### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### What happened?

A bug happened!Through static source code analysis of the dynamic MCP route handling logic in proxy_server.py, a potential context state leakage vulnerability was identified. When a request matches a cached toolset, the server mutates the ASGI scope and sets a context variable using token = _mcp_active_toolset_id.set(toolset.toolset_id).

While this is wrapped in a try...finally block to reset the token, abrupt asynchronous stream interruptions (e.g., unhandled asyncio.CancelledError from request.receive during _stream_mcp_asgi_response, or deep unhandled socket drops) could potentially disrupt the cleanup lifecycle. In highly concurrent scenarios, this might leave polluted scope dictionaries or dirty _mcp_active_toolset_id context states for subsequent requests utilizing the same async worker.

### Steps to Reproduce

Note: This issue was identified via static security analysis. The following is the theoretical reproduction path under high concurrency. 1. Send a high volume of concurrent HTTP requests targeting a valid cached mcp_server_name (…