Model comparison
Claude Sonnet 5 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: Claude Sonnet 5 #29 (Estimated); Mellum2-12B-A2.5B-Thinking unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Sonnet 5 and Mellum2-12B-A2.5B-Thinking share 0 comparable benchmark results. 1 of 8 categories are comparable. 36 results are unique to Claude Sonnet 5; 5 to Mellum2-12B-A2.5B-Thinking.
Updated July 23, 2026- Shared results
- 0
- Claude Sonnet 5 only
- 36
- Mellum2-12B-A2.5B-Thinking only
- 5
- Comparable categories
- 1 / 8
Treat this as a split decision. Claude Sonnet 5 makes more sense if you need the larger 1M context window; Mellum2-12B-A2.5B-Thinking is the better fit if knowledge is the priority.
Confidence note. This is a partial-evidence comparison with 0 shared benchmark results across 0 evidence categories; 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 Sonnet 5 and Mellum2-12B-A2.5B-Thinking 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 Sonnet 5 gives you the larger context window at 1M, compared with 128K for Mellum2-12B-A2.5B-Thinking.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Sonnet 5 | Mellum2-12B-A2.5B-Thinking | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Sonnet 5$2 input / $10 output | Mellum2-12B-A2.5B-ThinkingNot available | A complete price comparison is not available. |
| Generation speedtokens per second | Claude Sonnet 5Not available | Mellum2-12B-A2.5B-ThinkingNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Sonnet 5Not available | Mellum2-12B-A2.5B-ThinkingNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Sonnet 51M | Mellum2-12B-A2.5B-Thinking128K | Claude Sonnet 5 lists the larger context window. |
Benchmark Deep Dive
Agentic14 benchmarks
| Benchmark | Claude Sonnet 5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 80.4% | — | Not comparable |
| BrowseCompSource | 84.7% | — | Not comparable |
| HLE w/ toolsSource | 57.4% | — | Not comparable |
| OSWorld-VerifiedSource | 81.2% | — | Not comparable |
| GDPval-AASource | 1607 | — | Not comparable |
| AA Agentic IndexSource | 46.7% | — | Not comparable |
| GDPval-AASource | 55.4% | — | Not comparable |
| AA BriefcaseSource | 1388 | — | Not comparable |
| AA AutomationBenchSource | 39.2% | — | Not comparable |
| AA EnterpriseOps-GymSource | 44.7% | — | Not comparable |
| AA Harvey LABSource | 90.1% | — | Not comparable |
| AA Tau3 BankingSource | 28.2% | — | Not comparable |
| aaTerminalBench21Source | 80.5% | — | Not comparable |
| BFCL v4Source | — | 45.6% | Not comparable |
Coding9 benchmarks
| Benchmark | Claude Sonnet 5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| SWE-bench VerifiedSource | 85.2% | — | Not comparable |
| SWE-bench ProSource | 63.2% | — | Not comparable |
| SWE MultilingualSource | 78.3% | — | Not comparable |
| SWE MultimodalSource | 28.1% | — | Not comparable |
| Terminal-Bench 2.0Source | 80.4% | — | Not comparable |
| FrontierCode 1.1 MainSource | 42.7% | — | Not comparable |
| cursorBench32Source | 61.5% | — | Not comparable |
| AA Coding IndexSource | 71.5% | — | Not comparable |
| AA-SciCodeSource | 53.6% | — | Not comparable |
Reasoning2 benchmarks
KnowledgeMellum2-12B-A2.5B-Thinking wins11 benchmarks
| Benchmark | Claude Sonnet 5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| HLESource | 57.4% | — | Not comparable |
| HLE w/o toolsSource | 43.2% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | 53.4% | — | Not comparable |
| AA-GPQA DiamondSource | 91.1% | — | Not comparable |
| AA-HLESource | 39.6% | — | Not comparable |
| AA-Omniscience IndexSource | 15.3% | — | Not comparable |
| AA-Omniscience AccuracySource | 38.3% | — | Not comparable |
| AA-Omniscience Hallucination RateSource | 37.3% | — | Not comparable |
| MMLU-ReduxSource | — | 86.2% | Not comparable |
| GPQASource | — | 57.6% | Not comparable |
| GPQA-DSource | — | 57.6% | Not comparable |
Multimodal4 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude Sonnet 5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| IFEvalSource | — | 76.5% | Not comparable |
Frequently Asked Questions (2)
Which is better, Claude Sonnet 5 or Mellum2-12B-A2.5B-Thinking?
Claude Sonnet 5 and Mellum2-12B-A2.5B-Thinking 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 Sonnet 5 or Mellum2-12B-A2.5B-Thinking?
Mellum2-12B-A2.5B-Thinking has the edge for knowledge tasks in this comparison, averaging 57.6 versus 57.4. Claude Sonnet 5 stays close enough that the answer can still flip depending on your workload.
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