One-line verdict
Claude Code for quality-first, security-sensitive, and context-heavy work. Codex for cheap, fast, high-volume automated pipelines. Many teams run both and choose per task — they are not mutually exclusive.
The real difference is not "who is smarter" but cost structure vs quality perception. Codex wins on API price per token and edges ahead on benchmarks; Claude Code wins in human blind reviews by a wide margin and includes its large context window at standard pricing.
Feature comparison table
A 12-dimension side-by-side of the two most important AI coding terminal agents as of 2026:
| Dimension | Codex CLI | Claude Code | Winner |
|---|---|---|---|
| Maker / model | OpenAI (GPT-5.x) | Anthropic (Claude Opus/Sonnet 4.x) | — |
| Open source | Partial (official GitHub repo) | Closed source | Codex |
| API price per token | ~2.5–4× cheaper | Higher; significant at scale | Codex |
| Lowest subscription | $8/mo (Go) | $20/mo (Pro) | Codex |
| SWE-bench Verified | 88.7% (GPT-5.5) | 87.6% (Opus 4.7) | Codex (+1.1%) |
| Human "cleaner code" rating | 25% (blind review) | 67% (blind review) | Claude Code |
| Max context window | ~1.05M tokens (overage surcharge above 272K) | ~1M tokens (no surcharge) | Tie |
| Project memory file | AGENTS.md |
CLAUDE.md |
— |
| Non-interactive / CI mode | codex exec (built-in) |
Requires extra setup | Codex |
| Availability in China | Proxy required | Proxy required | Tie (both need proxy) |
| Sandbox safety | Supported (workspace-write / danger) | Better community reputation | Claude Code (perception) |
| IDE integration | Terminal-only | Terminal-only | Tie |
Pricing comparison
All prices as of 2026 and subject to change — verify on each vendor's pricing page before committing.
| Plan tier | Codex CLI (OpenAI) | Claude Code (Anthropic) |
|---|---|---|
| Free | $0 Free plan | No standalone free plan |
| Entry | $8/mo Go | — |
| Main | $20/mo Plus | $20/mo Pro |
| Mid-tier | $100/mo Pro (≈5× Plus, includes GPT-5.5 Pro) | $100/mo Max (5×) |
| Flagship | $200/mo Pro Max | $200/mo Max (20×) |
| API token cost | Lower roughly 2.5–4× cheaper per token | Higher adds up fast at scale |
A documented real-world data point (as of 2026, subject to change): the same Express.js refactor cost approximately $15 on Codex vs $155 on Claude Code. However, blind reviewers rated Claude Code's output "cleaner" 67% of the time vs Codex's 25%. Lower cost does not equal better output — whether the quality premium is worth it depends entirely on your use case.
Context window
| Spec | Codex CLI / GPT-5.4 | Claude Code / Opus 4.7 |
|---|---|---|
| Max context | ~1.05M tokens (long-context mode) | ~1M tokens (standard pricing) |
| Overage billing | ~2×/1.5× multiplier above ~272K input tokens | No extra multiplier at standard pricing |
| Project memory file | AGENTS.md |
CLAUDE.md |
The raw ceiling numbers are close. The practical difference is that Codex's extended context is a paid add-on with a billing multiplier once you cross the threshold, while Claude Code's million-token window is included at the flat subscription rate — better for continuous large-codebase sessions.
All figures above are as of 2026 and subject to change. If context length is a critical factor for your workflow, test both in your actual use case and check current billing documentation before deciding.
Benchmarks and code quality
| Metric | Codex / GPT-5.5 | Claude Code / Opus 4.7 | Notes |
|---|---|---|---|
| SWE-bench Verified | 88.7% | 87.6% | ~1.1 pt gap, as of 2026 |
| Terminal-Bench | 82.7% (GPT-5.5) | — | Terminal task benchmark |
| Blind review "cleaner" | 25% | 67% | Express.js refactor, double-blind reviewers |
| Same-task API cost | ~$15 | ~$155 | Express.js refactor example; actual costs vary |
The picture is clear: Codex edges ahead on automated benchmarks; Claude Code wins convincingly on human-perceived code quality. If your pipeline runs automated tests and CI tasks, benchmark performance matters. If your output goes into human code review or production, quality perception matters more.
