# OpenAI — Unlocking the Codex harness: how we built the App Server

- Company: OpenAI (openai.com)
- Announced: 2026-02-04T13:00:00+00:00
- Category: developer-tool-release
- Subject: GPT / ChatGPT / API
- Source: https://openai.com/index/unlocking-the-codex-harness
- Record: https://forck.live/items/283-unlocking-the-codex-harness-how-we-built-the-app-server

OpenAI describes how to embed the Codex agent using the Codex App Server, a bidirectional JSON-RPC API for streaming progress, tool use, approvals, and diffs.

## Evidence

Verbatim from https://openai.com/index/unlocking-the-codex-harness:

> Learn how to embed the Codex agent using the Codex App Server, a bidirectional JSON-RPC API powering streaming progress, tool use, approvals, and diffs.

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