Model comparison
GPT-OSS 20B vs Mellum2-12B-A2.5B-Thinking
Head-to-head evidence from 0 shared benchmark results across 0 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-OSS 20B #159 (Supported); Mellum2-12B-A2.5B-Thinking unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-OSS 20B and Mellum2-12B-A2.5B-Thinking share 0 comparable benchmark results. 0 of 8 categories are comparable. 18 results are unique to GPT-OSS 20B; 5 to Mellum2-12B-A2.5B-Thinking.
Updated July 23, 2026- Shared results
- 0
- GPT-OSS 20B only
- 18
- Mellum2-12B-A2.5B-Thinking only
- 5
- Comparable categories
- 0 / 8
Benchmark data for GPT-OSS 20B and Mellum2-12B-A2.5B-Thinking is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 0 shared benchmark results across 0 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.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-OSS 20B | Mellum2-12B-A2.5B-Thinking | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-OSS 20B$0 input / $0 output | Mellum2-12B-A2.5B-ThinkingNot available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-OSS 20B313 tok/s | Mellum2-12B-A2.5B-ThinkingNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-OSS 20B0.65 s | Mellum2-12B-A2.5B-ThinkingNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-OSS 20B128K | Mellum2-12B-A2.5B-Thinking128K | Listed context windows are equal. |
Benchmark Deep Dive
Agentic6 benchmarks
Coding3 benchmarks
Reasoning2 benchmarks
Knowledge9 benchmarks
| Benchmark | GPT-OSS 20B | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| 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 |
| MMLU-ReduxSource | — | 86.2% | Not comparable |
| GPQASource | — | 57.6% | Not comparable |
| GPQA-DSource | — | 57.6% | Not comparable |
Multimodal1 benchmarks
| Benchmark | GPT-OSS 20B | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| Design Arena WebsiteSource | 882 | — | Not comparable |
Frequently Asked Questions (3)
Can I compare GPT-OSS 20B and Mellum2-12B-A2.5B-Thinking 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 GPT-OSS 20B and Mellum2-12B-A2.5B-Thinking today?
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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