cto CLI is a free coding CLI that runs every frontier model without an API key. It's an opencode plugin + provider - opencode (Apache 2.0) is the agent running in your terminal; cto's provider is the cto.new gateway that handles LLM calls. Ad-supported, no credit card.
Install in one line
curl -fsSL https://cto.new/install | bash
That's it. The installer drops cto onto your PATH (Mac, Linux, Windows) and prints next-step instructions. Then in any project:
cto
First launch opens your browser to log you in (email or GitHub). Subsequent runs are silent.
What you get
- Every frontier model. Opus 4.8, Sonnet 4.6, GPT-5.5, GPT-5.3 Codex, Gemini 3.5 Flash, Gemini 3.1 Pro, GLM 5.1, Grok 4.20, Kimi K2.6, MiniMax M2.7. Pick via opencode's
/modelslash command - no API keys required. - opencode-native MCP. Configure your MCP servers (stdio or streamable HTTP) in opencode's standard config format. Same as vanilla opencode.
- Full opencode feature set. Agent loop, file editing, plan mode, worktrees, hooks, skills, slash commands, LSP. cto inherits all of it.
- Free forever, ad-supported. Rolling 24-hour and 7-day usage limits (not a calendar-day reset). No credit card, no per-token meter.
- Cross-platform. Mac, Linux, Windows.
The commands you'll use
cto Launch the cto coding agent
cto login Re-authenticate this device
cto logout Revoke credentials, forget the local copy
cto upgrade Update cto to the latest release
cto uninstall Remove cto + ~/.cto from this machine
cto --version Print the cto version
cto --licenses Print license + third-party notices
cto --help Show usage
Sub-commands not listed pass through to opencode. Inside the TUI, /cto-login and /cto-logout let you re-auth without quitting.
Quickstart inside the TUI
cto
# Inside the opencode TUI:
> write tests for the auth module and run them
> /model openai/gpt-5.5 # switch model per session
> /mcp # see configured MCP servers
The CLI is composable - tail -200 app.log | cto -p "find anomalies" works for one-shot piped use.
How it compares to other coding CLIs
| CLI | Free tier | API keys | Models |
|---|---|---|---|
| cto CLI | Free forever (ads), rolling 24h+7d | None - cto.new gateway handles it | 10+ frontier via /model |
| Claude Code | None (paid plan) | Required (Anthropic) | Claude + third-party providers |
| Cursor CLI | Hobby trial; Pro $20/mo per seat | Tied to Cursor account | Frontier menu via Cursor |
| Aider | Free CLI | BYOK per provider | Any via litellm |
| GitHub Copilot CLI | Copilot Free (tight caps) | GitHub Copilot account | Anthropic, Google, OpenAI |
| Codex CLI | None - needs ChatGPT or API key | OpenAI required | OpenAI only |
| Gemini CLI | 60/min, 1000/day with Google | Google account | Gemini only |
cto CLI is the free-forever option that doesn't ask you to bring keys.
Troubleshooting
cto: command not foundafter install: open a new terminal session (the installer adds to your PATH; existing sessions need to reload it).- Login browser doesn't open: copy the URL from the terminal output into your browser manually.
- Hit the rolling 24h limit: wait for it to slide forward, or upgrade to premium for the raised window.
Uninstall
cto uninstall
Removes the binary and ~/.cto. Confirms before deleting.
What's actually different about cto CLI
Three things that make this work in 2026:
- opencode underneath. The agent loop is open source. You can audit it, fork it, contribute back. cto adds the parts that make the free tier work - the managed gateway and the ads.
- No API keys. The cto.new gateway handles provider auth. You sign in once with cto; the CLI reaches every frontier model through one account.
- Free forever. Ad-supported with rolling 24h+7d limits. Most days of coding fit within the limits. Premium raises them for production use.