diff --git a/backend/app/api/auth.py b/backend/app/api/auth.py
index 291350c..f6e1941 100644
--- a/backend/app/api/auth.py
+++ b/backend/app/api/auth.py
@@ -56,14 +56,13 @@ _vanished: set[str] = set()
 AUTH_GENERATION_SYNC_SECONDS = 1.0
 AUTH_GENERATION_MAX_AGE_SECONDS = 2.0
 _generations_synced_at: float | None = None
-# One lock per login this node has not synced yet, so a concurrent HTTP
-# request and WS handshake for the same just-migrated login collapse into a
-# single SELECT instead of one each (lct-42).
+# Один lock на ещё неизвестный узлу логин: параллельные HTTP и WS входы
+# разделяют один запрос к БД до очередной синхронизации (lct-42).
 _lookup_locks: dict[str, asyncio.Lock] = {}
 
 
 class _AuthStateUnavailable(Exception):
-    """The one-shot lookup for a login unknown to this node could not reach PostgreSQL."""
+    """Разовая проверка неизвестного узлу логина не смогла обратиться к БД."""
 
 
 async def _close_revoked(ws: WebSocket) -> None:
@@ -116,15 +115,18 @@ async def load_generations() -> None:
 
 
 async def sync_generations() -> None:
-    """Refresh shared account epochs and close sockets revoked on peer nodes."""
+    """Сверить версии полномочий и закрыть отозванные на другом узле сокеты."""
+    known_before_query = set(_generations)
     async with get_sessionmaker()() as db:
         rows = (await db.execute(select(User.login, User.auth_version))).all()
     current = {login: version for login, version in rows}
     for login, version in current.items():
         previous = _generations.get(login)
+        # Снимок БД мог устареть за время запроса; меньшая версия не должна
+        # отменять локальный отзыв, который уже поднял поколение.
         if previous is None:
             _generations[login] = version
-        elif previous != version:
+        elif version > previous:
             invalidate_login(login, version)
     # Account deletion is not exposed by the application. Still close active
     # sockets if an operator removes one directly from the shared directory DB.
@@ -135,7 +137,9 @@ async def sync_generations() -> None:
     # lookup fall back to 0 and re-accept cookies issued before the revocation.
     synthetic = {"dev"} if get_settings().dev_auth_bypass else set()
     _vanished.intersection_update(_generations.keys() - current.keys())
-    for login in _generations.keys() - current.keys() - synthetic - _vanished:
+    # Разовая проверка могла найти учётку после снимка этого запроса.
+    # Её отсутствие в старом снимке не означает отзыв.
+    for login in known_before_query - current.keys() - synthetic - _vanished:
         invalidate_login(login)
         _vanished.add(login)
     global _generations_synced_at
@@ -143,32 +147,28 @@ async def sync_generations() -> None:
 
 
 async def _resolve_unknown_login(login: str) -> int | None:
-    """Look up a login absent from this node's cache without waiting a tick.
+    """Проверить неизвестный узлу логин сразу, не дожидаясь опроса БД.
 
