# Mellum2-12B-A2.5B-Thinking vs Qwen3.5-27B

> Side-by-side benchmark comparison for Mellum2-12B-A2.5B-Thinking and Qwen3.5-27B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/mellum2-12b-a2-5b-thinking-vs-qwen3-5-27b
- Last updated: September 4, 2026

- Shared sourced benchmarks: 2
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: Mellum2-12B-A2.5B-Thinking and Qwen3.5-27B share only 2 sourced benchmark rows.

## Summary

- Only 2 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Qwen3.5-27B has the larger published context window at 262K.

## Model Snapshot

| Property | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B |
|----------|----------|----------|
| Creator | JetBrains | Alibaba |
| Type | Open Weight | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 128K | 262K |
| Independent public score (not head-to-head) | null | 58.31 |
| Benchmarks Covered | 6 | 16 |
| Pricing (input/output) | N/A | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: 48.3 (Estimated · #76/151)
- Qwen3.5-27B public-lane score: 48.5 (Estimated · #75/151)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| BFCL v4 | 45.6% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | Coming soon | 41.6% | Coming soon |
| BrowseComp | Coming soon | 61% | Coming soon |
| OSWorld-Verified | Coming soon | 56.2% | Coming soon |
| Gert Labs | Coming soon | 39.41% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon
- Qwen3.5-27B public-lane score: 40.7 (Supported · #139/183)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| LiveCodeBench v6 | 69.9% | Coming soon | Coming soon |
| SWE-bench Verified | Coming soon | 72.4% | Coming soon |
| SWE-Rebench | Coming soon | 58.9% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon
- Qwen3.5-27B public-lane score: 70.5 (Unranked · 3 rankable rows)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| MMMU | Coming soon | 82.3% | Coming soon |
| MMVU | Coming soon | 73.3% | Coming soon |
| MathVision | Coming soon | 86.0% | Coming soon |
| V* | Coming soon | 93.7% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon
- Qwen3.5-27B public-lane score: 50.9 (Unranked · 3 rankable rows)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| LongBench v2 | Coming soon | 60.6% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: 48.8 (Estimated · #96/181)
- Qwen3.5-27B public-lane score: 48.5 (Supported · #100/181)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| MMLU-Redux | 86.2% | Coming soon | Coming soon |
| GPQA | 57.6% | 85.5% | Qwen3.5-27B |
| GPQA-D | 57.6% | Coming soon | Coming soon |
| MMLU-Pro | Coming soon | 86.1% | Coming soon |
| SuperGPQA | Coming soon | 65.6% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon
- Qwen3.5-27B public-lane score: 92.6 (#13/120)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| IFEval | 76.5% | 95% | Qwen3.5-27B |

### Multilingual

- Winner: Insufficient shared evidence
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon
- Qwen3.5-27B public-lane score: 36.8 (#9/12)

| Benchmark | Mellum2-12B-A2.5B-Thinking | Qwen3.5-27B | Winner |
|-----------|-----------|-----------|--------|
| MMLU-ProX | Coming soon | 82.2% | Coming soon |

## FAQ

### Is there enough evidence to pick between Mellum2-12B-A2.5B-Thinking and Qwen3.5-27B?

Not yet. The models share only 2 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

- [Mellum2-12B-A2.5B-Thinking vs Mellum2-12B-A2.5B-Instruct](/compare/mellum2-12b-a2-5b-instruct-vs-mellum2-12b-a2-5b-thinking)
- [Qwen3.5-27B vs Mellum2-12B-A2.5B-Instruct](/compare/mellum2-12b-a2-5b-instruct-vs-qwen3-5-27b)
- [Mellum2-12B-A2.5B-Thinking vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-mellum2-12b-a2-5b-thinking)
- [Qwen3.5-27B vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-qwen3-5-27b)

## Explore More

- [Mellum2-12B-A2.5B-Thinking profile](/models/mellum2-12b-a2-5b-thinking)
- [Qwen3.5-27B profile](/models/qwen3-5-27b)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)