diff --git a/server/tests/unit/db/repositories/AssistantAttachments.repository.test.ts b/server/tests/unit/db/repositories/AssistantAttachments.repository.test.ts
new file mode 100644
index 000000000..7047e62d8
--- /dev/null
+++ b/server/tests/unit/db/repositories/AssistantAttachments.repository.test.ts
@@ -0,0 +1,141 @@
+/**
+ * The files attached in a trip chat through their repository: an attachment
+ * is only reached in its own thread by the user who attached it, its text
+ * reaches the model only once it is shared, the first agreement's time stays,
+ * and the retention sweep finds, matches and drops rows by age and key.
+ */
+import { AssistantAttachments } from '../../../../src/db/entities/AssistantAttachments.entity';
+import { AssistantThreads } from '../../../../src/db/entities/AssistantThreads.entity';
+import type { AssistantAttachmentsRepository } from '../../../../src/db/repositories/AssistantAttachments.repository';
+import type { AssistantThreadsRepository } from '../../../../src/db/repositories/AssistantThreads.repository';
+import { createSnapshotTestDb } from '../../../helpers/db-mock';
+import { makeTripFile } from '../../../helpers/factories/files';
+import { makeTrip } from '../../../helpers/factories/trips';
+import { makeUser } from '../../../helpers/factories/users';
+import { resetTestDb } from '../../../helpers/test-db';
+import { createTestOrm, type TestOrm } from '../../../helpers/test-orm';
+
+import { afterAll, beforeAll, beforeEach, describe, expect, it } from 'vitest';
+
+const testDb = createSnapshotTestDb();
+let t: TestOrm;
+let attachments: AssistantAttachmentsRepository;
+let threads: AssistantThreadsRepository;
+
+beforeAll(async () => {
+  t = await createTestOrm(testDb);
+  attachments = t.repo(AssistantAttachments);
+  threads = t.repo(AssistantThreads);
+});
+beforeEach(() => {
+  resetTestDb(testDb);
+  t.clear();
+});
+afterAll(async () => {
+  await t.close();
+  testDb.close();
+});
+
+const AT = '2026-10-20 10:00:00';
+const LATER = '2026-10-21 10:00:00';
+const ID_A = '0b6c1f7e-3d2a-4c5b-9e8f-1a2b3c4d5e6f';
+const ID_B = '1c7d2a8f-4e3b-4d6c-8f9a-2b3c4d5e6f70';
+
+async function threadOf() {
+  const { user } = await makeUser(t);
+  const trip = await makeTrip(t, user.id);
+  const threadId = await threads.createThread(user.id, trip.id, 'Porto', AT);
+  return { userId: user.id, tripId: trip.id, threadId };
+}
+
+function attach(
+  at: { userId: number; tripId: number; threadId: number },
+  id: string,
+  over: { text?: string | null; createdAt?: string; storageKey?: string } = {},
+) {
+  return attachments.insertAttachment({
+    id,
+    threadId: at.threadId,
+    userId: at.userId,
+    tripId: at.tripId,
+    name: 'AirBnB Buchung.pdf',
+    mime: 'application/pdf',
+    size: 2048,
+    sha256: 'f'.repeat(64),
+    storageKey: over.storageKey ?? `assistant/${id}.pdf`,
+    text: over.text === undefined ? 'Check-in 14:00' : over.text,
+    textStatus: over.text === null ? 'empty' : 'ok',
+    createdAt: over.createdAt ?? AT,
+  });
+}
+
+describe('AssistantAttachmentsRepository', () => {
+  it('ASTATTREPO-001: an attachment is reached only in its own thread by the user who attached it', async () => {
+    const at = await threadOf();
+    const other = await threadOf();
+    await attach(at, ID_A);
+
+    const row = await attachments.findInThread(ID_A, at.threadId, at.userId);
+    expect(row).toMatchObject({ id: ID_A, name: 'AirBnB Buchung.pdf', text: 'Check-in 14:00', text_status: 'ok' });
+    expect(await attachments.findInThread(ID_A, other.threadId, at.userId)).toBeNull();
+    expect(await attachments.findInThread(ID_A, at.threadId, other.userId)).toBeNull();
+    expect(await attachments.findInThread(ID_B, at.threadId, at.userId)).toBeNull();
+  });
+
+  it('ASTATTREPO-002: a thread lists its attachments oldest first and without their text', async () => {
+    const at = await threadOf();
+    await attach(at, ID_B, { createdAt: LATER });
+    await attach(at, ID_A);
+
+    const listed = await attachments.listForThread(at.threadId, at.userId);
+    expect(listed.map((a) => a.id)).toEqual([ID_A, ID_B]);
+    expect(listed[0]).not.toHaveProperty('text');
+    expect(await attachments.listObjectsOfThread(at.threadId, at.userId)).toEqual(
+      expect.arrayContaining([
+        { id: ID_A, storage_key: `assistant/${ID_A}.pdf` },
+        { id: ID_B, storage_key: `assistant/${ID_B}.pdf` },
+      ]),
+    );
+  });
+
+  it('ASTATTREPO-003: a text reaches the model only once shared, and the first agreement keeps its time', async () => {
+    const at = await threadOf();
+    await attach(at, ID_A);
+    await attach(at, ID_B, { text: null });
+    expect(await attachments.listSharedTexts(at.threadId, at.userId)).toEqual([]);
+
+    expect(await attachments.markShared(ID_A, at.threadId, at.userId, AT)).toBe(true);
+    expect(await attachments.markShared(ID_A, at.threadId, at.userId, LATER)).toBe(false);
+    expect(await attachments.markShared(ID_B, at.threadId, at.userId, AT)).toBe(true);
+    expect((await attachments.findInThread(ID_A, at.threadId, at.userId))?.shared_at).toBe(AT);
+    // A shared attachment without text has nothing to send.
+    expect(await attachments.listSharedTexts(at.threadId, at.userId)).toEqual([{ id: ID_A, text: 'Check-in 14:00' }]);
+  });
+
+  it('ASTATTREPO-004: a kept attachment names its trip file', async () => {
+    const at = await threadOf();
+    await attach(at, ID_A);
+    const file = await makeTripFile(t, at.tripId);
+    await attachments.setFile(ID_A, file.id);
+    expect((await attachments.findInThread(ID_A, at.threadId, at.userId))?.file_id).toBe(file.id);
+  });
+
+  it('ASTATTREPO-005: the sweep finds old rows by age, matches known keys and drops rows by id', async () => {
+    const at = await threadOf();
+    await attach(at, ID_A);
+    await attach(at, ID_B, { createdAt: LATER });
+
+    expect(await attachments.listCreatedBefore(LATER, 10)).toEqual([
+      { id: ID_A, storage_key: `assistant/${ID_A}.pdf` },
+    ]);
+    expect(await attachments.listCreatedBefore('2026-10-22 00:00:00', 1)).toHaveLength(1);
+    expect(await attachments.listKnownKeys([`assistant/${ID_B}.pdf`, 'assistant/gone.pdf'])).toEqual([
+      `assistant/${ID_B}.pdf`,
+    ]);
+    expect(await attachments.listKnownKeys([])).toEqual([]);
+
+    expect(await attachments.deleteByIds([])).toBe(0);
+    expect(await attachments.deleteByIds([ID_A, 'not-there'])).toBe(1);
+    expect(await attachments.listForThread(at.threadId, at.userId)).toHaveLength(1);
+  });
+});