diff --git a/backend/tests/test_job_stall_and_cancel.py b/backend/tests/test_job_stall_and_cancel.py
index af75c62..64be23b 100644
--- a/backend/tests/test_job_stall_and_cancel.py
+++ b/backend/tests/test_job_stall_and_cancel.py
@@ -165,3 +165,44 @@ def test_run_slot_reap_release_prevents_zombie_release():
     pipeline_jobs.release_run_slot("jobB")
     assert pipeline_jobs.try_acquire_run_slot("jobC") is True
     pipeline_jobs.release_run_slot("jobC")
+
+
+# ── 手动取消 API 端点契约 (数据页「停止」按钮) ──────────────────────────
+
+def test_manual_cancel_endpoint_contract(monkeypatch, tmp_path):
+    """POST /api/pipeline/jobs/{id}/cancel: running/pending 可停, 终态 400, 未知 404。"""
+    from fastapi import FastAPI
+    from fastapi.testclient import TestClient
+
+    from app.api.pipeline import router
+
+    monkeypatch.setattr(preferences, "load", lambda: {})
+    store = JobStore(store_dir=tmp_path / "jobs")
+    monkeypatch.setattr("app.api.pipeline.job_store", store)
+
+    app = FastAPI()
+    app.include_router(router)
+    client = TestClient(app)
+
+    # 未知 job → 404
+    assert client.post("/api/pipeline/jobs/nope/cancel").status_code == 404
+
+    # running → 协作式终止: 标 failed + 置取消标志 + 释放执行槽
+    jid = _make_running_job(store, timeout_s=60)
+    pipeline_jobs.try_acquire_run_slot(jid)
+    resp = client.post(f"/api/pipeline/jobs/{jid}/cancel")
+    assert resp.status_code == 200
+    assert resp.json() == {"cancelled": jid}
+    j = store.get(jid)
+    assert j["status"] == "failed"
+    assert "手动取消" in j["error"]
+    assert pipeline_jobs.is_cancelled(jid)
+    assert pipeline_jobs.try_acquire_run_slot("next") is True
+
+    # 已终态 (failed) → 400 拒绝重复取消
+    assert client.post(f"/api/pipeline/jobs/{jid}/cancel").status_code == 400
+
+    # 停止后可再建新任务 (再次拉取走完整管道的单飞基础)
+    jid2, is_new = store.create(timeout_s=60)
+    assert is_new is True
+    assert store.active_id() == jid2
diff --git a/frontend/src/lib/api.ts b/frontend/src/lib/api.ts
index 4b51447..5533b70 100644
--- a/frontend/src/lib/api.ts
+++ b/frontend/src/lib/api.ts
@@ -2525,6 +2525,9 @@ export const api = {
     '/api/pipeline/run', { method: 'POST' },
   ),
   pipelineJob: (id: string) => request<PipelineJob>(`/api/pipeline/jobs/${id}`),
+  /** 手动停止一个 running/pending 的同步任务 (协作式: 当前分块完成后线程自行退出) */
+  pipelineJobCancel: (id: string) =>
+    request<{ cancelled: string }>(`/api/pipeline/jobs/${id}/cancel`, { method: 'POST' }),
   pipelineJobs: (limit = 20) =>
     request<{ active_id: string | null; jobs: PipelineJobSummary[] }>(
       `/api/pipeline/jobs?limit=${limit}`,
diff --git a/frontend/src/pages/Data.tsx b/frontend/src/pages/Data.tsx
index 99c122b..81695fe 100644
--- a/frontend/src/pages/Data.tsx
+++ b/frontend/src/pages/Data.tsx
@@ -4,6 +4,7 @@ import { motion, AnimatePresence } from 'framer-motion'
 import {
   Database,
   Play,
+  Square,
   Loader2,
   HardDrive,
   Clock,
@@ -106,6 +107,16 @@ export function Data() {
     },
   })
 
+  // 停止同步: 二次确认后调 cancel 端点 (协作式终止, 当前分块完成后线程自行退出)
+  const [showStopConfirm, setShowStopConfirm] = useState(false)
+  const stopSync = useMutation({
+    mutationFn: () => api.pipelineJobCancel(activeJobId!),
+    onSuccess: () => {
+      setShowStopConfirm(false)
+      qc.invalidateQueries({ queryKey: QK.pipelineJob(activeJobId!) })
+    },
+  })
+
   // 无除权因子能力时同步前置确认 (静默降级告知)
   const adjGate = useAdjFactorSyncGate()
 
