diff --git a/back/shared/runCron.ts b/back/shared/runCron.ts
index e5b9606e..af07debe 100644
--- a/back/shared/runCron.ts
+++ b/back/shared/runCron.ts
@@ -4,7 +4,6 @@ import taskLimit from './pLimit';
 import Logger from '../loaders/logger';
 import { ICron } from '../protos/cron';
 import { CrontabModel, CrontabStatus } from '../data/cron';
-import { killTask } from '../config/util';
 import { RunningInstanceModel, InstanceStatus } from '../data/runningInstance';
 import dayjs from 'dayjs';
 import { observeChildProcess, asError } from './childProcess';
@@ -17,7 +16,7 @@ export function runCron(
   const execute = async () => {
     try {
       if (!isCurrent()) return;
-      // Check if the cron is already running and stop it (only if multiple instances are not allowed)
+      // A single-instance trigger must not interrupt work already in progress.
       try {
         const existingCron = await CrontabModel.findOne({
           where: { id: Number(cron.id) },
@@ -30,35 +29,93 @@ export function runCron(
         const allowSingleInstances =
           existingCron?.allow_multiple_instances === 0;
 
-        if (
-          allowSingleInstances &&
-          existingCron &&
-          existingCron.pid &&
-          (existingCron.status === CrontabStatus.running ||
-            existingCron.status === CrontabStatus.queued)
-        ) {
-          Logger.info(
-            t('[schedule][停止已运行任务] 任务ID: %s, PID: %s'),
-            cron.id,
-            existingCron.pid,
-          );
-          await killTask(existingCron.pid, true);
-          // Mark old running instances as stopped
-          const stoppedAt = dayjs().unix();
-          await RunningInstanceModel.update(
-            { status: InstanceStatus.stopped, finished_at: stoppedAt },
-            {
+        if (allowSingleInstances) {
+          // A queued manual run is an active reservation, even if its stored PID
+          // belongs to a previous execution.
+          if (
+            existingCron.status === CrontabStatus.queued &&
+            existingCron.pid
+          ) {
+            Logger.info(
+              '[schedule][Skip queued single-instance task] Task ID: %s, PID: %s',
+              cron.id,
+              existingCron.pid,
+            );
+            return;
+          }
+          if (
+            existingCron.status === CrontabStatus.running &&
+            existingCron.pid
+          ) {
+            let missing = false;
+            try {
+              process.kill(existingCron.pid, 0);
+            } catch (error) {
+              const code = (error as NodeJS.ErrnoException).code;
+              if (code === 'ESRCH') missing = true;
+              else if (code !== 'EPERM') throw error;
+            }
+            if (!missing) {
+              Logger.info(
+                '[schedule][Skip active single-instance task] Task ID: %s, PID: %s',
+                cron.id,
+                existingCron.pid,
+              );
+              return;
+            }
+
+            // Capture old instance IDs before releasing the stale cron state so
+            // a concurrent replacement cannot have its instance marked stopped.
+            const staleInstances = await RunningInstanceModel.findAll({
+              attributes: ['id'],
               where: {
                 cron_id: Number(cron.id),
+                pid: existingCron.pid,
                 status: InstanceStatus.running,
               },
-            },
-          );
-          // Update the status to idle after killing
-          await CrontabModel.update(
-            { status: CrontabStatus.idle, pid: undefined },
-            { where: { id: Number(cron.id) } },
-          );
+            });
+            if (!isCurrent()) return;
+            const [recovered] = await CrontabModel.update(
+              {
+                status: CrontabStatus.idle,
+                pid: null,
+                queued_token: null,
+              } as any,
+              {
+                where: {
+                  id: Number(cron.id),
+                  pid: existingCron.pid,
+                  status: CrontabStatus.running,
+                  ...(existingCron.log_path !== undefined
+                    ? { log_path: existingCron.log_path }
+                    : {}),
+                  ...(existingCron.queued_token !== undefined
+                    ? { queued_token: existingCron.queued_token }
+                    : {}),
+                  ...(existingCron.last_execution_time !== undefined
+                    ? { last_execution_time: existingCron.last_execution_time }
+                    : {}),
+                  ...(existingCron.isDisabled !== undefined
+                    ? { isDisabled: existingCron.isDisabled }
+                    : {}),
+                  allow_multiple_instances: 0,
+                },
+              },
+            );
+            if (recovered !== 1) return;
+            const staleIds = staleInstances.map((instance) => instance.id!);
+            if (staleIds.length) {
+              await RunningInstanceModel.update(
+                { status: InstanceStatus.stopped, finished_at: dayjs().unix() },
+                { where: { id: staleIds, status: InstanceStatus.running } },
+              );
+            }
+            Logger.info(
+              '[schedule][Recovered stale single-instance task] Task ID: %s, PID: %s',
+              cron.id,
+              existingCron.pid,
+            );
+          }
         }
       } catch (error) {
         Logger.error(
@@ -69,7 +126,7 @@ export function runCron(
         throw error;
       }
 
-      // In particular, invalidation can happen while stopping a previous run.
