Comparison
Claude Sonnet 5 vs GPT-5.3 Codex: Coding AI Showdown 2026
Head-to-head comparison of Claude Sonnet 5 and GPT-5.3 Codex for coding with benchmarks, speed tests, and developer preferences.
February 2026
TL;DR
GPT-5.3 Codex leads in speed (2x faster) and terminal tasks (77.3% vs 68.4%). Claude Sonnet 5 leads in SWE-bench (80.9% vs 76.8%), context (500K vs 128K), and reasoning. Price similar. Many teams use both.
Benchmarks
| Benchmark | Sonnet 5 | Codex 5.3 |
|---|
| SWE-bench | 80.9% | 76.8% |
| Terminal-Bench | 68.4% | 77.3% |
| Context | 500K | 128K |
Recommendations
- Quick fixes: Codex 5.3
- Large refactoring: Sonnet 5
- Architecture: Sonnet 5
Conclusion
No universal winner. Use both strategically for maximum productivity.