Why should you test with the same transport you plan to use in production?

The behavior differences between STDIO and HTTP transports, and between stateful and stateless modes, can be significant. A server that works perfectly with STDIO locally may break when deployed with StreamableHTTP because sampling, progress notifications, and logging rely on server-to-client communication that HTTP may restrict. Testing with your production transport during development catches these issues early. If you develop with STDIO but deploy with stateless HTTP, you may discover at deployment that core features simply do not work.