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Claude 3 Opus vs gpt-oss-120b

2 vs 0 benchmarks won

Anthropic
Claude 3 Opus
OpenAI
gpt-oss-120b
Overview
CompanyAnthropicOpenAI
Release dateMar 4 2024Aug 5 2025
Model type
Open sourceNoYes
Specifications
Parameters
Context window
Benchmarks
Science reasoning
GPQA Diamond
50.4%
Software engineering
SWE-Bench Verified
33%
Multimodal understanding
MMMU
Timeline
Release gapClaude 3 Opus shipped 519 days before gpt-oss-120b

Which is better: Claude 3 Opus or gpt-oss-120b?

Claude 3 Opus leads gpt-oss-120b on 2 of the tracked benchmarks (GPQA Diamond, SWE-Bench Verified, MMMU). Claude 3 Opus shipped 519 days before gpt-oss-120b, so benchmark comparisons should account for the intervening progress.

gpt-oss-120b is an open-source / open-weight model; Claude 3 Opus is proprietary.

Direct benchmark comparisons are unavailable — at least one of these models has not published scores on GPQA Diamond, SWE-Bench Verified, or MMMU.

Frequently asked questions

When was Claude 3 Opus released?
Claude 3 Opus was released by Anthropic on Mar 4 2024.
When was gpt-oss-120b released?
gpt-oss-120b was released by OpenAI on Aug 5 2025.
Is Claude 3 Opus or gpt-oss-120b open source?
gpt-oss-120b is an open-source / open-weight model released by OpenAI. Claude 3 Opus is a proprietary model released by Anthropic.

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