README.md

@@ -133,6 +133,9 @@ export STACKCHAIN_DASHBOARD_SESSION_SECRET='<independent-cookie-signing-secret>'
 export STACKCHAIN_SESSION_DB='/var/lib/stackchain-dashboard/sessions.sqlite3'
 # Optional; defaults to eight hours.
 export STACKCHAIN_DASHBOARD_SESSION_TTL_SECONDS=28800
+# Optional; explicit pointer, keyboard, or touch activity renews this idle window.
+# Background polling and queued delivery do not. Defaults to 15 minutes.
+export STACKCHAIN_DASHBOARD_IDLE_TIMEOUT_SECONDS=900
 # Optional sign-in throttle: five failures per five minutes, up to 10,000 sources.
 export STACKCHAIN_LOGIN_MAX_FAILURES=5
 export STACKCHAIN_LOGIN_WINDOW_SECONDS=300
@@ -166,8 +169,9 @@ storage shared by all dashboard workers. Operators name a device at sign-in and
 open **Active devices** to review creation/expiry times, identify the current device,
 and revoke one remote session without interrupting other trusted devices. The API
 exposes only independent management IDs and bounded labels—never cookie values,
-session hashes, CSRF proofs, or source addresses. Existing two-column registries are
-migrated in place and their live sessions remain valid.
+session hashes, CSRF proofs, or source addresses. The registry also stores each
+session's last explicit activity. Existing two-column registries are migrated in
+place, their live sessions remain valid, and their idle clock starts at migration.
 
 High-impact actions—merging a pull request, closing an assigned issue, revoking a
 remote device, or signing out every device—require the operator access token again.
@@ -177,7 +181,12 @@ first use. Expired, replayed, cross-session, and target-substituted grants fail
 Gitea or session state is changed. The browser preserves the pending request and
 retries it once after the built-in mobile/keyboard-accessible authorization prompt.
 
-If an active session expires, the first authenticated API rejection replaces the
+After 15 minutes without pointer, keyboard, or touch activity (configurable through
+`STACKCHAIN_DASHBOARD_IDLE_TIMEOUT_SECONDS`), the server rejects the session even if
+polling or background delivery continued. The dashboard locks and background outbox
+delivery pauses, but drafts, Today/Later state, queued mutations, and caches remain on
+the device; signing in resumes the existing account-bound work. If an active session
+expires, the first authenticated API rejection replaces the
 dashboard with sign-in and explains that private drafts remain on the device; signing
 in again resumes account-bound queued delivery. Expiry recovery does not clear offline
 state. A selectively or globally revoked device instead receives a bounded revocation

frontend/login.js

@@ -35,6 +35,10 @@
       status.textContent = 'Your session expired. Private drafts remain on this device. Sign in to continue.';
       return;
     }
+    if (reason === 'session-idle') {
+      status.textContent = 'Stackchain locked after inactivity. Your drafts and queued work are still on this device. Sign in to resume.';
+      return;
+    }
     if (reason !== 'session-revoked') return;
     button.disabled = true;
     status.textContent = 'This device was remotely signed out. Clearing Stackchain private data…';

frontend/service-worker.js

@@ -115,6 +115,11 @@ async function purgeRevokedSessionData() {
   clients.forEach(client => client.postMessage?.({ type: 'stackchain-session-revoked' }));
 }
 
+async function notifyIdleSession() {
+  const clients = await self.clients.matchAll({ type: 'window', includeUncontrolled: true });
+  clients.forEach(client => client.postMessage?.({ type: 'stackchain-session-idle' }));
+}
+
 async function storeOfflineLease(expiresAt) {
   if (!Number.isInteger(expiresAt) || expiresAt <= 0) return;
   const cache = await caches.open(CACHE);
@@ -177,6 +182,9 @@ async function fetchJson(url, options = {}) {
     if (response.status === 401 && code === 'session_revoked') {
       await purgeRevokedSessionData();
     }
+    if (response.status === 401 && code === 'session_idle') {
+      await notifyIdleSession();
+    }
     const error = new Error(payload.error || payload.detail?.message || payload.detail || 'Background issue delivery failed.');
     error.status = response.status;
     error.code = code;

