Gemini CLI

Gemini CLI is Google's open-source AI agent that brings the power of Gemini directly into the terminal. Built in TypeScript under the Apache 2.0 license, it leverages Google's Gemini models with a massive 1M-token context window to help developers write, debug, and understand code from the command line. With over 98,000 GitHub stars, it is one of the most popular CLI coding agents in the ecosystem.¹⁾²⁾³⁾

GitHub: google-gemini/gemini-cli | Website: https://geminicli.com⁴⁾

Key Features

1M-Token Context Window — Processes entire codebases in a single session, enabling deep understanding of large projects
Plan Mode — Analyzes codebases and creates action plans before making changes, separating analysis from execution
MCP Integration — Supports Model Context Protocol for both client and server roles, extending capabilities through external tools
Multi-Tool Support — File editing, shell command execution, web search, and code analysis built in
GitHub Actions Integration — Automates issue triage, PR reviews, test generation, and commit workflows
Free Tier Access — Generous free usage through Google AI Studio authentication
Sandbox Execution — Runs commands in isolated environments for safety

Architecture

Gemini CLI is structured as a monorepo with multiple packages:

Core Engine — TypeScript-based agent loop handling conversation, tool dispatch, and streaming
Tool System — Modular tool architecture with file operations, shell execution, search, and MCP bridges
Configuration — Supports GEMINI.md instruction files (similar to Claude's CLAUDE.md) for project-level customization
Authentication — Google AI Studio OAuth, Vertex AI, and API key support

Usage Example

# Install globally via npm
npm install -g @anthropic-ai/gemini-cli
 
# Start interactive session in a project
cd my-project
gemini
 
# Use with a direct prompt
gemini "explain the authentication flow in this codebase"
 
# Use Plan Mode for complex changes
gemini "refactor the database layer to use connection pooling" --plan

How It Works

graph TD A[User Prompt] --> B[Gemini CLI Agent Loop] B --> C{Plan Mode?} C -->|Yes| D[Analysis Phase - Read Only] D --> E[Generate Action Plan] E --> F[User Approval] F --> G[Execution Phase] C -->|No| G G --> H[Tool Selection] H --> I[File Edit Tool] H --> J[Shell Execution Tool] H --> K[Search Tool] H --> L[MCP Tool Bridge] I --> M[Apply Changes] J --> M K --> M L --> M M --> N[Stream Response to Terminal] N --> B

Comparison

Feature	Gemini CLI	Claude Code
Context Window	1M tokens	200K tokens
Language	TypeScript	TypeScript
License	Apache 2.0	Proprietary
Model Lock-in	Gemini only	Claude only
MCP Support	Yes	Yes
Plan Mode	Yes	Yes
GitHub Stars	~99K	N/A