Claude Sonnet 4.5 vs gpt-oss-120b
Anthropic Claude Sonnet 4.5 | OpenAI gpt-oss-120b | |
|---|---|---|
| Overview | ||
| Company | Anthropic | OpenAI |
| Release date | Sep 29 2025 | Aug 5 2025 |
| Access | Proprietary | Open Weight |
| 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 | 11% |
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% | — |
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 | gpt-oss-120b shipped 55 days before Claude Sonnet 4.5 | |
Which is better: Claude Sonnet 4.5 or gpt-oss-120b?
Claude Sonnet 4.5 leads gpt-oss-120b on 1 of the 1 benchmark they both report (BullshitBench v2). gpt-oss-120b shipped 55 days before Claude Sonnet 4.5, so benchmark comparisons should account for the intervening progress.
Claude Sonnet 4.5 is proprietary, while gpt-oss-120b is open weight.
On BullshitBench v2, Claude Sonnet 4.5 leads at 79% vs gpt-oss-120b at 11%.
Frequently asked questions
Claude Sonnet 4.5 was released by Anthropic on Sep 29 2025.
gpt-oss-120b was released by OpenAI on Aug 5 2025.
Claude Sonnet 4.5 is a proprietary model released by Anthropic. gpt-oss-120b is an open weight model released by OpenAI.
Other comparisons
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