OpenAI Begins Article Series on Codex CLI Internals
Codex harness runs an LLM-driven agent loop that assembles prompts, manages context to reduce prompt cache misses, and invokes tools via the Responses API.
OpenAI spills technical details about how its AI coding agent works
OpenAI and Anthropic open-source their coding CLIs, while Codex's agent loop builds prioritized prompts from system, developer, user, assistant roles plus tools and inputs.