feat: add stateful responses API

backend/services/brains/workflow_brain.py

@@ -187,6 +187,7 @@ class WorkflowBrain(BaseBrain):
         self._next_message_token = 1
         self._pending_message: _MessageContinuation | None = None
         self._realtime_controller: WorkflowRealtimeController | None = None
+        self._restored_text_node_id: str | None = None
 
     async def greeting(self, _cfg: AssistantConfig) -> str:
         """Workflow opening speech belongs to an explicit Message or Agent."""
@@ -274,6 +275,18 @@ class WorkflowBrain(BaseBrain):
         if self._realtime_controller is not None:
             await self._realtime_controller.start()
             return
+        if self._restored_text_node_id:
+            node_id = self._restored_text_node_id
+            self._restored_text_node_id = None
+            self._state.enter(node_id, WorkflowStatus.WAITING_USER)
+            await self._emit_node_active(node_id)
+            await self._emit_variables(reason="restored", node_id=node_id)
+            if self._manager is None:
+                raise RuntimeError("Workflow FlowManager 尚未初始化")
+            node_config = await self._resolve_path(node_id)
+            await self._activate_node_config(node_config, initialize=True)
+            logger.info(f"工作流文本状态已恢复: 当前节点={self._manager.current_node}")
+            return
         self._state.enter(self._engine.start_id, WorkflowStatus.STARTING)
         await self._emit_node_active(self._engine.start_id)
         await self._emit_variables(
@@ -287,6 +300,33 @@ class WorkflowBrain(BaseBrain):
         await self._activate_node_config(node_config, initialize=True)
         logger.info(f"工作流模式启用: 当前节点={self._manager.current_node}")
 
+    def restore_text_state(self, snapshot: dict[str, Any]) -> None:
+        """Restore one stable Responses API workflow node before connecting."""
+        if not snapshot:
+            return
+        if snapshot.get("type") != "workflow":
+            raise ValueError("Responses runtime state does not belong to a workflow")
+        if snapshot.get("revision") != self._engine.revision:
+            raise ValueError("Workflow definition changed after the previous response")
+        node_id = str(snapshot.get("current_node_id") or "")
+        if not self._engine.node_type(node_id):
+            raise ValueError("Previous workflow node no longer exists")
+        self._restored_text_node_id = node_id
+
+    def text_state_snapshot(self) -> dict[str, Any]:
+        """Return the minimum durable state needed by the next text request."""
+        node_id = (
+            str(self._manager.current_node)
+            if self._manager is not None and self._manager.current_node
+            else self._state.current_node_id
+        )
+        return {
+            "type": "workflow",
+            "revision": self._engine.revision,
+            "current_node_id": node_id,
+            "status": self._state.status.value,
+        }
+
     async def _initial_node_config(self) -> NodeConfig:
         """Only a default-only Start advances before the first user turn."""
         outgoing = self._engine.outgoing(self._engine.start_id)