Refactor DeerFlow to use Gateway's LangGraph-compatible API

- Updated documentation and comments to reflect the transition from LangGraph Server to Gateway.
- Changed default URLs in ChannelManager and tests to point to Gateway.
- Removed references to LangGraph Server in deployment scripts and configurations.
- Updated Nginx configuration to route API traffic to Gateway.
- Adjusted frontend configurations to utilize Gateway's API.
- Removed LangGraph service from Docker Compose files, consolidating services under Gateway.
- Added regression tests to ensure Gateway integration works as expected.

Co-authored-by: Copilot <copilot@github.com>

docker/docker-compose.yaml

@@ -4,8 +4,7 @@
 # Services:
 #   - nginx:       Reverse proxy (port 2026, configurable via PORT env var)
 #   - frontend:    Next.js production server
-#   - gateway:     FastAPI Gateway API
-#   - langgraph:   LangGraph production server (Dockerfile generated by langgraph dockerfile)
+#   - gateway:     FastAPI Gateway API + agent runtime
 #   - provisioner: (optional) Sandbox provisioner for Kubernetes mode
 #
 # Key environment variables (set via environment/.env or scripts/deploy.sh):
@@ -30,12 +29,8 @@ services:
       - "${PORT:-2026}:2026"
     volumes:
       - ./nginx/nginx.conf:/etc/nginx/nginx.conf.template:ro
-    environment:
-      - LANGGRAPH_UPSTREAM=${LANGGRAPH_UPSTREAM:-langgraph:2024}
-      - LANGGRAPH_REWRITE=${LANGGRAPH_REWRITE:-/}
     command: >
-      sh -c "envsubst '$$LANGGRAPH_UPSTREAM $$LANGGRAPH_REWRITE'
-      < /etc/nginx/nginx.conf.template > /etc/nginx/nginx.conf
+      sh -c "cp /etc/nginx/nginx.conf.template /etc/nginx/nginx.conf
       && nginx -g 'daemon off;'"
     depends_on:
       - frontend
@@ -57,7 +52,6 @@ services:
     environment:
       - BETTER_AUTH_SECRET=${BETTER_AUTH_SECRET}
       - DEER_FLOW_INTERNAL_GATEWAY_BASE_URL=http://gateway:8001
-      - DEER_FLOW_INTERNAL_LANGGRAPH_BASE_URL=http://langgraph:2024
     env_file:
       - ../frontend/.env
     networks:
@@ -102,7 +96,7 @@ services:
       - DEER_FLOW_HOME=/app/backend/.deer-flow
       - DEER_FLOW_CONFIG_PATH=/app/backend/config.yaml
       - DEER_FLOW_EXTENSIONS_CONFIG_PATH=/app/backend/extensions_config.json
-      - DEER_FLOW_CHANNELS_LANGGRAPH_URL=${DEER_FLOW_CHANNELS_LANGGRAPH_URL:-http://langgraph:2024}
+      - DEER_FLOW_CHANNELS_LANGGRAPH_URL=${DEER_FLOW_CHANNELS_LANGGRAPH_URL:-http://gateway:8001/api}
       - DEER_FLOW_CHANNELS_GATEWAY_URL=${DEER_FLOW_CHANNELS_GATEWAY_URL:-http://gateway:8001}
       # DooD path/network translation
       - DEER_FLOW_HOST_BASE_DIR=${DEER_FLOW_HOME}
@@ -116,58 +110,6 @@ services:
       - deer-flow
     restart: unless-stopped
 
-  # ── LangGraph Server ───────────────────────────────────────────────────────
-  # TODO: switch to langchain/langgraph-api (licensed) once a license key is available.
-  # For now, use `langgraph dev` (no license required) with the standard backend image.
-  langgraph:
-    build:
-      context: ../
-      dockerfile: backend/Dockerfile
-      args:
-        APT_MIRROR: ${APT_MIRROR:-}
-        UV_IMAGE: ${UV_IMAGE:-ghcr.io/astral-sh/uv:0.7.20}
-        UV_INDEX_URL: ${UV_INDEX_URL:-https://pypi.org/simple}
-        UV_EXTRAS: ${UV_EXTRAS:-}
-    container_name: deer-flow-langgraph
-    command: sh -c 'cd /app/backend && args="--no-browser --no-reload --host 0.0.0.0 --port 2024 --n-jobs-per-worker $${LANGGRAPH_JOBS_PER_WORKER:-10}" && if [ "$${LANGGRAPH_ALLOW_BLOCKING:-0}" = "1" ]; then args="$$args --allow-blocking"; fi && uv run langgraph dev $$args'
-    volumes:
-      - ${DEER_FLOW_CONFIG_PATH}:/app/backend/config.yaml:ro
-      - ${DEER_FLOW_EXTENSIONS_CONFIG_PATH}:/app/backend/extensions_config.json:ro
-      - ${DEER_FLOW_HOME}:/app/backend/.deer-flow
-      - ../skills:/app/skills:ro
-      - ../backend/.langgraph_api:/app/backend/.langgraph_api
-      # DooD: same as gateway
-      - ${DEER_FLOW_DOCKER_SOCKET}:/var/run/docker.sock
-      # CLI auth directories for auto-auth (Claude Code + Codex CLI)
-      - type: bind
-        source: ${HOME:?HOME must be set}/.claude
-        target: /root/.claude
-        read_only: true
-        bind:
-          create_host_path: true
-      - type: bind
-        source: ${HOME:?HOME must be set}/.codex
-        target: /root/.codex
-        read_only: true
-        bind:
-          create_host_path: true
-    environment:
-      - CI=true
-      - DEER_FLOW_HOME=/app/backend/.deer-flow
-      - DEER_FLOW_CONFIG_PATH=/app/backend/config.yaml
-      - DEER_FLOW_EXTENSIONS_CONFIG_PATH=/app/backend/extensions_config.json
-      - DEER_FLOW_HOST_BASE_DIR=${DEER_FLOW_HOME}
-      - DEER_FLOW_HOST_SKILLS_PATH=${DEER_FLOW_REPO_ROOT}/skills
-      - DEER_FLOW_SANDBOX_HOST=host.docker.internal
-      # LangSmith tracing: set LANGSMITH_TRACING=true and LANGSMITH_API_KEY in .env to enable.
-    env_file:
-      - ../.env
-    extra_hosts:
-      - "host.docker.internal:host-gateway"
-    networks:
-      - deer-flow
-    restart: unless-stopped
-
   # ── Sandbox Provisioner (optional, Kubernetes mode) ────────────────────────
   provisioner:
     build: