Model comparison
GPT-5.4 Pro vs Mellum2-12B-A2.5B-Instruct
Head-to-head evidence from 0 shared benchmark results across 0 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.4 Pro #44 (Estimated); Mellum2-12B-A2.5B-Instruct unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.4 Pro and Mellum2-12B-A2.5B-Instruct share 0 comparable benchmark results. 1 of 8 categories are comparable. 12 results are unique to GPT-5.4 Pro; 5 to Mellum2-12B-A2.5B-Instruct.
Updated July 23, 2026- Shared results
- 0
- GPT-5.4 Pro only
- 12
- Mellum2-12B-A2.5B-Instruct only
- 5
- Comparable categories
- 1 / 8
Treat this as a split decision. GPT-5.4 Pro makes more sense if knowledge is the priority or you need the larger 1.05M context window; Mellum2-12B-A2.5B-Instruct is the better fit if you would rather avoid the extra latency and token burn of a reasoning model.
Confidence note. This is a partial-evidence comparison with 0 shared benchmark results across 0 evidence categories; 1 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
GPT-5.4 Pro and Mellum2-12B-A2.5B-Instruct finish on the same BenchAlign overall score, so this is less about a single winner and more about where the edge shows up. The BenchAlign headline says tie; the benchmark table is where the real choice happens.
GPT-5.4 Pro is the reasoning model in the pair, while Mellum2-12B-A2.5B-Instruct is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. GPT-5.4 Pro gives you the larger context window at 1.05M, compared with 128K for Mellum2-12B-A2.5B-Instruct.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.4 Pro | Mellum2-12B-A2.5B-Instruct | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.4 Pro$30 input / $180 output | Mellum2-12B-A2.5B-InstructNot available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.4 Pro74 tok/s | Mellum2-12B-A2.5B-InstructNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.4 Pro151.79 s | Mellum2-12B-A2.5B-InstructNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.4 Pro1.05M | Mellum2-12B-A2.5B-Instruct128K | GPT-5.4 Pro lists the larger context window. |
Benchmark Deep Dive
Agentic2 benchmarks
Reasoning2 benchmarks
KnowledgeGPT-5.4 Pro wins7 benchmarks
| Benchmark | GPT-5.4 Pro | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| HLESource | 58.7% | — | Not comparable |
| FrontierScienceSource | 36.7% | — | Not comparable |
| FrontierScience ResearchSource | 36.7% | — | Not comparable |
| HLE w/o toolsSource | 42.7% | — | Not comparable |
| MMLU-ReduxSource | — | 78.1% | Not comparable |
| GPQASource | — | 40.9% | Not comparable |
| GPQA-DSource | — | 40.9% | Not comparable |
Math4 benchmarks
Multimodal1 benchmarks
| Benchmark | GPT-5.4 Pro | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| MMMU-ProSource | 94% | — | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5.4 Pro | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| IFEvalSource | — | 75.8% | Not comparable |
Frequently Asked Questions (2)
Which is better, GPT-5.4 Pro or Mellum2-12B-A2.5B-Instruct?
GPT-5.4 Pro and Mellum2-12B-A2.5B-Instruct are tied on the BenchAlign overall score, so the right pick depends on which category matters most for your use case.
Which is better for knowledge tasks, GPT-5.4 Pro or Mellum2-12B-A2.5B-Instruct?
GPT-5.4 Pro has the edge for knowledge tasks in this comparison, averaging 58.7 versus 40.9. Mellum2-12B-A2.5B-Instruct stays close enough that the answer can still flip depending on your workload.
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