-    A revoked login stays cached in `_generations` (see `_vanished` above),
-    so absence from `_generations` unambiguously means "this node has not
-    synced this login yet" — an unrecognized login is checked directly
-    rather than treated as revoked. Returns the current epoch, or `None` if
-    the login is not (or no longer) in `users`. Raises
-    `_AuthStateUnavailable` if PostgreSQL cannot be reached; the caller
-    fails closed.
+    Отозванный логин остаётся в `_generations` (см. `_vanished`), поэтому
+    отсутствие в кэше означает, что этот узел ещё не видел учётку.
+    Возвращает версию или None, если строки в `users` нет. При недоступной
+    БД вызывает `_AuthStateUnavailable`, чтобы вход был закрыт с 503/1013.
     """
     lock = _lookup_locks.setdefault(login, asyncio.Lock())
     async with lock:
         cached = _generations.get(login)
         if cached is not None:
-            return cached  # a concurrent request already resolved it
+            return cached  # параллельный запрос уже получил версию
         try:
             async with get_sessionmaker()() as db:
                 version = await db.scalar(
                     select(User.auth_version).where(User.login == login)
                 )
-        except Exception as exc:  # noqa: BLE001 — fail closed, not FORBIDDEN
+        except Exception as exc:  # noqa: BLE001 — ошибка БД должна закрыть вход
             log.error("разовая проверка полномочий не удалась (%s)", type(exc).__name__)
             raise _AuthStateUnavailable from exc
-        # A concurrent local revoke or sync tick may have written a newer
-        # generation while the SELECT above was in flight; the stale read
-        # must never clobber it back to an older, already-revoked epoch.
+        # Пока шёл SELECT, локальный отзыв или синхронизация могли записать
+        # новую версию. Старый ответ не должен вернуть отозванную cookie.
         cached = _generations.get(login)
         if cached is not None:
             return cached
diff --git a/backend/tests/test_auth_hardening.py b/backend/tests/test_auth_hardening.py
index d39c759..e484462 100644
--- a/backend/tests/test_auth_hardening.py
+++ b/backend/tests/test_auth_hardening.py
@@ -135,6 +135,76 @@ def test_generation_sync_preserves_synthetic_dev_account(monkeypatch):
     asyncio.run(run())
 
 
+@pytest.mark.asyncio
+async def test_stale_generation_snapshot_does_not_revoke_newly_resolved_login(monkeypatch):
+    snapshot_read = asyncio.Event()
+    release_snapshot = asyncio.Event()
+
+    class FakeResult:
+        def all(self):
+            return []
+
+    class FakeDb:
+        async def execute(self, _query):
+            snapshot_read.set()
+            await release_snapshot.wait()
+            return FakeResult()
+
+        async def scalar(self, _query):
+            return 0
+
+    class FakeSession:
+        async def __aenter__(self):
+            return FakeDb()
+
+        async def __aexit__(self, *_args):
+            return None
+
+    auth.prime_generations({})
+    monkeypatch.setattr(auth, "get_settings", lambda: SimpleNamespace(dev_auth_bypass=False))
+    monkeypatch.setattr(auth, "get_sessionmaker", lambda: lambda: FakeSession())
+    sync = asyncio.create_task(auth.sync_generations())
+    await snapshot_read.wait()
+    assert await auth._resolve_unknown_login("just-created") == 0
+    release_snapshot.set()
+    await sync
+    assert auth._generations["just-created"] == 0
+    assert "just-created" not in auth._vanished
+
+
+@pytest.mark.asyncio
+async def test_stale_generation_snapshot_does_not_restore_revoked_cookie(monkeypatch):
+    snapshot_read = asyncio.Event()
+    release_snapshot = asyncio.Event()
+
+    class FakeResult:
+        def all(self):
+            return [("revoked", 0)]
+
+    class FakeDb:
+        async def execute(self, _query):
+            snapshot_read.set()
+            await release_snapshot.wait()
+            return FakeResult()
+
+    class FakeSession:
+        async def __aenter__(self):
+            return FakeDb()
+
+        async def __aexit__(self, *_args):
+            return None
+
+    auth.prime_generations({"revoked": 0})
+    monkeypatch.setattr(auth, "get_settings", lambda: SimpleNamespace(dev_auth_bypass=False))
+    monkeypatch.setattr(auth, "get_sessionmaker", lambda: lambda: FakeSession())
+    sync = asyncio.create_task(auth.sync_generations())
+    await snapshot_read.wait()
+    auth.invalidate_login("revoked", 1)
+    release_snapshot.set()
+    await sync
+    assert auth._generations["revoked"] == 1
+
+
 def test_cross_origin_browser_websocket_is_rejected_before_handshake(client):
     assert client.post("/api/auth/dev-token").status_code == 200
     with pytest.raises(WebSocketDisconnect) as exc:
diff --git a/scripts/test_cluster_failover.py b/scripts/test_cluster_failover.py
index 0ececc8..a907266 100644
--- a/scripts/test_cluster_failover.py
+++ b/scripts/test_cluster_failover.py
@@ -72,7 +72,7 @@ def login(base: str, login_name: str, password: str) -> str:
     return cookie
 
