Gemini CLI is an open‑source terminal client that provides direct access to Gemini models via npm; users can install it globally with `npm install -g @google/gemini-cli` inside a Conda environment that includes Node.js, or via `npx` without permanent installation. Preview builds are published each Tuesday at 23:59 UTC and are unvetted, while stable releases follow at 20:00 UTC on the same day, and nightly builds appear daily at 00:00 UTC representing the latest main‑branch code. Authentication is configured through environment variables such as `GOOGLE_CLOUD_PROJECT`, `GEMINI_API_KEY`, and optionally `GOOGLE_API_KEY` with `GOOGLE_GENAI_USE_VERTEXAI=true` for VertexAI integration, enabling paid‑tier or enterprise billing. The CLI supports model selection (e.g., `gemini -m gemini-2.5-flash`) and output modes including JSON (`--output-format json`) and streamed newline‑delimited JSON (`--output-format stream-json`) for real‑time monitoring. It also offers multimodal input from PDFs, images, or sketches, codebase editing, debugging, automated PR queries, and extensibility through MCP servers defined in `~/.gemini/settings.json`, as demonstrated by commands like `@github` or `@slack`. Additional capabilities include headless scripting, VS Code integration, sandboxing, trusted folder policies, telemetry, and a rich command reference, and the system notes that Gemini CLI is not optimized for the latest Gemini models, recommending Antigravity for optimal performance.