diff --git a/bun.lock b/bun.lock
index 69eb704..c1d53d6 100644
--- a/bun.lock
+++ b/bun.lock
@@ -14,6 +14,7 @@
         "ai": "^6",
         "ajv": "^8.20.0",
         "cheerio": "^1.2.0",
+        "croner": "^10.0.1",
         "es-toolkit": "^1.46.1",
         "pino": "^10.3.1",
         "pino-pretty": "^13.1.3",
@@ -497,6 +498,8 @@
 
     "cosmiconfig-typescript-loader": ["cosmiconfig-typescript-loader@6.3.0", "https://registry.npmmirror.com/cosmiconfig-typescript-loader/-/cosmiconfig-typescript-loader-6.3.0.tgz", { "dependencies": { "jiti": "2.6.1" }, "peerDependencies": { "@types/node": "*", "cosmiconfig": ">=9", "typescript": ">=5" } }, "sha512-Akr82WH1Wfqatyiqpj8HDkO2o2KmJRu1FhKfSNJP3K4IdXwHfEyL7MOb62i1AGQVLtIQM+iCE9CGOtrfhR+mmA=="],
 
+    "croner": ["croner@10.0.1", "", {}, "sha512-ixNtAJndqh173VQ4KodSdJEI6nuioBWI0V1ITNKhZZsO0pEMoDxz539T4FTTbSZ/xIOSuDnzxLVRqBVSvPNE2g=="],
+
     "cross-spawn": ["cross-spawn@7.0.6", "https://registry.npmmirror.com/cross-spawn/-/cross-spawn-7.0.6.tgz", { "dependencies": { "path-key": "^3.1.0", "shebang-command": "^2.0.0", "which": "^2.0.1" } }, "sha512-uV2QOWP2nWzsy2aMp8aRibhi9dlzF5Hgh5SHaB9OiTGEyDTiJJyx0uy51QXdyWbtAHNua4XJzUKca3OzKUd3vA=="],
 
     "css-select": ["css-select@5.2.2", "https://registry.npmmirror.com/css-select/-/css-select-5.2.2.tgz", { "dependencies": { "boolbase": "^1.0.0", "css-what": "^6.1.0", "domhandler": "^5.0.2", "domutils": "^3.0.1", "nth-check": "^2.0.1" } }, "sha512-TizTzUddG/xYLA3NXodFM0fSbNizXjOKhqiQQwvhlspadZokn1KDy0NZFS0wuEubIYAV5/c1/lAr0TaaFXEXzw=="],
diff --git a/package.json b/package.json
index 223ca86..5bd1eed 100644
--- a/package.json
+++ b/package.json
@@ -63,6 +63,7 @@
     "ai": "^6",
     "ajv": "^8.20.0",
     "cheerio": "^1.2.0",
+    "croner": "^10.0.1",
     "es-toolkit": "^1.46.1",
     "pino": "^10.3.1",
     "pino-pretty": "^13.1.3",
diff --git a/src/server/checker/engine.ts b/src/server/checker/engine.ts
index 594f0af..8bf8905 100644
--- a/src/server/checker/engine.ts
+++ b/src/server/checker/engine.ts
@@ -1,4 +1,4 @@
-import { groupBy, isError, Semaphore } from "es-toolkit";
+import { isError, Semaphore } from "es-toolkit";
 
 import type { Logger } from "../logger";
 import type { ProbeStore } from "./store";
@@ -11,14 +11,15 @@ import { checkerRegistry } from "./runner";
 const PRUNE_INTERVAL_MS = 3600000;
 
 export class ProbeEngine {
+  private abort: AbortController | null = null;
   private lastMatched = new Map<string, boolean>();
   private logger: Logger;
+  private pruneTimer: null | ReturnType<typeof setInterval> = null;
   private retentionMs: number;
   private semaphore: Semaphore;
   private store: ProbeStore;
   private targetIds = new Set<string>();
   private targets: ResolvedTargetBase[];
-  private timers: Array<ReturnType<typeof setInterval>> = [];
 
   constructor(
     store: ProbeStore,
@@ -37,32 +38,28 @@ export class ProbeEngine {
   }
 
   start(): void {
-    const groups = groupBy(this.targets, (t) => t.intervalMs);
+    this.abort = new AbortController();
+    const signal = this.abort.signal;
 
