diff --git a/README.md b/README.md
index 370bee2..72db3f6 100644
--- a/README.md
+++ b/README.md
@@ -417,8 +417,12 @@ systemd 定时备份示例为 `deploy/fluxip-backup.service` 和
 ## 健康检查与排错
 
 - `GET /healthz`：进程存活状态，返回 `status` 和应用版本；不探测 SQLite 或云端账号。
-- `GET /readyz`：检查 SQLite 是否可用；就绪时返回 HTTP 200，数据库异常时返回
-  HTTP 503 和 `degraded`。该接口不会调用 AWS 或 Cloudflare。
+- `GET /readyz`：检查 SQLite 和已启用调度器的运行状态；就绪时返回 HTTP 200，数据库
+  异常或已启用调度器意外退出时返回 HTTP 503 和 `degraded`。响应中的 `scheduler`
+  会显示开关、运行状态、最近扫描/派发/异常时间；该接口不会调用 AWS 或 Cloudflare。
+- **到期后没有自动轮换**：先检查 `/readyz` 的 `scheduler.enabled` 和 `running`。系统环境
+  变量优先于 `.env`；请删除意外继承的 `ROTATOR_SCHEDULER_ENABLED=false`，或明确设为
+  `true` 后重启。已逾期的实例组会在调度器启动后的首轮扫描立即执行。
 - **没有默认管理员**：首次打开页面自行创建；远程初始化需 Bootstrap Token。
 - **账号连接测试失败**：确认实例选中了正确类型的 AWS 与 Cloudflare 账号，账号密钥
   完整，并且 Region、Zone ID 和记录名属于对应账号。
diff --git a/app/container.py b/app/container.py
index 95fb3e4..4a2034c 100644
--- a/app/container.py
+++ b/app/container.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import logging
 from pathlib import Path
 
 from app.accounts.repository import AccountRepository
@@ -18,6 +19,8 @@ from app.rotation.repository import RotationRepository
 from app.rotation.schedule_service import SchedulerLoop
 from app.rotation.service import RotationService
 
+logger = logging.getLogger(__name__)
+
 
 class AppContainer:
     def __init__(self, settings: AppSettings) -> None:
@@ -72,6 +75,8 @@ class AppContainer:
         self.rotation_service.recover()
         if self.settings.scheduler_enabled:
             self.scheduler_loop.start(self.settings.scheduler_tick_seconds)
+        else:
+            logger.warning("scheduler_disabled")
 
     async def shutdown(self) -> None:
         await self.scheduler_loop.stop()
diff --git a/app/main.py b/app/main.py
index dc26f1f..44efa88 100644
--- a/app/main.py
+++ b/app/main.py
@@ -194,10 +194,17 @@ def create_app(settings: AppSettings | None = None) -> FastAPI:
 
     @application.get("/readyz", include_in_schema=False)
     async def ready(request: Request) -> JSONResponse:
-        healthy = request.app.state.container.database.health_check()
+        container = request.app.state.container
+        database_healthy = container.database.health_check()
+        scheduler = container.scheduler_loop.status(enabled=container.settings.scheduler_enabled)
+        healthy = database_healthy and bool(scheduler["healthy"])
         return JSONResponse(
             status_code=200 if healthy else 503,
-            content={"status": "ok" if healthy else "degraded", "database": healthy},
+            content={
+                "status": "ok" if healthy else "degraded",
+                "database": database_healthy,
+                "scheduler": scheduler,
+            },
         )
 
     if STATIC_DIR.exists():
diff --git a/app/rotation/schedule_service.py b/app/rotation/schedule_service.py
index 00fb5f4..ec18c23 100644
--- a/app/rotation/schedule_service.py
+++ b/app/rotation/schedule_service.py
@@ -2,8 +2,11 @@ from __future__ import annotations
 
 import asyncio
 import logging
+import time
+from typing import Any
 
 from app.core.errors import ConflictError
+from app.core.time import to_iso
 from app.rotation.repository import RotationRepository
 from app.rotation.service import RotationService
 
@@ -20,11 +23,27 @@ class SchedulerLoop:
         self.rotation_service = rotation_service
         self._task: asyncio.Task[None] | None = None
         self._stopping = asyncio.Event()
+        self._tick_seconds: float | None = None
+        self._started_at: str | None = None
+        self._last_tick_at: str | None = None
+        self._last_success_at: str | None = None
+        self._last_dispatch_at: str | None = None
+        self._last_error_at: str | None = None
+        self._consecutive_errors = 0
+        self._started_monotonic: float | None = None
+        self._last_tick_monotonic: float | None = None
 
