Introduction
In 2025, developers are witnessing a major shift in how AI tools integrate with daily workflows. Rather than relying solely on cloud-based assistants or IDE integrations, AI agents are now making their way into the command line itself. This new breed of terminal-native tools promises a more seamless, autonomous, and context-aware experience.
This post explores and compares three leading contenders in this space: OpenAI's Codex CLI, Anthropic's Claude CLI (Claude Code), and Google's Gemini CLI. We're not comparing AI models or benchmarks. Instead, we'll focus on how each tool performs in terms of agentic functionality, real-world task execution, and developer experience across a broad spectrum of use cases, from writing and refactoring code to running tests, managing repositories, and automating day-to-day tasks.
These CLI agents are redefining what it means to collaborate with an AI. No longer confined to static Q&A or isolated code snippets, these tools understand context, adapt to ongoing workflows, and integrate with the systems developers use every day. Whether you're fixing bugs in a legacy codebase, creating deployment scripts, writing technical documentation, or even automating repetitive git operations, these agents promise to reduce cognitive load and unlock new levels of productivity.
Overview of the Contenders
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Codex CLI: A lightweight terminal assistant by OpenAI that offers patch-based file editing, shell command assistance, and diff-based suggestions. It supports multi-file operations and includes a native Rust variant for high performance and sandbox security. Its safety-first design makes it a reliable partner for high-integrity editing workflows.
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Claude CLI: Anthropic's terminal interface for Claude 3.7, designed with agentic autonomy in mind. It offers rich developer interactions including hooks, full repo navigation, file management, git integration, and customizable behavior through markdown configuration. It's built to act with context and foresight.
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Gemini CLI: Google's open-source terminal AI assistant powered by Gemini 2.5 Pro. It delivers intelligent code support, task automation, and conversational context management. Gemini CLI is equally adept at assisting with debugging, document generation, research, and writing—not just DevOps and scripting. It thrives in any situation where fluid, context-rich interaction is essential.
Installation & Setup
| Tool | Install Command | Sign-In | Native Support |
|---|---|---|---|
| Codex CLI | npm install -g @openai/codex |
ChatGPT login | Optional Rust build |
| Claude CLI | npm install -g @anthropic-ai/claude-code |
Anthropic login | Fully open-source |
| Gemini CLI | npm install -g @google/gemini-cli |
Google OAuth | Cross-platform |
All three tools are simple to install and get started with. Codex CLI and Gemini CLI offer npx alternatives for quick execution without permanent installation. Claude CLI shines for developers who value openness and long-term configurability.
Gemini CLI also benefits from Google’s robust authentication and infrastructure, allowing users to plug into their existing developer ecosystem with minimal setup. It’s ideal for developers who want to integrate a conversational assistant without sacrificing speed or versatility.
Core Functional Capabilities
File and Code Interaction
| Feature | Codex CLI | Claude CLI | Gemini CLI |
|---|---|---|---|
| File Editing | ✅ | ✅ | ✅ |
| Multi-file Awareness | ✅ | ✅ | ✅ |
| Diff-based Changes | ✅ | ✅ | ✅ |
| Code Navigation | ✅ | ✅ | ✅ |
Codex CLI supports precise patch editing with multi-file awareness, providing developers with full visibility over proposed changes before anything is committed. Claude CLI further enhances this by understanding the full structure of the codebase and offering agentic, project-wide refactoring. Gemini CLI handles code navigation well and performs flexible edits across files, although it can sometimes require explicit prompting to maintain consistency.
Shell Command Execution
| Feature | Codex CLI | Claude CLI | Gemini CLI |
|---|---|---|---|
| Test & Script Execution | ⚠ | ✅ | ✅ |
| Reasoned Tool Usage | Partial | ✅ | ✅ |
| Output Parsing | Basic | Advanced | Moderate |
Claude CLI is capable of initiating tests, analyzing failures, making informed edits, and retrying—all autonomously. Gemini CLI also supports iterative execution and feedback loops, making it effective for diagnostics and adjustments during development. Codex CLI remains cautious, providing patches and feedback that require manual verification before proceeding.