+      // Invalidation can happen during the asynchronous database check.
       if (!isCurrent()) return;
       Logger.info(
         t('[schedule][开始执行任务] 参数 %s'),
diff --git a/test/back/single-instance-skip.test.cjs b/test/back/single-instance-skip.test.cjs
new file mode 100644
index 00000000..c9ad3e70
--- /dev/null
+++ b/test/back/single-instance-skip.test.cjs
@@ -0,0 +1,192 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const { spawnSync } = require('node:child_process');
+const load = require('../helpers/load-security-module.cjs');
+
+function fixture(row, { claim = true, onSpawn = () => {} } = {}) {
+  const spawned = [],
+    cronWrites = [],
+    instanceWrites = [],
+    instanceReads = [];
+  const { runCron } = load('back/shared/runCron.ts', {
+    './i18n': { t: (s) => s },
+    'cross-spawn': {
+      spawn: (cmd) => {
+        spawned.push(cmd);
+        onSpawn(row);
+        return { pid: process.pid };
+      },
+    },
+    './pLimit': {
+      runWithCronLimit: (_cron, execute) => execute(),
+      removeQueuedCron() {},
+    },
+    '../loaders/logger': { info() {}, error() {} },
+    '../data/cron': {
+      CrontabModel: {
+        findOne: async () => row,
+        update: async (...args) => {
+          cronWrites.push(args);
+          if (!claim) return [0];
+          Object.assign(row, args[0]);
+          return [1];
+        },
+      },
+      CrontabStatus: { running: 0, idle: 1, queued: 3 },
+    },
+    '../data/runningInstance': {
+      RunningInstanceModel: {
+        findAll: async (options) => {
+          instanceReads.push(options);
+          return [{ id: 7 }];
+        },
+        update: async (...args) => instanceWrites.push(args),
+      },
+      InstanceStatus: { running: 0, stopped: 2 },
+    },
+    dayjs: () => ({ unix: () => 123 }),
+    './childProcess': {
+      observeChildProcess: () => ({ completed: Promise.resolve({ code: 0 }) }),
+      asError: (e) => e,
+    },
+  });
+  return {
+    run: () => runCron('task example.py', { id: '1' }),
+    spawned,
+    cronWrites,
+    instanceWrites,
+    instanceReads,
+  };
+}
+
+function exitedPid() {
+  const child = spawnSync(process.execPath, ['-e', '']);
+  assert.equal(child.status, 0);
+  assert.throws(() => process.kill(child.pid, 0), { code: 'ESRCH' });
+  return child.pid;
+}
+
+test('running single-instance task stays untouched while its process is alive', async () => {
+  const f = fixture({
+    allow_multiple_instances: 0,
+    pid: process.pid,
+    status: 0,
+  });
+  await f.run();
+  assert.deepEqual(f.spawned, []);
+  assert.deepEqual(f.cronWrites, []);
+  assert.deepEqual(f.instanceWrites, []);
+});
+
+test('queued single-instance task keeps its reservation even with an exited PID', async () => {
+  const f = fixture({
+    allow_multiple_instances: 0,
+    pid: exitedPid(),
+    status: 3,
+  });
+  await f.run();
+  assert.deepEqual(f.spawned, []);
+  assert.deepEqual(f.cronWrites, []);
+  assert.deepEqual(f.instanceWrites, []);
+});
+
+test('exited running task is recovered and the next trigger sees the new active run', async () => {
+  const oldPid = exitedPid();
+  const f = fixture(
+    {
+      allow_multiple_instances: 0,
+      pid: oldPid,
+      status: 0,
+      log_path: 'old.log',
+      queued_token: 'old-token',
+      last_execution_time: 10,
+      isDisabled: 0,
+    },
+    {
+      onSpawn: (row) => {
+        row.status = 0;
+        row.pid = process.pid;
+      },
+    },
+  );
+  await f.run();
+  await f.run();
+  assert.equal(f.spawned.length, 1);
+  assert.deepEqual(f.instanceReads, [
+    {
+      attributes: ['id'],
+      where: { cron_id: 1, pid: oldPid, status: 0 },
+    },
+  ]);
+  assert.deepEqual(f.cronWrites, [
+    [
+      { status: 1, pid: null, queued_token: null },
+      {
+        where: {
+          id: 1,
+          pid: oldPid,
+          status: 0,
+          log_path: 'old.log',
+          queued_token: 'old-token',
+          last_execution_time: 10,
+          isDisabled: 0,
+          allow_multiple_instances: 0,
+        },
+      },
+    ],
+  ]);
