Model comparison
Claude Sonnet 4.5 vs Mellum2-12B-A2.5B-Thinking
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); 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 4.5 and Mellum2-12B-A2.5B-Thinking share 1 comparable benchmark result. 1 of 8 categories are comparable. 11 results are unique to Claude Sonnet 4.5; 4 to Mellum2-12B-A2.5B-Thinking.
Updated July 23, 2026- Shared results
- 1
- Claude Sonnet 4.5 only
- 11
- Mellum2-12B-A2.5B-Thinking only
- 4
- Comparable categories
- 1 / 8
Treat this as a split decision. Claude Sonnet 4.5 makes more sense if knowledge is the priority or you need the larger 200K context window; Mellum2-12B-A2.5B-Thinking is the better fit if you want the stronger reasoning-first profile.
Confidence note. This is a partial-evidence comparison with 1 shared benchmark result 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 Sonnet 4.5 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.
Mellum2-12B-A2.5B-Thinking is the reasoning model in the pair, while Claude Sonnet 4.5 is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. Claude Sonnet 4.5 gives you the larger context window at 200K, compared with 128K for Mellum2-12B-A2.5B-Thinking.
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 | Mellum2-12B-A2.5B-Thinking |
|---|---|---|---|
| Knowledge | Claude Sonnet 4.583.4 | Margin← 25.8 | Mellum2-12B-A2.5B-Thinking57.6 |
| Agentic | Claude Sonnet 4.555.4 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Coding | Claude Sonnet 4.577.2 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Reasoning | Claude Sonnet 4.513.6 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Math | Claude Sonnet 4.511.2 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Inst. Following | Claude Sonnet 4.5Not measured | MarginNo overlap | Mellum2-12B-A2.5B-Thinking76.5 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
GPQA
KnowledgeA 83.4%B 57.6%Winner: Claude Sonnet 4.5Δ 25.8GPQA: Claude Sonnet 4.5 scored 83.4%; Mellum2-12B-A2.5B-Thinking scored 57.6%. Claude Sonnet 4.5 wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Sonnet 4.5 | Mellum2-12B-A2.5B-Thinking | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Sonnet 4.5$3 input / $15 output | Mellum2-12B-A2.5B-ThinkingNot available | A complete price comparison is not available. |
| Generation speedtokens per second | Claude Sonnet 4.5Not available | Mellum2-12B-A2.5B-ThinkingNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Sonnet 4.5Not available | Mellum2-12B-A2.5B-ThinkingNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Sonnet 4.5200K | Mellum2-12B-A2.5B-Thinking128K | Claude Sonnet 4.5 lists the larger context window. |
Benchmark Deep Dive
Agentic6 benchmarks
Coding1 benchmarks
| Benchmark | Claude Sonnet 4.5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| SWE-bench VerifiedSource | 77.2% | — | Not comparable |
Reasoning1 benchmarks
| Benchmark | Claude Sonnet 4.5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| ARC-AGI-2Source | 13.6% | — | Not comparable |
KnowledgeClaude Sonnet 4.5 wins3 benchmarks
Math3 benchmarks
Multimodal1 benchmarks
| Benchmark | Claude Sonnet 4.5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| Design Arena WebsiteSource | 1219 | — | Not comparable |
Inst. Following1 benchmarks
| Benchmark | Claude Sonnet 4.5 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| IFEvalSource | — | 76.5% | Not comparable |
Frequently Asked Questions (2)
Which is better, Claude Sonnet 4.5 or Mellum2-12B-A2.5B-Thinking?
Claude Sonnet 4.5 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 4.5 or Mellum2-12B-A2.5B-Thinking?
Claude Sonnet 4.5 has the edge for knowledge tasks in this comparison, averaging 83.4 versus 57.6. Inside this category, GPQA is the benchmark that creates the most daylight between them.
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