Codex CLI vs Gemini CLI: OpenAI vs Google Terminal Coding Agents
A comprehensive comparison between OpenAI's Codex CLI and Google's Gemini CLI. Discover how these two tech giants' terminal-based AI coding agents stack up in performance, pricing, and features.
Codex CLI vs Gemini CLI: OpenAI vs Google Terminal Coding Agents
Two tech giants bring their AI to the terminal: Codex CLI from OpenAI, featuring GPT-5-Codex optimization and cloud task execution, versus Gemini CLI from Google, offering a generous free tier with 1M token context and 78% SWE-bench score. This comprehensive comparison helps you choose between these first-party tools from the leading AI labs.
Overview
Codex CLI
Codex CLI is OpenAI's open-source coding agent that runs locally from your terminal. Built in Rust for speed and efficiency, it features GPT-5-Codex optimization, cloud task integration, and is included with ChatGPT subscriptions.
Key Highlights:
- Open source (built in Rust)
- GPT-5-Codex optimized for software engineering
- Full-screen terminal UI with real-time collaboration
- Cloud integration for remote task execution
- Agent Skills system with SKILL.md files
- Built-in code review before commits
- Included with ChatGPT Plus/Pro/Business/Enterprise
Gemini CLI
Gemini CLI is Google's open-source AI agent that brings Gemini directly into your terminal. With over 1 million developers using it since launch, it offers a generous free tier, multimodal capabilities, and 78% SWE-bench Verified score with Gemini 3 Flash.
Key Highlights:
- Open source (Apache 2.0 License)
- Gemini 3 Flash with 78% SWE-bench Verified score
- Free tier: 60 requests/min, 1,000 requests/day
- 1M token context window
- Multimodal (images, PDFs, sketches)
- Extensions ecosystem with playbooks
- 1+ million developers
Benchmark Performance
Both tools showcase impressive model capabilities:
| Agent/Model | Benchmark | Score |
|---|---|---|
| Gemini 3 Flash | SWE-bench Verified | 78% |
| Gemini 3 Pro | SWE-bench Verified | ~75% |
| Codex CLI (GPT-5) | Terminal-Bench | 42.8% |
Note: SWE-bench measures automated bug fixing while Terminal-Bench tests end-to-end terminal tasks. Gemini 3 Flash's 78% SWE-bench score is exceptionally strong for code-related tasks.
Technical Architecture
| Aspect | Codex CLI | Gemini CLI |
|---|---|---|
| Developer | OpenAI | |
| Language | Rust | TypeScript |
| License | Open Source | Apache 2.0 |
| Runtime | Native binary | Node.js |
| Platform | macOS, Linux, Windows | macOS, Linux, Windows |
| Source Code | Available (GitHub) | Available (GitHub) |
| Cloud Integration | Yes (OpenAI cloud) | Yes (Google Cloud) |
Analysis: Both are open source but use different languages. Codex CLI's Rust provides native binary performance. Gemini CLI's TypeScript integrates well with the Node.js ecosystem.
AI Model Support
| Feature | Codex CLI | Gemini CLI |
|---|---|---|
| Primary Model | GPT-5-Codex | Gemini 3 Pro/Flash |
| Free Tier Model | None | Gemini 2.5 Pro |
| Context Window | ~128K tokens | 1M tokens |
| Reasoning Modes | Adjustable levels | Via model selection |
| Multimodal | Screenshots | Images, PDFs, sketches |
| Model Optimization | GPT-5-Codex specific | Gemini-native |
Analysis: Gemini CLI's 1M token context is approximately 8x larger than Codex CLI's, enabling work with massive codebases. Gemini CLI also offers broader multimodal support including PDFs and hand-drawn sketches.
Pricing and Access
Codex CLI
| Plan | Details |
|---|---|
| ChatGPT Plus | $20/month, includes Codex |
| ChatGPT Pro | Higher limits |
| ChatGPT Business | Team features |
| ChatGPT Enterprise | Custom plans |
Gemini CLI
| Tier | Details |
|---|---|
| Free | 60 requests/min, 1,000 requests/day |
| Gemini Code Assist Standard | Higher limits |
| Gemini Code Assist Enterprise | Full features |
| Google Cloud API | Pay-per-token |
Analysis: Gemini CLI's free tier is a significant advantage—1,000 requests per day with Gemini 2.5 Pro's 1M context window for $0. Codex CLI requires a ChatGPT subscription starting at $20/month.
Installation Methods
Codex CLI
# npm
npm install -g @openai/codex
# Homebrew
brew install openai/codex/codex
# Binary download from GitHub
Gemini CLI
# npm
npm install -g @google/gemini-cli
# Google Cloud SDK
gcloud components install gemini-cli
# Build from source
git clone https://github.com/google-gemini/gemini-cli
cd gemini-cli && npm install && npm run build
Analysis: Both support npm. Gemini CLI integrates with Google Cloud SDK. Codex CLI offers Homebrew and direct binary downloads.
