FS-133 Make scratchpad per request

backend/src/api/app.py

@@ -5,6 +5,7 @@
 from fastapi import FastAPI, HTTPException, Response, WebSocket, UploadFile
 from fastapi.responses import JSONResponse
 from fastapi.middleware.cors import CORSMiddleware
+from src.utils.scratchpad import ScratchPadMiddleware
 from src.chat_storage_service import get_chat_message
 from src.directors.report_director import report_on_file_upload
 from src.session.file_uploads import clear_session_file_uploads
@@ -45,6 +46,7 @@ async def lifespan(app: FastAPI):
 )
 
 app.add_middleware(RedisSessionMiddleware)
+app.add_middleware(ScratchPadMiddleware)
 
 health_prefix = "InferESG healthcheck: "
 further_guidance = "Please check the README files for further guidance."

backend/src/utils/scratchpad.py

@@ -1,4 +1,7 @@
 from typing import TypedDict
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette.requests import Request
+import contextvars
 import logging
 
 logger = logging.getLogger(__name__)
@@ -10,20 +13,23 @@ class Answer(TypedDict):
     result: str | None
     error: str | None
 
+scratchpad_context = contextvars.ContextVar("scratchpad", default=[])
 
 Scratchpad = list[Answer]
 
-scratchpad: Scratchpad = []
-
+class ScratchPadMiddleware(BaseHTTPMiddleware):
+    async def dispatch(self, request: Request, call_next):
+        scratchpad_context.set([])
+        return await call_next(request)
 
 def get_scratchpad() -> Scratchpad:
-    return scratchpad
+    return scratchpad_context.get()
 
 
 def update_scratchpad(agent_name=None, question=None, result=None, error=None):
-    scratchpad.append({"agent_name": agent_name, "question": question, "result": result, "error": error})
+    get_scratchpad().append({"agent_name": agent_name, "question": question, "result": result, "error": error})
 
 
 def clear_scratchpad():
     logger.debug("Scratchpad cleared")
-    scratchpad.clear()
+    get_scratchpad().clear()