frontend/session.js

@@ -15,6 +15,7 @@
       serviceWorker: root.navigator?.serviceWorker,
       MessageChannel: root.MessageChannel,
       location: root.location,
+      addActivityListener: (type, listener, options) => root.addEventListener(type, listener, options),
       confirmAction: message => root.confirm(message),
       promptAuthorization: details => root.prompt(
         `Confirm ${String(details.action || 'this action').replaceAll('_', ' ')} by entering your dashboard access token.`,
@@ -27,6 +28,7 @@
     });
     root.fetch = boundary.fetch;
     const attach = () => {
+      boundary.startActivityHeartbeat();
       const button = root.document.getElementById('sign-out');
       if (button) button.addEventListener('click', () => boundary.signOut());
       const allDevicesButton = root.document.getElementById('sign-out-all');
@@ -91,16 +93,19 @@
     root.stackchainSession = boundary;
   }
 })(typeof window !== 'undefined' ? window : this, function createSessionBoundary({
-  cookie, origin, base, fetchImpl, localStorage, sessionStorage, indexedDB, caches, serviceWorker, MessageChannel, location, confirmAction,
+  cookie, origin, base, fetchImpl, localStorage, sessionStorage, indexedDB, caches, serviceWorker, MessageChannel, location, confirmAction, addActivityListener,
   promptAuthorization = () => null,
   onExpired = () => {},
   onClearError = () => {},
   requestTimeoutMs = 15000,
+  activityHeartbeatIntervalMs = 60000,
   now = () => Date.now(),
   setTimer = (callback, delay) => setTimeout(callback, delay),
 }) {
   const SAFE_METHODS = new Set(['GET', 'HEAD', 'OPTIONS']);
   let expirationStarted = false;
+  let lastActivityHeartbeatAt = Number.NEGATIVE_INFINITY;
+  let activityHeartbeat = null;
 
   async function handleRemoteRevocation() {
     if (expirationStarted) return;
@@ -117,10 +122,19 @@
     location.replace(base + 'login?reason=session-expired');
   }
 
+  function handleSessionIdle() {
+    if (expirationStarted) return;
+    expirationStarted = true;
+    location.replace(base + 'login?reason=session-idle');
+  }
+
   async function handleServiceWorkerMessage(event) {
     if (event?.data?.type === 'stackchain-session-revoked') {
       await handleRemoteRevocation();
     }
+    if (event?.data?.type === 'stackchain-session-idle') {
+      handleSessionIdle();
+    }
     if (event?.data?.type === 'stackchain-session-expired') {
       await handleSessionExpiry();
     }
@@ -253,6 +267,9 @@
       if (payload.code === 'session_revoked') {
         expirationStarted = false;
         await handleRemoteRevocation();
+      } else if (payload.code === 'session_idle') {
+        expirationStarted = false;
+        handleSessionIdle();
       } else {
         expirationStarted = false;
         await handleSessionExpiry();
@@ -261,6 +278,27 @@
     return response;
   }
 
+  function recordActivity() {
+    const current = now();
+    if (
+      expirationStarted
+      || activityHeartbeat
+      || current - lastActivityHeartbeatAt < activityHeartbeatIntervalMs
+    ) return Promise.resolve(false);
+    lastActivityHeartbeatAt = current;
+    activityHeartbeat = sessionFetch(base + 'api/v1/session/activity', { method: 'POST' })
+      .then(response => response.ok)
+      .catch(() => false)
+      .finally(() => { activityHeartbeat = null; });
+    return activityHeartbeat;
+  }
+
+  function startActivityHeartbeat() {
+    ['pointerdown', 'keydown', 'touchstart'].forEach(type => {
+      addActivityListener?.(type, recordActivity, { passive: true });
+    });
+  }
+
   async function refreshOfflineLease() {
     try {
       const response = await sessionFetch(base + 'api/v1/session');
@@ -391,5 +429,7 @@
     handleServiceWorkerMessage,
     refreshOfflineLease,
     resumeQueuedWork,
+    recordActivity,
+    startActivityHeartbeat,
   };
 });

