A guide to using OpenAI Codex. Automatically generate code with Codex. Codex can also help with refactoring and writing tests. Learn through hands-on examples.
A source-code-level breakdown of how the OpenAI Codex agent loop works internally — from the while loop and tool call flow to context management, error retry strategies, and the TypeScript-to-Rust transition.
The Codex CLI agent loop repeats a cycle of Responses API calls, tool execution, and result feedback based on a while loop. This analysis covers agent-loop.ts internals, context management, error handling, and the Rust migration.
Covers OpenAI Codex CLI installation, authentication, GPT-5-Codex model API calls, AGENTS.md agent task configuration, and config.toml MCP integration with hands-on examples.
A step-by-step guide to building a GitHub Actions workflow where the Codex API analyzes diffs and auto-posts review comments on every pull request, with practical considerations for production use.
The three major AI coding agents of 2026 each use a different pricing model. OpenAI Codex switched to token-based billing, Claude uses dual session-runtime billing, and Gemini adopted per-user flat rates. A full comparison from token prices to monthly cost simulations.