Gemini CLI

# Check Node.js version (requires 18+, recommend 20+)
node --version

# Install globally via NPM
npm install -g @google/gemini-cli

# Or use without installation
npx @google/gemini-cli

# Start Gemini and follow OAuth flow
gemini
# Will open browser for Google authentication

# Get key from https://aistudio.google.com/
export GEMINI_API_KEY="your-api-key-here"

# Or create ~/.gemini/.env file
echo 'GEMINI_API_KEY="your-api-key-here"' > ~/.gemini/.env

# Quick prompt (manual approval required)
gemini -p "Explain this code: $(cat main.py)"

# YOLO mode (auto-approve all actions - RECOMMENDED for automation)
gemini --yolo -p "Analyze and optimize this codebase"

# Interactive session
gemini -i "Let's analyze my project"

# Include specific directories with YOLO
gemini --include-directories ./src,./tests --yolo -p "Review and improve this codebase"

# Use specific model with auto-execution
gemini -m gemini-2.5-flash --yolo -p "Generate tests for all functions"

# Read-only analysis (safe)
gemini --yolo -p "Analyze code quality in @./src and generate report"

# Documentation generation (low risk)
gemini --yolo -p "Add JSDoc comments to all functions in ./src"

# Small, atomic operations (verifiable)
gemini --yolo -p "Fix ESLint errors in @./utils.js"

# Idempotent operations (safe to retry)
gemini --yolo -p "Format all JavaScript files with Prettier"

# Always create backups first
git stash push -m "pre-yolo-backup"
gemini --yolo -p "Refactor authentication module"

# Use checkpointing for rollback
gemini --checkpointing --yolo -p "Major code modernization"

# Combine with dry-run preview
gemini --dry-run -p "Database migration"  # Review first
gemini --yolo -p "Execute reviewed migration"  # Then automate

# ❌ RISKY: One giant YOLO task
gemini --yolo -p "Complete Express.js to Fastify migration"

# ✅ SAFE: Claude-guided sequential steps
gemini -p "Step 1: Analyze Express dependencies"  # Review
gemini --yolo -p "Step 2: Install Fastify packages"  # Safe
gemini -p "Step 3: Convert first route"  # Review
gemini --yolo -p "Step 4: Run tests"  # Safe
# Continue iteratively...

# 1. Claude THINKS: Analyze the goal
# "I need to refactor the auth module. First, understand the structure."

# 2. Claude directs Gemini to ACT:
gemini -p "List all functions and their signatures in @./src/auth.js" > auth_analysis.txt

# 3. Claude OBSERVES the results
cat auth_analysis.txt
# Claude reviews and decides next step

# 4. Claude directs specific, atomic action:
gemini --yolo -p "Add try-catch error handling to the 'login' function in @./src/auth.js"

# 5. Claude verifies:
gemini --yolo -p "Run tests in tests/auth.test.js and report results"

# 6. Claude iterates based on test results

# Get structured data Claude can parse
gemini --output-format json -p "List all Python files in ./src" > files.json

# Claude can now reliably process the JSON
cat files.json | jq '.files[]'

# Structured analysis
gemini --output-format json -p "Analyze security issues in @./src/auth.js" > security_report.json

# Claude parses specific fields
jq '.vulnerabilities[] | .severity' security_report.json

# Claude previews the plan first
gemini --dry-run -p "Refactor the authentication system"
# Output shows planned tool calls without executing

# After Claude reviews and approves:
gemini --yolo -p "Execute the reviewed refactoring plan"

#!/bin/bash
# Claude-orchestrated workflow

# BAD: Too complex, unpredictable
# gemini --yolo -p "Create a complete Express.js API with authentication"

# GOOD: Sequential, verifiable steps
echo "Step 1: Initialize project"
gemini --yolo -p "Initialize Node.js project and create server.js"

echo "Step 2: Install dependencies"
gemini --yolo -p "Install express, cors, and body-parser"

echo "Step 3: Basic server"
gemini --yolo -p "Create basic Express server in server.js with hello world route"

echo "Step 4: Add authentication (review this step)"
gemini -p "Add JWT authentication middleware to server.js"
# Claude reviews before proceeding

echo "Step 5: Verify"
gemini --yolo -p "Run tests and report results"

# Discover what tools Gemini has
gemini tools list

# Get detailed tool schema
gemini tools describe fileSystem
gemini tools describe shell
gemini tools describe google_web_search

# Claude can then construct precise tool calls

#!/bin/bash
set -e  # Exit on error

# Claude-managed error recovery
if ! gemini --yolo -p "Run test suite"; then
  echo "Tests failed. Analyzing..."
  gemini -p "Analyze test failures and suggest fixes" > fixes.txt
  cat fixes.txt
  # Claude decides whether to apply fixes
fi

