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>

backend/tests/test_channels.py

@@ -495,7 +495,7 @@ class TestChannelManager:
             await _wait_for(lambda: len(outbound_received) >= 1)
             await manager.stop()
 
-            # Thread should be created on the LangGraph Server
+            # Thread should be created through Gateway
             mock_client.threads.create.assert_called_once()
 
             # Thread ID should be stored
@@ -1987,28 +1987,28 @@ class TestChannelService:
     def test_service_urls_fall_back_to_env(self, monkeypatch):
         from app.channels.service import ChannelService
 
-        monkeypatch.setenv("DEER_FLOW_CHANNELS_LANGGRAPH_URL", "http://langgraph:2024")
+        monkeypatch.setenv("DEER_FLOW_CHANNELS_LANGGRAPH_URL", "http://gateway:8001/api")
         monkeypatch.setenv("DEER_FLOW_CHANNELS_GATEWAY_URL", "http://gateway:8001")
 
         service = ChannelService(channels_config={})
 
-        assert service.manager._langgraph_url == "http://langgraph:2024"
+        assert service.manager._langgraph_url == "http://gateway:8001/api"
         assert service.manager._gateway_url == "http://gateway:8001"
 
     def test_config_service_urls_override_env(self, monkeypatch):
         from app.channels.service import ChannelService
 
-        monkeypatch.setenv("DEER_FLOW_CHANNELS_LANGGRAPH_URL", "http://langgraph:2024")
+        monkeypatch.setenv("DEER_FLOW_CHANNELS_LANGGRAPH_URL", "http://gateway:8001/api")
         monkeypatch.setenv("DEER_FLOW_CHANNELS_GATEWAY_URL", "http://gateway:8001")
 
         service = ChannelService(
             channels_config={
-                "langgraph_url": "http://custom-langgraph:2024",
+                "langgraph_url": "http://custom-gateway:8001/api",
                 "gateway_url": "http://custom-gateway:8001",
             }
         )
 
-        assert service.manager._langgraph_url == "http://custom-langgraph:2024"
+        assert service.manager._langgraph_url == "http://custom-gateway:8001/api"
         assert service.manager._gateway_url == "http://custom-gateway:8001"
 
     def test_disabled_channel_with_string_creds_emits_warning(self, caplog):

backend/tests/test_gateway_runtime_cleanup.py

@@ -0,0 +1,62 @@
+"""Regression coverage for the Gateway-owned LangGraph API runtime."""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+
+
+def _read(path: str) -> str:
+    return (REPO_ROOT / path).read_text(encoding="utf-8")
+
+
+def test_root_makefile_no_longer_exposes_transition_gateway_targets():
+    makefile = _read("Makefile")
+
+    assert "dev-pro" not in makefile
+    assert "start-pro" not in makefile
+    assert "dev-daemon-pro" not in makefile
+    assert "start-daemon-pro" not in makefile
+    assert "docker-start-pro" not in makefile
+    assert "up-pro" not in makefile
+    assert not re.search(r"serve\.sh .*--gateway", makefile)
+    assert "docker.sh start --gateway" not in makefile
+    assert "deploy.sh --gateway" not in makefile
+
+
+def test_service_launchers_always_use_gateway_runtime():
+    operational_files = {
+        "scripts/serve.sh": _read("scripts/serve.sh"),
+        "scripts/docker.sh": _read("scripts/docker.sh"),
+        "scripts/deploy.sh": _read("scripts/deploy.sh"),
+        "docker/docker-compose-dev.yaml": _read("docker/docker-compose-dev.yaml"),
+        "docker/docker-compose.yaml": _read("docker/docker-compose.yaml"),
+    }
+
+    for path, content in operational_files.items():
+        assert "start --gateway" not in content, path
+        assert "deploy.sh --gateway" not in content, path
+        assert "langgraph dev" not in content, path
+        assert "LANGGRAPH_UPSTREAM" not in content, path
+        assert "LANGGRAPH_REWRITE" not in content, path
+
+
+def test_nginx_routes_official_langgraph_prefix_to_gateway_api():
+    for path in ("docker/nginx/nginx.local.conf", "docker/nginx/nginx.conf"):
+        content = _read(path)
+
+        assert "/api/langgraph-compat" not in content
+        assert "proxy_pass http://langgraph" not in content
+        assert "rewrite ^/api/langgraph/(.*) /api/$1 break;" in content
+        assert "proxy_pass http://gateway" in content
+
+
+def test_frontend_rewrites_langgraph_prefix_to_gateway():
+    next_config = _read("frontend/next.config.js")
+    api_client = _read("frontend/src/core/api/api-client.ts")
+
+    assert "DEER_FLOW_INTERNAL_LANGGRAPH_BASE_URL" not in next_config
+    assert "http://127.0.0.1:2024" not in next_config
+    assert "langgraph-compat" not in api_client