diff --git a/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.spec.ts b/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.spec.ts
new file mode 100644
index 00000000..928702b3
--- /dev/null
+++ b/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.spec.ts
@@ -0,0 +1,80 @@
+import { EmbeddingIndexerService } from './embedding-indexer.service';
+import { PageRepo } from '@docmost/db/repos/page/page.repo';
+import { PageEmbeddingRepo } from '@docmost/db/repos/ai-chat/page-embedding.repo';
+import { KyselyDB } from '@docmost/db/types/kysely.types';
+import { AiService } from '../../../integrations/ai/ai.service';
+
+/**
+ * Unit tests for EmbeddingIndexerService.reindexWorkspace's batch control flow.
+ *
+ * The constructor body only stores its deps, so the service can be unit-built
+ * with lightweight mocks — no Nest module graph. We stub only the methods that
+ * reindexWorkspace actually touches:
+ *   - aiService.getEmbeddingModel -> a model string so the up-front configured
+ *     check passes,
+ *   - pageRepo.getIdsByWorkspace -> three page ids,
+ *   - service.reindexPage -> spied per test to drive the per-page outcome.
+ *
+ * The point under test is the catch block: a FATAL provider error (auth/billing)
+ * must abort the whole batch (re-throw, stop iterating), while a non-fatal error
+ * keeps per-page isolation (failed++, continue to the next page).
+ */
+describe('EmbeddingIndexerService.reindexWorkspace fail-fast', () => {
+  const WORKSPACE_ID = 'ws-1';
+
+  function makeService() {
+    const pageRepo = {
+      getIdsByWorkspace: jest.fn().mockResolvedValue(['p1', 'p2', 'p3']),
+    };
+    const pageEmbeddingRepo = {};
+    const aiService = {
+      getEmbeddingModel: jest.fn().mockResolvedValue('some-model'),
+    };
+    const db = {};
+
+    const service = new EmbeddingIndexerService(
+      pageRepo as unknown as PageRepo,
+      pageEmbeddingRepo as unknown as PageEmbeddingRepo,
+      aiService as unknown as AiService,
+      db as unknown as KyselyDB,
+    );
+    return { service, pageRepo, aiService };
+  }
+
+  it('aborts after the first page on a FATAL (401) provider error', async () => {
+    const { service } = makeService();
+    // A 401 "User not found" recurs identically on every page -> must abort.
+    const reindexPage = jest
+      .spyOn(service, 'reindexPage')
+      .mockRejectedValue({ statusCode: 401, message: 'User not found' });
+
+    await expect(service.reindexWorkspace(WORKSPACE_ID)).rejects.toMatchObject({
+      statusCode: 401,
+    });
+    // Aborted on the first page: pages 2 and 3 were never attempted.
+    expect(reindexPage).toHaveBeenCalledTimes(1);
+  });
+
+  it('keeps per-page isolation on a non-fatal error (plain Error, no statusCode)', async () => {
+    const { service } = makeService();
+    // No statusCode -> non-fatal -> isolate per page and continue.
+    const reindexPage = jest
+      .spyOn(service, 'reindexPage')
+      .mockRejectedValue(new Error('boom'));
+
+    // Resolves (does not throw) even though every page failed.
+    await expect(service.reindexWorkspace(WORKSPACE_ID)).resolves.toBeUndefined();
+    // All three pages were attempted despite the failures.
+    expect(reindexPage).toHaveBeenCalledTimes(3);
+  });
+
+  it('processes every page on the all-success path', async () => {
+    const { service } = makeService();
+    const reindexPage = jest
+      .spyOn(service, 'reindexPage')
+      .mockResolvedValue(undefined);
+
+    await expect(service.reindexWorkspace(WORKSPACE_ID)).resolves.toBeUndefined();
+    expect(reindexPage).toHaveBeenCalledTimes(3);
+  });
+});
diff --git a/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.ts b/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.ts
index 3a08c114..5b49d92d 100644
--- a/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.ts
+++ b/apps/server/src/core/ai-chat/embedding/embedding-indexer.service.ts
@@ -10,7 +10,10 @@ import { InjectKysely } from 'nestjs-kysely';
 import { executeTx } from '@docmost/db/utils';
 import { AiService } from '../../../integrations/ai/ai.service';
 import { AiEmbeddingNotConfiguredException } from '../../../integrations/ai/ai-embedding-not-configured.exception';
-import { describeProviderError } from '../../../integrations/ai/ai-error.util';
+import {
+  describeProviderError,
+  isFatalProviderError,
+} from '../../../integrations/ai/ai-error.util';
 import { jsonToText } from '../../../collaboration/collaboration.util';
 
 // NOTE: the `page_embeddings.embedding` column is now dimension-agnostic
@@ -229,8 +232,19 @@ export class EmbeddingIndexerService {
           );
         }
       } catch (err) {
-        // Per-page isolation: one failure (incl. an embedding timeout) must not
-        // abort the whole batch.
+        // A fatal provider error (invalid/missing key, no credits) recurs
+        // identically on EVERY remaining page. Abort the whole batch instead of
+        // issuing hundreds of doomed requests against the provider.
+        if (isFatalProviderError(err)) {
+          this.logger.error(
+            `reindexWorkspace: aborting at [${position}/${total}] for workspace ` +
+              `${workspaceId} — fatal provider error, remaining pages would fail ` +
+              `identically: ${describeProviderError(err)}`,
+          );
+          throw err;
+        }
+        // Per-page isolation: one non-fatal failure (incl. an embedding timeout)
+        // must not abort the whole batch.
         failed++;
         this.logger.error(
           `reindexWorkspace: [${position}/${total}] failed to reindex page ${pageId} ` +
diff --git a/apps/server/src/integrations/ai/ai-error.util.spec.ts b/apps/server/src/integrations/ai/ai-error.util.spec.ts
index 5828e6bd..e11f6160 100644
--- a/apps/server/src/integrations/ai/ai-error.util.spec.ts
+++ b/apps/server/src/integrations/ai/ai-error.util.spec.ts
@@ -1,4 +1,4 @@
-import { describeProviderError } from './ai-error.util';
+import { describeProviderError, isFatalProviderError } from './ai-error.util';
 
 /**
  * Unit tests for describeProviderError: the shared formatter used both for the
@@ -129,3 +129,58 @@ describe('describeProviderError', () => {
     expect(describeProviderError({ foo: 'bar' } as never)).toBe('Unknown error');
   });
 });
+
+/**
+ * Unit tests for isFatalProviderError: the predicate that decides whether a
+ * provider error should abort an ENTIRE batch (bulk reindex) rather than be
+ * isolated per item. Authentication (401/403) and billing (402) recur
+ * identically on every request and are fatal; a 429 rate limit is transient and
+ * intentionally NOT fatal (handled by per-item isolation / backoff). Anything
+ * without a recognised numeric statusCode is non-fatal.
+ */
+describe('isFatalProviderError', () => {
+  it('returns true for authentication errors (401/403)', () => {
+    expect(isFatalProviderError({ statusCode: 401, message: 'User not found' })).toBe(
+      true,
+    );
+    expect(isFatalProviderError({ statusCode: 403, message: 'Forbidden' })).toBe(
+      true,
+    );
+  });
+
+  it('returns true for a billing error (402)', () => {
+    expect(
+      isFatalProviderError({ statusCode: 402, message: 'Payment Required' }),
+    ).toBe(true);
+  });
+
+  it('returns false for a 429 rate limit (transient, intentionally non-fatal)', () => {
+    expect(
+      isFatalProviderError({ statusCode: 429, message: 'Too Many Requests' }),
+    ).toBe(false);
+  });
+
+  it('returns false for a 500 server error', () => {
+    expect(isFatalProviderError({ statusCode: 500, message: 'Server error' })).toBe(
+      false,
+    );
+  });
+
+  it('returns false for an embedding timeout (plain Error, no statusCode)', () => {
+    expect(
+      isFatalProviderError(new Error('Embedding request timed out after 60000ms')),
+    ).toBe(false);
+  });
+
+  it('returns false for non-object errors (null/undefined/string/number)', () => {
+    expect(isFatalProviderError(null)).toBe(false);
+    expect(isFatalProviderError(undefined)).toBe(false);
+    expect(isFatalProviderError('boom')).toBe(false);
+    // A bare numeric 401 is NOT an object carrying a statusCode field.
+    expect(isFatalProviderError(401)).toBe(false);
+  });
+
+  it('returns false for an object without a statusCode', () => {
+    expect(isFatalProviderError({})).toBe(false);
+  });
+});
diff --git a/apps/server/src/integrations/ai/ai-error.util.ts b/apps/server/src/integrations/ai/ai-error.util.ts
index 2d24ab47..2ac7d105 100644
--- a/apps/server/src/integrations/ai/ai-error.util.ts
+++ b/apps/server/src/integrations/ai/ai-error.util.ts
@@ -47,6 +47,20 @@ export function describeProviderError(
   return label ? `${label} — ${detail}` : detail;
 }
 
+/**
+ * Whether a provider error is FATAL for an ENTIRE batch operation rather than
+ * specific to one item. Authentication (401/403 — invalid or missing API key)
+ * and billing (402 — insufficient credits/quota) failures recur identically on
+ * every subsequent request, so a bulk reindex should abort immediately instead
+ * of issuing hundreds of doomed calls. A 429 rate limit is intentionally NOT
+ * fatal: it is transient and better handled by per-item isolation / backoff.
+ */
+export function isFatalProviderError(err: unknown): boolean {
+  if (typeof err !== 'object' || err === null) return false;
+  const status = (err as { statusCode?: number }).statusCode;
+  return status === 401 || status === 403 || status === 402;
+}
+
 // Map a small set of well-known provider HTTP statuses to a clear,
 // human-readable cause. Returns null for anything else so the existing
 // "<status>: <message> | response body: …" output is preserved unchanged.