Laravel MCP 1.0, released September 15, 2026, adds a middleware that rejects stateless requests with HTTP 400 and error code -32020 when three routing headers are missing or wrong.
A clean tool call worked on 0.9.6, and on 1.0.2 only after we added the headers and the `_meta` fields. Clients that still send `initialize` kept working, but `Request::sessionId()`, the
Upgrade now if you run your own clients or tests. Wait if a third-party client you do not control still sends the old handshake and you have not tried it against 1.0.