-    for (const [intervalMs, groupTargets] of Object.entries(groups)) {
-      void this.probeGroup(groupTargets);
-
-      const timer = setInterval(() => {
-        void this.probeGroup(groupTargets);
-      }, Number(intervalMs));
-
-      this.timers.push(timer);
+    for (const target of this.targets) {
+      void this.runLoop(target, signal);
     }
 
     if (this.retentionMs > 0) {
       this.store.prune(this.retentionMs);
-      const pruneTimer = setInterval(() => {
+      this.pruneTimer = setInterval(() => {
         this.store.prune(this.retentionMs);
       }, PRUNE_INTERVAL_MS);
-      this.timers.push(pruneTimer);
     }
   }
 
   stop(): void {
-    for (const timer of this.timers) {
-      clearInterval(timer);
+    this.abort?.abort();
+    this.abort = null;
+    if (this.pruneTimer) {
+      clearInterval(this.pruneTimer);
+      this.pruneTimer = null;
     }
-    this.timers = [];
   }
 
   private initStateCache(): void {
@@ -108,44 +105,6 @@ export class ProbeEngine {
     this.lastMatched.set(result.targetId, current);
   }
 
-  private async probeGroup(targets: ResolvedTargetBase[]): Promise<void> {
-    const results = await Promise.allSettled(
-      targets.map(async (target) => {
-        await this.semaphore.acquire();
-        try {
-          return await this.runCheck(target);
-        } finally {
-          this.semaphore.release();
-        }
-      }),
-    );
-
-    for (const [index, result] of results.entries()) {
-      if (result.status === "fulfilled") {
-        this.writeResult(result.value);
-        this.logStateChange(result.value);
-        this.logCheckDebug(result.value);
-      } else {
-        const target = targets[index];
-        if (target) {
-          this.logger.error(
-            { reason: formatReason(result.reason), targetId: target.id, targetType: target.type },
-            `探针执行失败: ${formatReason(result.reason)}`,
-          );
-          this.writeResult({
-            detail: null,
-            durationMs: null,
-            failure: errorFailure("internal", "engine", formatReason(result.reason)),
-            matched: false,
-            observation: null,
-            targetId: target.id,
-            timestamp: new Date().toISOString(),
-          });
-        }
-      }
-    }
-  }
-
   private refreshCache(): void {
     this.targetIds.clear();
     for (const target of this.store.getTargets()) {
@@ -165,6 +124,62 @@ export class ProbeEngine {
     }
   }
 
+  private async runLoop(target: ResolvedTargetBase, signal: AbortSignal): Promise<void> {
+    while (!signal.aborted) {
+      const start = performance.now();
+      try {
+        await this.runOnce(target, signal);
+      } catch {
+        break;
+      }
+
+      const elapsed = performance.now() - start;
+      if (elapsed > target.intervalMs) {
+        this.logger.warn(
+          { elapsed, intervalMs: target.intervalMs, targetId: target.id },
+          `拨测超时: ${target.id} 耗时 ${Math.round(elapsed)}ms > 间隔 ${target.intervalMs}ms`,
+        );
+      }
+      const delay = Math.max(0, target.intervalMs - elapsed);
+      try {
+        await sleep(delay, signal);
+      } catch {
+        break;
+      }
+    }
+  }
+
+  private async runOnce(target: ResolvedTargetBase, signal?: AbortSignal): Promise<CheckResult> {
+    await this.semaphore.acquire();
+    if (signal?.aborted) {
+      this.semaphore.release();
+      throw new DOMException("Aborted", "AbortError");
+    }
+    try {
+      const result = await this.runCheck(target);
+      this.writeResult(result);
+      this.logStateChange(result);
+      this.logCheckDebug(result);
+      return result;
+    } catch (error) {
+      const reason = formatReason(error);
+      this.logger.error({ reason, targetId: target.id, targetType: target.type }, `探针执行失败: ${reason}`);
+      const errorResult: CheckResult = {
+        detail: null,
+        durationMs: null,
+        failure: errorFailure("internal", "engine", reason),
+        matched: false,
+        observation: null,
+        targetId: target.id,
+        timestamp: new Date().toISOString(),
+      };
+      this.writeResult(errorResult);
+      return errorResult;
+    } finally {
+      this.semaphore.release();
+    }
+  }
+
   private writeResult(result: CheckResult): void {
     if (!this.targetIds.has(result.targetId)) return;
 