+  assert.deepEqual(f.instanceWrites, [
+    [{ status: 2, finished_at: 123 }, { where: { id: [7], status: 0 } }],
+  ]);
+});
+
+test('a lost stale-state claim does not spawn or change running instances', async () => {
+  const f = fixture(
+    { allow_multiple_instances: 0, pid: exitedPid(), status: 0 },
+    { claim: false },
+  );
+  await f.run();
+  assert.equal(f.cronWrites.length, 1);
+  assert.deepEqual(f.spawned, []);
+  assert.deepEqual(f.instanceWrites, []);
+});
+
+test('EPERM means an existing process must still block a new run', async () => {
+  const pid = exitedPid();
+  const originalKill = process.kill;
+  process.kill = (target, signal) => {
+    if (target === pid && signal === 0)
+      throw Object.assign(new Error('denied'), { code: 'EPERM' });
+    return originalKill(target, signal);
+  };
+  try {
+    const f = fixture({ allow_multiple_instances: 0, pid, status: 0 });
+    await f.run();
+    assert.deepEqual(f.spawned, []);
+    assert.deepEqual(f.cronWrites, []);
+  } finally {
+    process.kill = originalKill;
+  }
+});
+
+test('single-instance still starts idle tasks with a stale stored PID', async () => {
+  const f = fixture({
+    allow_multiple_instances: 0,
+    pid: exitedPid(),
+    status: 1,
+  });
+  await f.run();
+  assert.equal(f.spawned.length, 1);
+  assert.deepEqual(f.cronWrites, []);
+});
+
+test('multi-instance keeps its existing concurrent execution behavior', async () => {
+  const f = fixture({
+    allow_multiple_instances: 1,
+    pid: process.pid,
+    status: 0,
+  });
+  await f.run();
+  assert.equal(f.spawned.length, 1);
+  assert.deepEqual(f.cronWrites, []);
+});
diff --git a/test/back/stop-failure-feedback.test.cjs b/test/back/stop-failure-feedback.test.cjs
index 5b4290af..8f1ecc8e 100644
--- a/test/back/stop-failure-feedback.test.cjs
+++ b/test/back/stop-failure-feedback.test.cjs
@@ -4,75 +4,6 @@ const load = require('../helpers/load-security-module.cjs');
 
 const logger = { info() {}, error() {} };
 
-function cronFixture(killTask) {
-  const events = [];
-  const { runCron } = load('back/shared/runCron.ts', {
-    'cross-spawn': {
-      spawn: () => {
-        events.push('spawn');
-        return {};
-      },
-    },
-    './childProcess': {
-      observeChildProcess: () => ({ completed: Promise.resolve({ code: 0 }) }),
-      asError: (e) => e,
-    },
-    './pLimit': {
-      runWithCronLimit: async (_, fn) => fn(),
-      removeQueuedCron: () => events.push('release'),
-    },
-    '../loaders/logger': logger,
-    '../config/util': { killTask },
-    '../data/cron': {
-      CrontabModel: {
-        findOne: async () => ({
-          pid: 100,
-          status: 0,
-          allow_multiple_instances: 0,
-        }),
-        update: async () => events.push('idle'),
-      },
-      CrontabStatus: { running: 0, idle: 1, queued: 3 },
-    },
-    '../data/runningInstance': {
-      RunningInstanceModel: { update: async () => events.push('stopped') },
-      InstanceStatus: { running: 0, stopped: 2 },
-    },
-  });
-  return { run: () => runCron('ignored', { id: '1' }), events };
-}
-
-test('single-instance replacement does not spawn or finalize when termination fails', async () => {
-  const f = cronFixture(async () => {
-    throw Error('EPERM');
-  });
-  await f.run();
-  assert.deepEqual(f.events, ['release']);
-});
-
-test('single-instance replacement waits for verified exit before spawning', async () => {
-  let finish, entered, verified;
-  const pending = new Promise((resolve) => {
-    entered = resolve;
-  });
-  const gate = new Promise((resolve) => {
-    finish = resolve;
-  });
-  const f = cronFixture(async (pid, wait) => {
-    assert.equal(pid, 100);
-    verified = wait;
-    entered();
-    await gate;
-  });
-  const running = f.run();
-  await pending;
-  assert.deepEqual(f.events, []);
-  finish();
-  await running;
-  assert.equal(verified, true);
-  assert.deepEqual(f.events, ['stopped', 'idle', 'spawn', 'release']);
-});
-
 function subscriptionFixture(killTask) {
   const updates = [];
   const Service = load('back/services/subscription.ts', {