Table of contents
- Model capabilities and strengths
- Side‑by‑side comparison
- Key takeaways
- Complementing with AI code reviews: why and how
- Best practices and tips
- Frequently asked questions
This guide provides a comprehensive comparison of Claude Code (Anthropic's latest models including Sonnet 4 and Opus 4) and ChatGPT (o‑series models and Codex agent), examining their strengths, trade‑offs, and practical applications through real coding examples. We'll also explore why incorporating AI code‑reviewers like Graphite Graphite Agent significantly improves code quality and reduces manual review work, helping you make informed decisions about which tools best fit your development workflow.
Model capabilities and strengths
Anthropic’s Claude Code
- Agentic command-line interface: Claude Code is an agentic tool launched alongside Claude 4 (Opus 4 and Sonnet 4) on May 22, 2025—designed for terminal-first workflows. Developers can issue natural-language commands like
claude-code refactor --task "…", interact with streaming outputs (diffs, test results), and integrate directly with Git workflows—all without leaving the terminal interface. - Local-first execution: It operates locally, granting access to your project files while avoiding cloud uploads—beneficial for privacy-sensitive workflows.
- Reasoning and sustained performance: Backed by Claude Opus 4 (notably powerful in long-running, deeply reasoned tasks) and Sonnet 4 (leaner but still strong), the tool benefits from hybrid reasoning, extended thinking, and memory features that help maintain coherence over sustained sessions.
- Security-sensitive tasks: In a recent evaluation of vulnerability detection on real-world codebases, Claude Code (Sonnet 4) found significantly more true positives across several categories compared to Codex—especially in detecting IDOR bugs, though both had high false positive rates.
OpenAI’s Codex
- Agentic tooling in cloud and local modes: OpenAI Codex, historically derived from GPT-3 fine-tuned on code, powers tools like GitHub Copilot. In 2025, OpenAI released Codex CLI (in April) and a cloud-based agentic preview using
o3(in May), offering both local and cloud-based execution modes for code tasks. - Cloud sandboxed workflows: Codex agents run in isolated cloud containers with secure environments. They can pull repositories, run tests, and edit code via the ChatGPT interface. These workflows integrate well with broader developer tooling but involve cloud-based processing.
- Legacy code-focused model: The original Codex model (circa 2021) was a fine-tuned version of GPT-3 trained on public repositories and optimized for code generation. While powerful, it has known limitations in multi-step reasoning and occasional code inaccuracies.
Side‑by‑side comparison
| Model / tool | Execution environment | Reasoning & coherence | Developer workflow | Privacy / security consideration |
|---|---|---|---|---|
| Claude Code | Local terminal agent | Strong reasoning, long-term coherence, hybrid thinking | CLI-native workflows, Git integration | Local-first, avoids cloud uploads |
| OpenAI Codex agent | Cloud sandbox (or local CLI) | Rooted in GPT-3/o‑series; less advanced for multi-step tasks | Integrated with ChatGPT tools and CLI | Container-based isolation, cloud dependent |
Key takeaways
- Claude Code excels for developers who want terminal-driven interaction, strong long-form reasoning, local execution, and private workflows—backed by the powerful Claude 4 models.
- OpenAI Codex agent offers deep integration into the ChatGPT ecosystem and cloud-based development sandboxes—better for users already embedded in those workflows, though reasoning capabilities and coherence on complex tasks may lag behind.
Complementing with AI code reviews: why and how
Why you should review generated code
- Both models can hallucinate, produce insecure patterns, or omit edge cases—even when code looks valid.
Graphite Graphite Agent: an AI reviewer
- Graphite Agent (by Graphite) is a codebase-aware AI code review tool that integrates directly into GitHub to offer instant code review feedback—including logic issues, style, security, and edge cases—with low noise.
- Supports custom rules and lets teams enforce best practices, with one-click fixes and integration into workflows.
- Graphite emphasizes that AI reviews are supplements—not replacements—for human oversight.
Best practices and tips
- Prompt clearly: request modular design, tests, and edge handling.
- Choose the right model: Claude for complex and structured tasks, ChatGPT for quick snippets and debugging.
- Always review: combine AI generation with AI review tools—but keep humans in the loop.
- Use Graphite Graphite Agent early: catch logic errors before they slow your dev cycle.
Frequently asked questions
How large is the context window for Claude vs Codex?
The context window for Claude models (Opus 4 and Sonnet 4) is typically 200,000 tokens, extendable to 1 million tokens via API for Claude 4 Sonnet, whereas the OpenAI Codex model supports a context window of up to 192,000 tokens.
Is Graphite Graphite Agent free to use?
Graphite offers instant reviews for up to 100 PRs/month for free; more advanced plans start around $20 per active committer per month.
Can Claude or Codex replace human code reviewers?
No—both Anthropic and Graphite stress that AI tools should supplement, not replace, human review.
Where can I access Claude Code or Sonnet 4 / Opus 4?
Claude Sonnet 4 and Opus 4 are available via Anthropic's API, as well as Amazon Bedrock and Google Cloud's Vertex AI; sonnet 4 is available even to free users, while opus 4 is paid ($15/$75 per million tokens).