Refactor StreamHandler to simplify Vercel streaming response creation

templates/components/multiagent/python/app/api/callbacks/stream_handler.py

@@ -2,6 +2,7 @@
 from typing import List, Optional
 
 from llama_index.core.workflow.handler import WorkflowHandler
+from app.api.routers.vercel_response import VercelStreamResponse
 
 from app.api.callbacks.base import EventCallback
 
@@ -22,6 +23,10 @@ def __init__(
         self.callbacks = callbacks or []
         self.accumulated_text = ""
 
+    def vercel_stream(self):
+        """Create a streaming response with Vercel format."""
+        return VercelStreamResponse(stream_handler=self)
+
     async def cancel_run(self):
         """Cancel the workflow handler."""
         await self.workflow_handler.cancel_run()
@@ -49,3 +54,12 @@ async def stream_events(self):
     async def accumulate_text(self, text: str):
         """Accumulate text from the workflow handler."""
         self.accumulated_text += text
+
+    @classmethod
+    def from_default(
+        cls,
+        handler: WorkflowHandler,
+        callbacks: Optional[List[EventCallback]] = None,
+    ) -> "StreamHandler":
+        """Create a new instance with the given workflow handler and callbacks."""
+        return cls(workflow_handler=handler, callbacks=callbacks)

templates/components/multiagent/python/app/api/routers/chat.py

@@ -41,15 +41,13 @@ async def chat(
             chat_history=messages,
             stream=True,
         )
-        return VercelStreamResponse(
-            stream_handler=StreamHandler(
-                workflow_handler=handler,
-                callbacks=[
-                    LlamaCloudFileDownload.from_default(background_tasks),
-                    SuggestNextQuestions.from_default(data),
-                ],
-            ),
-        )
+        return StreamHandler.from_default(
+            handler=handler,
+            callbacks=[
+                LlamaCloudFileDownload.from_default(background_tasks),
+                SuggestNextQuestions.from_default(data),
+            ],
+        ).vercel_stream()
     except Exception as e:
         logger.exception("Error in chat engine", exc_info=True)
         raise HTTPException(