# GPT-5.4 mini vs Mellum2-12B-A2.5B-Instruct

> Side-by-side benchmark comparison for GPT-5.4 mini and Mellum2-12B-A2.5B-Instruct across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-4-mini-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-5.4 mini 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-5.4 mini has the larger published context window at 400K.

## Model Snapshot

| Property | GPT-5.4 mini | 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) | 62.63 | null |
| Benchmarks Covered | 19 | 6 |
| Pricing (input/output) | $0.75 / $4.50 | N/A |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 42.4 (Estimated · #113/151)
- Mellum2-12B-A2.5B-Instruct public-lane score: 47.8 (Estimated · #82/151)

| Benchmark | GPT-5.4 mini | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 60% | Coming soon | Coming soon |
| OSWorld-Verified | 72.1% | Coming soon | Coming soon |
| MCP Atlas | 57.7% | Coming soon | Coming soon |
| Toolathlon | 42.9% | Coming soon | Coming soon |
| τ²-bench results | 93.4% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 54.7% | Coming soon | Coming soon |
| BFCL v4 | Coming soon | 44.2% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 42.9 (Supported · #125/183)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.4 mini | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| Vibe Code Bench | 47.97% | Coming soon | Coming soon |
| FrontierCode 1.1 Main | 27.0% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 81.5% | Coming soon | Coming soon |
| SWE-bench (Vals) | 73.0% | Coming soon | Coming soon |
| LiveCodeBench v6 | Coming soon | 37.2% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 57.2 (#31/48)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.4 mini | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | 76.6% | Coming soon | Coming soon |
| MMMU-Pro w/ Python | 78% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 73.5 (Unranked · 2 rankable rows)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 56.3 (Supported · #53/181)
- Mellum2-12B-A2.5B-Instruct public-lane score: 48.1 (Estimated · #103/181)

| Benchmark | GPT-5.4 mini | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 88% | 40.9% | GPT-5.4 mini |
| HLE | 41.5% | Coming soon | Coming soon |
| HLE w/o tools | 28.2% | Coming soon | Coming soon |
| GPQA Diamond (Vals) | 83.1% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 84.6% | Coming soon | Coming soon |
| MMLU-Redux | Coming soon | 78.1% | Coming soon |
| GPQA-D | Coming soon | 40.9% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 89.6 (#23/120)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.4 mini | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 75.8% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.4 mini public-lane score: 44.5 (Unranked · 2 rankable rows)
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon

| Benchmark | GPT-5.4 mini | Mellum2-12B-A2.5B-Instruct | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 28.280% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 2.080% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-5.4 mini 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-5.4 mini vs GPT-5.4](/compare/gpt-5-4-vs-gpt-5-4-mini)
- [Mellum2-12B-A2.5B-Instruct vs GPT-5.4](/compare/gpt-5-4-vs-mellum2-12b-a2-5b-instruct)
- [GPT-5.4 mini vs GPT-5.4 nano](/compare/gpt-5-4-mini-vs-gpt-5-4-nano)
- [Mellum2-12B-A2.5B-Instruct vs GPT-5.4 nano](/compare/gpt-5-4-nano-vs-mellum2-12b-a2-5b-instruct)

## Explore More

- [GPT-5.4 mini profile](/models/gpt-5-4-mini)
- [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)