# GPT-5.2 vs Mellum2-12B-A2.5B-Instruct

> Side-by-side benchmark comparison for GPT-5.2 and Mellum2-12B-A2.5B-Instruct across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-2-vs-mellum2-12b-a2-5b-instruct
- 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: GPT-5.2 and Mellum2-12B-A2.5B-Instruct 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.
- GPT-5.2 has the larger published context window at 400K.

## Model Snapshot

| Property | GPT-5.2 | Mellum2-12B-A2.5B-Instruct |
|----------|----------|----------|
| Creator | OpenAI | JetBrains |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Non-Reasoning |
| Context | 400K | 128K |
| Independent public score (not head-to-head) | 65.45 | null |
| Benchmarks Covered | 15 | 6 |
| Pricing (input/output) | $1.75 / $14.00 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 43 (Supported · #108/151)
- Mellum2-12B-A2.5B-Instruct public-lane score: 47.8 (Estimated · #82/151)

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| BrowseComp | 65.8% | Coming soon | Coming soon |
| OSWorld-Verified | 47.3% | Coming soon | Coming soon |
| Gert Labs | 46.54% | Coming soon | Coming soon |
| JobBench | 34.3% | Coming soon | Coming soon |
| BFCL v4 | Coming soon | 44.2% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 47.3 (Supported · #91/183)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 80% | Coming soon | Coming soon |
| SWE-bench Pro | 55.6% | Coming soon | Coming soon |
| Vibe Code Bench | 53.50% | Coming soon | Coming soon |
| LiveCodeBench v6 | Coming soon | 37.2% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 66.3 (#23/48)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | 79.5% | Coming soon | Coming soon |
| MathVision | 83.0% | Coming soon | Coming soon |
| CharXiv | 82.1% | Coming soon | Coming soon |
| V* | 75.9% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 53.8 (Unranked · 3 rankable rows)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-2 | 52.9% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 62 (Supported · #30/181)
- Mellum2-12B-A2.5B-Instruct public-lane score: 48.1 (Estimated · #103/181)

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 92.4% | 40.9% | GPT-5.2 |
| MMLU-Redux | Coming soon | 78.1% | Coming soon |
| GPQA-D | Coming soon | 40.9% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 92.3 (#14/120)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 75.8% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.2 public-lane score: 57.5 (Unranked · 2 rankable rows)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.2 | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 40.700% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 18.800% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-5.2 and Mellum2-12B-A2.5B-Instruct?

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

- [GPT-5.2 vs GPT-5.2 Pro](/compare/gpt-5-2-vs-gpt-5-2-pro)
- [Mellum2-12B-A2.5B-Instruct vs GPT-5.2 Pro](/compare/gpt-5-2-pro-vs-mellum2-12b-a2-5b-instruct)
- [GPT-5.2 vs GPT-5.2 Instant](/compare/gpt-5-2-vs-gpt-5-2-instant)
- [Mellum2-12B-A2.5B-Instruct vs GPT-5.2 Instant](/compare/gpt-5-2-instant-vs-mellum2-12b-a2-5b-instruct)

## Explore More

- [GPT-5.2 profile](/models/gpt-5-2)
- [Mellum2-12B-A2.5B-Instruct profile](/models/mellum2-12b-a2-5b-instruct)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)