Model comparison
Claude Sonnet 4.5 vs GPT-OSS 20B
Head-to-head evidence from 1 shared benchmark result across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Sonnet 4.5 #96 (Estimated); GPT-OSS 20B #159 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Sonnet 4.5 and GPT-OSS 20B share 1 comparable benchmark result. 0 of 8 categories are comparable. 11 results are unique to Claude Sonnet 4.5; 17 to GPT-OSS 20B.
Updated July 22, 2026- Shared results
- 1
- Claude Sonnet 4.5 only
- 11
- GPT-OSS 20B only
- 17
- Comparable categories
- 0 / 8
Benchmark data for Claude Sonnet 4.5 and GPT-OSS 20B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 1 shared benchmark result across 1 evidence category; 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 Sonnet 4.5 is priced at $3.00 input / $15.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for GPT-OSS 20B. Claude Sonnet 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 Sonnet 4.5 | Δ | GPT-OSS 20B |
|---|---|---|---|
| Agentic | Claude Sonnet 4.555.4 | MarginNo overlap | GPT-OSS 20BNot measured |
| Coding | Claude Sonnet 4.577.2 | MarginNo overlap | GPT-OSS 20BNot measured |
| Reasoning | Claude Sonnet 4.513.6 | MarginNo overlap | GPT-OSS 20BNot measured |
| Knowledge | Claude Sonnet 4.583.4 | MarginNo overlap | GPT-OSS 20BNot measured |
| Math | Claude Sonnet 4.511.2 | 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 Sonnet 4.5 | GPT-OSS 20B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Sonnet 4.5$3 input / $15 output | GPT-OSS 20B$0 input / $0 output | GPT-OSS 20B has the lower combined listed price. |
| Generation speedtokens per second | Claude Sonnet 4.5Not available | GPT-OSS 20B313 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Sonnet 4.5Not available | GPT-OSS 20B0.65 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Sonnet 4.5200K | GPT-OSS 20B128K | Claude Sonnet 4.5 lists the larger context window. |
Benchmark Deep Dive
Agentic10 benchmarks
| Benchmark | Claude Sonnet 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 50% | — | Not comparable |
| OSWorld-VerifiedSource | 61.4% | — | Not comparable |
| VITA-BenchSource | 17.0% | — | Not comparable |
| Gert LabsSource | 48.51% | — | Not comparable |
| JobBenchSource | 27.7% | — | Not comparable |
| AA Agentic IndexSource | — | 3.1% | Not comparable |
| APEX-Agents-AASource | — | 0.7% | Not comparable |
| τ²-bench resultsSource | — | 60.2% | Not comparable |
| GDPval-AASource | — | 3.0% | Not comparable |
| GDPval-AASource | — | 559 | Not comparable |
Coding4 benchmarks
Reasoning3 benchmarks
Knowledge7 benchmarks
| Benchmark | Claude Sonnet 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| GPQASource | 83.4% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 14.9% | Not comparable |
| AA-GPQA DiamondSource | — | 68.8% | Not comparable |
| AA-HLESource | — | 9.8% | Not comparable |
| AA-Omniscience IndexSource | — | -63.9% | Not comparable |
| AA-Omniscience AccuracySource | — | 15.5% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 94.1% | Not comparable |
Math3 benchmarks
Multimodal1 benchmarks
| Benchmark | Claude Sonnet 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| Design Arena WebsiteSource | 1219 | 882 | Claude Sonnet 4.5 leads |
Inst. Following1 benchmarks
| Benchmark | Claude Sonnet 4.5 | GPT-OSS 20B | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 65.1% | Not comparable |
Frequently Asked Questions (3)
Can I compare Claude Sonnet 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 Sonnet 4.5 and GPT-OSS 20B today?
Claude Sonnet 4.5: $3.00 input / $15.00 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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