# Claude Opus 4.5 vs GPT-OSS 120B

> Side-by-side benchmark comparison for Claude Opus 4.5 and GPT-OSS 120B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-opus-4-5-vs-gpt-oss-120b
- Last updated: October 17, 2026

- Shared sourced benchmarks: 4
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Pick Claude Opus 4.5 if you want the stronger benchmark profile. GPT-OSS 120B only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- Claude Opus 4.5 leads overall 54.05 to 37.32.
- The clearest category separation is in instruction following, where the averages are 31.9 for Claude Opus 4.5 and 84.3 for GPT-OSS 120B.
- The biggest single benchmark swing is Gert Labs in Agentic, with scores of 64.23% and 29.61%.
- GPT-OSS 120B is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- Claude Opus 4.5 also has the larger context window at 200K.

## Model Snapshot

| Property | Claude Opus 4.5 | GPT-OSS 120B |
|----------|----------|----------|
| Creator | Anthropic | OpenAI |
| Type | Proprietary | Open Weight |
| Reasoning | Non-Reasoning | Non-Reasoning |
| Context | 200K | 128K |
| Overall Score | 54.05 | 37.32 |
| Benchmarks Covered | 61 | 8 |
| Pricing (input/output) | $5.00 / $25.00 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Directional only
- Claude Opus 4.5 public-lane score: 32.3 (Estimated · #89/128)
- GPT-OSS 120B public-lane score: 19.5 (Estimated · #110/128)

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 59.3% | Coming soon | Coming soon |
| OSWorld-Verified | 66.3% | Coming soon | Coming soon |
| OSWorld | 66.3% | Coming soon | Coming soon |
| Claw-Eval | 59.6% | Coming soon | Coming soon |
| QwenClawBench | 52.3% | Coming soon | Coming soon |
| τ³-bench results | 70.2% | Coming soon | Coming soon |
| VITA-Bench | 23.3% | Coming soon | Coming soon |
| DeepPlanning | 26.4% | Coming soon | Coming soon |
| Toolathlon | 43.5% | Coming soon | Coming soon |
| MCP Atlas | 42.3% | Coming soon | Coming soon |
| MCP-Tasks | 71.8% | Coming soon | Coming soon |
| WideResearch | 76.4% | Coming soon | Coming soon |
| CyberGym | 50.6% | Coming soon | Coming soon |
| Gert Labs | 64.23% | 29.61% | Claude Opus 4.5 |
| JobBench | 32.3% | Coming soon | Coming soon |

### Coding

- Winner: Directional only
- Claude Opus 4.5 public-lane score: 40.3 (Estimated · #64/150)
- GPT-OSS 120B public-lane score: 23 (Estimated · #111/150)

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 80.9% | 62.4% | Claude Opus 4.5 |
| LiveCodeBench v6 | 84.8% | Coming soon | Coming soon |
| SWE-bench Pro | 57.1% | Coming soon | Coming soon |
| SWE Multilingual | 77.5% | Coming soon | Coming soon |
| NL2Repo | 43.2% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | 59.3% | Coming soon | Coming soon |
| React Native Evals | Coming soon | 71.6% | Coming soon |

### Reasoning

- Winner: Not comparable
- Claude Opus 4.5 public-lane score: 78.3 (Unranked · 4 rankable rows)
- GPT-OSS 120B public-lane score: 61.6 (Unranked · 2 rankable rows)

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| LongBench v2 | 64.4% | Coming soon | Coming soon |
| AI-Needle | 74% | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Not comparable
- Claude Opus 4.5 public-lane score: 48.6 (#49/54)
- GPT-OSS 120B public-lane score: Coming soon

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| MMMU | 80.7% | Coming soon | Coming soon |
| MMMU-Pro | 70.6% | Coming soon | Coming soon |
| RealWorldQA | 77.0% | Coming soon | Coming soon |
| OmniDocBench 1.5 | 87.7% | Coming soon | Coming soon |
| Video-MME (with subtitle) | 77.6% | Coming soon | Coming soon |
| Video-MME (w/o subtitle) | 81.4% | Coming soon | Coming soon |
| MathVision | 74.3% | Coming soon | Coming soon |
| We-Math | 70.0% | Coming soon | Coming soon |
| DynaMath | 79.7% | Coming soon | Coming soon |
| SimpleVQA | 65.7% | Coming soon | Coming soon |
| CharXiv | 68.5% | Coming soon | Coming soon |
| CountBench | 90.6% | Coming soon | Coming soon |
| AI2D_TEST | 87.7% | Coming soon | Coming soon |
| ERQA | 46.8% | Coming soon | Coming soon |
| VideoMMMU | 84.4% | Coming soon | Coming soon |
| MLVU (M-Avg) | 81.7% | Coming soon | Coming soon |
| ScreenSpot Pro | 45.7% | Coming soon | Coming soon |
| V* | 67.0% | Coming soon | Coming soon |