Which should you pick? Two scenarios
Scenario A: High-volume automation and batch refactors
Pick Codex CLI
You have dozens of microservices that need a dependency upgrade, or your CI pipeline runs hundreds of automated fix-lint jobs per day. API cost per token dominates your budget. Output quality is good enough for automated validation — you are not doing human code review on every change. In these scenarios Codex's 2.5–4× cost advantage compounds quickly.
Start here: Install Codex CLI. Use an AGENTS.md file to embed project-level instructions for reproducible autonomous runs.
Scenario B: Security-sensitive work and quality-critical output
Pick Claude Code
You are refactoring a core authentication module, or you need the AI to understand an entire large monorepo before recommending an architectural change. The code goes straight into production — cleanliness and reasoning depth matter more than the cost of a single session. Claude Code's Opus 4.7 rated "cleaner" in blind reviews at nearly 3× the rate of Codex, and its 1M-token window has no billing multiplier.
If you run into connection issues see the Reconnecting fix guide — both tools share similar network setup requirements.
Can you run both at the same time?
Yes — and as of 2026 many teams do. The two tools are not mutually exclusive. A practical split:
| Task type | Recommended | Why |
|---|---|---|
| CI/CD auto-fixes, batch migrations | Codex | Low cost, strong automated benchmark |
| Interactive local development | Either | Comparable interactive UX; personal preference |
| Security audits, architecture refactors | Claude Code | Higher perceived quality, stable reasoning |
| Large-codebase full-context analysis | Claude Code | 1M tokens included at flat rate |
| Cost-sensitive API pipelines | Codex | API pricing ~2.5–4× lower per token |
Both tools use a project memory file — Codex reads AGENTS.md, Claude Code reads CLAUDE.md. You can maintain both files in the same repo without conflict. Each tool will simply pick up its own file and ignore the other.
Availability in China and restricted networks
A common misconception: some users assume one tool works better than the other in China. In fact, both require a proxy — neither Codex CLI nor Claude Code can connect directly from mainland China.
| Item | Codex CLI | Claude Code |
|---|---|---|
| Direct connection from China | ❌ Proxy required | ❌ Proxy required |
| How to configure proxy | export HTTPS_PROXY=... or config.toml |
Same terminal proxy env vars |
| TUN mode compatible | ✅ (Clash TUN, global proxy) | ✅ (same) |
| Account registration | OpenAI: harder since 2023 restrictions | Anthropic: also restricted in China |
The only practical difference: OpenAI and Anthropic have different account registration policies. Neither is easy from mainland China — but with a working proxy, both tools operate identically. See the Proxy setup guide for step-by-step configuration.
Decision tree: which to pick
🔀 Codex CLI vs Claude Code — quick selection guide
codex exec is built-in)FAQ
What is the difference between AGENTS.md and CLAUDE.md?
Both are plain Markdown project files used to inject persistent context and instructions into the agent session. AGENTS.md is read by Codex CLI; CLAUDE.md is read by Claude Code. You can maintain both in the same repository root — each tool reads only its own file.
Claude Code costs a lot more on API — is there a way to reduce that?
A few approaches: (1) use a subscription plan (Pro/Max) rather than pure pay-per-token API; (2) route repetitive high-volume tasks to Codex, using Claude Code only for quality-critical checkpoints; (3) keep context windows reasonably sized to avoid billing on irrelevant tokens.
Is there a meaningful security difference between the two?
Both support approval mode (user must confirm before file writes or shell commands execute). As of 2026, Claude Code has a slightly stronger community reputation for security-sensitive reasoning, but Codex continues to improve its sandboxing. For any security-critical use, test both in your actual environment and check the current documentation.
The benchmark gap is only ~1%, so aren't they basically the same?
On automated benchmarks, yes — the gap is narrow. But the human quality gap is much larger: blind reviewers rated Claude Code "cleaner" at nearly 3× the rate of Codex (67% vs 25%). Benchmarks measure automated task pass rates; human reviews measure readability and style. Both data points matter depending on who ultimately reviews the output.
Comparing more tools? See Codex CLI vs GitHub Copilot, vs Cursor, and vs Aider. Ready to integrate Codex in automation? See the CI/CD Integration Guide and AGENTS.md Guide.