OpenAI Codex CLI vs Claude Code vs Gemini CLI: AI Terminal Tools Compared

Terminal-based AI coding tools have become essential for developers who prefer the command line over IDEs. The three major players — OpenAI's Codex CLI, Anthropic's Claude Code, and Google's Gemini CLI — each take a different approach. Here's how they compare.

Overview#

Installation & Setup#

Codex CLI#

npm install -g @openai/codex

# Set API key
export OPENAI_API_KEY="sk-your-key"

# Or use Crazyrouter for lower costs
export OPENAI_API_KEY="your-crazyrouter-key"
export OPENAI_BASE_URL="https://api.crazyrouter.com/v1"

# Start
codex

Claude Code#

npm install -g @anthropic-ai/claude-code

# Set API key
export ANTHROPIC_API_KEY="sk-ant-your-key"

# Or use Crazyrouter
export ANTHROPIC_API_KEY="your-crazyrouter-key"
export ANTHROPIC_BASE_URL="https://api.crazyrouter.com"

# Start
claude

Gemini CLI#

npm install -g @google/gemini-cli

# Authenticate with Google
gemini auth login

# Start
gemini

Feature Comparison#

Code Generation Quality#

We tested all three tools on the same set of 20 coding tasks:

Winner: Claude Code — Claude's models consistently produce the most thoughtful, well-structured code. Codex CLI is close behind, especially for straightforward generation tasks.

Codebase Understanding#

Gemini CLI's 1M token context window is a significant advantage for large codebases. Claude Code compensates with better retrieval and summarization.

Safety & Sandboxing#

Codex CLI's Docker sandbox is the most robust. Claude Code's restricted shell is good but less isolated. Gemini CLI runs commands directly, which is faster but riskier.

Workflow Integration#

# Codex CLI — Git workflow
codex "Review the last 3 commits and suggest improvements"
codex "Create a PR description for the current branch"

# Claude Code — Project understanding
claude "Explain the authentication flow in this codebase"
claude "Find all places where we handle user permissions"

# Gemini CLI — Large codebase analysis
gemini "Analyze the entire src/ directory and create an architecture diagram"
gemini "Find potential security vulnerabilities across all files"

Real-World Usage Scenarios#

Scenario 1: Building a REST API#

# Codex CLI approach
codex "Create a REST API with Express.js for a todo app. 
Include CRUD endpoints, input validation, error handling, 
and PostgreSQL with Prisma ORM."

# Claude Code approach  
claude "Build a todo REST API. I want Express.js, Prisma with PostgreSQL,
proper error handling, input validation with Zod, and tests with Vitest."

# Gemini CLI approach
gemini "Generate a complete todo REST API using Express.js and Prisma.
Include all CRUD operations, validation, error handling, and unit tests."

Results:

• Codex CLI — Generated clean, working code. Good structure but minimal error handling until prompted.
• Claude Code — Most comprehensive output. Included middleware, error classes, and test files without being asked.
• Gemini CLI — Good code but occasionally verbose. Sometimes generates more files than needed.

Scenario 2: Debugging a Production Issue#

# Feed error logs
codex "Here's a stack trace from production. Find the root cause:
[paste stack trace]"

claude "Debug this production error. Check related files for the root cause:
[paste stack trace]"

gemini "Analyze this error and trace it through the codebase:
[paste stack trace]"

Results:

• Claude Code — Best at tracing through multiple files and identifying the root cause
• Codex CLI — Good at suggesting fixes but sometimes misses the deeper cause
• Gemini CLI — Can analyze more context (1M window) but sometimes gets lost in details

Scenario 3: Refactoring Legacy Code#

claude "Refactor the user service from callbacks to async/await. 
Maintain backward compatibility. Update tests."

Claude Code excels here — it understands the intent, makes changes across files, and updates tests. Codex CLI is comparable. Gemini CLI sometimes makes unnecessary changes.

Pricing#

Cost Per Session (Estimated)#

Cost Optimization with Crazyrouter#

Both Codex CLI and Claude Code support custom API endpoints. Route through Crazyrouter for significant savings:

# Codex CLI with Crazyrouter (30% savings)
export OPENAI_API_KEY="your-crazyrouter-key"
export OPENAI_BASE_URL="https://api.crazyrouter.com/v1"

# Claude Code with Crazyrouter (30% savings)
export ANTHROPIC_API_KEY="your-crazyrouter-key"  
export ANTHROPIC_BASE_URL="https://api.crazyrouter.com"

Which One Should You Choose?#

Quick Decision Guide#

The Pragmatic Approach#

Many developers use multiple tools:

• Gemini CLI for quick questions and large codebase analysis (free)
• Claude Code for complex refactoring and debugging (best quality)
• Codex CLI for code generation with sandbox safety

FAQ#

Can I use my own API key with these tools?#

Yes for Codex CLI and Claude Code. Gemini CLI uses Google authentication. For Codex and Claude Code, you can use Crazyrouter as a drop-in replacement for lower costs.

Which tool is best for beginners?#

Gemini CLI — it's free, easy to set up (just Google login), and the 1M context window is forgiving of imprecise prompts.

Do these tools work with any programming language?#

Yes. All three support major languages. Claude Code and Codex CLI perform best with Python, JavaScript/TypeScript, and Go. Gemini CLI has strong Java and Kotlin support.

Can I use these tools in CI/CD pipelines?#

Codex CLI is best suited for CI/CD with its Docker sandbox and non-interactive mode. Claude Code has a --print flag for scripting. Gemini CLI is primarily interactive.

How do they handle sensitive code?#

All three send code to their respective cloud APIs. For sensitive codebases, consider using local models via Ollama with tools like Aider, or ensure your organization's data policies allow cloud API usage.

Summary#

Claude Code leads in code quality and debugging. Codex CLI offers the best sandboxing and safety. Gemini CLI wins on price (free) and context window (1M tokens). The best approach is to use the right tool for each task.

For Codex CLI and Claude Code users, routing API calls through Crazyrouter saves 30% on costs with zero configuration changes — just set the base URL environment variable.