@@ -182,3 +197,24 @@ export class ProbeEngine {
 function formatReason(reason: unknown): string {
   return isError(reason) ? reason.message : String(reason);
 }
+
+function sleep(ms: number, signal: AbortSignal): Promise<void> {
+  return new Promise<void>((resolve, reject) => {
+    if (signal.aborted) {
+      reject(new DOMException("Aborted", "AbortError"));
+      return;
+    }
+
+    const timer = setTimeout(() => {
+      signal.removeEventListener("abort", onAbort);
+      resolve();
+    }, ms);
+
+    function onAbort() {
+      clearTimeout(timer);
+      reject(new DOMException("Aborted", "AbortError"));
+    }
+
+    signal.addEventListener("abort", onAbort, { once: true });
+  });
+}
diff --git a/tests/server/checker/engine.test.ts b/tests/server/checker/engine.test.ts
index 6d3a0ea..eaf0737 100644
--- a/tests/server/checker/engine.test.ts
+++ b/tests/server/checker/engine.test.ts
@@ -50,6 +50,14 @@ function ensureRegistered() {
   }
 }
 
+function getRunOnce(engine: ProbeEngine) {
+  return (
+    engine as unknown as {
+      runOnce: (t: ResolvedTargetBase) => Promise<Record<string, unknown>>;
+    }
+  ).runOnce.bind(engine);
+}
+
 function makeCommandTarget(name: string, overrides?: Partial<ResolvedCommandTarget>): ResolvedCommandTarget {
   return {
     cmd: {
@@ -70,6 +78,19 @@ function makeCommandTarget(name: string, overrides?: Partial<ResolvedCommandTarg
   };
 }
 
+function makeMockResult(targetId: string, overrides?: Partial<Record<string, unknown>>) {
+  return {
+    detail: null,
+    durationMs: 1,
+    failure: null,
+    matched: true,
+    observation: null,
+    targetId,
+    timestamp: new Date().toISOString(),
+    ...overrides,
+  };
+}
+
 describe("ProbeEngine", () => {
   test("start/stop 不抛错", () => {
     ensureRegistered();
@@ -81,15 +102,12 @@ describe("ProbeEngine", () => {
     expect(true).toBe(true);
   });
 
-  test("单次 probeGroup 执行 cmd 检查", async () => {
+  test("单次 runOnce 执行 cmd 检查", async () => {
     const target = makeCommandTarget("cmd-echo");
     const mockStore = createMockStore(["cmd-echo"]) as unknown as ProbeStore;
     const engine = new ProbeEngine(mockStore, [target]);
 
-    const probeGroup = (
-      engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-    ).probeGroup.bind(engine);
-    await probeGroup([target]);
+    await getRunOnce(engine)(target);
 
     const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
     expect(results.length).toBe(1);
@@ -119,11 +137,9 @@ describe("ProbeEngine", () => {
 
     const mockStore = createMockStore(["echo-a", "echo-b"]) as unknown as ProbeStore;
     const engine = new ProbeEngine(mockStore, [targetA, targetB]);
+    const runOnce = getRunOnce(engine);
 
-    const probeGroup = (
-      engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-    ).probeGroup.bind(engine);
-    await probeGroup([targetA, targetB]);
+    await Promise.all([runOnce(targetA), runOnce(targetB)]);
 
     const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
     expect(results.length).toBe(2);
@@ -143,11 +159,9 @@ describe("ProbeEngine", () => {
 
     const mockStore = createMockStore(["bad-cmd", "good-cmd"]) as unknown as ProbeStore;
     const engine = new ProbeEngine(mockStore, [badTarget, goodTarget]);
+    const runOnce = getRunOnce(engine);
 
-    const probeGroup = (
-      engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-    ).probeGroup.bind(engine);
-    await probeGroup([badTarget, goodTarget]);
+    await Promise.all([runOnce(badTarget), runOnce(goodTarget)]);
 
     const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
     expect(results.length).toBe(2);
@@ -173,27 +187,28 @@ describe("ProbeEngine", () => {
     const goodTarget = makeCommandTarget("good-cmd");
     const mockStore = createMockStore(["reject-cmd", "good-cmd"]) as unknown as ProbeStore;
     const engine = new ProbeEngine(mockStore, [rejectTarget, goodTarget]);
+    const runOnce = getRunOnce(engine);
 
