MCP server: Authentication lost in tool execution

[GregoireW]

trafficstars

Bug description

I'm in a situation where I have authentication with OIDC (so an access token basically).

When I set authentication required on the /sse and /mcp/** endpoint, then the client side only connect when I provide the correct access token. This is ok.

Even when the client send a call to a tool, the authentication is needed, but inside the executed code, I cannot access the authentication.

SecurityContextHolder.getContext().getAuthentication() and ReactiveSecurityContextHolder.getContext() return null.

Long story short, I cannot control data ownership so this is bad, and my MCP server also execute some api call that need to be authenticated, and I use the oauth2ClientRequestInterceptor to do token exchange so this also fail. ( the MCP core even with SYNC option goes through reactive code and the original servlet thread is put on hold, giving the execution to a 'boundedElactic' thread )

Environment

Spring MVC ( springboot 3.4 ) Spring AI 1.0.0-M6 ( spring-ai-mcp-server-webmvc-spring-boot-starter ) spring-boot-starter-oauth2-resource-server (for oauth2 authentication )

Steps to reproduce

Enable authentication on an application, create a Tool that just return the authenticated user.

Expected behavior

I expect to be able to find the security context when a tool is called from MCP

Minimal Complete Reproducible example

Enable authentication on a springboot with MCP server activated, Create a Tool

@Tool(description="Get your name")
    public String getYourName() {
        return SecurityContextHolder.getContext().getAuthentication().getName();
    }

call the tool. It should answer your sub and not null.