fix(config-backup): the retention fallback follows the folder, a clock-ahead snapshot cannot make every pass write a copy

test/config-backup.test.ts

@@ -465,6 +465,32 @@ describe('diffConfigBackups', () => {
   });
 });
 
+describe('createConfigBackup: a snapshot dated ahead of the clock', () => {
+  it('is not written again on every pass once the clock is corrected', () => {
+    put('settings.json', '{"v":0}');
+    createConfigBackup({ dataDir: data, backupDir: backups, reason: 'auto', now: T0 });
+    put('settings.json', '{"v":1}');
+    const ahead = createConfigBackup({ dataDir: data, backupDir: backups, reason: 'auto', now: T0 + 2 * 3_600_000 });
+    expect(ahead.status).toBe('created');
+    put('settings.json', '{"v":2}'); // the clock is back at T0 + 1 minute
+    const corrected = createConfigBackup({ dataDir: data, backupDir: backups, reason: 'auto', now: T0 + 60_000 });
+    expect(corrected.status).toBe('created');
+    const [newest, second] = listConfigBackups(backups);
+    expect(newest.id).toBe((corrected as { id: string }).id); // dated no earlier than the one before it
+    expect(newest.createdAt).toBeGreaterThan(second.createdAt);
+    for (let i = 0; i < 24; i++) {
+      const r = createConfigBackup({
+        dataDir: data,
+        backupDir: backups,
+        reason: 'auto',
+        now: T0 + 120_000 + i * 300_000,
+      });
+      expect(r.status, `pass ${i}`).toBe('unchanged');
+    }
+    expect(listConfigBackups(backups)).toHaveLength(3);
+  });
+});
+
 describe('instances sharing one backup folder', () => {
   it('keeps to its own snapshots: no churn, no prune, no restore of the other', () => {
     const other = join(root, 'other-data');
@@ -608,6 +634,12 @@ describe('restore trusts only what this module wrote', () => {
     put('settings.json', JSON.stringify({ displayName: 'new', configBackupDir: '/new', configBackupKeepDays: 7 }));
     restoreConfigBackup({ dataDir: data, backupDir: backups, id });
     const after = JSON.parse(readFileSync(join(data, 'settings.json'), 'utf8'));
-    expect(after).toEqual({ displayName: 'old', configBackupDir: '/new', configBackupKeepDays: 7 });
+    // the folder and days follow the live file; the live file has no keep count (reset), so the backup's 5 stays
+    expect(after).toEqual({
+      displayName: 'old',
+      configBackupDir: '/new',
+      configBackupKeepCount: 5,
+      configBackupKeepDays: 7,
+    });
   });
 });

test/routes/config-backup-routes.test.ts

@@ -250,6 +250,39 @@ describe('retention survives an unreadable or reset settings.json', () => {
     }
   );
 
+  it("re-entering a custom folder after a reset finds that folder's recorded retention", async () => {
+    const folder = join(custom, 'kept');
+    settings({ configBackupDir: folder, configBackupKeepCount: 100, configBackupKeepDays: 0 });
+    for (let i = 0; i < 30; i++) {
+      createConfigBackup({
+        dataDir: getDataDir(),
+        backupDir: folder,
+        reason: 'auto',
+        force: true,
+        now: BASE + i * DAY,
+        keepCount: 100,
+        keepDays: 0,
+      });
+    }
+    writeFileSync(SETTINGS_PATH, '{}'); // the reset drops the folder too
+    await runConfigBackup('auto'); // goes to the default folder, which holds none of those manifests
+    // the user enters the folder again and saves; the form no longer sends retention it only displayed
+    writeFileSync(SETTINGS_PATH, JSON.stringify({ configBackupDir: folder, configBackupEnabled: true }));
+    const { app } = await createRouteTestHarness(registerConfigBackupRoutes);
+    const reported = (await app.inject({ method: 'GET', url: '/api/config-backups' })).json().data.settings;
+    expect(reported).toMatchObject({ keepCount: 100, keepDays: 0 });
+    const out = await runConfigBackup('auto');
+    expect(out?.removed).toEqual([]);
+    expect(listConfigBackups(folder).length).toBeGreaterThanOrEqual(30);
+  });
+
+  it('only the retention key the file lacks falls back to the recorded one', async () => {
+    seed();
+    writeFileSync(SETTINGS_PATH, JSON.stringify({ configBackupKeepDays: 3650 }));
+    await runConfigBackup('auto');
+    expect(listConfigBackups(dir())).toHaveLength(31); // keepCount 100 from the manifests, not the default 20
+  });
+
   it('a settings.json that sets the retention still wins', async () => {
     seed();
     writeFileSync(SETTINGS_PATH, JSON.stringify({ configBackupKeepCount: 5, configBackupKeepDays: 0 }));