GitHub Copilot CLI Adds a First-Run Sandbox Opt-In and gemini-3.6-flash Support

Releasebot·medium signal

GitHub's 2026-07-23 update gives Copilot CLI a first-run splash for opting into the default sandbox, adds gemini-3.6-flash as a model option, and improves session handling, shell behavior, planning, and MCP setup, alongside fixes for upload retries, environment-variable preservation and oversized image handling. Separately, enterprise admins and org owners get a new Copilot metrics impact dashboard covering adoption depth, usage cohorts and trends. Sandbox-by-default with an explicit first-run prompt is now the norm across CLI agents rather than an advanced setting.