src/dashboard_auth.py

@@ -18,6 +18,7 @@ from src.session_store import SessionStore, SessionStoreError
 SESSION_COOKIE = "stackchain_session"
 CSRF_COOKIE = "stackchain_csrf"
 DEFAULT_TTL_SECONDS = 8 * 60 * 60
+DEFAULT_IDLE_TIMEOUT_SECONDS = 15 * 60
 STEP_UP_TTL_SECONDS = 90
 MIN_SECRET_LENGTH = 24
 OPERATOR_MODE = "operator"
@@ -96,6 +97,18 @@ def _session_store(now: int | None = None) -> SessionStore:
     return SessionStore(database, clock=current)
 
 
+def idle_timeout_seconds() -> int:
+    return max(
+        1,
+        int(
+            os.getenv(
+                "STACKCHAIN_DASHBOARD_IDLE_TIMEOUT_SECONDS",
+                str(DEFAULT_IDLE_TIMEOUT_SECONDS),
+            )
+        ),
+    )
+
+
 def issue_session(
     now: int | None = None, *, device_label: str = "This device"
 ) -> tuple[str, Session]:
@@ -146,7 +159,14 @@ def verify_session_with_reason(
         or not session.csrf
     ):
         return SessionVerification(None)
-    if not _session_store(now).is_active(session.session_id, session.expires_at):
+    status = _session_store(now).status(
+        session.session_id,
+        session.expires_at,
+        idle_timeout_seconds=idle_timeout_seconds(),
+    )
+    if status == "idle":
+        return SessionVerification(None, "session_idle")
+    if status != "active":
         return SessionVerification(None, "session_revoked")
     return SessionVerification(session)
 
@@ -167,6 +187,15 @@ async def active_devices(session: Session):
     return await asyncio.to_thread(_session_store().list_active, session.session_id)
 
 
+async def touch_session(session: Session) -> bool:
+    return await asyncio.to_thread(
+        _session_store().touch,
+        session.session_id,
+        session.expires_at,
+        idle_timeout_seconds=idle_timeout_seconds(),
+    )
+
+
 async def revoke_managed_session(management_id: str) -> bool:
     return await asyncio.to_thread(_session_store().revoke_managed, management_id)
 

src/main.py

@@ -670,18 +670,19 @@ async def require_operator_session(request: Request, call_next):
     if not public and session is None:
         if path.startswith("/api/"):
             payload = {"detail": "Authentication required"}
-            if session_reason == "session_revoked":
+            if session_reason in {"session_revoked", "session_idle"}:
                 payload["code"] = session_reason
             return JSONResponse(
                 payload,
                 status_code=401,
                 headers={"Cache-Control": "no-store"},
             )
-        login_redirect = (
-            "login?reason=session-revoked"
-            if session_reason == "session_revoked"
-            else _share_target_login_redirect(request)
-        )
+        if session_reason == "session_revoked":
+            login_redirect = "login?reason=session-revoked"
+        elif session_reason == "session_idle":
+            login_redirect = "login?reason=session-idle"
+        else:
+            login_redirect = _share_target_login_redirect(request)
         return RedirectResponse(
             login_redirect,
             status_code=303,
@@ -937,6 +938,29 @@ async def session_status(request: Request):
     return payload
 
 
+@app.post("/api/v1/session/activity")
+async def record_session_activity(request: Request):
+    session = request.state.dashboard_session
+    try:
+        active = await dashboard_auth.touch_session(session)
+    except dashboard_auth.SessionStoreError:
+        return JSONResponse(
+            {"detail": "Session registry is temporarily unavailable"},
+            status_code=503,
+            headers={"Cache-Control": "no-store"},
+        )
+    if not active:
+        return JSONResponse(
+            {"detail": "Authentication required"},
+            status_code=401,
+            headers={"Cache-Control": "no-store"},
+        )
+    return {
+        "active": True,
+        "idle_expires_at": int(time.time()) + dashboard_auth.idle_timeout_seconds(),
+    }
+
+
 def _today_store() -> TodayStore:
     return TodayStore(
         os.getenv("STACKCHAIN_TODAY_DB", str(_state_dir / "today.sqlite3")), limit=5

