Fix IM channel backend URLs in Docker (#1497)

* Fix IM channel backend URLs in Docker

* Address Copilot review comments

backend/app/channels/service.py

@@ -3,9 +3,10 @@
 from __future__ import annotations
 
 import logging
+import os
 from typing import Any
 
-from app.channels.manager import ChannelManager
+from app.channels.manager import DEFAULT_GATEWAY_URL, DEFAULT_LANGGRAPH_URL, ChannelManager
 from app.channels.message_bus import MessageBus
 from app.channels.store import ChannelStore
 
@@ -18,6 +19,19 @@ _CHANNEL_REGISTRY: dict[str, str] = {
     "telegram": "app.channels.telegram:TelegramChannel",
 }
 
+_CHANNELS_LANGGRAPH_URL_ENV = "DEER_FLOW_CHANNELS_LANGGRAPH_URL"
+_CHANNELS_GATEWAY_URL_ENV = "DEER_FLOW_CHANNELS_GATEWAY_URL"
+
+
+def _resolve_service_url(config: dict[str, Any], config_key: str, env_key: str, default: str) -> str:
+    value = config.pop(config_key, None)
+    if isinstance(value, str) and value.strip():
+        return value
+    env_value = os.getenv(env_key, "").strip()
+    if env_value:
+        return env_value
+    return default
+
 
 class ChannelService:
     """Manages the lifecycle of all configured IM channels.
@@ -30,8 +44,8 @@ class ChannelService:
         self.bus = MessageBus()
         self.store = ChannelStore()
         config = dict(channels_config or {})
-        langgraph_url = config.pop("langgraph_url", None) or "http://localhost:2024"
-        gateway_url = config.pop("gateway_url", None) or "http://localhost:8001"
+        langgraph_url = _resolve_service_url(config, "langgraph_url", _CHANNELS_LANGGRAPH_URL_ENV, DEFAULT_LANGGRAPH_URL)
+        gateway_url = _resolve_service_url(config, "gateway_url", _CHANNELS_GATEWAY_URL_ENV, DEFAULT_GATEWAY_URL)
         default_session = config.pop("session", None)
         channel_sessions = {name: channel_config.get("session") for name, channel_config in config.items() if isinstance(channel_config, dict)}
         self.manager = ChannelManager(