-    const probeGroup = (
-      engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-    ).probeGroup.bind(engine);
-    await probeGroup([rejectTarget, goodTarget]);
+    await Promise.all([runOnce(rejectTarget), runOnce(goodTarget)]);
 
     const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
     expect(results.length).toBe(2);
-    expect(results[0]!["targetId"]).toBe("reject-cmd");
-    expect(results[0]!["matched"]).toBe(false);
-    expect(results[0]!["durationMs"]).toBeNull();
-    expect(results[0]!["observation"]).toBeNull();
-    expect(results[0]!["failure"]).toEqual({
+
+    const rejectResult = results.find((r) => r["targetId"] === "reject-cmd");
+    const goodResult = results.find((r) => r["targetId"] === "good-cmd");
+    expect(rejectResult).toBeDefined();
+    expect(rejectResult!["matched"]).toBe(false);
+    expect(rejectResult!["durationMs"]).toBeNull();
+    expect(rejectResult!["observation"]).toBeNull();
+    expect(rejectResult!["failure"]).toEqual({
       kind: "error",
       message: "boom",
       path: "engine",
       phase: "internal",
     });
-    expect(typeof results[0]!["timestamp"]).toBe("string");
-    expect(results[1]!["targetId"]).toBe("good-cmd");
-    expect(results[1]!["matched"]).toBe(true);
+    expect(typeof rejectResult!["timestamp"]).toBe("string");
+    expect(goodResult).toBeDefined();
+    expect(goodResult!["matched"]).toBe(true);
     checker.execute = originalExecute;
   });
 
@@ -212,11 +227,9 @@ describe("ProbeEngine", () => {
 
     const mockStore = createMockStore(targets.map((t) => t.name ?? t.id)) as unknown as ProbeStore;
     const engine = new ProbeEngine(mockStore, targets, 2);
+    const runOnce = getRunOnce(engine);
 
-    const probeGroup = (
-      engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-    ).probeGroup.bind(engine);
-    await probeGroup(targets);
+    await Promise.all(targets.map((t) => runOnce(t)));
 
     const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
     expect(results.length).toBe(5);
@@ -225,7 +238,7 @@ describe("ProbeEngine", () => {
     }
   });
 
-  test("groupByInterval 按间隔分组", () => {
+  test("不同 interval 的 target 独立调度", () => {
     const targetA = makeCommandTarget("a", { intervalMs: 30000 });
     const targetB = makeCommandTarget("b", { intervalMs: 30000 });
     const targetC = makeCommandTarget("c", { intervalMs: 60000 });
@@ -242,10 +255,7 @@ describe("ProbeEngine", () => {
     const mockStore = createMockStore(["other-name"]) as unknown as ProbeStore;
     const engine = new ProbeEngine(mockStore, [target]);
 
-    const probeGroup = (
-      engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-    ).probeGroup.bind(engine);
-    await probeGroup([target]);
+    await getRunOnce(engine)(target);
 
     const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
     expect(results.length).toBe(0);
@@ -281,10 +291,7 @@ describe("ProbeEngine", () => {
       const mockStore = createMockStore(["http-test"]) as unknown as ProbeStore;
       const engine = new ProbeEngine(mockStore, [httpTarget]);
 
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([httpTarget]);
+      await getRunOnce(engine)(httpTarget);
 
       const results = (mockStore as unknown as { _results: Array<Record<string, unknown>> })._results;
       expect(results.length).toBe(1);
@@ -365,11 +372,9 @@ describe("ProbeEngine", () => {
         0,
         logger,
       );
+      const runOnce = getRunOnce(engine);
 
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget("fail-target"), makeCommandTarget("ok-target")]);
+      await Promise.all([runOnce(makeCommandTarget("fail-target")), runOnce(makeCommandTarget("ok-target"))]);
 
       const errorLogs = logger.entries.filter((e) => e.level === "error");
       expect(errorLogs.length).toBeGreaterThanOrEqual(1);
@@ -393,25 +398,17 @@ describe("ProbeEngine", () => {
       const originalExecute = checker.execute.bind(checker);
       checker.execute = async (target) => {
         if (target.id === targetId) {
-          return {
-            detail: null,
+          return makeMockResult(targetId, {
             durationMs: 10,
             failure: { kind: "error", message: "fail", path: "exitCode", phase: "body" },
             matched: false,
-            observation: null,
-            targetId,
-            timestamp: new Date().toISOString(),
-          };
+          });
         }
         return originalExecute(target, { signal: new AbortController().signal });
       };
 
