feat: migrate HTTP transport to stateless mode, upgrade go-sdk to v1.7.0 - #162

Pull request overview

This PR migrates the MCP HTTP transport from stateful (session/SSE-oriented) behavior to stateless JSON request/response mode, enabled via the go-sdk v1.7.0 StreamableHTTPOptions.Stateless support.

Changes:

• Upgrade github.com/modelcontextprotocol/go-sdk from v1.6.1 to v1.7.0.
• Switch the HTTP handler to stateless + JSON responses, and remove the now-inapplicable --mcp.session-timeout flag.
• Re-enable HTTP server WriteTimeout (previously disabled for SSE-style streaming).

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		// request/response cycles. Stateless HTTP transport uses
		// application/json responses that complete in a single round
		// trip, so standard timeouts apply.
		ReadTimeout:  30 * time.Second,
		WriteTimeout: *flagPrometheusTimeout + (5 * time.Second),

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Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.

		WriteTimeout: *flagPrometheusTimeout,

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	flagMcpKeepaliveInterval = kingpin.Flag(
		"mcp.keepalive-interval",
		"Interval for sending keepalive pings to connected MCP sessions."+
			" If the peer fails to respond, the session is closed."+
			" Most useful for stdio transport to prevent idle connections from dropping.",
	).Default("30s").Duration()

	handler := mcp.NewStreamableHTTPHandler(
		func(r *http.Request) *mcp.Server {
			return server
		},
		&mcp.StreamableHTTPOptions{
			Stateless:    true,
			JSONResponse: true,
			Logger:       logger,
		},

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.

		&mcp.ServerOptions{
			Instructions: instrx,
			Logger:       logger.WithGroup("go_sdk_logger"),
			Capabilities: caps,
		},

Thanks for getting this PR so fast after the official release! The approach overall is solid and the first-order mechanics of things that need changing in order to do the migration (like the unwiring the keepalive/timeout) are all sound. Thankfully, the transition to stateless is overall pretty easy/transparent to consumers. However, there are some (I think) inaccuracies in some of the implementation vs the literal spec. There are also second-order changes and implications that need to be fixed/addressed. I've left feedback inline where possible, but some of the second-order changes mentioned aren't in the changeset to comment on, so listing here:

1. this will break some telemetry. right now, the server ready metric gets set during the initialize method, but the new "stateless" version of the spec doesn't have an initialize, so the server ready metric goes dark
2. we should expand telemetry hooks in middleware.go to capture server/discover method, I think. it's not required for clients to use it, so it shouldn't indicate server readiness, though
3. the server ready metric will need to be re-homed. it didn't really live in the right place before anyway, as the initialize method required a client to connect, so the server would start up successfully and the metric would indicate "not ready" until the first client connected and completed an initialize. really, the server is "ready" once it's about to kick off serving MCP requests. so I would think that would mean:
   • when running an stdio server, setting as ready directly before starting the stdio server
   • when running an http server, setting as ready directly after adding the /mcp handler to the webserver, since a failure there would bubble up through through to oklog/run and kill the program
   • unset server ready during cleanup

Thanks for the help taking this on! Lemme know if you have any questions