feat: add session updates and message dialogs

backend/services/brains/base.py

@@ -44,6 +44,14 @@ class BrainSpec:
     owns_context: bool
 
 
+@dataclass(frozen=True)
+class SessionVariableUpdate:
+    """Result of one silent update to declared session variables."""
+
+    changed: list[str]
+    dynamic_variables: dict[str, str | int | float | bool]
+
+
 class CallEndPort(Protocol):
     """Small call-lifecycle surface available to a brain."""
 
@@ -144,6 +152,13 @@ class BaseBrain:
     async def on_client_ready(self) -> None:
         """Replay client-visible state after its app message channel is ready."""
 
+    async def on_session_update(
+        self,
+        dynamic_variables: dict[str, Any],
+    ) -> SessionVariableUpdate:
+        """Apply a silent client state update without starting an LLM turn."""
+        raise ValueError(f"助手类型 {self.spec.type} 不支持会话动态变量更新")
+
     def record_user_message(self, content: str) -> None:
         """Observe a committed user message for brain-owned routing state."""
 
@@ -194,6 +209,11 @@ class Brain(Protocol):
 
     async def on_client_ready(self) -> None: ...
 
+    async def on_session_update(
+        self,
+        dynamic_variables: dict[str, Any],
+    ) -> SessionVariableUpdate: ...
+
     def record_user_message(self, content: str) -> None: ...
 
     async def on_user_turn_end(self, content: str) -> bool: ...

backend/services/brains/prompt_brain.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from typing import Any
 from uuid import uuid4
 
 from models import AssistantConfig
@@ -15,10 +16,13 @@ from pipecat.services.llm_service import (
 )
 from pipecat.utils.time import time_now_iso8601
 
-from services.brains.base import BaseBrain, BrainRuntime, BrainSpec
-from services.runtime_variables import (
-    DynamicVariableStore,
+from services.brains.base import (
+    BaseBrain,
+    BrainRuntime,
+    BrainSpec,
+    SessionVariableUpdate,
 )
+from services.runtime_variables import DynamicVariableStore
 from services.tool_executor import ToolExecutionError, ToolExecutor
 from services.tool_policy import policy_for_tool
 
@@ -76,6 +80,18 @@ class PromptBrain(BaseBrain):
         self._store.record("user", content)
         self._refresh_prompt()
 
+    async def on_session_update(
+        self,
+        dynamic_variables: dict[str, Any],
+    ) -> SessionVariableUpdate:
+        changed = self._store.assign_declared_many(dynamic_variables)
+        if changed:
+            self._refresh_prompt()
+        return SessionVariableUpdate(
+            changed=changed,
+            dynamic_variables=self._store.public_values(),
+        )
+
     async def on_assistant_text_start(self, _turn_id: str) -> None:
         if self._runtime is not None:
             self._runtime.call_end.begin_response()

backend/services/brains/workflow_brain.py

@@ -28,7 +28,12 @@ from pipecat.services.llm_service import (
     FunctionCallParams,
     FunctionCallResultProperties,
 )
-from services.brains.base import BaseBrain, BrainRuntime, BrainSpec
+from services.brains.base import (
+    BaseBrain,
+    BrainRuntime,
+    BrainSpec,
+    SessionVariableUpdate,
+)
 from services.knowledge import search as search_knowledge
 from services.runtime_variables import DynamicVariableStore
 from services.tool_executor import ToolExecutionError, ToolExecutor
@@ -258,6 +263,27 @@ class WorkflowBrain(BaseBrain):
             node_id=current_node,
         )
 
+    async def on_session_update(
+        self,
+        dynamic_variables: dict[str, Any],
+    ) -> SessionVariableUpdate:
+        if self._ended:
+            raise ValueError("工作流会话已经结束")
+        changed = self._store.assign_declared_many(dynamic_variables)
+        current = self._state.current_node_id
+        if changed and current and self._engine.node_type(current) == "agent":
+            await self._refresh_agent_prompt(current)
+        if changed:
+            await self._emit_variables(
+                reason="session_update",
+                node_id=current or None,
+                changed=changed,
+            )
+        return SessionVariableUpdate(
+            changed=changed,
+            dynamic_variables=self._store.public_values(),
+        )
+
     def record_user_message(self, content: str) -> None:
         if content and not self._ended:
             self._store.record("user", content)