src/session_store.py

@@ -58,7 +58,8 @@ class SessionStore:
                         expires_at INTEGER NOT NULL,
                         management_id TEXT,
                         device_label TEXT,
-                        created_at INTEGER
+                        created_at INTEGER,
+                        last_active_at INTEGER
                     )
                     """
                 )
@@ -84,6 +85,7 @@ class SessionStore:
                     "management_id": "TEXT",
                     "device_label": "TEXT",
                     "created_at": "INTEGER",
+                    "last_active_at": "INTEGER",
                 }
                 for name, column_type in additions.items():
                     if name not in columns:
@@ -102,6 +104,10 @@ class SessionStore:
                     "UPDATE active_sessions SET created_at = ? WHERE created_at IS NULL",
                     (int(self.clock()),),
                 )
+                connection.execute(
+                    "UPDATE active_sessions SET last_active_at = ? WHERE last_active_at IS NULL",
+                    (int(self.clock()),),
+                )
                 connection.execute(
                     "CREATE UNIQUE INDEX IF NOT EXISTS active_sessions_management_id "
                     "ON active_sessions(management_id)"
@@ -122,14 +128,15 @@ class SessionStore:
                 )
                 connection.execute(
                     "INSERT INTO active_sessions("
-                    "session_hash, expires_at, management_id, device_label, created_at"
-                    ") VALUES (?, ?, ?, ?, ?)",
+                    "session_hash, expires_at, management_id, device_label, created_at, last_active_at"
+                    ") VALUES (?, ?, ?, ?, ?, ?)",
                     (
                         self._digest(session_id),
                         expires_at,
                         secrets.token_urlsafe(18),
                         label,
                         now,
+                        now,
                     ),
                 )
         except (OSError, sqlite3.Error) as exc:
@@ -147,6 +154,55 @@ class SessionStore:
             raise SessionStoreError("Session registry is temporarily unavailable") from exc
         return row is not None and row[0] == expires_at and expires_at > now
 
+    def status(
+        self, session_id: str, expires_at: int, *, idle_timeout_seconds: int
+    ) -> str:
+        now = int(self.clock())
+        query = (
+            "SELECT expires_at, last_active_at FROM active_sessions "
+            "WHERE session_hash = ?"
+        )
+        parameters = (self._digest(session_id),)
+        try:
+            try:
+                with self._connect() as connection:
+                    row = connection.execute(query, parameters).fetchone()
+            except sqlite3.OperationalError as exc:
+                if "no such column: last_active_at" not in str(exc):
+                    raise
+                with self._connect(initialize=True) as connection:
+                    row = connection.execute(query, parameters).fetchone()
+        except (OSError, sqlite3.Error) as exc:
+            raise SessionStoreError("Session registry is temporarily unavailable") from exc
+        if row is None or row[0] != expires_at or expires_at <= now:
+            return "revoked"
+        if row[1] + max(1, idle_timeout_seconds) <= now:
+            return "idle"
+        return "active"
+
+    def touch(
+        self, session_id: str, expires_at: int, *, idle_timeout_seconds: int
+    ) -> bool:
+        now = int(self.clock())
+        try:
+            with self._connect() as connection:
+                cursor = connection.execute(
+                    "UPDATE active_sessions SET last_active_at = ? "
+                    "WHERE session_hash = ? AND expires_at = ? AND expires_at > ? "
+                    "AND last_active_at + ? > ?",
+                    (
+                        now,
+                        self._digest(session_id),
+                        expires_at,
+                        now,
+                        max(1, idle_timeout_seconds),
+                        now,
+                    ),
+                )
+                return cursor.rowcount == 1
+        except (OSError, sqlite3.Error) as exc:
+            raise SessionStoreError("Session registry is temporarily unavailable") from exc
+
     def revoke(self, session_id: str) -> None:
         try:
             with self._connect(initialize=True) as connection:

tests/test_dashboard_auth.py

@@ -1,4 +1,5 @@
 import asyncio
+import sqlite3
 import time
 from urllib.parse import parse_qs, urlsplit
 
