fix(mcp): add auth interceptor with channel user_id and keep header propagation to mcp tools (#3294)

* 修复channel中的user_id传递到interceptor中的bug, mcp可通过header传递user_id到mcp工具

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(channel,mcp,gateway): normalize channel user_id and add regression tests

Normalize external channel user ids into filesystem-safe runtime context while preserving raw channel_user_id, and document gateway user_id propagation semantics. Add regression coverage for channel user_id context mapping, gateway user_id precedence/internal-role behavior, and MCP interceptor header forwarding via meta.headers.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(auth,mcp): harden user id normalization and header handling

Increase sanitized user-id digest suffix to 16 hex chars, replace internal system role magic string with a shared constant, and harden MCP header forwarding with Mapping type checks. Add regression tests for empty channel user_id handling, unsupported header types, and updated digest length behavior.

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: zhongli <335302680@qq.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_mcp_session_pool.py

@@ -256,6 +256,136 @@ async def test_session_pool_tool_wrapping():
     mock_session.call_tool.assert_awaited_once_with("navigate", {"url": "https://example.com"})
 
 
+@pytest.mark.asyncio
+async def test_session_pool_tool_forwards_interceptor_headers():
+    """Regression for PR #3294: when an interceptor sets ``request.headers``, the
+    pooled stdio call must forward them via ``meta={"headers": ...}`` so downstream
+    MCP servers can read auth/context headers.
+    """
+    from langchain_core.tools import StructuredTool
+    from pydantic import BaseModel, Field
+
+    from deerflow.mcp.tools import _make_session_pool_tool
+
+    class Args(BaseModel):
+        x: int = Field(..., description="x")
+
+    original_tool = StructuredTool(
+        name="srv_act",
+        description="test",
+        args_schema=Args,
+        coroutine=AsyncMock(),
+        response_format="content_and_artifact",
+    )
+
+    mock_session = AsyncMock()
+    mock_session.call_tool = AsyncMock(return_value=MagicMock(content=[], isError=False, structuredContent=None))
+    mock_cm = MagicMock()
+    mock_cm.__aenter__ = AsyncMock(return_value=mock_session)
+    mock_cm.__aexit__ = AsyncMock(return_value=False)
+
+    async def header_interceptor(request, handler):
+        return await handler(request.override(headers={"X-User-Id": "u-42"}))
+
+    with patch("langchain_mcp_adapters.sessions.create_session", return_value=mock_cm):
+        wrapped = _make_session_pool_tool(
+            original_tool,
+            "srv",
+            {"transport": "stdio", "command": "x", "args": []},
+            tool_interceptors=[header_interceptor],
+        )
+        await wrapped.coroutine(runtime=None, x=1)
+
+    mock_session.call_tool.assert_awaited_once_with("act", {"x": 1}, meta={"headers": {"X-User-Id": "u-42"}})
+
+
+@pytest.mark.asyncio
+async def test_session_pool_tool_no_headers_omits_meta():
+    """When no interceptor sets headers, the pooled call must not pass a ``meta``
+    kwarg (falls back to the plain two-argument ``call_tool``).
+    """
+    from langchain_core.tools import StructuredTool
+    from pydantic import BaseModel, Field
+
+    from deerflow.mcp.tools import _make_session_pool_tool
+
+    class Args(BaseModel):
+        x: int = Field(..., description="x")
+
+    original_tool = StructuredTool(
+        name="srv_act",
+        description="test",
+        args_schema=Args,
+        coroutine=AsyncMock(),
+        response_format="content_and_artifact",
+    )
+
+    mock_session = AsyncMock()
+    mock_session.call_tool = AsyncMock(return_value=MagicMock(content=[], isError=False, structuredContent=None))
+    mock_cm = MagicMock()
+    mock_cm.__aenter__ = AsyncMock(return_value=mock_session)
+    mock_cm.__aexit__ = AsyncMock(return_value=False)
+
+    async def passthrough_interceptor(request, handler):
+        return await handler(request)
+
+    with patch("langchain_mcp_adapters.sessions.create_session", return_value=mock_cm):
+        wrapped = _make_session_pool_tool(
+            original_tool,
+            "srv",
+            {"transport": "stdio", "command": "x", "args": []},
+            tool_interceptors=[passthrough_interceptor],
+        )
+        await wrapped.coroutine(runtime=None, x=1)
+
+    mock_session.call_tool.assert_awaited_once_with("act", {"x": 1})
+
+
+@pytest.mark.asyncio
+async def test_session_pool_tool_ignores_unsupported_header_type(caplog):
+    """Defensive path: non-mapping truthy headers should be ignored safely."""
+    from langchain_core.tools import StructuredTool
+    from pydantic import BaseModel, Field
+
+    from deerflow.mcp.tools import _make_session_pool_tool
+
+    class Args(BaseModel):
+        x: int = Field(..., description="x")
+
+    class TruthyHeaders:
+        def __bool__(self) -> bool:
+            return True
+
+    original_tool = StructuredTool(
+        name="srv_act",
+        description="test",
+        args_schema=Args,
+        coroutine=AsyncMock(),
+        response_format="content_and_artifact",
+    )
+
+    mock_session = AsyncMock()
+    mock_session.call_tool = AsyncMock(return_value=MagicMock(content=[], isError=False, structuredContent=None))
+    mock_cm = MagicMock()
+    mock_cm.__aenter__ = AsyncMock(return_value=mock_session)
+    mock_cm.__aexit__ = AsyncMock(return_value=False)
+
+    async def invalid_header_interceptor(request, handler):
+        return await handler(request.override(headers=TruthyHeaders()))
+
+    with patch("langchain_mcp_adapters.sessions.create_session", return_value=mock_cm):
+        wrapped = _make_session_pool_tool(
+            original_tool,
+            "srv",
+            {"transport": "stdio", "command": "x", "args": []},
+            tool_interceptors=[invalid_header_interceptor],
+        )
+        await wrapped.coroutine(runtime=None, x=1)
+
+    mock_session.call_tool.assert_awaited_once_with("act", {"x": 1})
+    assert "unsupported type" in caplog.text
+
+
 @pytest.mark.asyncio
 async def test_session_pool_tool_extracts_thread_id():
     """Thread ID is extracted from runtime.config when not in context."""