# Claude 3.5 Sonnet vs Mellum2-12B-A2.5B-Thinking

> Side-by-side benchmark comparison for Claude 3.5 Sonnet and Mellum2-12B-A2.5B-Thinking across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-3-5-sonnet-vs-mellum2-12b-a2-5b-thinking
- Last updated: September 4, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: Claude 3.5 Sonnet and Mellum2-12B-A2.5B-Thinking share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Claude 3.5 Sonnet has the larger published context window at 200K.

## Model Snapshot

| Property | Claude 3.5 Sonnet | Mellum2-12B-A2.5B-Thinking |
|----------|----------|----------|
| Creator | Anthropic | JetBrains |
| Type | Proprietary | Open Weight |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 200K | 128K |
| Independent public score (not head-to-head) | 31.93 | null |
| Benchmarks Covered | 4 | 6 |
| Pricing (input/output) | $3.00 / $15.00 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Claude 3.5 Sonnet public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: 48.3 (Estimated · #76/151)

| Benchmark | Claude 3.5 Sonnet | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| BFCL v4 | Coming soon | 45.6% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Claude 3.5 Sonnet public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude 3.5 Sonnet | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 49% | Coming soon | Coming soon |
| LiveCodeBench v6 | Coming soon | 69.9% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Claude 3.5 Sonnet public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: 48.8 (Estimated · #96/181)

| Benchmark | Claude 3.5 Sonnet | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 59.4% | 57.6% | Claude 3.5 Sonnet |
| MMLU-Redux | Coming soon | 86.2% | Coming soon |
| GPQA-D | Coming soon | 57.6% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Claude 3.5 Sonnet public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude 3.5 Sonnet | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 76.5% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- Claude 3.5 Sonnet public-lane score: 25.7 (Unranked · 2 rankable rows)
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Claude 3.5 Sonnet | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 2.069% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 0.000% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between Claude 3.5 Sonnet and Mellum2-12B-A2.5B-Thinking?

Not yet. The models share only 1 sourced benchmark row, 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 3.5 Sonnet vs Mellum2-12B-A2.5B-Instruct](/compare/claude-3-5-sonnet-vs-mellum2-12b-a2-5b-instruct)
- [Mellum2-12B-A2.5B-Thinking vs Mellum2-12B-A2.5B-Instruct](/compare/mellum2-12b-a2-5b-instruct-vs-mellum2-12b-a2-5b-thinking)
- [Claude 3.5 Sonnet vs Claude Fable 5.1](/compare/claude-3-5-sonnet-vs-claude-fable-5-1)
- [Mellum2-12B-A2.5B-Thinking vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-mellum2-12b-a2-5b-thinking)

## Explore More

- [Claude 3.5 Sonnet profile](/models/claude-3-5-sonnet)
- [Mellum2-12B-A2.5B-Thinking profile](/models/mellum2-12b-a2-5b-thinking)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)