Rubber Duck is a new experimental mode in GitHub Copilot CLI that uses a second model from a different AI family to review plans, implementations, and tests before the agent moves forward. It is designed to catch architectural mistakes, edge cases, and cross-file issues earlier.

Copilot CLI is GitHub’s terminal-based coding agent. It accepts instructions, edits files, runs commands, and connects to MCP servers. Defaults to Claude Sonnet 4 but can switch to other models. Usage is billed via Copilot plans.

Start and track GitHub Copilot coding agent tasks from Raycast 🤖

GitHub Copilot has a new feature: a coding agent that can implement a task or issue, run in the background with GitHub Actions, and more.