docs: clarify LangGraph compatibility entrypoints (#2914)

backend/README.md

@@ -242,6 +242,10 @@ backend/
 └── Dockerfile                  # Container build
 ```
 
+`langgraph.json` is not the default service entrypoint.  The scripts and Docker
+deployments run the Gateway embedded runtime; the file is kept for LangGraph
+tooling, Studio, or direct LangGraph Server compatibility.
+
 ---
 
 ## Configuration

backend/app/gateway/langgraph_auth.py

@@ -1,8 +1,12 @@
-"""LangGraph Server auth handler — shares JWT logic with Gateway.
+"""LangGraph compatibility auth handler — shares JWT logic with Gateway.
 
-Loaded by LangGraph Server via langgraph.json ``auth.path``.
+The default DeerFlow runtime is embedded in the FastAPI Gateway; scripts and
-Reuses the same ``decode_token`` / ``get_auth_config`` as Gateway,
+Docker deployments do not load this module.  It is retained for LangGraph
-so both modes validate tokens with the same secret and rules.
+tooling, Studio, or direct LangGraph Server compatibility through
+``langgraph.json``'s ``auth.path``.
+
+When that compatibility path is used, this module reuses the same JWT and CSRF
+rules as Gateway so both modes validate sessions consistently.
 
 Two layers:
   1. @auth.authenticate — validates JWT cookie, extracts user_id,

backend/docs/ARCHITECTURE.md

@@ -63,7 +63,8 @@ The agent runtime is embedded in the FastAPI Gateway and built on LangGraph for
 - Tool execution orchestration
 - SSE streaming for real-time responses
 
-**Graph registry**: `langgraph.json` remains available for tooling and Studio compatibility.
+**Graph registry**: `langgraph.json` remains available for tooling, Studio, or direct LangGraph Server compatibility.
+It is not the default service entrypoint; scripts and Docker deployments run the Gateway embedded runtime.
 
 ```json
 {