Anthropic Claude 3.5 Sonnet vs OpenAI GPT-5.3-Codex — side-by-side specs.
Anthropic Claude 3.5 Sonnet | OpenAI GPT-5.3-Codex | |
|---|---|---|
| Overview | ||
| Company | Anthropic | OpenAI |
| Release date | Jun 20 2024 | Feb 5 2026 |
| Model type | — | — |
| Open source | No | No |
| Specifications | ||
Parameters | — | — |
Context window | — | — |
| Benchmarks | ||
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. | 33.4% | — |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 59.4% | — |
| Timeline | ||
| Release gap | Claude 3.5 Sonnet shipped 595 days before GPT-5.3-Codex | |
Claude 3.5 Sonnet and GPT-5.3-Codex don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Claude 3.5 Sonnet shipped 595 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.
Direct benchmark comparisons are unavailable — Claude 3.5 Sonnet and GPT-5.3-Codex don't publish scores on any of the same benchmarks.