fix(anilist): dedupe failures during retry cooldown and block dead-lette

- Ignore markFailure calls while an item is still within its retry backoff window
- Prevent enqueue from re-adding keys already in the dead-letter queue

changes/anilist-retry-dedupe.md

@@ -0,0 +1,4 @@
+type: fixed
+area: anilist
+
+- Prevent repeated missing-token checks from rapidly exhausting AniList retry attempts or duplicating dead-letter entries for the same episode.

src/core/services/anilist/anilist-update-queue.test.ts

@@ -71,7 +71,7 @@ test('anilist update queue applies retry backoff and dead-letter', () => {
   assert.equal((pendingPayload.pending[0]?.nextAttemptAt ?? now) - now, 30_000);
 
   for (let attempt = 2; attempt <= 8; attempt += 1) {
-    queue.markFailure('k2', `fail-${attempt}`, now);
+    queue.markFailure('k2', `fail-${attempt}`, now + attempt * 6 * 60 * 60 * 1000);
   }
 
   const snapshot = queue.getSnapshot(Number.MAX_SAFE_INTEGER);
@@ -83,6 +83,52 @@ test('anilist update queue applies retry backoff and dead-letter', () => {
   );
 });
 
+test('anilist update queue ignores duplicate failures while retry is cooling down', () => {
+  const queueFile = createTempQueueFile();
+  const loggerState = createLogger();
+  const queue = createAnilistUpdateQueue(queueFile, loggerState.logger);
+
+  const now = 1_700_000 * 1_000_000;
+  queue.enqueue('k2', 'Backoff Demo', 2);
+  queue.markFailure('k2', 'fail-1', now);
+
+  for (let attempt = 2; attempt <= 12; attempt += 1) {
+    queue.markFailure('k2', `duplicate-${attempt}`, now + attempt);
+  }
+
+  const payload = JSON.parse(fs.readFileSync(queueFile, 'utf-8')) as {
+    pending: Array<{ attemptCount: number; lastError: string | null }>;
+    deadLetter: Array<unknown>;
+  };
+  assert.equal(payload.pending[0]?.attemptCount, 1);
+  assert.equal(payload.pending[0]?.lastError, 'fail-1');
+  assert.deepEqual(queue.getSnapshot(Number.MAX_SAFE_INTEGER), {
+    pending: 1,
+    ready: 1,
+    deadLetter: 0,
+  });
+});
+
+test('anilist update queue does not re-enqueue dead-lettered keys', () => {
+  const queueFile = createTempQueueFile();
+  const loggerState = createLogger();
+  const queue = createAnilistUpdateQueue(queueFile, loggerState.logger);
+
+  const now = 1_700_000 * 1_000_000;
+  queue.enqueue('k4', 'Dead Letter Demo', 4);
+  for (let attempt = 1; attempt <= 8; attempt += 1) {
+    queue.markFailure('k4', `fail-${attempt}`, now + attempt * 6 * 60 * 60 * 1000);
+  }
+
+  queue.enqueue('k4', 'Dead Letter Demo', 4);
+
+  assert.deepEqual(queue.getSnapshot(Number.MAX_SAFE_INTEGER), {
+    pending: 0,
+    ready: 0,
+    deadLetter: 1,
+  });
+});
+
 test('anilist update queue persists and reloads from disk', () => {
   const queueFile = createTempQueueFile();
   const loggerState = createLogger();

src/core/services/anilist/anilist-update-queue.ts

@@ -108,7 +108,8 @@ export function createAnilistUpdateQueue(
 
   return {
     enqueue(key: string, title: string, episode: number, season: number | null = null): void {
-      const existing = pending.find((item) => item.key === key);
+      const existing =
+        pending.find((item) => item.key === key) || deadLetter.find((item) => item.key === key);
       if (existing) {
         return;
       }
@@ -147,6 +148,9 @@ export function createAnilistUpdateQueue(
       if (!item) {
         return;
       }
+      if (item.attemptCount > 0 && item.nextAttemptAt > nowMs) {
+        return;
+      }
       item.attemptCount += 1;
       item.lastError = reason;
       if (item.attemptCount >= MAX_ATTEMPTS) {