What configuration settings can limit StreamableHTTP functionality?

Two key settings control StreamableHTTP behavior: stateless_http and json_response. Both default to false. When set to true, they can break core MCP functionality including progress notifications, logging, and server-initiated requests like sampling. If your MCP application works perfectly with STDIO transport locally but breaks when deployed with HTTP transport, these settings are likely the cause. Certain deployment scenarios may force you to enable them, but doing so means accepting reduced functionality in exchange for simpler HTTP compatibility.