diff --git a/backend/routes/background_tasks.py b/backend/routes/background_tasks.py
index d2837b8..e2228ab 100644
--- a/backend/routes/background_tasks.py
+++ b/backend/routes/background_tasks.py
@@ -12,7 +12,6 @@ router = APIRouter(prefix="/api/background-tasks", tags=["background-tasks"], de
 
 class SubmitTask(CamelModel):
     assistant_id: str
-    tool_id: str
     instruction: str = Field(min_length=1, max_length=12000)
     request_id: str = Field(min_length=1, max_length=80)
 
@@ -32,12 +31,15 @@ async def submit_task(body: SubmitTask, db=Depends(get_session)):
     cfg = await resolve_runtime_config(db, body.assistant_id)
     if cfg.type != "prompt" or cfg.runtimeMode != "pipeline":
         raise HTTPException(400, "后台任务仅支持提示词 Pipeline")
-    bound = {binding.tool_id for binding in cfg.tool_bindings}
-    tool = next((tool for tool in cfg.tools if tool.id == body.tool_id and tool.id in bound and tool.type == "task"), None)
-    if not tool:
-        raise HTTPException(400, "助手未绑定该任务工具")
+    if cfg.task_backend is None:
+        raise HTTPException(400, "助手未绑定任务后端")
     try:
-        return await task_service.submit(assistant_id=body.assistant_id, conversation_id="web_" + body.assistant_id, tool=tool, instruction=body.instruction, invocation_id=body.request_id)
+        return await task_service.submit(
+            assistant_id=body.assistant_id, conversation_id="web_" + body.assistant_id,
+            backend=cfg.task_backend, instruction=body.instruction, invocation_id=body.request_id,
+            variable_state={"values": cfg.dynamic_variables, "definitions": cfg.dynamic_variable_definitions,
+                            "secrets": cfg.secret_dynamic_variables},
+        )
     except ValueError as exc:
         raise HTTPException(400, str(exc)) from exc
 
