Claude Sonnet 4.5 vs GPT-5.3-Codex
Anthropic Claude Sonnet 4.5 | OpenAI GPT-5.3-Codex | |
|---|---|---|
| Overview | ||
| Company | Anthropic | OpenAI |
| Release date | Sep 29 2025 | Feb 5 2026 |
| Access | Proprietary | Proprietary |
| Benchmarks | ||
Nonsense detection BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | 79%Best | 24% |
Coding SWE-Bench VerifiedReal coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better. | 77.2% | — |
Next.js coding Next.js EvalsVercel's open eval of how well AI coding agents build and migrate real Next.js apps — measured as the share of tasks the agent completes successfully. Higher is better. | 50% | 83%Best |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 83.4% | — |
Multimodal MMMUTests the AI on understanding images and text together across many college subjects. Higher is better. | 68% | — |
Community preference (code) Arena Elo (Code)Like the text arena, but people vote on which AI writes better code. The votes become a chess-style Elo rating on arena.ai. Higher is better. | — | 1406 |
| Timeline | ||
| Release gap | Claude Sonnet 4.5 shipped 129 days before GPT-5.3-Codex | |
Which is better: Claude Sonnet 4.5 or GPT-5.3-Codex?
Claude Sonnet 4.5 and GPT-5.3-Codex are evenly matched across the 2 benchmarks they both report (BullshitBench v2, Next.js Evals). Claude Sonnet 4.5 shipped 129 days before GPT-5.3-Codex, so benchmark comparisons should account for the intervening progress.
Published specifications for these two models are limited — see each model page for the latest details.
On BullshitBench v2, Claude Sonnet 4.5 leads at 79% vs GPT-5.3-Codex at 24%. On Next.js Evals, GPT-5.3-Codex leads at 83% vs Claude Sonnet 4.5 at 50%.
Frequently asked questions
Claude Sonnet 4.5 was released by Anthropic on Sep 29 2025.
GPT-5.3-Codex was released by OpenAI on Feb 5 2026.
GPT-5.3-Codex leads on Next.js Evals — Claude Sonnet 4.5 50% vs GPT-5.3-Codex 83%.
Other comparisons
Claude Sonnet 4.5 vs Gemini OmniGPT-5.3-Codex vs Gemini OmniClaude Sonnet 4.5 vs Muse Spark 1.1GPT-5.3-Codex vs Muse Spark 1.1Claude Sonnet 4.5 vs Grok 4.5GPT-5.3-Codex vs Grok 4.5Claude Sonnet 4.5 vs DeepSeek-V4-ProGPT-5.3-Codex vs DeepSeek-V4-ProClaude Sonnet 4.5 vs Mistral Medium 3.5GPT-5.3-Codex vs Mistral Medium 3.5Claude Sonnet 4.5 vs Kimi K2.7 CodeGPT-5.3-Codex vs Kimi K2.7 Code