# Mellum2.1-12B-A2.5B-Thinking vs o1

> Side-by-side benchmark comparison for Mellum2.1-12B-A2.5B-Thinking and o1 across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/mellum2-1-12b-a2-5b-thinking-vs-o1
- Last updated: October 8, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: Mellum2.1-12B-A2.5B-Thinking and o1 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.
- Mellum2.1-12B-A2.5B-Thinking has the lower published output-token price.
- o1 has the larger published context window at 200K.

## Model Snapshot

| Property | Mellum2.1-12B-A2.5B-Thinking | o1 |
|----------|----------|----------|
| Creator | JetBrains | OpenAI |
| Type | Open Weight | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 128K | 200K |
| Independent public score (not head-to-head) | null | 39.09 |
| Benchmarks Covered | 7 | 4 |
| Pricing (input/output) | $0.00 / $0.00 | $15.00 / $60.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon
- o1 public-lane score: Coming soon

| Benchmark | Mellum2.1-12B-A2.5B-Thinking | o1 | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.1 | 17.4% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon
- o1 public-lane score: 29 (Estimated · #96/146)

| Benchmark | Mellum2.1-12B-A2.5B-Thinking | o1 | Winner |
|-----------|-----------|-----------|--------|
| LiveCodeBench v6 | 82.0% | Coming soon | Coming soon |
| SWE-bench Verified | 47% | Coming soon | Coming soon |
| SWE-bench Pro | 28% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon
- o1 public-lane score: 67 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Insufficient shared evidence
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon
- o1 public-lane score: 40.9 (Supported · #103/174)

| Benchmark | Mellum2.1-12B-A2.5B-Thinking | o1 | Winner |
|-----------|-----------|-----------|--------|
| MMLU-Redux | 87.8% | Coming soon | Coming soon |
| GPQA-D | 64.6% | Coming soon | Coming soon |
| MMLU | Coming soon | 91.8% | Coming soon |
| GPQA | Coming soon | 75.7% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon
- o1 public-lane score: 84.5 (#40/125)

| Benchmark | Mellum2.1-12B-A2.5B-Thinking | o1 | Winner |
|-----------|-----------|-----------|--------|
| IFEval | 90.6% | 92.2% | o1 |

### Mathematics

- Winner: Insufficient shared evidence
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon
- o1 public-lane score: 32.5 (Unranked · 1 rankable row)

| Benchmark | Mellum2.1-12B-A2.5B-Thinking | o1 | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | Coming soon | 9.310% | Coming soon |

## FAQ

### Is there enough evidence to pick between Mellum2.1-12B-A2.5B-Thinking and o1?

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

- [Mellum2.1-12B-A2.5B-Thinking vs o1-preview](/compare/mellum2-1-12b-a2-5b-thinking-vs-o1-preview)
- [o1 vs o1-preview](/compare/o1-vs-o1-preview)
- [Mellum2.1-12B-A2.5B-Thinking vs o1-pro](/compare/mellum2-1-12b-a2-5b-thinking-vs-o1-pro)
- [o1 vs o1-pro](/compare/o1-vs-o1-pro)

## Explore More

- [Mellum2.1-12B-A2.5B-Thinking profile](/models/mellum2-1-12b-a2-5b-thinking)
- [o1 profile](/models/o1)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)