diff --git a/backend/services/background_tasks/opencode.py b/backend/services/background_tasks/opencode.py
index ee9be5d..1a2028b 100644
--- a/backend/services/background_tasks/opencode.py
+++ b/backend/services/background_tasks/opencode.py
@@ -76,9 +76,21 @@ class OpenCodeExecutor:
             async with client.stream("GET", "event") as stream:
                 stream.raise_for_status()
                 if not resume:
+                    payload = {"messageID": handle["message_id"], "parts": [{"type": "text", "text": instruction}]}
+                    if self.config.get("agent"):
+                        payload["agent"] = self.config["agent"]
+                    if self.config.get("model_provider_id") and self.config.get("model_id"):
+                        payload["model"] = {"providerID": self.config["model_provider_id"], "modelID": self.config["model_id"]}
+                    backend = self.config.get("_backend") or {}
+                    from services.runtime_variables import DynamicVariableStore
+                    store = DynamicVariableStore(self.config.get("_variables") or {})
+                    assistant_instructions = store.render(str(backend.get("instructions") or ""))
+                    instructions = "\n\n".join(value for value in (self.config.get("instructions"), assistant_instructions) if value)
+                    if instructions:
+                        payload["system"] = instructions
                     response = await client.post(
                         f"session/{handle['session_id']}/prompt_async",
-                        json={"messageID": handle["message_id"], "parts": [{"type": "text", "text": instruction}]},
+                        json=payload,
                     )
                     response.raise_for_status()
                     await emit({"status": "submitted", "summary": "远端已接收，等待执行"})
diff --git a/backend/services/background_tasks/reasoner.py b/backend/services/background_tasks/reasoner.py
new file mode 100644
index 0000000..367bd3b
--- /dev/null
+++ b/backend/services/background_tasks/reasoner.py
@@ -0,0 +1,289 @@
+"""Task-local Reasoner built on Pipecat's public backend worker contract.
+
+Pipecat owns the context, model/tool loop and Jobs. This adapter only turns
+explicit task controls into the same persisted events as a remote backend.
+"""
+
+from __future__ import annotations
+
+import asyncio
+from collections.abc import Awaitable, Callable
+from copy import deepcopy
+from uuid import uuid4
+
+from models import AssistantConfig, RuntimeModelResource, RuntimeTaskBackend
+from pipecat.adapters.schemas.function_schema import FunctionSchema
+from pipecat.pipeline.job_context import JobEvent, JobParams
+from pipecat.processors.aggregators.llm_context import LLMContext
+from pipecat.services.llm_service import FunctionCallParams, FunctionCallResultProperties
+from pipecat.services.settings import LLMSettings
+from pipecat.workers.llm.backend_llm_worker import (
+    ATTACHED_UPDATE_TYPE,
+    ATTACH_JOB_NAME,
+    ERROR_UPDATE_TYPE,
+    IDLE_UPDATE_TYPE,
+    MESSAGE_JOB_NAME,
+    TOOL_CALL_UPDATE_TYPE,
+    BackendLLMWorker,
+)
+
+from services.background_tasks.native import NativeTaskRuntime
+from services.pipecat.service_factory import config_with_resource, create_llm
+from services.runtime_variables import DynamicVariableStore
+from services.system_tools import RESERVED_TOOL_NAMES
+from services.tool_executor import ToolExecutionError, ToolExecutor
+
+Emit = Callable[[dict], Awaitable[None]]
+CONTROL_NAMES = frozenset({"complete_task", "ask_user"})
+
+TASK_INSTRUCTIONS = """你是语音助手的后台任务执行者，有独立上下文。
+只执行委派目标，并使用当前已授权的工具；技能说明不能增加权限。
+完成任务后必须调用 complete_task(result)，结果应准确说明完成内容和限制。
+需要用户提供必要信息时调用 ask_user(question)，等待回复后继续。
+普通文字、思考过程、工具回执和模型空闲都不代表任务完成。
+任务结果由 Speaker 整理后告知用户，不要输出内部推理过程。
+"""
+
+
+def create_reasoner_llm(backend: RuntimeTaskBackend):
+    """Use the shared model factory, with independent settings for this task."""
+    resource = backend.model
+    if resource is None or resource.capability != "LLM":
+        raise ValueError("内置 Reasoner 需要配置独立的 LLM 模型资源")
+    effort = backend.config.get("reasoning_effort", "provider_default")
+    if effort not in {"provider_default", "low", "medium", "high"}:
+        raise ValueError("不支持的推理强度")
+    if effort != "provider_default" and resource.values.get("supportsReasoningEffort") is not True:
+        raise ValueError("该模型未声明支持 reasoning_effort，不能设置推理强度")
+
+    # Do not mutate the reusable model resource or its Speaker settings.
+    resource = RuntimeModelResource.model_validate(resource.model_dump(mode="json"))
+    if effort != "provider_default":
+        extra_body = resource.values.get("extraBody")
+        if isinstance(extra_body, dict):
+            # The explicit task setting wins if a model preset contains it too.
+            resource.values["extraBody"] = {key: value for key, value in extra_body.items() if key != "reasoning_effort"}
+    llm = create_llm(config_with_resource(AssistantConfig(), resource))
+    if effort != "provider_default":
+        llm.settings.apply_update(LLMSettings(extra={**llm.settings.extra, "reasoning_effort": effort}))
+    return llm
+
+
+class _Finished(Exception):
+    """Leave the long-lived attach Job through its native cancellation path."""
+
+    def __init__(self, result: dict):
+        super().__init__("task finished")
+        self.result = result
+
+
+class ReasonerExecutor:
+    def __init__(self, config: dict, secrets: dict, *, runtime: NativeTaskRuntime):
+        self.config = config
+        self.runtime = runtime
+        self.backend = RuntimeTaskBackend.model_validate(config["_backend"])
+        self._worker: BackendLLMWorker | None = None
+        self._emit: Emit | None = None
+        self._pending: dict = {}
+        self._final: dict | None = None
+        self._confirmed: dict | None = None
+        self._registered: list[str] = []
+        self._stopped = False
+        self._sending_input = False
+        self._cleanup_lock = asyncio.Lock()
+        self._tools = ToolExecutor(DynamicVariableStore.from_config(AssistantConfig(
+            dynamic_variables=deepcopy(config.get("_variables") or {}),
+            dynamic_variable_definitions=deepcopy(config.get("_variable_definitions") or {}),
+            secret_dynamic_variables=deepcopy(config.get("_secret_variables") or {}),
+        )))
+
+    async def prepare(self) -> dict:
+        return {"kind": "reasoner", "task_id": self.config["_task_id"]}
+
+    def _system_prompt(self) -> str:
+        parts = [
+            TASK_INSTRUCTIONS,
+            str(self.backend.config.get("instructions") or "").strip(),
+            self._tools.store.render(self.backend.instructions).strip(),
+        ]
+        for skill in self.backend.config.get("skills") or []:
+            parts.append(f"技能：{skill['name']}\n{skill['content']}")
+        return "\n\n".join(part for part in parts if part)
+
+    def _build_worker(self) -> BackendLLMWorker:
+        bindings = {binding.tool_id: binding for binding in self.backend.tool_bindings}
+        names = set(CONTROL_NAMES | RESERVED_TOOL_NAMES | {"delegate_task"})
+        schemas = []
+        callbacks = []
+        for tool in self.backend.tools:
+            if tool.type not in {"http", "mcp"}:
+                raise ValueError("Reasoner 仅允许 HTTP/MCP 服务端工具")
+            if tool.function_name in names:
+                raise ValueError("Reasoner 工具函数名重复或与任务控制函数冲突")
+            names.add(tool.function_name)
+            binding = bindings.get(tool.id)
+            if binding is None:
+                raise ValueError("Reasoner 工具必须显式绑定才可执行")
+            properties, required = self._tools.schema_parts(tool, binding)
+            schemas.append(FunctionSchema(name=tool.function_name, description=tool.description or tool.name,
+                                          properties=properties, required=required))
+
+            async def execute(params, current_tool=tool, current_binding=binding):
+                if self._pending or self._final or self._stopped:
+                    await params.result_callback({"status": "error", "message": "任务已暂停或结束，不执行新工具"},
+                                                 properties=FunctionCallResultProperties(run_llm=False))
+                    return
+                try:
+                    result = await self._tools.execute(current_tool, dict(params.arguments or {}), binding=current_binding)
+                except (ToolExecutionError, ValueError):
+                    # Tool errors can carry URLs or sensitive payloads. Let the
+                    # model report a useful failure without exposing those.
+                    result = {"status": "error", "message": "服务端工具执行失败，请检查工具配置或稍后重试"}
+                await params.result_callback(result, properties=FunctionCallResultProperties(
+                    run_llm=not (self._pending or self._final or self._stopped),
+                ))
+
+            callbacks.append((tool.function_name, execute))
+
+        schemas.extend([
+            FunctionSchema(name="complete_task", description="明确完成任务并提交最终结果。",
+                           properties={"result": {"type": "string", "description": "完成结果、依据和未完成的限制。"}}, required=["result"]),
+            FunctionSchema(name="ask_user", description="需要必要信息时暂停任务，向用户提出一个问题。",
+                           properties={"question": {"type": "string", "description": "需要用户回答的问题。"}}, required=["question"]),
+        ])
+        llm = create_reasoner_llm(self.backend)
+        for name, callback in callbacks + [("complete_task", self._complete_task), ("ask_user", self._ask_user)]:
+            # Synchronous native tools drive BackendLLMWorker's existing loop.
+            llm.register_function(name, callback, cancel_on_interruption=True)
+            self._registered.append(name)
+        return BackendLLMWorker(
+            name="reasoner-" + uuid4().hex,
+            llm=llm,
+            context=LLMContext([{"role": "system", "content": self._system_prompt()}], tools=schemas),
+            pairing_instruction="任务由 Speaker 发送给你。使用任务控制函数提交结果或提问；普通输出不作为给用户的通知。",
+        )
+
+    async def _complete_task(self, params: FunctionCallParams):
+        result = str(params.arguments.get("result") or "").strip()
+        if not result or self._pending or self._stopped:
+            await params.result_callback(
+                {"status": "error", "message": "需要非空结果，且任务不能处于等待输入或停止状态"},
+                properties=FunctionCallResultProperties(run_llm=not (self._pending or self._stopped)),
+            )
+            return
+        self._final = {"status": "succeeded", "summary": "任务已完成", "result": result}
+        await params.result_callback({"status": "accepted"}, properties=FunctionCallResultProperties(run_llm=False))
+
+    async def _ask_user(self, params: FunctionCallParams):
+        question = str(params.arguments.get("question") or "").strip()
+        if not question or self._pending or self._final or self._stopped:
+            await params.result_callback(
+                {"status": "error", "message": "请在任务运行时提出一个非空问题"},
+                properties=FunctionCallResultProperties(run_llm=not (self._pending or self._final or self._stopped)),
+            )
+            return
+        self._pending = {"id": "question_" + uuid4().hex, "kind": "question",
+                         "questions": [{"header": "补充信息", "question": question, "options": [], "custom": True}]}
+        await self._emit({"status": "waiting_input", "summary": "任务需要补充信息", "input_request": deepcopy(self._pending)})
+        await params.result_callback({"status": "waiting_input"}, properties=FunctionCallResultProperties(run_llm=False))
+
+    async def _message(self, text: str):
+        if self._worker is None or self._stopped:
+            raise ValueError("内置 Reasoner 已停止，不能继续当前任务")
+        async with self.runtime.coordinator.job(self._worker.name, params=JobParams(
+            name=MESSAGE_JOB_NAME, payload={"request": text}, timeout=15,
+        )):
+            pass
+
+    async def run(self, handle: dict, instruction: str, emit: Emit, *, resume=False) -> dict:
+        if resume:
+            return {"status": "failed", "summary": "内置任务执行曾中断，不会自动重放工具", "result": "请核查已有操作后重新创建任务。"}
+        if self.runtime.runner is None:
+            raise ValueError("后台任务运行器尚未启动")
+        self._emit = emit
+        self._worker = self._build_worker()
+        try:
+            await self.runtime.runner.add_workers(self._worker)
+            async with self.runtime.coordinator.job(self._worker.name, params=JobParams(name=ATTACH_JOB_NAME)) as attached:
+                async for event in attached:
+                    if event.type != JobEvent.UPDATE:
+                        continue
+                    data = event.data or {}
+                    kind = data.get("type")
+                    if kind == ATTACHED_UPDATE_TYPE:
+                        await emit({"status": "running", "summary": "内置 Reasoner 正在执行任务"})
+                        await self._message(instruction)
+                    elif kind == TOOL_CALL_UPDATE_TYPE and data.get("function_name") not in CONTROL_NAMES:
+                        if not self._pending:
+                            await emit({"status": "running", "summary": f"服务端工具 · {data.get('function_name', '')}"[:300]})
+                    elif kind == ERROR_UPDATE_TYPE:
+                        raise _Finished({"status": "failed", "summary": "内置推理服务执行失败", "result": "请检查模型连接和工具配置。"})
+                    elif kind == IDLE_UPDATE_TYPE:
+                        # An old idle update can already be on the bus when a
+                        # user reply starts the next native message Job.
+                        if self._sending_input or self._worker.working:
+                            continue
+                        if self._final:
+                            raise _Finished(self._final)
+                        if not self._pending:
+                            raise _Finished({"status": "failed", "summary": "模型没有明确完成任务", "result": "模型已停止生成，但没有调用 complete_task 或 ask_user；请调整任务指令或模型后重试。"})
+            return {"status": "failed", "summary": "内置任务连接已中断", "result": "不会自动重放工具调用。"}
+        except _Finished as finished:
+            self._confirmed = finished.result
+            return finished.result
+        finally:
+            await self._cleanup()
+
+    async def _cleanup(self):
+        async with self._cleanup_lock:
+            worker = self._worker
+            self._stopped = True
+            if worker is None:
+                return
+            # This is PipelineWorker.cancel(), which cancels only this pipeline.
+            # BaseWorker.cancel()/runner.cancel() would stop unrelated tasks too.
+            await worker.cancel(reason="task finished or cancelled")
+            await asyncio.wait_for(worker.wait(), 10)
+            # WorkerRunner retains ended worker registrations. Release transcript
+            # and handler captures through public APIs instead of editing Pipecat.
+            worker.context.set_messages([])
+            worker.context.set_tools([])
+            for name in self._registered:
+                worker.llm.unregister_function(name)
+            self._registered.clear()
+            self._worker = None
+
+    async def cancel(self, handle: dict) -> bool:
+        if self._worker is not None:
+            await self._cleanup()
+        return True
+
+    async def snapshot(self, handle: dict) -> dict:
+        if self._confirmed and self._worker is None:
+            return dict(self._confirmed)
+        if self._pending:
+            return {"status": "waiting_input", "summary": "任务需要补充信息", "input_request": deepcopy(self._pending)}
+        if self._stopped:
+            return {"status": "failed", "summary": "内置任务已中断", "result": "不会自动重放工具调用。"}
+        return {"status": "running", "summary": "内置 Reasoner 正在执行任务"}
+
+    async def send_input(self, request: dict, value: dict):
+        if not self._pending or request.get("id") != self._pending["id"]:
+            raise ValueError("该问题已处理或不属于当前任务")
+        answers = value.get("answers")
+        if not isinstance(answers, list) or len(answers) != 1 or not isinstance(answers[0], list):
+            raise ValueError("请回答当前任务的问题")
+        text = "\n".join(str(answer).strip() for answer in answers[0]).strip()
+        if not text:
+            raise ValueError("回答不能为空")
+        previous = self._pending
+        self._pending = {}
+        self._sending_input = True
+        try:
+            await self._message("用户补充信息：\n" + text)
+        except Exception:
+            if not self._pending and not self._stopped:
+                self._pending = previous
+            raise
+        finally:
+            self._sending_input = False
diff --git a/backend/services/background_tasks/records.py b/backend/services/background_tasks/records.py
index bdfe52e..f967781 100644
--- a/backend/services/background_tasks/records.py
+++ b/backend/services/background_tasks/records.py
@@ -23,6 +23,9 @@ class TaskRecord:
     origin_key: str
     connection: dict
     secrets: dict
+    backend_id: str = ""
+    backend_type: str = "opencode"
+    deadline_at: str | None = None
     status: str = "queued"
     summary: str = "任务已排队"
     result: str = ""
diff --git a/backend/services/background_tasks/service.py b/backend/services/background_tasks/service.py
index 0615efe..b827989 100644
--- a/backend/services/background_tasks/service.py
+++ b/backend/services/background_tasks/service.py
@@ -1,8 +1,9 @@
-"""Business entry point backed by native Pipecat Jobs."""
+"""Task records and backend selection around application-owned Pipecat Jobs."""
 