-    def start(self, tick_seconds: int) -> None:
+    def start(self, tick_seconds: float) -> None:
         if self._task and not self._task.done():
             return
+        self._stopping = asyncio.Event()
+        self._tick_seconds = tick_seconds
+        self._started_at = to_iso()
+        self._started_monotonic = time.monotonic()
+        self._last_tick_monotonic = None
         self._task = asyncio.create_task(self._run(tick_seconds), name="fleet-schedule-loop")
+        self._task.add_done_callback(self._task_done)
+        logger.info("scheduler_started", extra={"tick_seconds": tick_seconds})
 
     async def stop(self) -> None:
         self._stopping.set()
@@ -32,27 +51,114 @@ class SchedulerLoop:
             self._task.cancel()
             await asyncio.gather(self._task, return_exceptions=True)
 
-    async def _run(self, tick_seconds: int) -> None:
+    def status(self, *, enabled: bool) -> dict[str, Any]:
+        running = bool(self._task and not self._task.done())
+        state = "disabled" if not enabled else "running" if running else "stopped"
+        healthy = not enabled or (
+            running and self._consecutive_errors < 3 and self._tick_is_fresh()
+        )
+        return {
+            "enabled": enabled,
+            "running": running,
+            "healthy": healthy,
+            "state": state,
+            "tick_seconds": self._tick_seconds,
+            "started_at": self._started_at,
+            "last_tick_at": self._last_tick_at,
+            "last_success_at": self._last_success_at,
+            "last_dispatch_at": self._last_dispatch_at,
+            "last_error_at": self._last_error_at,
+            "consecutive_errors": self._consecutive_errors,
+        }
+
+    async def _run(self, tick_seconds: float) -> None:
         while not self._stopping.is_set():
-            for group_id in self.repository.due_group_ids():
-                try:
-                    self.rotation_service.start_group(group_id, trigger="scheduled")
-                    break
-                except ConflictError:
-                    break
-                except Exception:
-                    logger.exception(
-                        "Scheduled group rotation dispatch failed",
-                        extra={"group_id": group_id},
-                    )
-                    try:
-                        self.repository.defer_group(group_id)
-                    except Exception:
-                        logger.exception(
-                            "Failed to defer group schedule",
-                            extra={"group_id": group_id},
-                        )
+            self._last_tick_at = to_iso()
+            self._last_tick_monotonic = time.monotonic()
+            try:
+                tick_succeeded = self._dispatch_due_group()
+            except asyncio.CancelledError:
+                raise
+            except Exception:
+                self._record_error()
+                self._consecutive_errors += 1
+                logger.exception("scheduler_tick_failed")
+            else:
+                if tick_succeeded:
+                    self._last_success_at = to_iso()
+                    self._consecutive_errors = 0
+                else:
+                    self._consecutive_errors += 1
             try:
                 await asyncio.wait_for(self._stopping.wait(), timeout=tick_seconds)
             except TimeoutError:
                 continue
+
+    def _dispatch_due_group(self) -> bool:
+        succeeded = True
+        due_group_ids = self.repository.due_group_ids()
+        if due_group_ids:
+            logger.info(
+                "scheduler_due_groups_found",
+                extra={"due_group_count": len(due_group_ids)},
+            )
+        for group_id in due_group_ids:
+            try:
+                run = self.rotation_service.start_group(group_id, trigger="scheduled")
+            except ConflictError as exc:
+                logger.warning(
+                    "scheduler_dispatch_conflict",
+                    extra={"group_id": group_id, "code": exc.code},
+                )
+                if exc.code == "ROTATION_IN_PROGRESS":
+                    break
+            except Exception:
+                self._record_error()
+                succeeded = False
+                logger.exception("scheduler_dispatch_failed", extra={"group_id": group_id})
+                try:
+                    self.repository.defer_group(group_id)
+                except Exception:
