Model comparison
Claude Opus 4.5 vs GPT-OSS 20B
Head-to-head evidence from 12 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Opus 4.5 #34 (Supported); GPT-OSS 20B #159 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Opus 4.5 and GPT-OSS 20B share 12 comparable benchmark results. 0 of 8 categories are comparable. 47 results are unique to Claude Opus 4.5; 6 to GPT-OSS 20B.
Updated July 20, 2026- Shared results
- 12
- Claude Opus 4.5 only
- 47
- GPT-OSS 20B only
- 6
- Comparable categories
- 0 / 8
Benchmark data for Claude Opus 4.5 and GPT-OSS 20B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 12 shared benchmark results across 6 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Claude Opus 4.5 is priced at $5.00 input / $25.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for GPT-OSS 20B. Claude Opus 4.5 has the larger context window at 200K, compared with 128K for GPT-OSS 20B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Claude Opus 4.5 | Δ | GPT-OSS 20B |
|---|---|---|---|
| Agentic | Claude Opus 4.562.6 | MarginNo overlap | GPT-OSS 20BNot measured |
| Coding | Claude Opus 4.571.7 | MarginNo overlap | GPT-OSS 20BNot measured |
| Reasoning | Claude Opus 4.564.4 | MarginNo overlap | GPT-OSS 20BNot measured |
| Knowledge | Claude Opus 4.558.1 | MarginNo overlap | GPT-OSS 20BNot measured |
| Math | Claude Opus 4.557.5 | MarginNo overlap | GPT-OSS 20BNot measured |
| Multilingual | Claude Opus 4.585.7 | MarginNo overlap | GPT-OSS 20BNot measured |
| Multimodal | Claude Opus 4.569.9 | MarginNo overlap | GPT-OSS 20BNot measured |
| Inst. Following | Claude Opus 4.569.5 | MarginNo overlap | GPT-OSS 20BNot measured |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Opus 4.5 | GPT-OSS 20B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Opus 4.5$5 input / $25 output | GPT-OSS 20B$0 input / $0 output | GPT-OSS 20B has the lower combined listed price. |
| Generation speedtokens per second | Claude Opus 4.546 tok/s | GPT-OSS 20B313 tok/s | GPT-OSS 20B has the higher measured throughput. |
| First-answer latencyseconds to first token | Claude Opus 4.51.01 s | GPT-OSS 20B0.65 s | GPT-OSS 20B reaches the first token sooner. |
| Context windowmaximum listed tokens | Claude Opus 4.5200K | GPT-OSS 20B128K | Claude Opus 4.5 lists the larger context window. |
Benchmark Deep Dive
Agentic20 benchmarks
| Benchmark | Claude Opus 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 59.3% | — | Not comparable |
| OSWorld-VerifiedSource | 66.3% | — | Not comparable |
| OSWorldSource | 66.3% | — | Not comparable |
| Claw-EvalSource | 59.6% | — | Not comparable |
| QwenClawBenchSource | 52.3% | — | Not comparable |
| τ³-bench resultsSource | 70.2% | — | Not comparable |
| VITA-BenchSource | 23.3% | — | Not comparable |
| DeepPlanningSource | 26.4% | — | Not comparable |
| ToolathlonSource | 43.5% | — | Not comparable |
| MCP AtlasSource | 42.3% | — | Not comparable |
| MCP-TasksSource | 71.8% | — | Not comparable |
| WideResearchSource | 76.4% | — | Not comparable |
| CyberGymSource | 50.6% | — | Not comparable |
| τ²-bench resultsSource | 86.3% | 60.2% | Claude Opus 4.5 leads |
| Gert LabsSource | 64.23% | — | Not comparable |
| JobBenchSource | 32.3% | — | Not comparable |
| AA Agentic IndexSource | — | 3.1% | Not comparable |
| APEX-Agents-AASource | — | 0.7% | Not comparable |
| GDPval-AASource | — | 3.0% | Not comparable |
| GDPval-AASource | — | 559 | Not comparable |
Coding8 benchmarks
| Benchmark | Claude Opus 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| SWE-bench VerifiedSource | 80.9% | — | Not comparable |
| LiveCodeBench v6Source | 84.8% | — | Not comparable |
| SWE-bench ProSource | 57.1% | — | Not comparable |
| SWE MultilingualSource | 77.5% | — | Not comparable |
| NL2RepoSource | 43.2% | — | Not comparable |
| AA-SciCodeSource | 47.0% | 34.4% | Claude Opus 4.5 leads |
| React Native EvalsSource | — | 71% | Not comparable |
| AA Coding IndexSource | — | 20.7% | Not comparable |
Reasoning4 benchmarks
Knowledge13 benchmarks
| Benchmark | Claude Opus 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| GPQASource | 87% | — | Not comparable |
| SuperGPQASource | 70.6% | — | Not comparable |
| MMLU-ProSource | 89.5% | — | Not comparable |
| MMLU-ReduxSource | 96.6% | — | Not comparable |
| C-EvalSource | 92.2% | — | Not comparable |
| HLESource | 30.8% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | 34.7% | 14.9% | Claude Opus 4.5 leads |
| AA-GPQA DiamondSource | 81.0% | 68.8% | Claude Opus 4.5 leads |
| AA-HLESource | 12.9% | 9.8% | Claude Opus 4.5 leads |
| AA-Omniscience IndexSource | -3.9% | -63.9% | Claude Opus 4.5 leads |
| AA-Omniscience AccuracySource | 40.7% | 15.5% | Claude Opus 4.5 leads |
| AA-Omniscience Hallucination RateSource | 75.4% | 94.1% | Claude Opus 4.5 leads |
| AA MMLU-ProSource | 88.9% | — | Not comparable |
Math7 benchmarks
| Benchmark | Claude Opus 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| AIME26Source | 95.1% | — | Not comparable |
| HMMT Feb 2025Source | 92.9% | — | Not comparable |
| HMMT Nov 2025Source | 93.3% | — | Not comparable |
| HMMT Feb 2026Source | 85.3% | — | Not comparable |
| MMAnswerBenchSource | 84.0% | — | Not comparable |
| FrontierMath v2 (Tiers 1-3)Source | 20.690% | — | Not comparable |
| FrontierMath v2 (Tier 4)Source | 4.167% | — | Not comparable |
Multilingual2 benchmarks
Multimodal8 benchmarks
| Benchmark | Claude Opus 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| MMMU-ProSource | 70.6% | — | Not comparable |
| MathVisionSource | 74.3% | — | Not comparable |
| CharXivSource | 68.5% | — | Not comparable |
| VideoMMMUSource | 84.4% | — | Not comparable |
| ScreenSpot ProSource | 45.7% | — | Not comparable |
| V*Source | 67.0% | — | Not comparable |
| AA-MMMU-ProSource | 71.2% | — | Not comparable |
| Design Arena WebsiteSource | 1279 | 885 | Claude Opus 4.5 leads |
Frequently Asked Questions (3)
Can I compare Claude Opus 4.5 and GPT-OSS 20B on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for Claude Opus 4.5 and GPT-OSS 20B today?
Claude Opus 4.5: $5.00 input / $25.00 output per 1M tokens GPT-OSS 20B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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