@@ -589,13 +600,23 @@ export function Data() {
               disabled={isStarting}
               className="inline-flex items-center gap-1.5 px-3 py-1.5 rounded-btn bg-gradient-to-r from-accent/25 to-accent/10 border border-accent/30 text-accent text-xs font-medium hover:from-accent/35 hover:to-accent/20 disabled:opacity-40 transition-all duration-150"
             >
-              {(isRunning || isStarting) ? (
+              {(isStarting || isRunning) ? (
                 <Loader2 className="h-3.5 w-3.5 animate-spin" />
               ) : (
                 <Play className="h-3.5 w-3.5" />
               )}
               {isStarting ? '启动中…' : isRunning ? '同步中…' : '立即同步'}
             </button>
+            {isRunning && !!activeJobId && (
+              <button
+                onClick={() => setShowStopConfirm(true)}
+                title="停止当前同步任务"
+                className="inline-flex items-center gap-1.5 px-3 py-1.5 rounded-btn bg-danger/12 border border-danger/30 text-danger text-xs font-medium hover:bg-danger/20 transition-all duration-150"
+              >
+                <Square className="h-3 w-3 fill-current" />
+                停止
+              </button>
+            )}
             <button
               onClick={() => setOpenSettings('pipeline-scope')}
               className="inline-flex items-center gap-1 px-2 py-1 rounded-btn text-secondary hover:text-accent hover:bg-accent/8 text-xs transition-colors duration-150"
@@ -1155,6 +1176,64 @@ export function Data() {
         )}
       </AnimatePresence>
 
+      {/* 停止同步二次确认弹窗 */}
+      <AnimatePresence>
+        {showStopConfirm && (
+          <div className="fixed inset-0 z-50 flex items-center justify-center">
+            <motion.div
+              initial={{ opacity: 0 }}
+              animate={{ opacity: 1 }}
+              exit={{ opacity: 0 }}
+              transition={{ duration: 0.15 }}
+              className="absolute inset-0 bg-black/60 backdrop-blur-sm"
+              onClick={() => !stopSync.isPending && setShowStopConfirm(false)}
+            />
+            <motion.div
+              initial={{ opacity: 0, scale: 0.95, y: 12 }}
+              animate={{ opacity: 1, scale: 1, y: 0 }}
+              exit={{ opacity: 0, scale: 0.97, y: 8 }}
+              transition={{ duration: 0.2, ease: [0.16, 1, 0.3, 1] }}
+              className="relative w-[90vw] max-w-[420px] rounded-card border border-border bg-base shadow-2xl p-6"
+            >
+              <div className="flex items-start gap-3">
+                <div className="shrink-0 h-10 w-10 rounded-full bg-danger/12 flex items-center justify-center">
+                  <AlertTriangle className="h-5 w-5 text-danger" />
+                </div>
+                <div className="min-w-0">
+                  <h3 className="text-sm font-semibold text-foreground mb-1.5">确认停止数据同步？</h3>
+                  <p className="text-xs text-secondary leading-relaxed">
+                    当前任务将在<span className="text-foreground font-medium">正在拉取的分块完成后</span>中断（协作式停止，不会损坏已写入的数据）。
+                  </p>
+                  <p className="mt-2 text-[11px] text-danger/90 leading-relaxed">
+                    停止后再次拉取需要重新走完整管道（拉取 → 指标计算 → 监控规则），无法从停止处续跑。
+                  </p>
+                  <div className="mt-2 flex items-start gap-1.5 text-[11px] text-muted">
+                    <Info className="h-3.5 w-3.5 shrink-0 mt-px text-muted" />
+                    <span>已写入的部分数据会保留，下次同步时覆盖或补齐。</span>
+                  </div>
+                </div>
+              </div>
+              <div className="flex items-center justify-end gap-2 mt-5">
+                <button
+                  onClick={() => setShowStopConfirm(false)}
+                  disabled={stopSync.isPending}
+                  className="px-3 py-1.5 rounded-btn bg-elevated text-secondary hover:bg-elevated/80 text-sm transition-colors disabled:opacity-50"
+                >
+                  取消
+                </button>
+                <button
+                  onClick={() => stopSync.mutate()}
+                  disabled={stopSync.isPending}
+                  className="px-3 py-1.5 rounded-btn bg-danger/90 text-base text-sm font-medium hover:bg-danger disabled:opacity-50 transition-colors"
+                >
+                  {stopSync.isPending ? '停止中…' : '确认停止'}
+                </button>
+              </div>
+            </motion.div>
+          </div>
+        )}
+      </AnimatePresence>
+
       {/* 清除数据二次确认弹窗 */}
       <AnimatePresence>
         {adjGate.dialog}