CONF-020: Protocol version is read from each request, not remembered

Severity	Applies to	Spec section
error	modern era, stdio	2026-07-28/basic/index#statelessness

Starts a fresh server process and sends a request declaring version 1900-01-01, then a valid 2026-07-28 request, then the 1900-01-01 request again. Servers MUST NOT rely on prior requests over the same connection to establish context such as the protocol version, so the last request MUST still get UnsupportedProtocolVersionError (-32022). If the very first request is already accepted, the server does not check versions at all; that is reported by CONF-003, and this check is skipped. stdio only, because the probe cannot restart an HTTP server to get a first request.

From the command line: mcpprobe checks explain CONF-020. To leave it out of a run, add "CONF-020" to [checks] disable in mcpprobe.toml; to change how much it counts, use severity_overrides.