diff --git a/src/aiTaskWorker.js b/src/aiTaskWorker.js
index 6f191b7..9781ae0 100644
--- a/src/aiTaskWorker.js
+++ b/src/aiTaskWorker.js
@@ -152,6 +152,15 @@ async function clearPollerState(taskDbId) {
   await pool.query("DELETE FROM generation_task_pollers WHERE task_id = $1", [taskDbId]);
 }
 
+async function getPersistedLeaseToken(taskDbId) {
+  await ensureTaskPollerStore();
+  const { rows } = await pool.query(
+    "SELECT lease_token FROM generation_task_pollers WHERE task_id = $1 LIMIT 1",
+    [taskDbId],
+  );
+  return rows[0]?.lease_token || null;
+}
+
 async function getLeaseKey(leaseToken) {
   if (!leaseToken) return null;
   const { rows } = await pool.query(
@@ -880,6 +889,29 @@ function stopPolling(taskDbId) {
   clearPollerState(taskDbId).catch(() => {});
 }
 
+async function cancelTaskRuntimeState(taskDbId, keyManager) {
+  const poller = activePollers.get(taskDbId);
+  if (poller) {
+    clearInterval(poller.interval);
+    activePollers.delete(taskDbId);
+  }
+
+  const leaseToken = poller?.leaseToken || await getPersistedLeaseToken(taskDbId).catch(() => null);
+  await clearPollerState(taskDbId).catch(() => {});
+  if (leaseToken && keyManager) {
+    await keyManager.releaseKey(leaseToken).catch((err) => {
+      console.error(`[aiTaskWorker] failed to release lease for cancelled task ${taskDbId}:`, err.message);
+    });
+  }
+  await publishTaskEvent({
+    taskId: taskDbId,
+    status: "cancelled",
+    progress: 100,
+    resultUrl: null,
+    error: "任务已取消",
+  });
+}
+
 function getActiveCount() {
   return activePollers.size;
 }
@@ -1064,6 +1096,7 @@ function stopPollerRecovery() {
 module.exports = {
   startPolling,
   stopPolling,
+  cancelTaskRuntimeState,
   updateTaskInDb,
   getActiveCount,
   extractProviderTaskId,
diff --git a/src/routes/ai.js b/src/routes/ai.js
index 5a6cf78..3c5e012 100644
--- a/src/routes/ai.js
+++ b/src/routes/ai.js
@@ -16,6 +16,7 @@ const {
 } = require("../enterpriseVideoBilling");
 const {
   startPolling,
+  cancelTaskRuntimeState,
   updateTaskInDb,
   extractProviderTaskId,
   extractImageUrl,
@@ -1742,6 +1743,35 @@ function registerAiRoutes(router) {
     }
   });
 
+  const streamTaskStatusPoll = async (taskId, userId, emit) => {
+    const { rows } = await pool.query(
+      "SELECT * FROM generation_tasks WHERE id = $1 AND user_id = $2",
+      [taskId, userId],
+    );
+    const row = rows[0];
+    if (!row) return { found: false, terminal: true };
+
+    if (row.status === "pending" || row.status === "running") {
+      pool.query(
+        "UPDATE generation_tasks SET last_poll_at = NOW() WHERE id = $1",
+        [taskId],
+      ).catch(() => {});
+    }
+
+    const event = {
+      taskId: row.id,
+      status: row.status,
+      progress: Number(row.progress || 0),
+      resultUrl: row.result_url || null,
+      error: row.error || null,
+    };
+    emit(event);
+    return {
+      found: true,
+      terminal: ["completed", "failed", "cancelled"].includes(row.status),
+    };
+  };
+
   router.get("/ai/tasks/:taskId/stream", requireAuth, async (req, res) => {
     const { taskId } = req.params;
     try {
@@ -1773,16 +1803,43 @@ function registerAiRoutes(router) {
         return;
       }
 
+      let closed = false;
+      let lastSnapshot = JSON.stringify(initial);
+      let dbPollTimer = null;
+      const endStream = () => {
+        if (closed) return;
+        closed = true;
+        if (dbPollTimer) clearInterval(dbPollTimer);
+        taskEvents.off(`task:${taskId}`, onUpdate);
+        res.end();
+      };
+      const emitIfChanged = (evt) => {
+        if (closed) return;
+        const snapshot = JSON.stringify(evt);
+        if (snapshot === lastSnapshot) return;
+        lastSnapshot = snapshot;
+        res.write(`data: ${snapshot}\n\n`);
+      };
       const onUpdate = (evt) => {
-        res.write(`data: ${JSON.stringify(evt)}\n\n`);
+        emitIfChanged(evt);
         if (["completed", "failed", "cancelled"].includes(evt.status)) {
-          res.end();
+          endStream();
         }
       };
       taskEvents.on(`task:${taskId}`, onUpdate);
 
+      dbPollTimer = setInterval(() => {
+        streamTaskStatusPoll(taskId, req.user.id, emitIfChanged)
+          .then((result) => {
+            if (!result.found || result.terminal) endStream();
+          })
+          .catch((pollErr) => {
+            console.error(`[ai/task-stream] db poll failed for task ${taskId}:`, pollErr.message);
+          });
+      }, 3000);
+
       req.on("close", () => {
-        taskEvents.off(`task:${taskId}`, onUpdate);
+        endStream();
       });
     } catch (err) {
       if (!res.headersSent) res.status(err.name === "AbortError" ? 504 : 500).json({ error: err.name === "AbortError" ? "AI 上游响应超时，请重试" : err.message });
@@ -1799,6 +1856,7 @@ function registerAiRoutes(router) {
         [taskId, req.user.id],
       );
       if (rows.length === 0) return res.status(404).json({ error: "Task not found or not in active state" });
+      await cancelTaskRuntimeState(taskId, keyManager);
       res.json({ id: rows[0].id, status: rows[0].status });
     } catch (err) {
       console.error("[ai/task-cancel] error:", err.message);