Comparison
| FreeChaOS | Claude Code | OpenAI Codex CLI | |
|---|---|---|---|
| License | Apache-2.0 | Proprietary | Apache-2.0 |
| Provider lock-in | None - Chaos-ABI supports any provider | Anthropic only | OpenAI only |
| Models | Any (OpenAI, Anthropic, Ollama, local) | Claude only | OpenAI only |
| Architecture | Provider-agnostic ABI, adapters are peers | Monolithic | Hardcoded to Responses API |
| MCP support | Full (client + server, .mcp.json) |
Partial (no elicitation, limited resources) | Stubs (announced, mostly unimplemented) |
| Sandbox | Landlock + seccomp (Linux), seatbelt (macOS) | Container-based | Landlock + seatbelt |
| Platforms | Linux, macOS, FreeBSD | Linux, macOS, Windows | Linux, macOS, Windows |
| External contributors | Welcome | Not accepted | Not accepted |
| Binary | chaos + sidecar daemons |
Single claude binary |
Multiple binaries |
| Runtime | Native Rust | Node.js | Native Rust |
| Phone home | Never | Telemetry (opt-out) | Update checker + telemetry |
| Age verification | Everyone is 47 | None | None |
| Extended thinking | Native per-provider (ABI maps effort levels) | Native | Via Responses API only |
| Prompt caching | Per-provider (native where supported) | Native | OpenAI only |
| Tool streaming | Per-provider | Native | Via Responses API only |
| Config format | runtime DB + .mcp.json + config.toml |
settings.json + .mcp.json |
config.toml |
| Session resume | chaos resume |
claude --continue |
codex resume |
| Non-interactive | chaos exec |
claude -p |
Separate codex-exec binary |
| Code review | chaos exec review |
Not built-in | codex review |
Why FreeChaOS?
Section titled “Why FreeChaOS?”FreeChaOS is a fork of OpenAI’s Codex CLI that broke free from provider lock-in. The core speaks a neutral ABI - the Chaos-ABI - so adding a new model provider means writing one adapter, not rewiring the entire codebase.
It ships as a small set of native binaries with no update checker, no telemetry, no phone home. It runs on Linux, macOS, and FreeBSD.
Claude Code is excellent but proprietary and Anthropic-only. OpenAI Codex CLI is open source but hardcoded to OpenAI’s wire format. FreeChaOS takes the best of both: free software, native performance, any provider.