+                    self._record_error()
+                    logger.exception("scheduler_defer_failed", extra={"group_id": group_id})
+            else:
+                self._last_dispatch_at = to_iso()
+                logger.info(
+                    "scheduler_group_dispatched",
+                    extra={"group_id": group_id, "run_id": run.id},
+                )
+                break
+        return succeeded
+
+    def _record_error(self) -> None:
+        self._last_error_at = to_iso()
+
+    def _tick_is_fresh(self) -> bool:
+        reference = self._last_tick_monotonic or self._started_monotonic
+        if reference is None:
+            return False
+        allowed_silence = max((self._tick_seconds or 10) * 3, 10)
+        return time.monotonic() - reference <= allowed_silence
+
+    def _task_done(self, task: asyncio.Task[None]) -> None:
+        if task.cancelled():
+            if self._stopping.is_set():
+                logger.info("scheduler_stopped")
+            else:
+                self._record_error()
+                self._consecutive_errors += 1
+                logger.error("scheduler_cancelled_unexpectedly")
+            return
+        try:
+            task.result()
+        except Exception:
+            self._record_error()
+            self._consecutive_errors += 1
+            logger.exception("scheduler_exited_unexpectedly")
+            return
+        if not self._stopping.is_set():
+            self._record_error()
+            self._consecutive_errors += 1
+            logger.error("scheduler_exited_unexpectedly")
+        else:
+            logger.info("scheduler_stopped")
diff --git a/tests/test_schedule_service.py b/tests/test_schedule_service.py
new file mode 100644
index 0000000..bab32db
--- /dev/null
+++ b/tests/test_schedule_service.py
@@ -0,0 +1,215 @@
+from __future__ import annotations
+
+import asyncio
+from collections.abc import Callable
+from datetime import timedelta
+from types import SimpleNamespace
+from typing import cast
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.core.errors import ConflictError
+from app.core.time import to_iso, utc_now
+from app.rotation.repository import RotationRepository
+from app.rotation.schedule_service import SchedulerLoop
+from app.rotation.service import RotationService
+
+
+class RecordingRotationService:
+    def __init__(self, outcomes: dict[str, Exception] | None = None) -> None:
+        self.outcomes = outcomes or {}
+        self.calls: list[tuple[str, str]] = []
+        self.dispatched = asyncio.Event()
+
+    def start_group(self, group_id: str, trigger: str = "manual") -> SimpleNamespace:
+        self.calls.append((group_id, trigger))
+        outcome = self.outcomes.get(group_id)
+        if outcome is not None:
+            raise outcome
+        self.dispatched.set()
+        return SimpleNamespace(id=f"run-{group_id}")
+
+
+class ScriptedRepository:
+    def __init__(self, scans: list[list[str] | Exception]) -> None:
+        self.scans = scans
+        self.scan_count = 0
+        self.deferred: list[str] = []
+
+    def due_group_ids(self) -> list[str]:
+        self.scan_count += 1
+        result = self.scans.pop(0) if self.scans else []
+        if isinstance(result, Exception):
+            raise result
+        return result
+
+    def defer_group(self, group_id: str) -> None:
+        self.deferred.append(group_id)
+
+
+def scheduler_for(
+    repository: RotationRepository | ScriptedRepository,
+    service: RecordingRotationService,
+) -> SchedulerLoop:
+    return SchedulerLoop(
+        cast(RotationRepository, repository),
+        cast(RotationService, service),
+    )
+
+
+async def wait_until(predicate: Callable[[], bool], timeout: float = 0.5) -> None:
+    deadline = asyncio.get_running_loop().time() + timeout
+    while not predicate():
+        if asyncio.get_running_loop().time() >= deadline:
+            pytest.fail("等待调度器状态变化超时")
+        await asyncio.sleep(0.005)
+
+
+@pytest.mark.asyncio
+async def test_scheduler_dispatches_due_group_from_sqlite(
+    client: TestClient,
+    managed_instance_payload: dict[str, object],
+    group_payload: dict[str, object],
+) -> None:
+    container = client.app.state.container
+    container.fleet_repository.create_instance(managed_instance_payload)
+    group = container.fleet_repository.create_group(group_payload)
+    with container.database.connect() as connection, connection:
+        connection.execute(
+            "UPDATE instance_groups SET next_run_at = ? WHERE id = ?",
