g

README

A lightweight Gemini CLI and TUI written in Go
A love letter to Google's Gemini CLI

Why g? • Installation • Quick Start • MCP • Benchmarks

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⚡ Why g?

The official Gemini CLI is an amazing tool with excellent MCP support and seamless Google authentication. However, for scripting and automation, its Node.js runtime adds startup overhead.

g reimplements the core functionality in Go, achieving 37x faster startup while maintaining full compatibility with the official CLI's authentication.

$ time g "hi" > /dev/null
0.02s user 0.01s system

$ time gemini -p "hi" > /dev/null
0.94s user 0.20s system

📦 Installation

⚠️ Prerequisites (Required)

g does not have its own authentication. You must authenticate once using the official Gemini CLI first:

npm install -g @google/gemini-cli
gemini  # Choose "Login with Google"

g reuses these credentials automatically from ~/.gemini/. Your free tier quota or Workspace Code Assist quota applies.

Homebrew

brew install k-sub1995/tap/g

Go

go install github.com/k-sub1995/g@latest

Binary

Download from Releases

🚀 Quick Start

CLI Mode

Pass a prompt directly:

g "What is the capital of Japan?"

TUI Mode

Launch interactive TUI (Text User Interface):

g

The TUI provides:

• Interactive prompt editing with arrow key navigation
• Real-time streaming responses
• Command history

📋 Usage

g [prompt] [flags]
g mcp <command>
g version

Flags:
  -p, --prompt string          Prompt (alternative to positional arg)
  -m, --model string           Model (default "gemini-2.5-flash")
  -f, --file strings           Files to include
  -o, --output-format string   text, json, stream-json (default "text")
  -t, --timeout duration       Timeout (default 5m)
      --debug                  Debug output
  -v, --version                Version

MCP Commands:
  g mcp list                 List MCP servers and tools
  g mcp call <server> <tool> Call an MCP tool

Version Command:
  g version                  Print the version number of g

🔌 MCP Support

g supports Model Context Protocol servers.

Configure in ~/.gemini/settings.json:

{
  "mcpServers": {
    "my-server": {
      "command": "/path/to/mcp-server"
    }
  }
}

# List available tools
g mcp list

# Call a tool
g mcp call my-server tool-name arg=value

📊 Benchmarks

Metric	g	Official CLI	Improvement
Startup	23ms	847ms	37x
Binary	5.6MB	~200MB	35x
Runtime	None	Node.js	-

🏗️ Build

git clone https://github.com/k-sub1995/g.git
cd g
make build          # Current platform
make cross-compile  # All platforms

🚫 What's NOT Included

• OAuth flow → authenticate with official CLI first
• API Key / Vertex AI auth

📄 License

Apache License 2.0 — See LICENSE

This project is a derivative work based on Gemini CLI by Google LLC.

🙏 Acknowledgments

• Google Gemini CLI — The incredible original
• Google Gemini API — The underlying API