Unlocking the Codex harness: how we built the App Server

📰 OpenAI News

OpenAI's Codex App Server enables embedding the Codex agent using a bidirectional JSON-RPC API

intermediate Published 4 Feb 2026

Action Steps

Understand the Codex agent and its capabilities
Explore the Codex App Server API documentation
Implement the bidirectional JSON-RPC API for streaming progress, tool use, approvals, and diffs
Integrate the Codex App Server into your application

Who Needs to Know This

Developers and software engineers on a team can benefit from this knowledge to integrate Codex into their applications, while product managers can understand the potential of Codex App Server for their product roadmap

Key Insight

💡 The Codex App Server provides a flexible and powerful way to embed the Codex agent into applications