Add FastAPI integration example with StreamingResponse and agent astream

README.md

@@ -200,6 +200,46 @@ agent = create_react_agent("openai:gpt-4.1", tools)
 math_response = await agent.ainvoke({"messages": "what's (3 + 5) x 12?"})
 ```
 
+Use it with `FastAPI`'s `StreamingResponse` and `astream`:
+
+```python
+# Use server from examples/servers/streamable-http-stateless/
+
+import json
+from typing import AsyncGenerator
+
+import uvicorn
+from fastapi import FastAPI, Request
+from fastapi.responses import StreamingResponse
+
+from langchain_core.messages import AIMessageChunk
+from langchain_mcp_adapters.tools import load_mcp_tools
+from langgraph.prebuilt import create_react_agent
+
+from mcp import ClientSession
+from mcp.client.streamable_http import streamablehttp_client
+
+async def response_generator() -> AsyncGenerator[str, None]:
+    async with streamablehttp_client("http://localhost:8080/mcp") as (read_stream, write_stream, _):
+        async with ClientSession(read_stream, write_stream) as session:
+            await session.initialize()
+            tools = await load_mcp_tools(session)
+            agent = create_react_agent("openai:gpt-4.1", tools)
+            async for msg, _ in agent.astream({"messages": "what's (3 + 5) x 12?"}, stream_mode="messages"):
+                if isinstance(msg, AIMessageChunk):
+                    json_str = json.dumps({ "content": msg.content }, ensure_ascii=False)
+                    yield f"data: {json_str}\n\n"
+            yield "data: [DONE]\n\n"
+
+app = FastAPI()
+@app.route("/")
+async def root(request: Request):
+    return StreamingResponse(response_generator(), media_type="text/event-stream")
+
+if __name__ == "__main__":
+    uvicorn.run(app)
+```
+
 ## Using with LangGraph StateGraph
 
 ```python