Context Window Comparison
| Feature | Codex CLI | Gemini CLI |
|---|---|---|
| Max Context | ~128K tokens | 1,000,000 tokens |
| Relative Size | 1x | ~8x larger |
| Large Codebase | Selective context | Full project in context |
| File Handling | Prioritized selection | Many files directly |
| Long Sessions | Context management | Extended without trimming |
Analysis: Gemini CLI's 1M token context is transformative for large projects. You can load entire codebases into context without selective pruning. Codex CLI requires more careful context management.
Multimodal Capabilities
Codex CLI
Supported Inputs:
- Text prompts
- Screenshots
- Code snippets
Gemini CLI
Supported Inputs:
- Text prompts
- Images (screenshots, diagrams)
- PDFs (documentation, specs)
- Hand-drawn sketches
- Code snippets
Use Cases:
- Generate code from UI mockups
- Analyze architecture diagrams
- Extract requirements from PDF specs
- Convert whiteboard drawings to code
Analysis: Gemini CLI's multimodal capabilities are significantly broader. PDF analysis and sketch interpretation enable unique workflows impossible with Codex CLI.
Terminal User Interface
| Feature | Codex CLI | Gemini CLI |
|---|---|---|
| Framework | Custom (Rust) | Custom (TypeScript) |
| UI Style | Full-screen collaborative | Standard TUI |
| Plan Preview | Shows plan before changes | ReAct reasoning |
| Screenshot Input | Yes | Yes (plus PDFs, sketches) |
| Built-in Search | Web search (opt-in) | Google Search grounding |
Analysis: Codex CLI emphasizes full-screen real-time collaboration. Gemini CLI's ReAct (reason and act) loop provides transparent reasoning steps.
Skills and Extensions
Codex CLI Agent Skills
SKILL.md System:
name: api-generator
description: Generates REST API endpoints
tools:
- shell
- file_write
- web_search
- Markdown skill definitions
- Asset bundling
- Shared CLI and IDE
Gemini CLI Extensions
Extension System:
- Pre-packaged integrations
- Built-in playbooks (teach AI how to use tools)
- Third-party ecosystem
- Databases, design tools, payment APIs
Analysis: Different approaches to extensibility. Codex CLI uses self-contained SKILL.md files. Gemini CLI's Extensions come with playbooks that guide the AI in using external tools effectively.
Cloud Integration
Codex CLI Cloud
# Submit task to cloud
codex cloud exec "Refactor authentication"
# Apply cloud diff locally
codex cloud apply
# Interactive cloud picker
codex cloud
- Remote task execution on OpenAI infrastructure
- Diff synchronization
- Heavy workload offloading
Gemini CLI Cloud
- Google Cloud integration
- Vertex AI connection
- Enterprise deployment options
- Google Workspace integration
Analysis: Codex CLI's cloud focuses on compute offloading. Gemini CLI's cloud integration is broader, connecting with Google's enterprise ecosystem.
CI/CD Integration
Codex CLI
# Non-interactive execution
codex exec "Fix failing tests"
# Short form
codex e "Run linting"
execmode for pipelines- Structured output
- Single-task automation
Gemini CLI
# Native GitHub Action
- uses: google/gemini-cli-action@v1
with:
task: review-pr
Features:
- Native GitHub Actions support
- PR review automation
- Issue summarization
- Commit message drafting
- Git diff analysis
Analysis: Gemini CLI has deeper GitHub Actions integration out of the box. Codex CLI provides flexible exec mode for general CI/CD pipelines.
Code Review
Codex CLI
Built-in code review:
codex review
- Dedicated review command
- Pre-commit integration
- Separate agent reviews code
Gemini CLI
- Review via GitHub Actions
- PR analysis integration
- Git diff analysis
- No dedicated terminal command
Analysis: Codex CLI has first-class terminal code review. Gemini CLI focuses on CI-integrated review via GitHub Actions.
MCP (Model Context Protocol) Support
| Feature | Codex CLI | Gemini CLI |
|---|---|---|
| MCP Support | Yes | Yes |
| Transport | Stdio, HTTP | Stdio, HTTP |
| Configuration | ~/.codex/config.toml | Config files |
| Run as Server | Yes | Not documented |
| Management | codex mcp commands | CLI commands |
Analysis: Both support MCP for extensibility. Codex CLI can uniquely run as an MCP server, allowing other agents to consume its capabilities.
IDE Integration
| IDE | Codex CLI | Gemini CLI |
|---|---|---|
| VS Code | Extension | Gemini Code Assist |
| JetBrains | Extension | Gemini Code Assist |
| Skills/Extensions | Shared with CLI | Shared with CLI |
| Web Interface | Via ChatGPT | Via Google Cloud |
Analysis: Both have comprehensive IDE integration. Codex CLI shares skills between CLI and IDE. Gemini CLI integrates with Google's Gemini Code Assist.
