OpenAI's open-source terminal coding agent with sandboxed code execution.
Codex CLI is OpenAI's open-source, terminal-native coding agent. It runs in your shell, reads your codebase, writes code, and executes commands inside a secure sandbox. Built on the o3 and o4-mini reasoning models, it is optimized for multi-step problem solving: plan → implement → test → iterate without manual intervention.
AgenticCLIOpen SourceOpenAI
Published Mar 15, 2026
Visual coming soon
Use Cases
Automated bug fixing: describe the bug, let Codex reproduce and patch it
Script generation and execution in a sandboxed environment
Multi-file refactoring with automatic test verification
Code review and explanation of unfamiliar codebases
Specifications
InterfaceCLI (terminal), open source
Modelo3-mini, o4-mini (reasoning models)
ExecutionSandboxed shell with network/disk controls