+            (to_iso(utc_now() - timedelta(seconds=1)), group.id),
+        )
+    service = RecordingRotationService()
+    scheduler = scheduler_for(container.rotation_repository, service)
+
+    scheduler.start(0.01)
+    try:
+        await wait_until(service.dispatched.is_set)
+        status = scheduler.status(enabled=True)
+    finally:
+        await scheduler.stop()
+
+    assert service.calls[0] == (group.id, "scheduled")
+    assert status["state"] == "running"
+    assert status["last_tick_at"] is not None
+    assert status["last_success_at"] is not None
+    assert status["last_dispatch_at"] is not None
+
+
+@pytest.mark.asyncio
+async def test_scheduler_recovers_after_scan_error(caplog: pytest.LogCaptureFixture) -> None:
+    repository = ScriptedRepository([RuntimeError("database is temporarily locked"), ["group"]])
+    service = RecordingRotationService()
+    scheduler = scheduler_for(repository, service)
+
+    scheduler.start(0.01)
+    try:
+        await wait_until(service.dispatched.is_set)
+        status = scheduler.status(enabled=True)
+    finally:
+        await scheduler.stop()
+
+    assert repository.scan_count >= 2
+    assert service.calls == [("group", "scheduled")]
+    assert status["running"] is True
+    assert status["last_error_at"] is not None
+    assert status["consecutive_errors"] == 0
+    assert "scheduler_tick_failed" in caplog.messages
+
+
+@pytest.mark.asyncio
+async def test_scheduler_reports_unhealthy_after_repeated_scan_errors() -> None:
+    repository = ScriptedRepository([RuntimeError("database locked") for _ in range(100)])
+    service = RecordingRotationService()
+    scheduler = scheduler_for(repository, service)
+
+    scheduler.start(0.01)
+    try:
+        await wait_until(lambda: repository.scan_count >= 3)
+        status = scheduler.status(enabled=True)
+    finally:
+        await scheduler.stop()
+
+    assert status["running"] is True
+    assert status["healthy"] is False
+    assert int(status["consecutive_errors"]) >= 3
+
+
+@pytest.mark.asyncio
+async def test_non_active_conflict_does_not_block_next_due_group() -> None:
+    repository = ScriptedRepository([["disabled-group", "ready-group"]])
+    service = RecordingRotationService(
+        {
+            "disabled-group": ConflictError(
+                "实例组计划未启用",
+                code="GROUP_SCHEDULE_DISABLED",
+            )
+        }
+    )
+    scheduler = scheduler_for(repository, service)
+
+    scheduler.start(0.01)
+    try:
+        await wait_until(service.dispatched.is_set)
+    finally:
+        await scheduler.stop()
+
+    assert service.calls == [
+        ("disabled-group", "scheduled"),
+        ("ready-group", "scheduled"),
+    ]
+    assert repository.deferred == []
+
+
+@pytest.mark.asyncio
+async def test_unexpected_scheduler_cancellation_is_reported(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    repository = ScriptedRepository([[]])
+    service = RecordingRotationService()
+    scheduler = scheduler_for(repository, service)
+    scheduler.start(1)
+    await wait_until(lambda: repository.scan_count >= 1)
+    task = scheduler._task
+    assert task is not None
+
+    task.cancel()
+    await asyncio.gather(task, return_exceptions=True)
+    await asyncio.sleep(0)
+    status = scheduler.status(enabled=True)
+
+    assert status["state"] == "stopped"
+    assert status["healthy"] is False
+    assert status["last_error_at"] is not None
+    assert "scheduler_cancelled_unexpectedly" in caplog.messages
+
+
+def test_readyz_reports_scheduler_disabled(client: TestClient) -> None:
+    response = client.get("/readyz")
+
+    assert response.status_code == 200
+    assert response.json()["scheduler"] == {
+        "enabled": False,
+        "running": False,
+        "healthy": True,
+        "state": "disabled",
+        "tick_seconds": None,
+        "started_at": None,
+        "last_tick_at": None,
+        "last_success_at": None,
+        "last_dispatch_at": None,
+        "last_error_at": None,
+        "consecutive_errors": 0,
+    }
+
+
+def test_readyz_is_degraded_when_enabled_scheduler_is_not_running(client: TestClient) -> None:
+    client.app.state.container.settings.scheduler_enabled = True
+
+    response = client.get("/readyz")
+
+    assert response.status_code == 503
+    assert response.json()["status"] == "degraded"
+    assert response.json()["scheduler"]["healthy"] is False
+    assert response.json()["scheduler"]["state"] == "stopped"