@@ -245,10 +246,14 @@ async def test_session_status_reuses_the_middleware_validation(access_control, m
         lookups = 0
 
         class CountingStore:
-            def is_active(self, session_id, expires_at):
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
                 nonlocal lookups
                 lookups += 1
-                return original_store.is_active(session_id, expires_at)
+                return original_store.status(
+                    session_id,
+                    expires_at,
+                    idle_timeout_seconds=idle_timeout_seconds,
+                )
 
         monkeypatch.setattr(main.dashboard_auth, "_session_store", lambda now=None: CountingStore())
         response = await client.get("/api/v1/session")
@@ -291,6 +296,52 @@ async def test_anonymous_session_status_discloses_no_offline_lease(access_contro
     assert response.headers["cache-control"] == "no-store"
 
 
+@pytest.mark.anyio
+async def test_idle_session_is_rejected_with_distinct_api_and_page_recovery(access_control, monkeypatch):
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_IDLE_TIMEOUT_SECONDS", "900")
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="https://test") as client:
+        await client.post(
+            "/api/v1/session", json={"access_token": "correct horse battery staple"}
+        )
+        with sqlite3.connect(main.dashboard_auth._session_store().path) as connection:
+            connection.execute(
+                "UPDATE active_sessions SET last_active_at = ?", (int(time.time()) - 900,)
+            )
+
+        api_response = await client.get("/api/v1/session")
+        page_response = await client.get("/")
+
+    assert api_response.status_code == 401
+    assert api_response.json() == {
+        "detail": "Authentication required",
+        "code": "session_idle",
+    }
+    assert page_response.status_code == 303
+    assert page_response.headers["location"] == "login?reason=session-idle"
+
+
+@pytest.mark.anyio
+async def test_activity_heartbeat_extends_the_server_idle_deadline(access_control, monkeypatch):
+    monkeypatch.setenv("STACKCHAIN_DASHBOARD_IDLE_TIMEOUT_SECONDS", "900")
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="https://test") as client:
+        await client.post(
+            "/api/v1/session", json={"access_token": "correct horse battery staple"}
+        )
+        heartbeat = await client.post(
+            "/api/v1/session/activity",
+            headers={
+                "Origin": "https://test",
+                "X-CSRF-Token": client.cookies["stackchain_csrf"],
+            },
+        )
+
+    assert heartbeat.status_code == 200
+    assert heartbeat.json()["active"] is True
+    assert heartbeat.json()["idle_expires_at"] >= int(time.time()) + 899
+
+
 @pytest.mark.anyio
 async def test_merge_requires_single_use_fresh_authorization_bound_to_exact_target(
     access_control, monkeypatch
@@ -615,8 +666,8 @@ async def test_sign_out_all_devices_registry_failure_sets_no_cookies(access_cont
         grant = await fresh_grant(client, "revoke_all_sessions", "all")
 
         class BrokenStore:
-            def is_active(self, session_id, expires_at):
-                return True
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
+                return "active"
 
             def consume_step_up(self, grant, session_id, *, action, target):
                 return True
@@ -693,9 +744,9 @@ async def test_session_registry_latency_does_not_block_the_event_loop(access_con
         )
 
         class SlowStore:
-            def is_active(self, session_id, expires_at):
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
                 time.sleep(0.15)
-                return True
+                return "active"
 
         monkeypatch.setattr(main.dashboard_auth, "_session_store", lambda now=None: SlowStore())
         private_request = asyncio.create_task(client.get("/api/v1/session"))
@@ -847,9 +898,9 @@ async def test_single_session_revocation_does_not_block_the_event_loop(
         csrf = client.cookies["stackchain_csrf"]
 
         class SlowStore:
-            def is_active(self, session_id, expires_at):
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
                 time.sleep(0.02)
-                return True
+                return "active"
 
