A Connector is what actually runs a coding agent's process on your behalf. Claude Code, Codex CLI, Gemini CLI, and Grok CLI are all fully built out and verified end to end — runs, tool calls, terminal-session sync, and Frontier's own MCP tools work through any of them. Gemini CLI signs in with a Gemini API key or a Google Cloud project; Google no longer lets a personal account use it. Grok CLI signs in by running grok login, or with an xAI API key.
Setting one up is a single step: during a new context's guided setup (and again any time from Settings → General → Connectors), tick the installed CLIs you want wired up, pick which one runs by default, and continue. A CLI that isn't installed on your machine shows greyed out until it is.
You can pick a different connector for the whole app, or override it for a single workspace — see Choosing a connector per workspace — from that workspace's own Settings — no need to touch anything else.
You can also install an open model to run on your own machine, which costs nothing per run — see Running a model on your own machine.
One other connector, Aider, exists as an early starting point, not a finished guarantee — see What "scaffolded" means for a connector before you lean on it for something that matters.