# Claude Opus 4.6 vs Mellum2.1-12B-A2.5B-Thinking

> Side-by-side benchmark comparison for Claude Opus 4.6 and Mellum2.1-12B-A2.5B-Thinking across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-opus-4-6-vs-mellum2-1-12b-a2-5b-thinking
- Last updated: October 8, 2026

- Shared sourced benchmarks: 3
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: Claude Opus 4.6 and Mellum2.1-12B-A2.5B-Thinking share only 3 sourced benchmark rows.

## Summary

- Only 3 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Mellum2.1-12B-A2.5B-Thinking has the lower published output-token price.
- Claude Opus 4.6 has the larger published context window at 1M.

## Model Snapshot

| Property | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking |
|----------|----------|----------|
| Creator | Anthropic | JetBrains |
| Type | Proprietary | Open Weight |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 1M | 128K |
| Independent public score (not head-to-head) | 61.92 | null |
| Benchmarks Covered | 34 | 7 |
| Pricing (input/output) | $5.00 / $25.00 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 44.5 (Supported · #54/122)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 65.4% | Coming soon | Coming soon |
| BrowseComp | 83.7% | Coming soon | Coming soon |
| OSWorld-Verified | 72.7% | Coming soon | Coming soon |
| Claw-Eval | 70.4% | Coming soon | Coming soon |
| DeepSearchQA | 73.7% | Coming soon | Coming soon |
| CyberGym | 66.6% | Coming soon | Coming soon |
| Gert Labs | 61.85% | Coming soon | Coming soon |
| ResearchClawBench | 19.9% | Coming soon | Coming soon |
| JobBench | 36.7% | Coming soon | Coming soon |
| ApprenticeBench | 5% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 17.4% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 47.5 (Supported · #48/146)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 80.8% | 47% | Claude Opus 4.6 |
| SWE-bench Verified* | 75.6% | Coming soon | Coming soon |
| LiveCodeBench Pro | 70.7% | Coming soon | Coming soon |
| SWE-bench Pro | 53.4% | 28% | Claude Opus 4.6 |
| SWE-Rebench | 65.3% | Coming soon | Coming soon |
| React Native Evals | 84.1% | Coming soon | Coming soon |
| Vibe Code Bench | 57.57% | Coming soon | Coming soon |
| FrontierCode 1.1 Main | 26.9% | Coming soon | Coming soon |
| LiveCodeBench v6 | Coming soon | 82.0% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 68.3 (Unranked · 2 rankable rows)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 60.6 (#29/49)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | 77.3% | Coming soon | Coming soon |
| ERQA | 51.6% | Coming soon | Coming soon |
| ScreenSpot Pro | 83.1% | Coming soon | Coming soon |
| MedXpertQA (MM) | 64.8% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 58.3 (Estimated · #45/174)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 91.3% | Coming soon | Coming soon |
| GPQA-D | 89.2% | 64.6% | Claude Opus 4.6 |
| SuperGPQA | 95% | Coming soon | Coming soon |
| MMLU-Pro | 82% | Coming soon | Coming soon |
| MMLU-Pro (Arcee) | 89.1% | Coming soon | Coming soon |
| HLE | 53% | Coming soon | Coming soon |
| HLE w/o tools | 40% | Coming soon | Coming soon |
| HealthBench Hard | 14.8% | Coming soon | Coming soon |
| MedXpertQA (Text) | 52.1% | Coming soon | Coming soon |
| MMLU-Redux | Coming soon | 87.8% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 51 (#79/125)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 90.6% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- Claude Opus 4.6 public-lane score: 58.5 (Unranked · 3 rankable rows)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude Opus 4.6 | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| AIME25 (Arcee) | 99.8% | Coming soon | Coming soon |
| FrontierMath v2 (Tiers 1-3) | 40.700% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 22.900% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between Claude Opus 4.6 and Mellum2.1-12B-A2.5B-Thinking?

Not yet. The models share only 3 sourced benchmark rows, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Claude Opus 4.6 vs Claude Opus 4.6 (Adaptive)](/compare/claude-opus-4-6-vs-claude-opus-4-6-thinking)
- [Mellum2.1-12B-A2.5B-Thinking vs Claude Opus 4.6 (Adaptive)](/compare/claude-opus-4-6-thinking-vs-mellum2-1-12b-a2-5b-thinking)
- [Claude Opus 4.6 vs Claude Opus 5.5](/compare/claude-opus-4-6-vs-claude-opus-5-5)
- [Mellum2.1-12B-A2.5B-Thinking vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-mellum2-1-12b-a2-5b-thinking)

## Explore More

- [Claude Opus 4.6 profile](/models/claude-opus-4-6)
- [Mellum2.1-12B-A2.5B-Thinking profile](/models/mellum2-1-12b-a2-5b-thinking)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)