 
-async def send_control(ws_base: str, session_id: UUID, cookie: str, payload: dict) -> None:
+async def send_control(ws_base: str, session_id: UUID, cookie: str, payload: dict) -> float:
     async with websockets.connect(
         f"{ws_base}/ws/control/{session_id}",
         additional_headers={"Cookie": cookie},
@@ -81,7 +81,9 @@ async def send_control(ws_base: str, session_id: UUID, cookie: str, payload: dic
         ping_interval=None,
     ) as socket:
         await socket.send(json.dumps(payload, ensure_ascii=False))
+        sent_at = time.monotonic()
         await asyncio.sleep(0.15)
+        return sent_at
 
 
 async def probe_ws(ws_base: str, path: str, cookie: str) -> dict:
@@ -220,7 +222,7 @@ async def main(args: argparse.Namespace) -> int:
     factory = async_sessionmaker(engine, expire_on_commit=False)
     observer_engine = create_async_engine(database_url, poolclass=NullPool)
     run_id = uuid4().hex[:12]
-    session_id = uuid4()
+    session_id = args.session_id or uuid4()
     trainee = Trainee(name=f"Failover smoke {run_id}")
     instructor_login = f"fo-i-{run_id}"
     trainee_login = f"fo-t-{run_id}"
@@ -232,6 +234,7 @@ async def main(args: argparse.Namespace) -> int:
     fault_stopped = False
     result: dict = {"session_id": str(session_id), "checks": {}}
     backend = f"http://127.0.0.1:{args.backend_port}"
+    result["login_node"] = "backend-a"
     ws_base = args.frontend_url.replace("https://", "wss://").replace("http://", "ws://")
     instructor_cookie = trainee_cookie = None
     try:
@@ -249,12 +252,18 @@ async def main(args: argparse.Namespace) -> int:
             await db.commit()
 
         instructor_cookie = login(backend, instructor_login, instructor_password)
+        login_completed_at = time.monotonic()
         trainee_cookie = login(backend, trainee_login, trainee_password)
-        await send_control(ws_base, session_id, instructor_cookie, {
+        control_sent_at = await send_control(ws_base, session_id, instructor_cookie, {
             "type": "scenario.start", "scenario_id": args.scenario,
             "trainee": trainee.name, "trainee_id": str(trainee.id),
             "mode": "training", "exercise": "dds",
         })
+        result["login_to_control_seconds"] = round(control_sent_at - login_completed_at, 4)
+        if args.expect_initial_owner == "backend-b":
+            result["checks"]["control_sent_within_first_second"] = (
+                result["login_to_control_seconds"] < 1
+            )
 
         async def session_row():
             async with factory() as db:
@@ -289,6 +298,12 @@ async def main(args: argparse.Namespace) -> int:
         old_epoch = row.backend_fencing_epoch
         result["initial_owner"] = row.backend_node_id
         result["initial_epoch"] = old_epoch
+        if args.expect_initial_owner and row.backend_node_id != args.expect_initial_owner:
+            raise RuntimeError(
+                f"session routed to {row.backend_node_id}, expected {args.expect_initial_owner}"
+            )
+        if args.expect_initial_owner == "backend-b":
+            result["checks"]["login_a_initial_control_b"] = True
 
         # Commit real DDS work before the fault. These actions must survive the
         # checkpoint handoff and remain part of the final scored report.
@@ -642,4 +657,6 @@ if __name__ == "__main__":
     parser.add_argument("--reconnect-attempts", type=int, default=5)
     parser.add_argument("--rest-timeout", type=float, default=60)
     parser.add_argument("--failure-mode", choices=("kill", "partition"), default="kill")
+    parser.add_argument("--expect-initial-owner", choices=("backend-a", "backend-b"))
+    parser.add_argument("--session-id", type=UUID)
     raise SystemExit(asyncio.run(main(parser.parse_args())))