Enterprise Features
| Feature | Codex CLI | Gemini CLI |
|---|---|---|
| Enterprise Plan | ChatGPT Enterprise | Gemini Code Assist Enterprise |
| SSO/SAML | Via OpenAI | Via Google Cloud |
| Data Residency | OpenAI options | Google Cloud regions |
| Admin Controls | Enterprise dashboard | Google Workspace |
| Compliance | SOC 2, etc. | Google Cloud compliance |
Analysis: Both offer enterprise features through their parent company's infrastructure. Choice may depend on existing cloud relationships.
Unique Features
Codex CLI Exclusive
- Rust Performance - Native binary speed
- GPT-5-Codex - Model optimized for coding
- Cloud Tasks - Remote execution, diff sync
- SKILL.md - Asset-bundled skill definitions
- Built-in Code Review - Dedicated
codex review - Run as MCP Server - Other agents can consume it
- Full-screen TUI - Real-time collaboration UI
- Plan Preview - See plan before execution
Gemini CLI Exclusive
- Free Tier - 1,000 requests/day for $0
- 1M Token Context - 8x larger than Codex CLI
- 78% SWE-bench - Top-tier benchmark score
- PDF Analysis - Process documents directly
- Sketch Input - Hand-drawn diagrams to code
- Extensions + Playbooks - Guided integrations
- GitHub Actions - Native CI/CD integration
- Google Search - Built-in search grounding
- Apache 2.0 - Permissive open source license
Use Case Recommendations
Choose Codex CLI If You:
- Are already a ChatGPT subscriber
- Want GPT-5-Codex optimization
- Need cloud task offloading
- Want built-in terminal code review
- Need to run the agent as an MCP server
- Prefer full-screen collaborative UI
- Value Rust's native performance
- Want plan preview before execution
Choose Gemini CLI If You:
- Want to start free (1,000 requests/day)
- Work with large codebases (1M token context)
- Need PDF document analysis
- Want to convert sketches to code
- Need native GitHub Actions integration
- Use Google Cloud/Workspace
- Prefer Apache 2.0 licensing
- Want Extensions with playbooks
Head-to-Head Comparison
| Category | Winner | Reason |
|---|---|---|
| Free Tier | Gemini CLI | 1,000 requests/day free |
| Context Window | Gemini CLI | 1M vs ~128K tokens |
| Benchmark | Gemini CLI | 78% SWE-bench |
| Native Performance | Codex CLI | Rust binary |
| Multimodal | Gemini CLI | PDFs, sketches |
| Cloud Compute | Codex CLI | Task offloading |
| Code Review | Codex CLI | Built-in command |
| CI/CD | Gemini CLI | Native GitHub Actions |
| Skills/Extensions | Gemini CLI | Playbook-based |
| MCP Flexibility | Codex CLI | Can run as server |
| Cost Value | Gemini CLI | Generous free tier |
| Open Source | Tie | Both open source |
Migration Considerations
From Codex CLI to Gemini CLI
- Can start immediately (free tier)
- Skills need conversion to Extensions
- Note: Cloud tasks not available
- Note: Built-in review unavailable
- Benefit: 8x larger context
- Benefit: PDF/sketch support
- Benefit: Free daily usage
From Gemini CLI to Codex CLI
- Requires ChatGPT subscription
- Context reduction (1M → ~128K)
- Extensions need SKILL.md conversion
- Note: PDF analysis unavailable
- Benefit: Cloud task offloading
- Benefit: Built-in code review
- Benefit: Rust performance
Conclusion
Codex CLI and Gemini CLI represent terminal coding agents from the two most prominent AI labs:
Codex CLI excels in OpenAI ecosystem integration and developer workflow features. GPT-5-Codex optimization, cloud task offloading, and built-in code review make it powerful for developers committed to the OpenAI platform. The Rust implementation provides native performance, and the ability to run as an MCP server enables unique integration scenarios.
Gemini CLI excels in accessibility and scale. Its free tier (1,000 requests/day), 1M token context window, and 78% SWE-bench score make it ideal for developers who want powerful AI without upfront costs or for those working with large codebases. The broader multimodal support (PDFs, sketches) and native GitHub Actions integration add significant workflow value.
For budget-conscious developers or large codebase work: Gemini CLI's free tier and 1M context are hard to beat.
For OpenAI ecosystem users needing cloud offloading and code review: Codex CLI delivers integrated value.
Both represent excellent choices from industry leaders, each optimized around their respective platforms' strengths.
Looking for more flexibility? Discover NovaKit CLI - combining semantic code search, full LSP integration, and support for multiple AI providers in one powerful tool.