Model comparison
Claude Opus 4.6 vs Mellum2-12B-A2.5B-Instruct
Head-to-head evidence from 2 shared benchmark results across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Opus 4.6 #16 (Supported); Mellum2-12B-A2.5B-Instruct unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Opus 4.6 and Mellum2-12B-A2.5B-Instruct share 2 comparable benchmark results. 1 of 8 categories are comparable. 44 results are unique to Claude Opus 4.6; 3 to Mellum2-12B-A2.5B-Instruct.
Updated July 23, 2026- Shared results
- 2
- Claude Opus 4.6 only
- 44
- Mellum2-12B-A2.5B-Instruct only
- 3
- Comparable categories
- 1 / 8
Treat this as a split decision. Claude Opus 4.6 makes more sense if knowledge is the priority or you need the larger 1M context window; Mellum2-12B-A2.5B-Instruct is the better fit if its strengths line up with your actual workload.
Confidence note. This is a partial-evidence comparison with 2 shared benchmark results across 1 evidence category; 1 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
Claude Opus 4.6 and Mellum2-12B-A2.5B-Instruct finish on the same BenchAlign overall score, so this is less about a single winner and more about where the edge shows up. The BenchAlign headline says tie; the benchmark table is where the real choice happens.
Claude Opus 4.6 gives you the larger context window at 1M, compared with 128K for Mellum2-12B-A2.5B-Instruct.
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 4.6 | Δ | Mellum2-12B-A2.5B-Instruct |
|---|---|---|---|
| Knowledge | Claude Opus 4.669.1 | Margin← 28.2 | Mellum2-12B-A2.5B-Instruct40.9 |
| Agentic | Claude Opus 4.673.0 | MarginNo overlap | Mellum2-12B-A2.5B-InstructNot measured |
| Coding | Claude Opus 4.668.1 | MarginNo overlap | Mellum2-12B-A2.5B-InstructNot measured |
| Math | Claude Opus 4.636.3 | MarginNo overlap | Mellum2-12B-A2.5B-InstructNot measured |
| Multimodal | Claude Opus 4.677.3 | MarginNo overlap | Mellum2-12B-A2.5B-InstructNot measured |
| Inst. Following | Claude Opus 4.6Not measured | MarginNo overlap | Mellum2-12B-A2.5B-Instruct75.8 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
GPQA
KnowledgeA 91.3%B 40.9%Winner: Claude Opus 4.6Δ 50.4GPQA: Claude Opus 4.6 scored 91.3%; Mellum2-12B-A2.5B-Instruct scored 40.9%. Claude Opus 4.6 wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Opus 4.6 | Mellum2-12B-A2.5B-Instruct | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Opus 4.6$5 input / $25 output | Mellum2-12B-A2.5B-InstructNot available | A complete price comparison is not available. |
| Generation speedtokens per second | Claude Opus 4.640 tok/s | Mellum2-12B-A2.5B-InstructNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Opus 4.61.78 s | Mellum2-12B-A2.5B-InstructNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Opus 4.61M | Mellum2-12B-A2.5B-Instruct128K | Claude Opus 4.6 lists the larger context window. |
Benchmark Deep Dive
Agentic11 benchmarks
| Benchmark | Claude Opus 4.6 | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 65.4% | — | Not comparable |
| BrowseCompSource | 83.7% | — | Not comparable |
| OSWorld-VerifiedSource | 72.7% | — | Not comparable |
| τ²-bench resultsSource | 84.8% | — | Not comparable |
| Claw-EvalSource | 70.4% | — | Not comparable |
| DeepSearchQASource | 73.7% | — | Not comparable |
| CyberGymSource | 66.6% | — | Not comparable |
| Gert LabsSource | 61.85% | — | Not comparable |
| ResearchClawBenchSource | 19.9% | — | Not comparable |
| JobBenchSource | 36.7% | — | Not comparable |
| BFCL v4Source | — | 44.2% | Not comparable |
Coding9 benchmarks
| Benchmark | Claude Opus 4.6 | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| SWE-bench VerifiedSource | 80.8% | — | Not comparable |
| SWE-bench Verified*Source | 75.6% | — | Not comparable |
| LiveCodeBench ProSource | 70.7% | — | Not comparable |
| SWE-bench ProSource | 53.4% | — | Not comparable |
| SWE-RebenchSource | 65.3% | — | Not comparable |
| React Native EvalsSource | 84.1% | — | Not comparable |
| Vibe Code BenchSource | 57.57% | — | Not comparable |
| AA-SciCodeSource | 45.7% | — | Not comparable |
| FrontierCode 1.1 MainSource | 26.9% | — | Not comparable |
Reasoning2 benchmarks
KnowledgeClaude Opus 4.6 wins16 benchmarks
| Benchmark | Claude Opus 4.6 | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| GPQASource | 91.3% | 40.9% | Claude Opus 4.6 leads |
| GPQA-DSource | 89.2% | 40.9% | Claude Opus 4.6 leads |
| SuperGPQASource | 95% | — | Not comparable |
| MMLU-ProSource | 82% | — | Not comparable |
| MMLU-Pro (Arcee)Source | 89.1% | — | Not comparable |
| HLESource | 53% | — | Not comparable |
| HLE w/o toolsSource | 40% | — | Not comparable |
| HealthBench HardSource | 14.8% | — | Not comparable |
| MedXpertQA (Text)Source | 52.1% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | 37.8% | — | Not comparable |
| AA-GPQA DiamondSource | 84.0% | — | Not comparable |
| AA-HLESource | 18.6% | — | Not comparable |
| AA-Omniscience IndexSource | 3.5% | — | Not comparable |
| AA-Omniscience AccuracySource | 45.2% | — | Not comparable |
| AA-Omniscience Hallucination RateSource | 76.0% | — | Not comparable |
| MMLU-ReduxSource | — | 78.1% | Not comparable |
Math3 benchmarks
Multimodal6 benchmarks
Frequently Asked Questions (2)
Which is better, Claude Opus 4.6 or Mellum2-12B-A2.5B-Instruct?
Claude Opus 4.6 and Mellum2-12B-A2.5B-Instruct are tied on the BenchAlign overall score, so the right pick depends on which category matters most for your use case.
Which is better for knowledge tasks, Claude Opus 4.6 or Mellum2-12B-A2.5B-Instruct?
Claude Opus 4.6 has the edge for knowledge tasks in this comparison, averaging 69.1 versus 40.9. Inside this category, GPQA is the benchmark that creates the most daylight between them.
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