
+  private readonly writeLock = {
+    locked: false,
+    reasons: new Set<'flush' | 'delete-maintenance' | 'lexical-rollup-backfill'>(),
+  };
   private readonly destroyDeleteMaintenanceRunner: () => void;
   private readonly runVocabularySummaryTask: (
     knownWords: ReadonlySet<string> | null,
@@ -471,10 +474,10 @@ export class ImmersionTrackerService {
       runTask: (task) => runDeleteMaintenanceTask(this.dbPath, task),
       onBusy: () => {
         this.requireWriteQueueDrained('delete maintenance');
-        this.writeLock.locked = true;
+        this.setWriteLock('delete-maintenance', true);
       },
       onIdle: () => {
-        this.writeLock.locked = false;
+        this.setWriteLock('delete-maintenance', false);
         if (!this.isDestroyed && this.queue.length > 0) this.scheduleFlush(0);
       },
     });
@@ -558,14 +561,6 @@ export class ImmersionTrackerService {
     this.db = new Database(this.dbPath);
     applyPragmas(this.db);
     ensureSchema(this.db);
-    if (!areLexicalDailyRollupsReady(this.db)) {
-      void this.runLexicalRollupBackfillTask().catch((error: unknown) => {
-        this.logger.warn(
-          'Lexical daily rollup backfill failed; it will retry on next startup',
-          error,
-        );
-      });
-    }
     const reconciledSessions = reconcileStaleActiveSessions(this.db);
     if (reconciledSessions > 0) {
       this.logger.info(
@@ -594,6 +589,7 @@ export class ImmersionTrackerService {
       }
     }
     this.preparedStatements = createTrackerPreparedStatements(this.db);
+    if (!areLexicalDailyRollupsReady(this.db)) this.startLexicalRollupBackfill();
     this.scheduleMaintenance();
     this.scheduleFlush();
   }
@@ -967,6 +963,31 @@ export class ImmersionTrackerService {
     }
   }
 
+  private setWriteLock(
+    reason: 'flush' | 'delete-maintenance' | 'lexical-rollup-backfill',
+    active: boolean,
+  ): void {
+    if (active) this.writeLock.reasons.add(reason);
+    else this.writeLock.reasons.delete(reason);
+    this.writeLock.locked = this.writeLock.reasons.size > 0;
+  }
+
+  private startLexicalRollupBackfill(): void {
+    this.requireWriteQueueDrained('lexical rollup backfill');
+    this.setWriteLock('lexical-rollup-backfill', true);
+    void this.runLexicalRollupBackfillTask()
+      .catch((error: unknown) => {
+        this.logger.warn(
+          'Lexical daily rollup backfill failed; it will retry on next startup',
+          error,
+        );
+      })
+      .finally(() => {
+        this.setWriteLock('lexical-rollup-backfill', false);
+        if (!this.isDestroyed && this.queue.length > 0) this.scheduleFlush(0);
+      });
+  }
+
   async reassignAnimeAnilist(
     animeId: number,
     info: {
@@ -2022,7 +2043,7 @@ export class ImmersionTrackerService {
     }
 
     const batch = this.queue.splice(0, Math.min(this.batchSize, this.queue.length));
-    this.writeLock.locked = true;
+    this.setWriteLock('flush', true);
     try {
       this.db.exec('BEGIN IMMEDIATE');
       for (const write of batch) {
@@ -2034,7 +2055,7 @@ export class ImmersionTrackerService {
       this.queue.unshift(...batch);
       this.logger.warn('Immersion tracker flush failed, retrying later', error as Error);
     } finally {
-      this.writeLock.locked = false;
+      this.setWriteLock('flush', false);
       this.flushScheduled = false;
       if (this.queue.length > 0) {
         this.scheduleFlush(this.flushIntervalMs);