Agentic Behavior & Autonomy
| Capability | Codex CLI | Claude CLI | Gemini CLI |
|---|---|---|---|
| Self-Directed Planning | ❌ | ✅ | ✅ |
| Multi-Step Reasoning | ✅ | ✅ | ✅ |
| Custom Hooks | ❌ | ✅ | ✅ |
| Local Context Files | ✅ | ✅ | ✅ |
Claude CLI stands out for its robust support for autonomy. Developers can define behaviors in a CLAUDE.md file, guiding the assistant through organization-specific standards or workflows. Gemini CLI offers agent-like behavior as well, parsing long prompts and chaining tasks where needed. Codex CLI emphasizes safety and clarity—prioritizing user approval at each step.
Tooling Ecosystem & Extensibility
| Feature | Codex CLI | Claude CLI | Gemini CLI |
|---|---|---|---|
| Plugin Support | ❌ | ✅ | ❌ |
| Workflow Hooks | ❌ | ✅ | ✅ |
| CLI Script Integration | ⚠ | ✅ | ✅ |
| Custom Context Files | Basic | Advanced | Intermediate |
Claude CLI allows for dynamic, event-based behaviors with custom hooks and markdown configurations—enabling deeply integrated project-specific tooling. Gemini CLI supports command chaining and scripting, which is particularly helpful for automating tasks or embedding AI into continuous integration pipelines. Codex CLI, while more limited, offers reliable core functionality within a well-guarded sandbox.
Real-World Use Cases
Debugging Test Failures: Claude CLI can autonomously identify failing tests, trace the problem, make corrections, and re-run tests to verify resolution. Gemini CLI also performs well here, especially when guided with thoughtful prompts. Codex CLI can provide clean diffs and accurate suggestions, though it expects the user to drive the process.
Cross-file Refactoring: Codex CLI is efficient at making coherent changes across multiple files. Claude excels at this, as it actively tracks logical relationships in the code. Gemini offers breadth in refactoring but sometimes lacks granularity unless carefully directed.
Knowledge Retrieval & Contextual Assistance: Gemini CLI's access to grounded search allows it to retrieve external documentation or examples, which can be a significant productivity booster. Claude can simulate this through local context and workflows. Codex, by design, avoids reaching outside the local environment.
Hungry for Tokens: A cautionary note is on how each tool consumes its AI services. Codex CLI uses the OpenAI API, so even if you have the high-end ChatGPT subscription, the tool will not use that subscription. You pay token for token. Gemini CLI is similar as it uses Google's Vertex API service. Claude CLI is different, it appears to use your existing subscription for the service, but it is very easy to exhaust your quota of tokens. The tool informs you well in advance, and you do not need to worry about invoice shock. OpenAI will gladly take your money as I found out by heavy use of their o3-pro model. Likewise for Google's gemini-2.5-pro.
UX, Ergonomics, and Developer Experience
| Metric | Codex CLI | Claude CLI | Gemini CLI |
|---|---|---|---|
| Responsiveness | ✅ | ✅ | ⚠ |
| Configuration Flexibility | Low | High | Medium |
| Debuggability | Medium | High | High |
| Security & Permissions | High | Configurable | Moderate |
Claude provides a smooth, highly responsive environment with detailed output, traceable actions, and custom configurability. Gemini delivers a friendly experience with flexible prompting and task integration, but may slow down when resolving complex tool calls. Codex CLI’s interface is streamlined and reliable, with low friction and high predictability.
Final Comparison Table
| Feature Area | Best CLI |
|---|---|
| Agent Autonomy | Claude |
| Security & Sandboxing | Codex |
| CI/CD Scripting | Gemini |
| Context Handling | Claude |
| Simplicity | Codex |
| Customization | Claude |
Conclusion
The terminal is no longer a place of isolation—it's becoming an intelligent workspace. AI-powered CLI agents are making development more efficient, contextual, and even collaborative. Whether you're looking for a hyper-autonomous tool that can drive entire workflows, a safe assistant that helps you edit and debug with confidence, or a conversational partner that adapts to a range of creative and technical tasks, there's a strong contender ready for you.
- Claude CLI is for developers who want autonomy, flexibility, and rich context awareness.
- Codex CLI suits those who value precision, sandboxing, and simplicity.
- Gemini CLI provides a versatile middle ground with great support for everything from writing code to reasoning through prose.
No matter your choice, these tools are not just conveniences—they’re becoming essential members of the development team.