Enhance conversation history and runtime variable management

- Update ConversationRecorder to include source and nodeId metadata in transcripts for better context tracking.
- Introduce optional variable handling in DynamicVariableStore, allowing for unset variables to be rendered as empty without raising errors.
- Refactor WorkflowBrain to apply turn configurations and manage interaction policies dynamically, improving agent responsiveness.
- Implement tests to ensure proper handling of updated session variables and workflow metadata in various scenarios.

frontend/src/hooks/use-voice-preview.ts

@@ -46,6 +46,22 @@ export type ChatMessage = {
 };
 
 type AppMessage = Record<string, unknown> & { type?: string };
+type DynamicVariableValue = string | number | boolean;
+
+function publicVariableSnapshot(
+  value: unknown,
+): Record<string, DynamicVariableValue> {
+  if (!value || typeof value !== "object" || Array.isArray(value)) return {};
+  return Object.fromEntries(
+    Object.entries(value).filter(([name, item]) =>
+      !name.startsWith("system__") &&
+      !name.startsWith("secret__") &&
+      (typeof item === "string" ||
+        typeof item === "number" ||
+        typeof item === "boolean"),
+    ) as [string, DynamicVariableValue][],
+  );
+}
 
 class AppSmallWebRTCTransport extends SmallWebRTCTransport {
   onAppMessage?: (message: AppMessage) => void;
@@ -185,6 +201,9 @@ export function useVoicePreview(
   const [videoStream, setVideoStream] = useState<MediaStream | null>(null);
   const [remoteStream, setRemoteStream] = useState<MediaStream | null>(null);
   const [messages, setMessages] = useState<ChatMessage[]>([]);
+  const [sessionVariables, setSessionVariables] = useState<
+    Record<string, DynamicVariableValue>
+  >({});
   const [callEnded, setCallEnded] = useState(false);
   const [networkQuality, setNetworkQuality] =
     useState<NetworkQuality>("unknown");
@@ -387,6 +406,8 @@ export function useVoicePreview(
       );
     } else if (msg.type === "node-active" && typeof msg.nodeId === "string") {
       onNodeActiveRef.current?.(msg.nodeId);
+    } else if (msg.type === "workflow-variables") {
+      setSessionVariables(publicVariableSnapshot(msg.variables));
     } else if (msg.type === "call-ended") {
       endedByServerRef.current = true;
       setCallEnded(true);
@@ -407,6 +428,7 @@ export function useVoicePreview(
     setError(null);
     setMicWarning(null);
     setMessages([]);
+    setSessionVariables(publicVariableSnapshot(options.dynamicVariables ?? {}));
     pendingAssistantTurnsRef.current.clear();
     setCallEnded(false);
     endedByServerRef.current = false;
@@ -593,6 +615,7 @@ export function useVoicePreview(
     videoStream,
     remoteStream,
     messages,
+    sessionVariables,
     callEnded,
     networkQuality,
     audioInputs,