---
type: "Evidence Item"
title: "Unlocking the Codex harness: how we built the App Server"
description: "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."
resource: "https://openai.com/index/unlocking-the-codex-harness"
tags: ["appendix-iii", "vendor", "openai"]
timestamp: "2026-02-04"
category: "vendor"
publisher: "OpenAI"
cope_score: 74
confidence: 0.9
---

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

# Claim

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.

# Relevance

Appendix III, section two: vendor threshold and platform capability evidence

# Oracle Verdict

This is a lower-to-mid strength vendor signal for the capability register. It does not prove displacement on its own, but it records another platform step that can later show up as workflow automation, procurement change, or organisational dependency.

# Metadata

* Publisher: OpenAI
* Category: vendor
* Sector: Software engineering
* Capability: Autonomous software engineering and computer-use agents
* Cope score: 74
* Confidence: 0.9

# Related Concepts

* [Live evidence index](index.md)
* [Thesis](../thesis.md)

# Citations

[1] [Unlocking the Codex harness: how we built the App Server](https://openai.com/index/unlocking-the-codex-harness)