 import asyncio
 from collections import defaultdict
 from copy import deepcopy
+from datetime import UTC, datetime, timedelta
 from uuid import uuid4
 
 from loguru import logger
@@ -12,18 +13,19 @@ from services.background_tasks.records import TaskRecord, TaskRepository, TERMIN
 
 
 class TaskService:
-    def __init__(self, repository=None, executor_factory=OpenCodeExecutor):
+    def __init__(self, repository=None, executor_factory=None):
         self.repository = repository or TaskRepository()
         self.executor_factory = executor_factory
         self.runtime = None
         self._listeners = defaultdict(set)
         self._jobs = {}
+        self._executors = {}
         self._submit_lock = asyncio.Lock()
         self._closing = False
 
     async def start(self):
         self._closing = False
-        self.runtime = NativeTaskRuntime(self._execute, self._cancel_remote, self._on_update, self._on_result)
+        self.runtime = NativeTaskRuntime(self._execute, self._cancel_backend, self._on_update, self._on_result)
         await self.runtime.start()
         try:
             records = await self.repository.list(active=True)
@@ -31,10 +33,12 @@ class TaskService:
             await self.close()
             raise
         for record in records:
-            if record.remote_handle:
+            if record.backend_type == "reasoner":
+                await self.repository.patch(record.id, status="failed", summary="服务重启，内置任务已中断；未自动重放工具，请核查已执行操作")
+            elif record.remote_handle:
                 await self._dispatch(record)
             else:
-                await self.repository.patch(record.id, status="unknown", summary="服务曾中断，未自动重新提交；请核查远端后再创建任务")
+                await self.repository.patch(record.id, status="unknown", summary="服务曾中断，未自动重新提交；请核查执行后端后再创建任务")
 
     async def close(self):
         self._closing = True
@@ -43,8 +47,9 @@ class TaskService:
         self.runtime = None
         self._listeners.clear()
         self._jobs.clear()
+        self._executors.clear()
 
-    async def submit(self, *, assistant_id, conversation_id, instruction, invocation_id, backend=None, tool=None):
+    async def submit(self, *, assistant_id, conversation_id, backend, instruction, invocation_id, variable_state=None):
         if not self.runtime:
             raise ValueError("后台任务服务尚未启动")
         if not assistant_id or not conversation_id:
@@ -52,32 +57,42 @@ class TaskService:
         text = instruction.strip()
         if not text or len(text) > 12000:
             raise ValueError("任务指令必须为 1-12000 个字符")
-        if backend is not None:
-            if backend.type != "opencode":
-                raise ValueError("该任务后端尚未接通")
-            backend_id = backend.id
-            connection = deepcopy(backend.config)
-            connection["_backend_type"] = backend.type
-            secrets = deepcopy(backend.secrets)
-        else:
-            # F0 transition: retired when saved Tool bindings migrate in F1.
-            if tool is None or tool.type != "task":
-                raise ValueError("请选择任务后端")
-            backend_id, connection, secrets = tool.id, deepcopy(tool.definition["config"]), deepcopy(tool.secrets)
+        if backend.type not in {"reasoner", "opencode"}:
+            raise ValueError("不支持该任务后端")
+        snapshot = backend.model_dump(mode="json") if hasattr(backend, "model_dump") else {
+            "id": backend.id, "name": getattr(backend, "name", ""), "type": backend.type,
+            "config": deepcopy(backend.config), "secrets": deepcopy(backend.secrets),
+        }
+        connection = deepcopy(backend.config)
+        connection["_backend_type"] = backend.type
+        connection["_backend"] = snapshot
+        state = variable_state or {}
+        connection["_variables"] = deepcopy(state.get("values", {}))
+        connection["_variable_definitions"] = deepcopy(state.get("definitions", {}))
+        connection["_secret_variables"] = deepcopy(state.get("secrets", {}))
+        timeout = int(connection.get("timeout_seconds", 600))
+        deadline = (datetime.now(UTC) + timedelta(seconds=timeout)).isoformat()
         async with self._submit_lock:
             record = await self.repository.create(TaskRecord(
                 id="task_" + uuid4().hex,
-                assistant_id=assistant_id, conversation_id=conversation_id,
-                tool_id=backend_id, instruction=text,
-                origin_key=f"{conversation_id}:{invocation_id}"[:256],
-                connection=connection, secrets=secrets,
+                assistant_id=assistant_id, conversation_id=conversation_id, tool_id="",
+                backend_id=backend.id, backend_type=backend.type, deadline_at=deadline,
+                instruction=text, origin_key=f"{conversation_id}:{invocation_id}"[:256],
+                connection=connection, secrets=deepcopy(backend.secrets),
             ))
             if not record.job_id and record.status == "queued":
                 await self._dispatch(record)
-        return record.public()
+        return (await self.get(record.id)).public()
 
     async def _dispatch(self, record):
-        job_id = await self.runtime.submit(record.id, record.connection.get("timeout_seconds", 600))
+        timeout = float(record.connection.get("timeout_seconds", 600))
+        if record.deadline_at:
+            timeout = (datetime.fromisoformat(record.deadline_at) - datetime.now(UTC)).total_seconds()
+        if timeout <= 0:
+            await self._save(record.id, status="cancel_requested", summary="任务已超过等待时限，正在核查停止状态")
+            await self._stop_record(await self.get(record.id))
+            return
+        job_id = await self.runtime.submit(record.id, timeout)
         self._jobs[job_id] = record.id
         await self.repository.patch(record.id, job_id=job_id)
 
@@ -107,23 +122,36 @@ class TaskService:
         await self._publish(record)
         return record
 
+    def _executor(self, record):
+        if record.id in self._executors:
+            return self._executors[record.id]
+        config = {**record.connection, "_task_id": record.id}
+        if self.executor_factory:
+            return self.executor_factory(config, record.secrets)
+        if record.backend_type == "reasoner":
+            from services.background_tasks.reasoner import ReasonerExecutor
+            return ReasonerExecutor(config, record.secrets, runtime=self.runtime)
+        return OpenCodeExecutor(config, record.secrets)
+
     async def _execute(self, message, worker):
         task_id = message.payload["task_id"]
         self._jobs[message.job_id] = task_id
         record = await self.get(task_id)
+        if record.status in TERMINAL:
+            return {"task_id": 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)
+        executor = self._executor(record)
+        self._executors[task_id] = executor
         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")
+                if any(other.id != task_id and other.backend_type == "opencode" 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；本任务未提交到后端")
                     return {"task_id": task_id}
-                handle = await executor.prepare()
-                record = await self.repository.patch(task_id, remote_handle=handle)
+                record = await self.repository.patch(task_id, remote_handle=await executor.prepare())
             last_event = None
             async def emit(event):
                 nonlocal last_event
@@ -132,8 +160,9 @@ class TaskService:
                 last_event = deepcopy(event)
                 await self.repository.patch(task_id, **event)
                 await worker.send_job_update(message.job_id, {"task_id": task_id})
-            # Reconnect only observations; never repeat a mutating prompt.
-            for attempt in range(5):
+            # Only OpenCode can reconnect observations without replaying work.
+            attempts = 1 if record.backend_type == "reasoner" else 5
+            for attempt in range(attempts):
                 try:
                     result = await executor.run(record.remote_handle, record.instruction, emit, resume=resume)
                     await self.repository.patch(task_id, **result, input_request={})
@@ -141,32 +170,35 @@ class TaskService:
                 except asyncio.CancelledError:
                     raise
                 except Exception:
+                    if attempt == attempts - 1:
+                        raise
                     resume = True
                     await emit({"summary": "远端连接中断，正在核查任务状态"})
-                    if attempt == 4:
-                        raise
                     await asyncio.sleep(min(2 ** attempt, 10))
         except asyncio.CancelledError:
             raise
         except Exception:
-            await self.repository.patch(task_id, status="unknown", summary="无法确认远端执行状态，请检查远端服务；不会自动重复提交")
+            if record.backend_type == "reasoner":
+                await self.repository.patch(task_id, status="failed", summary="内置推理任务中断；未自动重复执行，请核查任务配置与已执行操作")
+            else:
+                await self.repository.patch(task_id, status="unknown", summary="无法确认远端执行状态，请检查远端服务；不会自动重复提交")
             return {"task_id": task_id}
 