             def revoke(self, session_id):
                 time.sleep(0.15)
@@ -893,7 +944,7 @@ async def test_session_registry_read_failure_fails_closed_before_gitea(
         )
 
         class BrokenStore:
-            def is_active(self, session_id, expires_at):
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
                 raise SessionStoreError("database path and secret details")
 
         monkeypatch.setattr(main.dashboard_auth, "_session_store", lambda now=None: BrokenStore())
@@ -938,8 +989,8 @@ async def test_logout_registry_failure_does_not_claim_revocation(access_control,
         csrf = client.cookies["stackchain_csrf"]
 
         class BrokenStore:
-            def is_active(self, session_id, expires_at):
-                return True
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
+                return "active"
 
             def revoke(self, session_id):
                 raise SessionStoreError("database path and secret details")
@@ -966,7 +1017,7 @@ async def test_public_routes_skip_session_registry_validation(access_control, mo
         )
 
         class BrokenStore:
-            def is_active(self, session_id, expires_at):
+            def status(self, session_id, expires_at, *, idle_timeout_seconds):
                 raise SessionStoreError("public routes must not read the registry")
 
         monkeypatch.setattr(main.dashboard_auth, "_session_store", lambda now=None: BrokenStore())

tests/test_dashboard_session_frontend.py

@@ -14,7 +14,7 @@ SESSION_JS = ROOT / "frontend" / "session.js"
 def run_session_scenario(scenario: str) -> dict:
     harness = f"""
 const createSessionBoundary = require({json.dumps(str(SESSION_JS))});
-const state = {{ requests: [], removed: [], deletedDatabases: [], deletionCompleted: false, deletedCaches: [], assigned: '', replaced: [], assignedAfterDeletion: false, replacedAfterDeletion: false, expiredAfterDeletion: false, workerMessages: [], confirmations: [], prompts: [], clearErrors: [], responseStatus: 200, responsePayload: {{}}, responses: [] }};
+const state = {{ requests: [], removed: [], deletedDatabases: [], deletionCompleted: false, deletedCaches: [], assigned: '', replaced: [], assignedAfterDeletion: false, replacedAfterDeletion: false, expiredAfterDeletion: false, workerMessages: [], confirmations: [], prompts: [], clearErrors: [], activityListeners: {{}}, now: 100000, responseStatus: 200, responsePayload: {{}}, responses: [] }};
 const storage = {{
   values: new Map([['stackchain.private', 'secret'], ['gitea.preference', 'keep']]),
   get length() {{ return this.values.size; }},
@@ -57,6 +57,8 @@ const boundary = createSessionBoundary({{
   }},
   onClearError: error => state.clearErrors.push(error.message),
   onExpired: () => {{ state.expiredAfterDeletion = state.deletionCompleted; }},
+  addActivityListener: (type, listener) => {{ state.activityListeners[type] = listener; }},
+  now: () => state.now,
   setTimer: (_callback, delay) => {{ state.leaseDelay = delay; return 1; }},
   confirmAction: message => {{ state.confirmations.push(message); return true; }},
   promptAuthorization: details => {{ state.prompts.push(details); return 'correct horse battery staple'; }},
@@ -232,6 +234,29 @@ process.stdout.write(JSON.stringify(state));
     assert result["requests"][0]["headers"]["x-csrf-token"] == "csrf-proof"
 
 
+def test_user_activity_heartbeat_is_throttled_across_pointer_keyboard_and_touch_events():
+    result = run_session_scenario(
+        """
+boundary.startActivityHeartbeat();
+await state.activityListeners.pointerdown();
+await state.activityListeners.keydown();
+state.now += 60000;
+await state.activityListeners.touchstart();
+process.stdout.write(JSON.stringify(state));
+"""
+    )
+
+    assert [request["url"] for request in result["requests"]] == [
+        "/dashboard/api/v1/session/activity",
+        "/dashboard/api/v1/session/activity",
+    ]
+    assert all(request["method"] == "POST" for request in result["requests"])
+    assert all(
+        request["headers"]["x-csrf-token"] == "csrf-proof"
+        for request in result["requests"]
+    )
+
+
 def test_authenticated_session_status_persists_offline_lease_for_worker_and_expiry_timer():
     result = run_session_scenario(
         """
@@ -350,6 +375,24 @@ process.stdout.write(JSON.stringify(state));
     assert result["replacedAfterDeletion"] is True
 
