Anthropic Claude Sonnet 4.5 vs OpenAI GPT-5.3-Instant — side-by-side specs.
Anthropic Claude Sonnet 4.5 | OpenAI GPT-5.3-Instant | |
|---|---|---|
| Overview | ||
| Company | Anthropic | OpenAI |
| Release date | Sep 29 2025 | Mar 3 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. | 77.2% | — |
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% | — |
| Timeline | ||
| Release gap | Claude Sonnet 4.5 shipped 155 days before GPT-5.3-Instant | |
Claude Sonnet 4.5 and GPT-5.3-Instant don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Claude Sonnet 4.5 shipped 155 days before GPT-5.3-Instant, 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 Sonnet 4.5 and GPT-5.3-Instant don't publish scores on any of the same benchmarks.