     async def _on_update(self, message):
         task_id = (message.update or {}).get("task_id")
         if task_id:
-            record = await self.get(task_id)
-            await self._publish(record)
+            await self._publish(await self.get(task_id))
 
     async def _on_result(self, message):
-        if self._closing:
-            return
         task_id = self._jobs.pop(message.job_id, None)
         if not task_id:
             return
+        self._executors.pop(task_id, None)
+        if self._closing:
+            return
         record = await self.get(task_id)
         if record.status not in TERMINAL and str(message.status) in {"error", "failed"}:
-            await self._save(task_id, status="unknown", summary="任务运行中断，请核查远端状态")
+            await self._save(task_id, status="unknown", summary="任务运行中断，请核查执行后端状态")
         else:
             await self._publish(record)
 
@@ -174,13 +206,13 @@ class TaskService:
         record = await self.get(task_id, assistant_id)
         if record.status in TERMINAL:
             return record.public()
-        await self._save(task_id, status="cancel_requested", summary="正在请求远端停止")
+        await self._save(task_id, status="cancel_requested", summary="正在请求停止任务")
         accepted = bool(self.runtime and record.job_id and await self.runtime.cancel(record.job_id))
         if not accepted:
             await self._stop_record(record)
         return (await self.get(task_id)).public()
 
-    async def _cancel_remote(self, message):
+    async def _cancel_backend(self, message):
         task_id = self._jobs.get(message.job_id)
         if not task_id or self._closing:
             return
@@ -190,38 +222,41 @@ class TaskService:
         if record.status in TERMINAL:
             return
         if not record.remote_handle:
-            await self._save(record.id, status="cancelled", summary="已取消，尚未向远端提交指令")
+            await self._save(record.id, status="cancelled", summary="已取消，尚未向任务后端提交指令")
             return
         try:
-            stopped = await self.executor_factory(record.connection, record.secrets).cancel(record.remote_handle)
+            stopped = await self._executor(record).cancel(record.remote_handle)
         except Exception:
             stopped = False
-        await self._save(record.id, status="cancelled" if stopped else "cancel_requested", summary="远端已停止" if stopped else "停止尚未确认，请检查远端服务")
+        summary = "已停止内置推理；已发出的工具请求结果请核查" if record.backend_type == "reasoner" else "远端已停止"
+        await self._save(record.id, status="cancelled" if stopped else "cancel_requested", summary=summary if stopped else "停止尚未确认，请检查执行后端")
 
     async def reconcile(self, task_id):
         record = await self.get(task_id)
         if not record.remote_handle or record.status in TERMINAL:
             return record.public()
-        executor = self.executor_factory(record.connection, record.secrets)
         if record.status == "cancel_requested":
             await self._stop_record(record)
         else:
-            snapshot = await executor.snapshot(record.remote_handle)
-            # Session status does not describe pending questions/permissions.
-            # Keep the saved request visible until a reply or terminal result.
+            snapshot = await self._executor(record).snapshot(record.remote_handle)
             if snapshot["status"] == "running" and record.input_request:
-                snapshot.update(status="waiting_input", summary="远端等待确认或补充信息")
+                snapshot.update(status="waiting_input", summary="任务后端等待补充信息")
             await self._save(task_id, **snapshot)
             if snapshot["status"] not in TERMINAL and self.runtime and record.job_id not in self.runtime.coordinator.job_groups:
-                await self._dispatch(await self.get(task_id))
+                if record.backend_type == "reasoner":
+                    await self._save(task_id, status="failed", summary="内置任务已中断，不自动重放工具")
+                else:
+                    await self._dispatch(await self.get(task_id))
         return (await self.get(task_id)).public()
 
     async def send_input(self, task_id, value, assistant_id=None):
         record = await self.get(task_id, assistant_id)
         if record.status != "waiting_input" or not record.input_request:
             raise ValueError("任务当前没有待处理的确认或问题")
-        await self.executor_factory(record.connection, record.secrets).send_input(record.input_request, value)
-        await self._save(task_id, status="running", summary="已发送回复，等待远端继续", input_request={})
+        await self._executor(record).send_input(record.input_request, value)
+        latest = await self.get(task_id)
+        if latest.input_request.get("id") == record.input_request.get("id"):
+            await self._save(task_id, status="running", summary="已发送回复，等待任务后端继续", input_request={})
         return (await self.get(task_id)).public()
 
 
diff --git a/backend/services/brains/prompt_brain.py b/backend/services/brains/prompt_brain.py
index c94cc7c..7ee0746 100644
--- a/backend/services/brains/prompt_brain.py
+++ b/backend/services/brains/prompt_brain.py
@@ -102,7 +102,7 @@ class PromptBrain(BaseBrain):
 
     def system_prompt(self, cfg: AssistantConfig) -> str:
         prompt = self._store.render(cfg.prompt) if self._dynamic_enabled else cfg.prompt
-        if cfg.runtimeMode == "pipeline" and any(tool.type == "task" for tool in cfg.tools):
+        if cfg.runtimeMode == "pipeline" and cfg.task_backend is not None:
             from services.brains.prompt_tasks import TASK_HINT
             prompt += "\n" + TASK_HINT
         return prompt
@@ -158,20 +158,6 @@ class PromptBrain(BaseBrain):
             ):
                 logger.warning(f"跳过客户端未上报的工具: {tool.function_name}")
                 continue
-            if tool.type == "task":
-                if cfg.runtimeMode != "pipeline":
-                    raise ValueError("后台任务工具仅支持提示词 Pipeline")
-                from services.brains.prompt_tasks import PromptTaskBridge
-                if self._task_bridge is not None:
-                    raise ValueError("最多绑定一个后台任务工具")
-                self._task_bridge = PromptTaskBridge(cfg, runtime, self._tools)
-                for schema, handler in self._task_bridge.functions(tool, binding_by_id[tool.id]):
-                    if schema.name in registered_names:
-                        raise ValueError("后台任务函数名与已有工具冲突")
-                    schemas.append(schema)
-                    registered_names.add(schema.name)
-                    runtime.llm.register_function(schema.name, handler, cancel_on_interruption=False)
-                continue
             if tool.type == "system":
                 schema, handler = self._make_system_tool(tool, runtime)
             elif tool.type in {"http", "mcp", "client"}:
@@ -195,6 +181,17 @@ class PromptBrain(BaseBrain):
                 handler,
                 cancel_on_interruption=policy.cancel_on_interruption,
             )
+        if cfg.task_backend is not None:
+            if cfg.runtimeMode != "pipeline":
+                raise ValueError("任务后端仅支持提示词 Pipeline")
+            from services.brains.prompt_tasks import PromptTaskBridge
+            self._task_bridge = PromptTaskBridge(cfg, runtime, self._tools)
+            for schema, handler in self._task_bridge.functions():
+                if schema.name in registered_names:
+                    raise ValueError("任务委派函数名与已有工具冲突")
+                schemas.append(schema)
+                registered_names.add(schema.name)
+                runtime.llm.register_function(schema.name, handler, cancel_on_interruption=False)
         runtime.set_tools(schemas)
 
     async def close(self):
diff --git a/backend/services/brains/prompt_tasks.py b/backend/services/brains/prompt_tasks.py
index e031b52..b22d6d4 100644
--- a/backend/services/brains/prompt_tasks.py
+++ b/backend/services/brains/prompt_tasks.py
@@ -7,7 +7,8 @@ from services.background_tasks.records import TERMINAL
 
