Propagate user access tokens to specific MCP servers using MultiServerMCPClient

[ykoer]

I’m working on a setup where I want to build secure MCP servers that can act on behalf of a user. Specifically, I’m experimenting with langchain-mcp-adapters and would like to ensure that a user’s access token (e.g., from a browser or frontend client) is passed all the way down to the specific MCP server implementation.

I see that MultiServerMCPClient supports a headers field, but this seems to only allow for static headers. Is there a supported way to dynamically pass per-request headers — such as authentication tokens — through to the final MCP server?

Has anyone implemented this pattern, or is there a recommended approach for securely propagating user identity across the full request chain?

Thanks in advance!