Codex App Server Protocol

JSON-RPC stdio protocol for headless Codex sessions: initialize/initialized/thread-start/turn-start handshake, continuation turns reuse thread_id, dynamic tool calls for token-isolated tool injection — and, since MCP spec 2026-07-28 deleted sessions and the initialize handshake outright, the protocol pair has diverged on statefulness: MCP walked away from session semantics while session semantics are this protocol's entire subject matter