 CONTROL_NAMES = {"get_background_task", "cancel_background_task", "send_background_task_message"}
 TASK_HINT = """
-你可以把需要远程 coding agent 执行的工作交给后台任务工具。提交回执仅表示已接受，
+你负责及时交流、澄清需求和播报进度；复杂推理或执行任务可调用 delegate_task 委派给任务后端。
+任务后端拥有独立上下文，请在任务要求中提供完整目标和必要背景。提交回执仅表示已接受，
 不能据此宣称代码已经修改或测试通过。后台执行时继续回答用户；查询进度用任务查询工具。
 用户明确要求停止时调用取消工具，普通插话不会停止任务。收到后台任务结果后用简洁口语
 告知用户一次，依据实际结果描述成功或失败。任务状态未知时如实告知，不要重复提交。
@@ -24,19 +25,40 @@ class PromptTaskBridge:
     def close(self):
         self._detach()
 
-    def functions(self, tool, binding):
-        properties, required = self.executor.schema_parts(tool, binding)
+    def functions(self):
+        backend = self.cfg.task_backend
+        if backend is None:
+            raise ValueError("助手未绑定任务后端")
+        source = backend.instruction_source or {"source": "model"}
+        model_supplied = source.get("source") == "model"
+        properties = {"instruction": {"type": "string", "description": "完整任务目标、必要背景和验收要求"}} if model_supplied else {}
+        required = ["instruction"] if model_supplied else []
 
         async def submit(params):
             if self.runtime.tool_executor_factory is not None:
                 await params.result_callback({"status": "error", "message": "自动测试不启动真实后台任务，请使用语音调试验证"})
                 return
             try:
-                arguments = self.executor.resolve_arguments(tool, binding, params.arguments or {})
+                kind = source.get("source")
+                if kind == "model":
+                    instruction = (params.arguments or {}).get("instruction")
+                elif kind == "literal":
+                    instruction = source.get("value")
+                elif kind == "variable":
+                    instruction = self.executor.store.value(str(source.get("variable_name") or source.get("variableName") or ""))
+                elif kind == "template":
+                    instruction = self.executor.store.render_data(source.get("value"))
+                else:
+                    raise ValueError("不支持的任务指令来源")
+                if not isinstance(instruction, str):
+                    raise ValueError("任务指令必须是字符串")
                 result = await self.service.submit(
                     assistant_id=self.cfg.dynamic_variables.get("system__agent_id", ""),
                     conversation_id=self.cfg.conversation_id,
-                    tool=tool, instruction=arguments["instruction"], invocation_id=params.tool_call_id,
+                    backend=backend, instruction=instruction, invocation_id=params.tool_call_id,
+                    variable_state={"values": self.executor.store.values,
+                                    "definitions": self.cfg.dynamic_variable_definitions,
+                                    "secrets": self.executor.store.secrets},
                 )
                 await params.result_callback({"status": "accepted", "task": result})
             except ValueError as exc:
@@ -64,10 +86,10 @@ class PromptTaskBridge:
             except ValueError as exc:
                 await params.result_callback({"status": "error", "message": str(exc)})
 
-        schemas = [(FunctionSchema(name=tool.function_name, description=tool.description or "把编程工作交给远程后台任务执行，立即返回任务编号", properties=properties, required=required), submit)]
+        schemas = [(FunctionSchema(name="delegate_task", description="委派复杂推理或执行任务给已配置的任务后端，立即返回任务编号", properties=properties, required=required), submit)]
         for name, description in (
             ("get_background_task", "查询当前助手后台任务的真实进度和结果"),
-            ("cancel_background_task", "用户明确要求停止时，请求停止远程后台任务"),
+            ("cancel_background_task", "用户明确要求停止时，请求停止后台任务"),
             ("send_background_task_message", "回答后台任务当前提出的一个问题；权限确认请用户在网页操作"),
         ):
             props = {"task_id": {"type": "string", "description": "提交回执中的任务id"}}
diff --git a/backend/services/tool_executor.py b/backend/services/tool_executor.py
index cce80cd..02fa48a 100644
--- a/backend/services/tool_executor.py
+++ b/backend/services/tool_executor.py
@@ -43,8 +43,6 @@ class ToolExecutor:
     @staticmethod
     def input_schema(tool: RuntimeTool) -> tuple[dict[str, Any], list[str]]:
         config = (tool.definition or {}).get("config") or {}
-        if tool.type == "task":
-            return {"instruction": {"type": "string", "description": "需要远程执行的完整任务要求"}}, ["instruction"]
         if tool.type == "mcp":
             schema = config.get("input_schema") or {}
             return (
diff --git a/backend/tests/test_background_tasks.py b/backend/tests/test_background_tasks.py
index 530773a..5f31df8 100644
--- a/backend/tests/test_background_tasks.py
+++ b/backend/tests/test_background_tasks.py
@@ -6,8 +6,6 @@ from types import SimpleNamespace
 
 from services.background_tasks.service import TaskService
 from services.background_tasks.records import TERMINAL
-from schemas import ToolUpsert
-from routes.tools import _payload
 
 
 class MemoryRepository:
@@ -58,7 +56,7 @@ class TaskServiceTest(unittest.IsolatedAsyncioTestCase):
         SimulatedExecutor.confirms_stop = True
         self.service = TaskService(MemoryRepository(), SimulatedExecutor)
         await self.service.start()
-        self.tool = SimpleNamespace(type="task", id="tool_task", definition={"config": {"url": "https://remote.test", "directory": "/demo", "timeout_seconds": 30}}, secrets={"password": "never-public"})
+        self.backend = SimpleNamespace(type="opencode", id="backend_test", config={"url": "https://remote.test", "directory": "/demo", "timeout_seconds": 30}, secrets={"password": "never-public"})
     async def asyncTearDown(self):
         await self.service.close()
     async def wait_status(self, task_id, expected):
@@ -66,7 +64,7 @@ class TaskServiceTest(unittest.IsolatedAsyncioTestCase):
             while (await self.service.get(task_id)).status != expected:
                 await asyncio.sleep(.005)
     async def submit(self, key="call_1"):
-        return await self.service.submit(assistant_id="asst_1", conversation_id="conv_1", tool=self.tool, instruction="执行测试", invocation_id=key)
+        return await self.service.submit(assistant_id="asst_1", conversation_id="conv_1", backend=self.backend, instruction="执行测试", invocation_id=key)
     async def test_idempotence_public_projection_and_completion(self):
         task = await self.submit()
         again = await self.submit()
@@ -152,12 +150,6 @@ class TaskServiceTest(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(result["status"], "waiting_input")
         self.assertEqual(result["inputRequest"], question)
 
