TLDR Tech / Dev
How Codex is built
OpenAI's coding agent, Codex, has a Rust-based architecture, open-source CLI, and an 'agent loop' that orchestrates user-model-tool interactions. Codex builds itself, generating over 90% of its own code, turning engineers into 'agent managers' who oversee multiple parallel agents for tasks like feature implementation, code review, and bug fixing.
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