Codex App Server README
Source: openai/codex GitHub repository Topic: Canonical implementation documentation for the Codex App Server protocol.
1. Durable session protocol
The README defines the App Server as the persistent boundary between Codex core and clients. It exposes a structured protocol with thread/start, thread/resume, and thread/fork, plus durable thread identifiers rather than a flat transcript model.
2. Rich turn and item lifecycle
The protocol distinguishes threads, turns, and items, with evented notifications for progress and streaming updates. This gives clients a principled way to observe tool calls, diffs, and review work.
3. Reviews and approvals
The README documents explicit review flows such as review/start and approval requests that pause work until the client responds. This confirms that review and permission handling are first-class protocol concerns rather than UI hacks.
4. Tool and file operations
The surface covers command execution, filesystem operations, and configuration negotiation during initialization. In other words, the App Server is not merely a chat transport; it is the operational control plane for Codex sessions.