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write_method_not_found_pre_init

lean_ctx::mcp_stdio

Function write_method_not_found_pre_init 

Source 
pub fn write_method_not_found_pre_init(
    id: &Value,
    method: &str,
    protocol: &SharedProtocol,
)
Expand description

GH #1454: a well-formed JSON-RPC request with an unrecognized method reached the pre-init handshake loop. rmcp’s ClientRequest union has a CustomRequest catch-all, so the message deserialized fine — the #1434 handler in try_parse_with_compatibility (deser-failure path) never fired — and the pre-init loop rejected it with ServerInitializeError::ExpectedInitializeRequest. Modern clients (MCP Go SDK >= 1.7, e.g. Antigravity) probe with server/discover first and fall back to the legacy initialize handshake ONLY after a spec-compliant -32601. Reply with the same framing the client established, and keep the process alive so the fallback initialize lands on this connection.

The message mirrors the legacy-handshake-only contract so dual-era clients can detect the server class and proceed.