-    def test_task_tool_preserves_masked_password(self):
-        body = ToolUpsert(name="后台编程", functionName="coding_task", definition={"type": "task", "config": {"url": "https://remote.test", "directory": "/demo"}}, secrets={"password": "****"})
-        data = _payload(body, {"password": "old-password"})
-        self.assertEqual(data["secrets"]["password"], "old-password")
-
-
 class TaskApiTest(unittest.IsolatedAsyncioTestCase):
     async def test_admin_auth_and_real_native_job_through_http_api(self):
         import httpx
@@ -174,14 +166,14 @@ class TaskApiTest(unittest.IsolatedAsyncioTestCase):
         async def database():
             yield None
         app.dependency_overrides[get_session] = database
-        cfg = SimpleNamespace(type="prompt", runtimeMode="pipeline", tool_bindings=[SimpleNamespace(tool_id="tool_task")], tools=[SimpleNamespace(type="task", id="tool_task", definition={"config": {"url": "https://remote.test", "directory": "/demo", "timeout_seconds": 30}}, secrets={})])
+        cfg = SimpleNamespace(type="prompt", runtimeMode="pipeline", task_backend=SimpleNamespace(type="opencode", id="backend_test", config={"url": "https://remote.test", "directory": "/demo", "timeout_seconds": 30}, secrets={}), dynamic_variables={}, dynamic_variable_definitions={}, secret_dynamic_variables={})
         try:
             async with httpx.AsyncClient(transport=httpx.ASGITransport(app=app), base_url="https://platform.test") as client:
                 unauthenticated = await client.get("/api/background-tasks?assistant_id=asst_1")
                 self.assertEqual(unauthenticated.status_code, 401)
                 app.dependency_overrides[require_admin] = lambda: {"username": "test"}
                 with patch.object(routes, "task_service", service), patch.object(routes, "resolve_runtime_config", AsyncMock(return_value=cfg)):
-                    response = await client.post("/api/background-tasks", json={"assistantId": "asst_1", "toolId": "tool_task", "instruction": "测试请求", "requestId": "request_1"})
+                    response = await client.post("/api/background-tasks", json={"assistantId": "asst_1", "instruction": "测试请求", "requestId": "request_1"})
                     self.assertEqual(response.status_code, 200)
                     task_id = response.json()["id"]
                     self.assertEqual(response.json()["assistantId"], "asst_1")
diff --git a/backend/tests/test_opencode_tasks.py b/backend/tests/test_opencode_tasks.py
index b2ab340..5cc89d7 100644
--- a/backend/tests/test_opencode_tasks.py
+++ b/backend/tests/test_opencode_tasks.py
@@ -32,7 +32,11 @@ class OpenCodeTaskTest(unittest.IsolatedAsyncioTestCase):
                 return httpx.Response(200, text="".join("data: " + json.dumps(e) + "\n\n" for e in events))
             if request.url.path.endswith("prompt_async"):
                 self.assertFalse(submitted)
-                self.assertEqual(json.loads(request.content)["messageID"], "msg_test")
+                payload = json.loads(request.content)
+                self.assertEqual(payload["messageID"], "msg_test")
+                self.assertEqual(payload["agent"], "build")
+                self.assertEqual(payload["model"], {"providerID": "test-provider", "modelID": "test-model"})
+                self.assertEqual(payload["system"], "通用说明\n\n项目 demo")
                 submitted = True
                 return httpx.Response(204)
             if request.url.path.endswith("/message"):
@@ -42,7 +46,10 @@ class OpenCodeTaskTest(unittest.IsolatedAsyncioTestCase):
             if request.url.path == "/session/status":
                 return httpx.Response(200, json={})
             raise AssertionError(request.url)
-        executor = OpenCodeExecutor({"url": "https://remote.test", "directory": "/workspace/demo"}, {}, transport=httpx.MockTransport(respond))
+        executor = OpenCodeExecutor({"url": "https://remote.test", "directory": "/workspace/demo", "agent": "build",
+                                     "model_provider_id": "test-provider", "model_id": "test-model",
+                                     "instructions": "通用说明", "_backend": {"instructions": "项目 {{project}}"},
+                                     "_variables": {"project": "demo"}}, {}, transport=httpx.MockTransport(respond))
         async def emit(event):
             updates.append(event)
         result = await executor.run(handle, "修复测试", emit)
diff --git a/backend/tests/test_prompt_background_tasks.py b/backend/tests/test_prompt_background_tasks.py
index a0c8d78..90b23c1 100644
--- a/backend/tests/test_prompt_background_tasks.py
+++ b/backend/tests/test_prompt_background_tasks.py
@@ -1,22 +1,24 @@
 import unittest
 from types import SimpleNamespace
 from unittest.mock import AsyncMock, Mock
-from models import AssistantConfig, RuntimeTool, RuntimeToolBinding
+from models import AssistantConfig, RuntimeTaskBackend
 from services.brains.prompt_tasks import PromptTaskBridge
 from services.tool_executor import ToolExecutor
 from services.runtime_variables import DynamicVariableStore
 
 
 class PromptTaskBridgeTest(unittest.IsolatedAsyncioTestCase):
+    def config(self, **kwargs):
+        return AssistantConfig(task_backend=RuntimeTaskBackend(id="backend_1", type="opencode"), **kwargs)
+
     async def test_receipt_and_single_terminal_notification(self):
-        cfg = AssistantConfig(conversation_id="conv_1", dynamic_variables={"system__agent_id": "asst_1"})
+        cfg = self.config(conversation_id="conv_1", dynamic_variables={"system__agent_id": "asst_1"})
         runtime = SimpleNamespace(session_id="conv_1", transport=object(), tool_executor_factory=None, call_end=SimpleNamespace(ending=False), queue_frame=AsyncMock(), llm=SimpleNamespace(queue_frame=AsyncMock()))
         detach = Mock()
         service = SimpleNamespace(subscribe=Mock(return_value=detach), submit=AsyncMock(return_value={"id": "task_1", "status": "queued"}))
         bridge = PromptTaskBridge(cfg, runtime, ToolExecutor(DynamicVariableStore({})), service)
-        tool = RuntimeTool(id="tool_task", name="coding", function_name="coding_task", type="task", definition={"type": "task", "config": {}})
-        binding = RuntimeToolBinding(toolId=tool.id, argumentBindings={"instruction": {"source": "model"}})
-        functions = bridge.functions(tool, binding)
+        functions = bridge.functions()
+        self.assertEqual(functions[0][0].name, "delegate_task")
         callback = AsyncMock()
         await functions[0][1](SimpleNamespace(arguments={"instruction": "修复测试"}, tool_call_id="call_1", result_callback=callback))
         self.assertEqual(callback.await_args.args[0]["status"], "accepted")
@@ -31,22 +33,39 @@ class PromptTaskBridgeTest(unittest.IsolatedAsyncioTestCase):
     async def test_test_runtime_never_submits_a_real_task(self):
         runtime = SimpleNamespace(session_id="conv_1", transport=None, tool_executor_factory=object())
         service = SimpleNamespace(submit=AsyncMock())
-        bridge = PromptTaskBridge(AssistantConfig(), runtime, ToolExecutor(DynamicVariableStore({})), service)
-        tool = RuntimeTool(id="tool_task", name="coding", function_name="coding_task", type="task", definition={"type": "task", "config": {}})
+        bridge = PromptTaskBridge(self.config(), runtime, ToolExecutor(DynamicVariableStore({})), service)
         callback = AsyncMock()
-        await bridge.functions(tool, None)[0][1](SimpleNamespace(result_callback=callback))
+        await bridge.functions()[0][1](SimpleNamespace(result_callback=callback))
         service.submit.assert_not_awaited()
         self.assertEqual(callback.await_args.args[0]["status"], "error")
 
