# A.X K2 vs Mellum2-12B-A2.5B-Thinking

> Side-by-side benchmark comparison for A.X K2 and Mellum2-12B-A2.5B-Thinking across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/a-x-k2-vs-mellum2-12b-a2-5b-thinking
- Last updated: September 10, 2026

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

## Quick Verdict

Evidence is too thin for a benchmark verdict: A.X K2 and Mellum2-12B-A2.5B-Thinking 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.
- A.X K2 has the larger published context window at 262K.

## Model Snapshot

| Property | A.X K2 | Mellum2-12B-A2.5B-Thinking |
|----------|----------|----------|
| Creator | SK Telecom | JetBrains |
| Type | Open Weight | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 262K | 128K |
| Independent public score (not head-to-head) | null | null |
| Benchmarks Covered | 10 | 6 |
| Pricing (input/output) | $0.00 / $0.00 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- A.X K2 public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: 45.8 (Estimated · #79/152)

| Benchmark | A.X K2 | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.1 | 36.0% | Coming soon | Coming soon |
| BFCL v4 | Coming soon | 45.6% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- A.X K2 public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | A.X K2 | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| LiveCodeBench v6 | 84.0% | 69.9% | A.X K2 |
| SciCode | 41% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 36.0% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- A.X K2 public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: 46.3 (Estimated · #103/183)

| Benchmark | A.X K2 | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| HLE | 27.8% | Coming soon | Coming soon |
| GPQA-D | 85.6% | 57.6% | A.X K2 |
| MMLU-Redux | Coming soon | 86.2% | Coming soon |
| GPQA | Coming soon | 57.6% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- A.X K2 public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | A.X K2 | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| IFBench | 75.9% | Coming soon | Coming soon |
| IFEval | Coming soon | 76.5% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- A.X K2 public-lane score: Coming soon
- Mellum2-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | A.X K2 | Mellum2-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| AIME26 | 97.1% | Coming soon | Coming soon |
| Apex | 45.8% | Coming soon | Coming soon |
| Apex Shortlist | 88.6% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between A.X K2 and Mellum2-12B-A2.5B-Thinking?

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

- [A.X K2 vs A.X series](/compare/a-x-k2-vs-skt-ax)
- [Mellum2-12B-A2.5B-Thinking vs A.X series](/compare/mellum2-12b-a2-5b-thinking-vs-skt-ax)
- [A.X K2 vs Mellum2-12B-A2.5B-Instruct](/compare/a-x-k2-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)

## Explore More

- [A.X K2 profile](/models/a-x-k2)
- [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)