 
+def test_idle_response_locks_without_clearing_private_queued_work():
+    result = run_session_scenario(
+        """
+state.responseStatus = 401;
+state.responsePayload = {detail:'Authentication required', code:'session_idle'};
+await boundary.fetch('/dashboard/api/v1/live');
+state.remaining = Array.from(storage.values.keys());
+process.stdout.write(JSON.stringify(state));
+"""
+    )
+
+    assert result["remaining"] == ["stackchain.private", "gitea.preference"]
+    assert result["deletedDatabases"] == []
+    assert result["deletedCaches"] == []
+    assert result["workerMessages"] == []
+    assert result["replaced"] == ["/dashboard/login?reason=session-idle"]
+
+
 def test_worker_revocation_message_clears_window_storage_before_login():
     result = run_session_scenario(
         """
@@ -363,6 +406,19 @@ process.stdout.write(JSON.stringify(state));
     assert result["replaced"] == ["/dashboard/login?reason=session-revoked"]
 
 
+def test_worker_idle_message_locks_without_clearing_window_storage():
+    result = run_session_scenario(
+        """
+await boundary.handleServiceWorkerMessage({data:{type:'stackchain-session-idle'}});
+state.remaining = Array.from(storage.values.keys());
+process.stdout.write(JSON.stringify(state));
+"""
+    )
+
+    assert result["remaining"] == ["stackchain.private", "gitea.preference"]
+    assert result["replaced"] == ["/dashboard/login?reason=session-idle"]
+
+
 def test_worker_expiry_message_clears_window_storage_before_expired_login():
     result = run_session_scenario(
         """

tests/test_login_frontend.py

@@ -37,6 +37,28 @@ process.stdout.write(JSON.stringify({{ expired, ignored: status.textContent }}))
     assert state["ignored"] == state["expired"]
 
 
+def test_idle_session_reason_explains_that_saved_work_will_resume():
+    harness = f"""
+const createLoginController = require({json.dumps(str(LOGIN_JS))});
+const status = {{ textContent: '' }};
+const controller = createLoginController({{
+  form: {{ reset: () => {{}} }}, status, button: {{ disabled: false }},
+  fetchImpl: async () => new Response('{{}}', {{ status: 200 }}),
+  location: {{ replace: () => {{}} }},
+}});
+controller.showReason('session-idle');
+process.stdout.write(JSON.stringify({{ status: status.textContent }}));
+"""
+    result = subprocess.run(
+        ["node", "-e", harness], text=True, capture_output=True, check=True
+    )
+
+    assert json.loads(result.stdout)["status"] == (
+        "Stackchain locked after inactivity. Your drafts and queued work are still "
+        "on this device. Sign in to resume."
+    )
+
+
 def test_revoked_session_reason_clears_private_data_before_enabling_sign_in():
     harness = f"""
 const createLoginController = require({json.dumps(str(LOGIN_JS))});

tests/test_service_worker.py

@@ -237,6 +237,26 @@ def test_revoked_background_session_purges_worker_data_and_notifies_dashboard_cl
     ]
 
 
+def test_idle_background_session_preserves_outbox_and_notifies_dashboard_clients():
+    result = run_worker_scenario(
+        """
+  state.clientMessages=[];
+  state.clientList=[{postMessage:message=>state.clientMessages.push(message)}];
+  context.fetch=async()=>new Response(JSON.stringify({detail:'Authentication required',code:'session_idle'}),{status:401,headers:{'Content-Type':'application/json'}});
+  const outcome=await context.self.__testFetchJson('/dashboard/api/v1/repos/o/r/issues',{method:'POST'})
+    .then(()=>({ok:true}),error=>({status:error.status,code:error.code}));
+  process.stdout.write(JSON.stringify({state,outcome}));
+"""
+    )
+
+    assert result["outcome"] == {"status": 401, "code": "session_idle"}
+    assert result["state"]["outboxPurges"] == 0
+    assert result["state"]["deleted"] == []
+    assert result["state"]["clientMessages"] == [
+        {"type": "stackchain-session-idle"}
+    ]
+
+
 def test_authenticated_page_message_resumes_queued_background_delivery():
     result = run_worker_scenario(
         """