       const engine = new ProbeEngine(mockStore, [makeCommandTarget(targetId)], 20, 0, logger);
-
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget(targetId)]);
+      await getRunOnce(engine)(makeCommandTarget(targetId));
 
       const stateLogs = logger.entries.filter((e) => e.level === "warn" && e.msg.includes("UP → DOWN"));
       expect(stateLogs.length).toBe(1);
@@ -432,11 +429,7 @@ describe("ProbeEngine", () => {
       } as unknown as ProbeStore;
 
       const engine = new ProbeEngine(mockStore, [makeCommandTarget(targetId)], 20, 0, logger);
-
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget(targetId)]);
+      await getRunOnce(engine)(makeCommandTarget(targetId));
 
       const recoverLogs = logger.entries.filter((e) => e.level === "info" && e.msg.includes("DOWN → UP"));
       expect(recoverLogs.length).toBe(1);
@@ -455,11 +448,7 @@ describe("ProbeEngine", () => {
       } as unknown as ProbeStore;
 
       const engine = new ProbeEngine(mockStore, [makeCommandTarget(targetId)], 20, 0, logger);
-
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget(targetId)]);
+      await getRunOnce(engine)(makeCommandTarget(targetId));
 
       const stateChangeLogs = logger.entries.filter(
         (e) => e.msg.includes("UP → DOWN") || e.msg.includes("DOWN → UP") || e.msg.includes("首次 DOWN"),
@@ -477,25 +466,17 @@ describe("ProbeEngine", () => {
       const originalExecute = checker.execute.bind(checker);
       checker.execute = async (target) => {
         if (target.id === targetId) {
-          return {
-            detail: null,
+          return makeMockResult(targetId, {
             durationMs: 10,
             failure: { kind: "error", message: "fail", path: "exitCode", phase: "body" },
             matched: false,
-            observation: null,
-            targetId,
-            timestamp: new Date().toISOString(),
-          };
+          });
         }
         return originalExecute(target, { signal: new AbortController().signal });
       };
 
       const engine = new ProbeEngine(mockStore, [makeCommandTarget(targetId)], 20, 0, logger);
-
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget(targetId)]);
+      await getRunOnce(engine)(makeCommandTarget(targetId));
 
       const firstDownLogs = logger.entries.filter((e) => e.level === "warn" && e.msg.includes("首次 DOWN"));
       expect(firstDownLogs.length).toBe(1);
@@ -510,11 +491,7 @@ describe("ProbeEngine", () => {
       const mockStore = createMockStore([targetId]) as unknown as ProbeStore;
 
       const engine = new ProbeEngine(mockStore, [makeCommandTarget(targetId)], 20, 0, logger);
-
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget(targetId)]);
+      await getRunOnce(engine)(makeCommandTarget(targetId));
 
       const debugLogs = logger.entries.filter((e) => e.level === "debug");
       expect(debugLogs.length).toBeGreaterThanOrEqual(1);
@@ -527,11 +504,186 @@ describe("ProbeEngine", () => {
       ensureRegistered();
       const mockStore = createMockStore(["no-log"]) as unknown as ProbeStore;
       const engine = new ProbeEngine(mockStore, [makeCommandTarget("no-log")]);
+      await getRunOnce(engine)(makeCommandTarget("no-log"));
+    });
+  });
 
