diff --git a/backend/package/yuxi/agents/context.py b/backend/package/yuxi/agents/context.py
index d263ebc9..fec0f6e6 100644
--- a/backend/package/yuxi/agents/context.py
+++ b/backend/package/yuxi/agents/context.py
@@ -320,12 +320,26 @@ async def resolve_agent_resource_options(
 
     if "tools" in fields_to_load:
         from yuxi.agents.toolkits.service import get_tool_metadata
+        from yuxi.external_systems.infrastructure.container import (
+            create_use_cases_from_db,
+        )
+        from yuxi.external_systems.use_cases.dto.tool import (
+            ListToolOptionsInput,
+        )
 
         options["tools"] = [
             _resource_option(tool["slug"], tool.get("name"), tool.get("description"))
             for tool in get_tool_metadata(category="buildin")
             if tool.get("slug")
         ]
+        try:
+            use_cases = create_use_cases_from_db(db)
+            output = await use_cases.tool_service.list_tool_options(
+                ListToolOptionsInput(),
+            )
+            options["tools"].extend(output.items)
+        except Exception as e:
+            logger.warning(f"Failed to load external tool options: {e}")
     if "knowledges" in fields_to_load:
         from yuxi.knowledge import knowledge_base
 
diff --git a/backend/package/yuxi/agents/toolkits/service.py b/backend/package/yuxi/agents/toolkits/service.py
index 73b606a1..39af703c 100644
--- a/backend/package/yuxi/agents/toolkits/service.py
+++ b/backend/package/yuxi/agents/toolkits/service.py
@@ -96,6 +96,13 @@ def get_tool_instances_by_category(category: str) -> list[Any]:
 
 async def resolve_configured_runtime_tools(context) -> list[Any]:
     from yuxi.agents.mcp.service import get_enabled_mcp_tools
+    from yuxi.external_systems.infrastructure.container import (
+        create_use_cases_from_db,
+    )
+    from yuxi.external_systems.use_cases.dto.tool import (
+        BuildRuntimeToolsInput,
+    )
+    from yuxi.storage.postgres.manager import pg_manager
 
     selected_tools = []
     selected_tool_names: set[str] = set()
@@ -130,4 +137,24 @@ async def resolve_configured_runtime_tools(context) -> list[Any]:
             selected_tools.append(tool)
             selected_tool_names.add(tool.name)
 
+    # 追加加载外部系统工具（按 slug 匹配 context.tools 中的选择）
+    external_tool_names = [
+        name
+        for name in getattr(context, "tools", None) or []
+        if isinstance(name, str) and name not in selected_tool_names
+    ]
+    if external_tool_names:
+        async with pg_manager.get_async_session_context() as db:
+            use_cases = create_use_cases_from_db(db)
+            output = await use_cases.tool_service.build_runtime_tools(
+                BuildRuntimeToolsInput(slugs=external_tool_names),
+            )
+        selected_tools.extend(output.items)
+        selected_tool_names.update(tool.name for tool in output.items)
+        # 构建失败的工具 slug 必须显式记录，避免用户配置的工具被静默丢失
+        if output.failed_slugs:
+            logger.warning(
+                f"Failed to build external runtime tools, skipped: {output.failed_slugs}"
+            )
+
     return selected_tools
diff --git a/backend/server/main.py b/backend/server/main.py
index d3b9e7dd..5502e089 100644
--- a/backend/server/main.py
+++ b/backend/server/main.py
@@ -20,6 +20,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse
 from starlette.middleware.base import BaseHTTPMiddleware
 
+from yuxi.external_systems.exceptions import ExternalSystemError
 from server.routers import router
 from server.utils.lifespan import lifespan
 from server.utils.auth_middleware import is_public_path
@@ -41,6 +42,27 @@ app = FastAPI(lifespan=lifespan)
 # 所有业务接口统一挂载到 /api，具体分组在 server.routers 中集中注册。
 app.include_router(router, prefix="/api")
 
+
+@app.exception_handler(ExternalSystemError)
+async def external_system_error_handler(_request: Request, exc: ExternalSystemError) -> JSONResponse:
+    """外部系统限界上下文异常统一映射为 HTTP 响应。
+
+    - ``status_code`` 来自异常类。
+    - ``details`` 透传到响应体，供前端结构化处理。
+    - 429/503 且 ``details`` 含 ``retry_after`` 时，自动设置 ``Retry-After`` 响应头。
+    """
+    headers: dict[str, str] = {}
+    if exc.status_code in (429, 503):
+        retry_after = exc.details.get("retry_after")
+        if retry_after is not None:
+            headers["Retry-After"] = str(retry_after)
+    return JSONResponse(
+        status_code=exc.status_code,
+        content={"detail": exc.message, "details": exc.details},
+        headers=headers,
+    )
+
+
 # CORS 设置
 app.add_middleware(
     CORSMiddleware,
diff --git a/backend/server/utils/lifespan.py b/backend/server/utils/lifespan.py
index 2f4cef64..17d2044d 100644
--- a/backend/server/utils/lifespan.py
+++ b/backend/server/utils/lifespan.py
@@ -9,6 +9,7 @@ from yuxi.agents.mcp.service import ensure_builtin_mcp_servers_in_db
 from yuxi.models.providers.service import ensure_builtin_model_providers_in_db
 from yuxi.services.run_queue_service import close_queue_clients, get_redis_client
 from yuxi.storage.postgres.manager import pg_manager
+from yuxi.external import register_adapters
 from yuxi.knowledge import knowledge_base
 from yuxi.utils import logger
 from yuxi.agents.backends.sandbox import init_sandbox_provider, shutdown_sandbox_provider
@@ -17,6 +18,14 @@ from yuxi import get_version
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
+
+    # 注册外部系统适配器（避免模块导入副作用）
+    try:
+        register_adapters()
+    except Exception as e:
+        logger.error(f"Failed to register external system adapters during startup: {e}")
+
+
     """FastAPI lifespan事件管理器"""
     # 初始化数据库连接
     try:
@@ -24,6 +33,7 @@ async def lifespan(app: FastAPI):
         await pg_manager.create_tables()
         await pg_manager.ensure_business_schema()
         await pg_manager.ensure_knowledge_schema()
+        await pg_manager.ensure_external_schema()
     except Exception as e:
         logger.error(f"Failed to initialize database during startup: {e}")