OpenAI's Codex is a large language model that can perform tasks such as writing code. The Codex App Server is an interface for interacting with the model, allowing developers to embed it in their applications using a bidirectional JSON-RPC API. This API enables features like streaming progress, tool use, approvals, and diffs. Developers can use this server to integrate the Codex agent into their workflows. --- Why it matters: This matters because it provides a standardized interface for integrating large language models like Codex into various applications, making it easier for developers to leverage these powerful tools in their projects. Source: https://openai.com/index/unlocking-the-codex-harness