-      const probeGroup = (
-        engine as unknown as { probeGroup: (t: ResolvedTargetBase[]) => Promise<void> }
-      ).probeGroup.bind(engine);
-      await probeGroup([makeCommandTarget("no-log")]);
+  describe("runLoop 调度行为", () => {
+    test("首次立即执行", async () => {
+      ensureRegistered();
+      let callCount = 0;
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = (target) => {
+        callCount++;
+        return Promise.resolve(makeMockResult(target.id));
+      };
+
+      const target = makeCommandTarget("immediate", { intervalMs: 60000 });
+      const mockStore = createMockStore(["immediate"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target]);
+      engine.start();
+
+      await Bun.sleep(20);
+      expect(callCount).toBeGreaterThanOrEqual(1);
+      engine.stop();
+
+      checker.execute = originalExecute;
+    });
+
+    test("正常调度间隔", async () => {
+      ensureRegistered();
+      const callTimes: number[] = [];
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = (target) => {
+        callTimes.push(performance.now());
+        return Promise.resolve(makeMockResult(target.id));
+      };
+
+      const target = makeCommandTarget("interval", { intervalMs: 100 });
+      const mockStore = createMockStore(["interval"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target]);
+      engine.start();
+
+      await Bun.sleep(280);
+      engine.stop();
+
+      expect(callTimes.length).toBeGreaterThanOrEqual(2);
+      const gap = callTimes[1]! - callTimes[0]!;
+      expect(gap).toBeGreaterThanOrEqual(80);
+      expect(gap).toBeLessThan(200);
+
+      checker.execute = originalExecute;
+    });
+
+    test("catch-up 语义：超时后立即补执行", async () => {
+      ensureRegistered();
+      const callTimes: number[] = [];
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = async (target) => {
+        callTimes.push(performance.now());
+        if (callTimes.length === 1) {
+          await Bun.sleep(150);
+        }
+        return makeMockResult(target.id);
+      };
+
+      const target = makeCommandTarget("catchup", { intervalMs: 100 });
+      const mockStore = createMockStore(["catchup"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target]);
+      engine.start();
+
+      await Bun.sleep(350);
+      engine.stop();
+
+      expect(callTimes.length).toBeGreaterThanOrEqual(2);
+      const gap = callTimes[1]! - callTimes[0]!;
+      expect(gap).toBeGreaterThanOrEqual(140);
+      expect(gap).toBeLessThan(220);
+
+      checker.execute = originalExecute;
+    });
+
+    test("overrun warn 日志", async () => {
+      ensureRegistered();
+      const logger = createMemoryLogger();
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = async (target) => {
+        await Bun.sleep(150);
+        return makeMockResult(target.id, { durationMs: 150 });
+      };
+
+      const target = makeCommandTarget("overrun", { intervalMs: 100 });
+      const mockStore = createMockStore(["overrun"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target], 20, 0, logger);
+      engine.start();
+
+      await Bun.sleep(250);
+      engine.stop();
+
+      const warnLogs = logger.entries.filter((e) => e.level === "warn" && e.msg.includes("拨测超时"));
+      expect(warnLogs.length).toBeGreaterThanOrEqual(1);
+      expect(warnLogs[0]!.obj).toBeDefined();
+      expect(warnLogs[0]!.obj!["targetId"]).toBe("overrun");
+
+      checker.execute = originalExecute;
+    });
+
+    test("无并发重叠：同一 target 不会并发执行", async () => {
+      ensureRegistered();
+      let running = 0;
+      let maxConcurrent = 0;
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = async (target) => {
+        running++;
+        maxConcurrent = Math.max(maxConcurrent, running);
+        await Bun.sleep(60);
+        running--;
+        return makeMockResult(target.id, { durationMs: 60 });
+      };
+
+      const target = makeCommandTarget("no-overlap", { intervalMs: 70 });
+      const mockStore = createMockStore(["no-overlap"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target]);
+      engine.start();
+
+      await Bun.sleep(350);
+      engine.stop();
+
+      expect(maxConcurrent).toBeLessThanOrEqual(1);
+
+      checker.execute = originalExecute;
+    });
+
+    test("优雅停止：stop() 后循环快速退出", async () => {
+      ensureRegistered();
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = (target) => Promise.resolve(makeMockResult(target.id));
+
+      const target = makeCommandTarget("graceful", { intervalMs: 60000 });
+      const mockStore = createMockStore(["graceful"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target]);
+      engine.start();
+
+      await Bun.sleep(20);
+      const stopStart = performance.now();
+      engine.stop();
+      const stopDuration = performance.now() - stopStart;
+
+      expect(stopDuration).toBeLessThan(1000);
+
+      checker.execute = originalExecute;
+    });
+
+    test("错误隔离：runCheck 抛异常后循环继续", async () => {
+      ensureRegistered();
+      let callCount = 0;
+      const checker = checkerRegistry.get("cmd");
+      const originalExecute = checker.execute.bind(checker);
+      checker.execute = (target) => {
+        callCount++;
+        if (callCount === 1) {
+          return Promise.reject(new Error("first fail"));
+        }
+        return Promise.resolve(makeMockResult(target.id));
+      };
+
+      const target = makeCommandTarget("error-isolation", { intervalMs: 50 });
+      const mockStore = createMockStore(["error-isolation"]) as unknown as ProbeStore;
+      const engine = new ProbeEngine(mockStore, [target]);
+      engine.start();
+
+      await Bun.sleep(180);
+      engine.stop();
+
+      expect(callCount).toBeGreaterThanOrEqual(2);
+
+      checker.execute = originalExecute;
     });
   });
 });