     async def test_test_runtime_never_controls_an_existing_real_task(self):
         runtime = SimpleNamespace(session_id="conv_1", transport=None, tool_executor_factory=object())
         service = SimpleNamespace(get=AsyncMock(), cancel=AsyncMock(), send_input=AsyncMock())
-        bridge = PromptTaskBridge(AssistantConfig(), runtime, ToolExecutor(DynamicVariableStore({})), service)
-        tool = RuntimeTool(id="tool_task", name="coding", function_name="coding_task", type="task", definition={"type": "task", "config": {}})
-        for schema, handler in bridge.functions(tool, None)[1:]:
+        bridge = PromptTaskBridge(self.config(), runtime, ToolExecutor(DynamicVariableStore({})), service)
+        for schema, handler in bridge.functions()[1:]:
             callback = AsyncMock()
             await handler(SimpleNamespace(function_name=schema.name, arguments={"task_id": "real_task", "message": "yes"}, result_callback=callback))
             self.assertEqual(callback.await_args.args[0]["status"], "error")
         service.get.assert_not_awaited()
         service.cancel.assert_not_awaited()
         service.send_input.assert_not_awaited()
+
+    async def test_bound_instruction_sources_and_snapshot_ignore_model_overrides(self):
+        cases = [({"source": "literal", "value": "固定任务"}, "固定任务"),
+                 ({"source": "template", "value": "检查 {{project}}"}, "检查 demo"),
+                 ({"source": "variable", "variable_name": "project"}, "demo")]
+        for source, expected in cases:
+            with self.subTest(source=source):
+                cfg = self.config(conversation_id="conv_1", dynamic_variables={"system__agent_id": "asst_1"})
+                cfg.task_backend.instruction_source = source
+                runtime = SimpleNamespace(session_id="conv_1", transport=None, tool_executor_factory=None)
+                service = SimpleNamespace(submit=AsyncMock(return_value={"id": "task_1"}))
+                store = DynamicVariableStore({"project": "demo"})
+                bridge = PromptTaskBridge(cfg, runtime, ToolExecutor(store), service)
+                schema, handler = bridge.functions()[0]
+                self.assertEqual(schema.to_default_dict()["parameters"]["properties"], {})
+                callback = AsyncMock()
+                await handler(SimpleNamespace(arguments={"instruction": "unauthorized override"}, tool_call_id="call_1", result_callback=callback))
+                self.assertEqual(service.submit.await_args.kwargs["instruction"], expected)
+                self.assertEqual(service.submit.await_args.kwargs["variable_state"]["values"], store.values)
diff --git a/backend/tests/test_reasoner_backend.py b/backend/tests/test_reasoner_backend.py
new file mode 100644
index 0000000..c6d55d4
--- /dev/null
+++ b/backend/tests/test_reasoner_backend.py
@@ -0,0 +1,207 @@
+"""Real native backend workers, with model output explicitly simulated.
+
+No test in this module contacts a model provider or executes a remote task.
+"""
+
+from __future__ import annotations
+
+import asyncio
+from copy import deepcopy
+import unittest
+from unittest.mock import AsyncMock, patch
+
+from models import RuntimeTaskBackend
+from pipecat.frames.frames import (
+    FunctionCallFromLLM,
+    LLMContextFrame,
+    LLMFullResponseEndFrame,
+    LLMFullResponseStartFrame,
+    LLMTextFrame,
+)
+from pipecat.services.llm_service import LLMService
+from pipecat.services.settings import LLMSettings
+from services.background_tasks.native import NativeTaskRuntime
+from services.background_tasks.reasoner import ReasonerExecutor, create_reasoner_llm
+
+
+def backend_config(**overrides):
+    backend = {
+        "id": "backend_reasoner", "type": "reasoner", "name": "Reasoner",
+        "config": {"reasoning_effort": "provider_default", "skills": [{"name": "核查", "content": "先检查依据，再给结论。"}]},
+        "model": {"id": "model_reasoner", "capability": "LLM", "interface_type": "openai-llm",
+                  "values": {"modelId": "simulated", "apiUrl": "https://model.example.invalid/v1"},
+                  "secrets": {"apiKey": "simulated-key"}},
+        **overrides,
+    }
+    return {"_backend": backend, "_task_id": "task_reasoner"}
+
+
+class SimulatedLLM(LLMService):
+    """Feeds declared outputs into Pipecat's actual aggregation/tool loop."""
+
+    def __init__(self, steps):
+        super().__init__(settings=LLMSettings(
+            model="simulated", temperature=None, max_tokens=None, top_p=None, top_k=None,
+            frequency_penalty=None, presence_penalty=None, seed=None,
+            filter_incomplete_user_turns=False, user_turn_completion_config=None,
+        ))
+        self.steps = iter(steps)
+        self.contexts = []
+
+    async def process_frame(self, frame, direction):
+        await super().process_frame(frame, direction)
+        if not isinstance(frame, LLMContextFrame):
+            await self.push_frame(frame, direction)
+            return
+        self.contexts.append(deepcopy(frame.context.messages))
+        step = next(self.steps, "simulated output without explicit completion")
+        await self.push_frame(LLMFullResponseStartFrame())
+        if isinstance(step, str):
+            await self.push_frame(LLMTextFrame(step))
+        else:
+            await self.run_function_calls([
+                FunctionCallFromLLM(function_name=name, tool_call_id=f"call_{len(self.contexts)}_{index}", arguments=arguments, context=frame.context)
+                for index, (name, arguments) in enumerate(step)
+            ])
+        await self.push_frame(LLMFullResponseEndFrame())
+
+
+class ReasonerSettingsTest(unittest.TestCase):
+    def test_nondefault_effort_requires_explicit_model_support(self):
+        config = backend_config()
+        config["_backend"]["config"]["reasoning_effort"] = "high"
+        with self.assertRaisesRegex(ValueError, "未声明"):
+            create_reasoner_llm(RuntimeTaskBackend.model_validate(config["_backend"]))
+
+    def test_effort_is_sent_as_real_parameter_without_changing_shared_model(self):
+        config = backend_config()
+        config["_backend"]["config"]["reasoning_effort"] = "high"
+        config["_backend"]["model"]["values"].update(
+            supportsReasoningEffort=True, extraBody={"reasoning_effort": "low", "provider_option": True},
+        )
+        backend = RuntimeTaskBackend.model_validate(config["_backend"])
+        service = create_reasoner_llm(backend)
+        params = service.build_chat_completion_params({"messages": []})
+        self.assertEqual(params["reasoning_effort"], "high")
+        self.assertEqual(params["extra_body"], {"provider_option": True})
+        self.assertEqual(backend.model.values["extraBody"]["reasoning_effort"], "low")
+
+
+class ReasonerNativeTest(unittest.IsolatedAsyncioTestCase):
+    async def asyncSetUp(self):
+        self.events = []
+        self.results = []
+        self.finished = asyncio.Event()
+        self.executor = None
+
+        async def execute(message, worker):
+            handle = await self.executor.prepare()
+            result = await self.executor.run(handle, "完成本次测试目标", self.emit)
+            self.results.append(result)
+            return result
+
+        async def cancel(message):
+            await self.executor.cancel(await self.executor.prepare())
+
+        async def on_result(message):
+            if message.source == self.runtime.executor.name:
+                self.finished.set()
+
+        self.runtime = NativeTaskRuntime(execute, cancel, self.ignore, on_result)
+        await self.runtime.start()
+
+    async def asyncTearDown(self):
+        await self.runtime.close()
+
+    async def ignore(self, message):
+        pass
+
+    async def emit(self, event):
+        self.events.append(event)
+
+    async def start_reasoner(self, steps, config=None):
+        self.model = SimulatedLLM(steps)
+        self.executor = ReasonerExecutor(config or backend_config(), {}, runtime=self.runtime)
+        patcher = patch("services.background_tasks.reasoner.create_reasoner_llm", return_value=self.model)
+        patcher.start()
+        self.addCleanup(patcher.stop)
+        return await self.runtime.submit("task_reasoner", 10)
+
+    async def wait_status(self, status):
+        async def wait():
+            while not any(event.get("status") == status for event in self.events):
+                await asyncio.sleep(0.01)
+        await asyncio.wait_for(wait(), 5)
+
+    async def test_explicit_completion_uses_actual_native_backend_and_clears_context(self):
+        await self.start_reasoner([[('complete_task', {"result": "显式模拟结果"})]])
+        await asyncio.wait_for(self.finished.wait(), 5)
+        self.assertEqual(self.results[0]["status"], "succeeded")
+        self.assertEqual(self.results[0]["result"], "显式模拟结果")
+        self.assertIn("核查", self.model.contexts[0][0]["content"])
+        self.assertIsNone(self.executor._worker)
+        self.assertTrue(self.runtime._run and not self.runtime._run.done())
+        self.assertFalse(any("显式模拟结果" in event.get("summary", "") for event in self.events))
+
+    async def test_plain_output_idle_does_not_claim_success_or_expose_reasoning(self):
+        await self.start_reasoner(["simulated private reasoning text"])
+        await asyncio.wait_for(self.finished.wait(), 5)
+        self.assertEqual(self.results[0]["status"], "failed")
+        self.assertIn("complete_task", self.results[0]["result"])
+        self.assertNotIn("private reasoning", str(self.events))
+
+    async def test_question_reply_continues_same_native_context(self):
+        await self.start_reasoner([
+            [('ask_user', {"question": "需要哪一天的数据？"})],
+            [('complete_task', {"result": "已按用户回答完成"})],
+        ])
+        await self.wait_status("waiting_input")
+        self.assertFalse(self.finished.is_set())
+        request = next(event["input_request"] for event in self.events if event.get("status") == "waiting_input")
+        with self.assertRaisesRegex(ValueError, "已处理"):
+            await self.executor.send_input({**request, "id": "other_question"}, {"answers": [["周一"]]})
+        await self.executor.send_input(request, {"answers": [["周一"]]})
+        await asyncio.wait_for(self.finished.wait(), 5)
+        self.assertEqual(self.results[0]["status"], "succeeded")
+        self.assertEqual(len(self.model.contexts), 2)
+        self.assertIn("周一", str(self.model.contexts[1]))
+
+    async def test_cancellation_stops_only_the_task_pipeline(self):
+        job_id = await self.start_reasoner([[('ask_user', {"question": "等待测试回复"})]])
+        await self.wait_status("waiting_input")
+        await self.runtime.cancel(job_id)
+        await asyncio.wait_for(self.finished.wait(), 5)
+        self.assertIsNone(self.executor._worker)
+        self.assertTrue(self.runtime._run and not self.runtime._run.done())
+
+    async def test_http_tool_uses_binding_and_task_local_variable_store(self):
+        config = backend_config(tools=[{
+            "id": "tool_lookup", "name": "查询", "function_name": "lookup", "type": "http",
+            "definition": {"type": "http", "config": {"url": "https://tool.example.invalid", "parameters": [{"name": "customer", "required": True}]}},
+        }], tool_bindings=[{"tool_id": "tool_lookup", "argument_bindings": {"customer": {"source": "variable", "variable_name": "customer"}},
+                            "result_assignments": {"answer": "answer"}}])
+        variables = {"customer": "local-customer", "answer": "before"}
+        config["_variables"] = variables
+        config["_variable_definitions"] = {name: {"type": "string"} for name in variables}
+
+        # Isolate the HTTP side effect while retaining real argument/result handling.
+        with patch("services.tool_executor.ToolExecutor._execute_http", AsyncMock(return_value={"status": "ok", "data": {"answer": "after"}})) as http:
+            await self.start_reasoner([[('lookup', {})], [('complete_task', {"result": "查询完成"})]], config)
+            await asyncio.wait_for(self.finished.wait(), 5)
+        self.assertEqual(self.results[0]["status"], "succeeded")
+        self.assertEqual(http.await_args.args[1], {"customer": "local-customer"})
+        self.assertEqual(self.executor._tools.store.values["answer"], "after")
+        self.assertEqual(variables["answer"], "before")
+
+    async def test_client_tools_and_control_name_collisions_are_rejected_before_model_start(self):
+        for kind, name in [("client", "browser_action"), ("http", "complete_task")]:
+            config = backend_config(tools=[{"id": "bad", "name": "bad", "type": kind, "function_name": name}])
+            executor = ReasonerExecutor(config, {}, runtime=self.runtime)
+            with patch("services.background_tasks.reasoner.create_reasoner_llm") as factory:
+                with self.assertRaises(ValueError):
+                    executor._build_worker()
+                factory.assert_not_called()
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/backend/tests/test_task_backend_spine.py b/backend/tests/test_task_backend_spine.py
index 4f37982..73b2b0e 100644
--- a/backend/tests/test_task_backend_spine.py
+++ b/backend/tests/test_task_backend_spine.py
@@ -4,9 +4,12 @@ import json
 from pathlib import Path
 from types import SimpleNamespace
 import unittest
+from unittest.mock import patch
 
