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/packages/harness/deerflow/mcp/tools.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import logging
+from collections.abc import Mapping
 from typing import Any
 
 from langchain_core.tools import BaseTool, StructuredTool
@@ -137,7 +138,15 @@ def _make_session_pool_tool(
             from langchain_mcp_adapters.interceptors import MCPToolCallRequest
 
             async def base_handler(request: MCPToolCallRequest) -> Any:
-                return await session.call_tool(request.name, request.args)
+                # Preserve interceptor-injected headers for stdio MCP calls by
+                # forwarding them through MCP call meta.
+                call_kwargs: dict[str, Any] = {}
+                if request.headers:
+                    if isinstance(request.headers, Mapping):
+                        call_kwargs["meta"] = {"headers": dict(request.headers)}
+                    else:
+                        logger.warning("Ignoring MCP interceptor headers with unsupported type: %s", type(request.headers).__name__)
+                return await session.call_tool(request.name, request.args, **call_kwargs)
 
             handler = base_handler
             for interceptor in reversed(tool_interceptors):