Codex as a platform: build on the open agent harness | OpenAI Developers

This post introduces the open-source Codex harness as a foundational component for building agentic applications. It details how the harness provides a reusable agent loop for context management, tool use, sandbox enforcement, and approval workflows. The post emphasizes integrating this harness into custom applications via the Codex app-server or SDK, allowing developers to build software around specific workflows (e.g., security investigations, operations dashboards) rather than reproducing a generic chat interface. It highlights the flexibility of exposing application-owned context, tools, and approval flows to the agent, exemplified by the Relay operations application.