+from models import RuntimeTaskBackend
 from services.background_tasks.service import TaskService
 from tests.test_background_tasks import MemoryRepository, SimulatedExecutor
+from tests.test_reasoner_backend import SimulatedLLM, backend_config
 
 
 class TaskBackendSpineTest(unittest.IsolatedAsyncioTestCase):
@@ -29,3 +32,89 @@ class TaskBackendSpineTest(unittest.IsolatedAsyncioTestCase):
             artifact.write_text(json.dumps({"simulated_remote": True, "native_job": "completed", "backend_id": backend.id, "tool_definition_required": False}) + "\n")
         finally:
             await service.close()
+
+
+class ReasonerServiceTest(unittest.IsolatedAsyncioTestCase):
+    """Full business lifecycle with a real native worker and simulated model."""
+
+    async def asyncSetUp(self):
+        self.service = TaskService(MemoryRepository())
+        await self.service.start()
+        self.backend = RuntimeTaskBackend.model_validate(backend_config()["_backend"])
+
+    async def asyncTearDown(self):
+        await self.service.close()
+
+    async def wait_task(self, task_id, predicate):
+        async with asyncio.timeout(5):
+            while True:
+                record = await self.service.get(task_id)
+                if predicate(record):
+                    return record
+                await asyncio.sleep(.005)
+
+    async def submit(self, *, variable_state=None):
+        return await self.service.submit(
+            assistant_id="asst_reasoner", conversation_id="conv_reasoner", backend=self.backend,
+            instruction="显式模拟任务", invocation_id="call_reasoner", variable_state=variable_state,
+        )
+
+    async def test_snapshot_is_frozen_and_business_projection_has_no_secrets(self):
+        model = SimulatedLLM([[('complete_task', {"result": "模拟任务完成"})]])
+        self.backend.instructions = "为 {{customer}} 核查结果"
+        self.backend.config["instructions"] = "字面模板 {{customer}}"
+        state = {"values": {"customer": "before"}, "definitions": {"customer": {"type": "string"}}, "secrets": {"secret__token": "private-token"}}
+        with patch("services.background_tasks.reasoner.create_reasoner_llm", return_value=model):
+            task = await self.submit(variable_state=state)
+            self.backend.config["skills"][0]["content"] = "changed after submission"
+            state["values"]["customer"] = "changed after submission"
+            record = await self.wait_task(task["id"], lambda item: item.status == "succeeded")
+        self.assertEqual(record.backend_type, "reasoner")
+        self.assertEqual(record.connection["_variables"]["customer"], "before")
+        self.assertEqual(record.connection["_secret_variables"]["secret__token"], "private-token")
+        self.assertNotIn("changed after submission", str(model.contexts))
+        self.assertIn("为 before 核查结果", model.contexts[0][0]["content"])
+        self.assertIn("字面模板 {{customer}}", model.contexts[0][0]["content"])
+        self.assertNotIn("private-token", str(record.public()))
+        self.assertNotIn("simulated-key", str(record.public()))
+        self.assertNotIn("_backend", record.public())
+
+    async def test_immediate_next_question_survives_reply_projection_update(self):
+        model = SimulatedLLM([
+            [('ask_user', {"question": "选择日期？"})],
+            [('ask_user', {"question": "选择范围？"})],
+            [('complete_task', {"result": "两个问题均已回答"})],
+        ])
+        with patch("services.background_tasks.reasoner.create_reasoner_llm", return_value=model):
+            task = await self.submit()
+            first = await self.wait_task(task["id"], lambda item: item.status == "waiting_input")
+            await self.service.send_input(task["id"], {"answers": [["周一"]]})
+            second = await self.wait_task(task["id"], lambda item: item.status == "waiting_input" and item.input_request.get("id") != first.input_request["id"])
+            self.assertEqual(second.input_request["questions"][0]["question"], "选择范围？")
+            await self.service.send_input(task["id"], {"answers": [["本部门"]]})
+            finished = await self.wait_task(task["id"], lambda item: item.status == "succeeded")
+        self.assertEqual(finished.result, "两个问题均已回答")
+        self.assertFalse(finished.input_request)
+
+    async def test_shutdown_restart_does_not_replay_reasoner(self):
+        model = SimulatedLLM([[('ask_user', {"question": "需要补充信息"})]])
+        with patch("services.background_tasks.reasoner.create_reasoner_llm", return_value=model) as factory:
+            task = await self.submit()
+            await self.wait_task(task["id"], lambda item: item.status == "waiting_input")
+            await self.service.close()
+            await self.service.start()
+            record = await self.wait_task(task["id"], lambda item: item.status == "failed")
+            self.assertIn("未自动重放工具", record.summary)
+            self.assertEqual(factory.call_count, 1)
+
+    async def test_business_cancel_cleans_only_current_reasoner(self):
+        model = SimulatedLLM([[('ask_user', {"question": "需要补充信息"})]])
+        with patch("services.background_tasks.reasoner.create_reasoner_llm", return_value=model):
+            task = await self.submit()
+            await self.wait_task(task["id"], lambda item: item.status == "waiting_input")
+            executor = self.service._executors[task["id"]]
+            await self.service.cancel(task["id"])
+            record = await self.wait_task(task["id"], lambda item: item.status == "cancelled")
+        self.assertIsNone(executor._worker)
+        self.assertIn("已发出的工具请求", record.summary)
+        self.assertTrue(self.service.runtime._run and not self.service.runtime._run.done())
diff --git a/implement-stage/task-backends/BUILD_NOTE.md b/implement-stage/task-backends/BUILD_NOTE.md
index 371bd9f..985e445 100644
--- a/implement-stage/task-backends/BUILD_NOTE.md
+++ b/implement-stage/task-backends/BUILD_NOTE.md
@@ -4,13 +4,15 @@
 |------|---------|--------------------|------|--------|
 | F0 | 新后端输入→原生Job→记录主线 | cd backend && .venv/bin/python -m unittest tests.test_task_backend_spine | MUST | passed |
 | F1 | 后端资源、助手配置、旧数据迁移 | cd backend && .venv/bin/python -m unittest tests.test_task_backend_resources | MUST | passed |
-| F2 | 原生Reasoner、OpenCode、委派桥 | cd backend && .venv/bin/python -m unittest tests.test_reasoner_backend tests.test_prompt_background_tasks tests.test_background_tasks | MUST | pending |
-| F3 | 任务后端资源页与提示词编辑器 | cd frontend && npx tsc --noEmit | MUST | pending |
+| F2 | 原生Reasoner、OpenCode、委派桥 | cd backend && .venv/bin/python -m unittest tests.test_reasoner_backend tests.test_prompt_background_tasks tests.test_background_tasks | MUST | passed |
+| F3 | 任务后端资源页与提示词编辑器 | cd frontend && npx tsc --noEmit | MUST | passed |
 | F4 | 全量回归、隔离数据库迁移与审阅 | make test | MUST | pending |
 
 ## Run record
 - F0：新后端资源输入 + 原生Jobs + 旧生命周期累计测试14项，exit 0。显式模拟执行器；backend-spine-smoke.json 已生成。
 - F1：12项资源专项测试通过，连同原生主线、桥接、生命周期累计33项通过，exit 0；真实隔离 PostgreSQL 17 完成0026旧数据→0027迁移及CRUD/助手复制/运行时解析，见database-smoke.json。
+- F2：make test-backend，391项测试通过，exit 0；包含真实 Pipecat BackendLLMWorker 与模拟模型的13项Reasoner/服务主线检查、绑定指令来源、OpenCode固定agent/model/system负载及现有回归。
+- F3：TypeScript、lint及4项前端契约测试通过，exit 0；lint保留既有BatchTestPage警告。生产构建并入F4。
 
 ## Deferred
 - 真实模型/OpenCode联调：尚无服务地址与凭据。