fix: preserve task stop intent and guard remote execution boundaries

backend/services/background_tasks/opencode.py

@@ -51,11 +51,11 @@ class OpenCodeExecutor:
                    item.get("info", {}).get("parentID") == handle["message_id"]]
         errors = [item["info"]["error"] for item in matched if item["info"].get("error")]
         if errors:
-            return {"status": "failed", "summary": "远端执行失败", "result": json.dumps(errors[-1], ensure_ascii=False)[:8000]}
+            return {"status": "failed", "summary": "远端执行失败", "result": json.dumps(errors, ensure_ascii=False)}
         completed = [item for item in matched if item["info"].get("time", {}).get("completed")]
         if remote_status.get("type") == "idle" and completed:
             text = "\n".join(part.get("text", "") for item in completed for part in item.get("parts", []) if part.get("type") == "text")
-            return {"status": "succeeded", "summary": "任务已完成", "result": text[-16000:]}
+            return {"status": "succeeded", "summary": "任务已完成", "result": text}
         return {"status": "running", "summary": "远端任务执行中", "result": ""}
 
     async def snapshot(self, handle: dict) -> dict:

backend/services/background_tasks/records.py

@@ -60,7 +60,7 @@ class TaskRepository:
             return from_row(row) if row else None
 
     async def list(self, assistant_id: str | None = None, *, active=False) -> list[TaskRecord]:
-        statement = select(BackgroundTask).order_by(BackgroundTask.created_at.desc())
+        statement = select(BackgroundTask).order_by(BackgroundTask.status.in_(ACTIVE).desc(), BackgroundTask.created_at.desc())
         if not active:
             statement = statement.limit(100)
         if assistant_id:

backend/services/background_tasks/service.py

@@ -101,10 +101,17 @@ class TaskService:
         task_id = message.payload["task_id"]
         self._jobs[message.job_id] = task_id
         record = await self.get(task_id)
+        if record.status == "cancel_requested":
+            await self._stop_record(record)
+            return {"task_id": task_id}
         executor = self.executor_factory(record.connection, record.secrets)
         resume = bool(record.remote_handle)
         try:
             if not resume:
+                outstanding = await self.repository.list(active=True)
+                if any(other.id != task_id and other.remote_handle for other in outstanding):
+                    await self.repository.patch(task_id, status="failed", summary="另一远端任务尚未结束，请先核查或停止该任务；本任务未提交到远端")
+                    return {"task_id": task_id}
                 handle = await executor.prepare()
                 record = await self.repository.patch(task_id, remote_handle=handle)
             last_event = None