tests/test_session_store.py

@@ -77,6 +77,43 @@ def test_expired_sessions_are_rejected_without_writing_during_validation(tmp_pat
         assert connection.execute("SELECT COUNT(*) FROM active_sessions").fetchone() == (1,)
 
 
+def test_session_status_reports_idle_without_background_validation_extending_activity(tmp_path):
+    now = [1_000.0]
+    store = SessionStore(tmp_path / "sessions.sqlite3", clock=lambda: now[0])
+    store.activate("phone-session", 3_000)
+
+    now[0] = 1_899.0
+    assert store.status("phone-session", 3_000, idle_timeout_seconds=900) == "active"
+    now[0] = 1_900.0
+    assert store.status("phone-session", 3_000, idle_timeout_seconds=900) == "idle"
+
+
+def test_touch_extends_only_the_matching_live_session(tmp_path):
+    now = [1_000.0]
+    store = SessionStore(tmp_path / "sessions.sqlite3", clock=lambda: now[0])
+    store.activate("phone-session", 3_000)
+    store.activate("laptop-session", 3_000)
+
+    now[0] = 1_800.0
+    assert store.touch("phone-session", 3_000, idle_timeout_seconds=900) is True
+    now[0] = 2_000.0
+
+    assert store.status("phone-session", 3_000, idle_timeout_seconds=900) == "active"
+    assert store.status("laptop-session", 3_000, idle_timeout_seconds=900) == "idle"
+    assert store.touch("missing-session", 3_000, idle_timeout_seconds=900) is False
+
+
+def test_touch_cannot_revive_a_session_at_the_idle_boundary(tmp_path):
+    now = [1_000.0]
+    store = SessionStore(tmp_path / "sessions.sqlite3", clock=lambda: now[0])
+    store.activate("phone-session", 3_000)
+
+    now[0] = 1_900.0
+
+    assert store.touch("phone-session", 3_000, idle_timeout_seconds=900) is False
+    assert store.status("phone-session", 3_000, idle_timeout_seconds=900) == "idle"
+
+
 def test_active_devices_are_listed_without_exposing_session_secrets(tmp_path):
     store = SessionStore(tmp_path / "sessions.sqlite3", clock=lambda: 1_000.0)
     store.activate("phone-session-secret", 2_000, device_label="Pixel 9")
@@ -121,6 +158,25 @@ def test_existing_session_registry_migrates_without_invalidating_sessions(tmp_pa
     assert next(device for device in devices if device.current).device_label == "Existing device"
 
 
+def test_idle_status_migrates_existing_registry_and_starts_legacy_idle_clock_now(tmp_path):
+    database = tmp_path / "sessions.sqlite3"
+    digest = SessionStore._digest("existing-session")
+    with sqlite3.connect(database) as connection:
+        connection.execute(
+            "CREATE TABLE active_sessions (session_hash TEXT PRIMARY KEY, expires_at INTEGER NOT NULL)"
+        )
+        connection.execute("INSERT INTO active_sessions VALUES (?, ?)", (digest, 2_000))
+
+    store = SessionStore(database, clock=lambda: 1_000.0)
+
+    assert store.status("existing-session", 2_000, idle_timeout_seconds=900) == "active"
+    with sqlite3.connect(database) as connection:
+        last_active_at = connection.execute(
+            "SELECT last_active_at FROM active_sessions WHERE session_hash = ?", (digest,)
+        ).fetchone()[0]
+    assert last_active_at == 1_000
+
+
 def test_existing_session_can_mint_first_step_up_grant_during_schema_upgrade(tmp_path):
     database = tmp_path / "sessions.sqlite3"
     digest = SessionStore._digest("existing-session")