fix(http): plumb per-request auth user into handler state#9
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The JWT HTTP transport's handleMCPRequestCore invoked the user-supplied mcp_handler_init hook only on the first initialize request to the server-process-wide singleton MCPServerState, after which the authenticated MCPHandlerUser was discarded for every subsequent request. servant-auth still gated each request, but the identity threaded into tool handlers was permanently that of whoever ran initialize first. In a multi-tenant deployment this meant any authenticated caller transparently impersonated the first-arriving user. Add mcp_current_user to MCPServerState, set it from the current request while processMethod runs, and expose getCurrentUser for handlers.
Clear mcp_current_user after each handler run and run client-input continuations with the originating request user instead of whatever user last touched shared state. Update test states for the new field and add an integration tool/test that initializes as one user, then verifies a later request sees its own JWT identity.
nuttycom
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May 27, 2026
nuttycom
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post-hoc ACK, thank you for the quick merge!
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Summary
This fixes a JWT HTTP transport identity bug where
mcp_handler_initonly ran for the firstinitializerequest against the process-wideMCPServerState, causing later authenticated HTTP requests to run handlers with state initialized for the first user.The first commit is the supplied patch, credited to Kris Nuttycombe. Follow-up commits keep that patch separate and add hardening/tests:
mcp_current_userafter each handler runProcessClientInputcontinuations with the originating request userThis also fixes the Docker CI build so it uses the committed
cabal.project.freezedependency plan and installspkg-config, which the frozenzlibflags require.Credit
Original patch provided by Kris Nuttycombe (@nuttycom).
Validation
cabal test allmcp-types: 101 examples, 0 failuresmcp: 82 examples, 0 failures26519296957