Codex Harness: How OpenAI Built an Embeddable Agent OS in 135 Rust Crates
This article dissects OpenAI's Codex Harness, a 146K-line Rust workspace of 135 crates that powers ChatGPT, CLI, and IDE extensions as an embeddable agent platform, detailing its agent loop, context engineering, JSON-RPC protocol, multi-OS sandboxing, and multi-agent architecture with measurable benchmark gains on ARC-AGI-3.