# Let Claude select relevant context
gemini --include-directories ./src/auth,./tests/auth \
       -p "Focus only on authentication module"

# Use @ syntax for precise file references
gemini -p "Compare @./src/auth-old.js with @./src/auth-new.js"

# Web context
gemini -p "Compare my implementation @./src/api.js with @https://example.com/best-practices"

# Claude creates checkpoint before risky operations
gemini --checkpointing --yolo -p "Major refactoring of core module"

# If something goes wrong:
gemini checkpoint list
gemini checkpoint restore <checkpoint-id>

# Analyze entire project (auto-execute)
gemini --include-directories . \
       --exclude-directories node_modules,.git \
       --yolo -p "Analyze this codebase and suggest improvements"

# Code review with auto-fixes
gemini --yolo -p "Review and fix security issues: @./src/auth.js"

# Generate tests automatically
gemini --yolo -p "Generate comprehensive tests for: @./src/utils.js"

# Manual review (when unsure)
gemini -p "Explain the architecture of this complex module: @./src/core.js"

# Generate README (auto-create files)
gemini --include-directories . --yolo -p "Generate a comprehensive README.md for this project"

# API documentation (auto-generate)
gemini --yolo -p "Generate complete API documentation for: @./src/api/"

# Code comments (bulk operation)
gemini --yolo -p "Add detailed JSDoc comments to all functions in: @./src/"

# Manual review for complex docs
gemini -p "Explain the documentation strategy for: @./complex_algorithm.py"

# Analyze images (read-only, safe for YOLO)
gemini --yolo -p "Describe this architecture diagram: @./docs/architecture.png"

# Compare designs (analysis only)
gemini --yolo -p "Compare these UI designs and suggest improvements: @./design1.png @./design2.png"

# Extract and format text
gemini --yolo -p "Extract and format the text from: @./screenshot.png"

# Research with web search (auto-execute)
gemini --yolo -p "Research best practices for React performance optimization and create summary"

# Fetch and analyze (read-only)
gemini --yolo -p "Analyze this documentation: @https://docs.example.com/api"

# Compare implementations (analysis)
gemini --yolo -p "Compare my implementation with: @https://github.com/example/repo and suggest improvements"

# In interactive mode:
/help              # Show all commands
/tools             # List available tools
/mcp               # Show MCP servers
/compress          # Summarize conversation
/copy              # Copy last response
/clear             # Clear context
/checkpoint        # Save project state
/restore           # Restore checkpoint
/ide install       # Setup VS Code
/ide enable        # Connect to VS Code

# Auto-approve tool calls (careful!)
gemini --yolo -p "Create a Python script that processes all CSV files"

# Sandbox mode (safer)
gemini --sandbox -p "Set up a new React project"

# Manual approval (default)
gemini -p "Organize my project files"

# List MCP servers
gemini mcp list

# Add MCP server
gemini mcp add

# Remove MCP server
gemini mcp remove <name>

# Use with MCP tools
gemini -p "Use the database MCP server to query user data"

# Enable checkpointing
gemini --checkpointing -p "Refactor this entire module"

# List checkpoints
gemini checkpoint list

# Restore checkpoint
gemini checkpoint restore <id>

{
  "model": "gemini-2.5-pro",
  "defaultFlags": {
    "checkpointing": true,
    "includeDirectories": ["./src", "./tests"],
    "excludeDirectories": ["node_modules", ".git", "dist"]
  },
  "tools": {
    "shell": {
      "enabled": false,
      "requireConfirmation": true
    },
    "fileSystem": {
      "enabled": true,
      "allowedPaths": ["./"]
    },
    "web": {
      "enabled": true,
      "allowedDomains": ["github.com", "docs.google.com"]
    }
  }
}

# Authentication
export GEMINI_API_KEY="your-key"

# Vertex AI (Enterprise)
export GOOGLE_CLOUD_PROJECT="your-project"
export GOOGLE_CLOUD_LOCATION="us-central1"
export GOOGLE_APPLICATION_CREDENTIALS="/path/to/service-account.json"

# Model selection
export GEMINI_MODEL="gemini-2.5-pro"

# Default directories
export GEMINI_INCLUDE_DIRS="./src,./lib"
export GEMINI_EXCLUDE_DIRS="node_modules,.git"

# Use Claude for planning, Gemini for execution
echo "Claude, create a plan for refactoring auth module"
# ... get plan from Claude ...

gemini -p "Execute this refactoring plan: [paste plan]"

# Get different perspectives
echo "Analyze security of auth.js" | tee \
  >(claude-cli) \
  >(gemini -p -)

# Compare outputs
PROMPT="Generate unit tests for utils.js"
echo "Claude:" && claude-cli "$PROMPT"
echo "Gemini:" && gemini -p "$PROMPT"