### Knowledge

- Winner: Directional only
- Claude Opus 4.5 public-lane score: 51.2 (Estimated · #77/184)
- GPT-OSS 120B public-lane score: 38.6 (Supported · #122/184)

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 87% | 80.1% | Claude Opus 4.5 |
| SuperGPQA | 70.6% | Coming soon | Coming soon |
| MMLU-Pro | 89.5% | Coming soon | Coming soon |
| MMLU-Redux | 96.6% | Coming soon | Coming soon |
| C-Eval | 92.2% | Coming soon | Coming soon |
| HLE | 30.8% | 14.9% | Claude Opus 4.5 |
| MMLU | Coming soon | 90% | Coming soon |

### Multilingual

- Winner: Not comparable
- Claude Opus 4.5 public-lane score: 96.5 (#2/17)
- GPT-OSS 120B public-lane score: Coming soon

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| MMLU-ProX | 85.7% | Coming soon | Coming soon |
| NOVA-63 | 56.7% | Coming soon | Coming soon |
| INCLUDE | 86.2% | Coming soon | Coming soon |
| PolyMath | 79.0% | Coming soon | Coming soon |
| MAXIFE | 79.2% | Coming soon | Coming soon |

### Instruction Following

- Winner: Directional only
- Claude Opus 4.5 public-lane score: 31.9 (#131/148)
- GPT-OSS 120B public-lane score: 84.3 (#50/148)

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| IFEval | 90.9% | Coming soon | Coming soon |
| IFBench | 58% | Coming soon | Coming soon |

### Mathematics

- Winner: Not comparable
- Claude Opus 4.5 public-lane score: 61.3 (#9/12)
- GPT-OSS 120B public-lane score: Coming soon

| Benchmark | Claude Opus 4.5 | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| AIME26 | 95.1% | Coming soon | Coming soon |
| HMMT Feb 2025 | 92.9% | Coming soon | Coming soon |
| HMMT Nov 2025 | 93.3% | Coming soon | Coming soon |
| HMMT Feb 2026 | 85.3% | Coming soon | Coming soon |
| MMAnswerBench | 84.0% | Coming soon | Coming soon |
| FrontierMath v2 (Tiers 1-3) | 34.386% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 4.878% | Coming soon | Coming soon |
| AIME 2024 | Coming soon | 95.8% | Coming soon |
| AIME 2025 | Coming soon | 92.5% | Coming soon |

## FAQ

### Which is better overall, Claude Opus 4.5 or GPT-OSS 120B?

Claude Opus 4.5 is ahead overall on BenchLM right now.

### Where is the biggest gap between Claude Opus 4.5 and GPT-OSS 120B?

The widest category gap is in instruction following, where the averages are 31.9 for Claude Opus 4.5 and 84.3 for GPT-OSS 120B.

### How many benchmarks does Claude Opus 4.5 cover on BenchLM?

Claude Opus 4.5 currently has 61 sourced benchmark scores on BenchLM.

### How many benchmarks does GPT-OSS 120B cover on BenchLM?

GPT-OSS 120B currently has 8 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Claude Opus 4.5 vs Claude Opus 4.5 Thinking](/compare/claude-opus-4-5-vs-claude-opus-4-5-thinking)
- [GPT-OSS 120B vs Claude Opus 4.5 Thinking](/compare/claude-opus-4-5-thinking-vs-gpt-oss-120b)
- [Claude Opus 4.5 vs GPT-OSS 20B](/compare/claude-opus-4-5-vs-gpt-oss-20b)
- [GPT-OSS 120B vs GPT-OSS 20B](/compare/gpt-oss-120b-vs-gpt-oss-20b)

## Explore More

- [Claude Opus 4.5 profile](/models/claude-opus-4-5)
- [GPT-OSS 120B profile](/models/gpt-oss-120b)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)