Model comparison
GPT-5.4 vs Mellum2-12B-A2.5B-Thinking
Head-to-head evidence from 2 shared benchmark results across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.4 #8 (Supported); Mellum2-12B-A2.5B-Thinking unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.4 and Mellum2-12B-A2.5B-Thinking share 2 comparable benchmark results. 1 of 8 categories are comparable. 50 results are unique to GPT-5.4; 3 to Mellum2-12B-A2.5B-Thinking.
Updated July 23, 2026- Shared results
- 2
- GPT-5.4 only
- 50
- Mellum2-12B-A2.5B-Thinking only
- 3
- Comparable categories
- 1 / 8
Treat this as a split decision. GPT-5.4 makes more sense if you need the larger 1.05M context window; Mellum2-12B-A2.5B-Thinking is the better fit if its strengths line up with your actual workload.
Confidence note. This is a partial-evidence comparison with 2 shared benchmark results across 1 evidence category; 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 and Mellum2-12B-A2.5B-Thinking 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 gives you the larger context window at 1.05M, compared with 128K for Mellum2-12B-A2.5B-Thinking.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.4 | Δ | Mellum2-12B-A2.5B-Thinking |
|---|---|---|---|
| Knowledge | GPT-5.457.6 | MarginTie | Mellum2-12B-A2.5B-Thinking57.6 |
| Agentic | GPT-5.477.2 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Coding | GPT-5.457.7 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Math | GPT-5.442.5 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Multimodal | GPT-5.473.2 | MarginNo overlap | Mellum2-12B-A2.5B-ThinkingNot measured |
| Inst. Following | GPT-5.4Not measured | MarginNo overlap | Mellum2-12B-A2.5B-Thinking76.5 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
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- Source ↗
GPQA
KnowledgeA 92.8%B 57.6%Winner: GPT-5.4Δ 35.2GPQA: GPT-5.4 scored 92.8%; Mellum2-12B-A2.5B-Thinking scored 57.6%. GPT-5.4 wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.4 | Mellum2-12B-A2.5B-Thinking | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.4$2.5 input / $15 output | Mellum2-12B-A2.5B-ThinkingNot available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.474 tok/s | Mellum2-12B-A2.5B-ThinkingNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.4151.79 s | Mellum2-12B-A2.5B-ThinkingNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.41.05M | Mellum2-12B-A2.5B-Thinking128K | GPT-5.4 lists the larger context window. |
Benchmark Deep Dive
Agentic18 benchmarks
| Benchmark | GPT-5.4 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 75.1% | — | Not comparable |
| CyberGymSource | 79.0% | — | Not comparable |
| BrowseCompSource | 82.7% | — | Not comparable |
| OSWorld-VerifiedSource | 75% | — | Not comparable |
| MCP AtlasSource | 70.6% | — | Not comparable |
| ToolathlonSource | 54.6% | — | Not comparable |
| τ²-bench resultsSource | 87.1% | — | Not comparable |
| Claw-EvalSource | 60.3% | — | Not comparable |
| DeepSearchQASource | 73.6% | — | Not comparable |
| AA Agentic IndexSource | 41.1% | — | Not comparable |
| APEX-Agents-AASource | 33.3% | — | Not comparable |
| GDPval-AASource | 44.7% | — | Not comparable |
| GDPval-AASource | 1395 | — | Not comparable |
| Gert LabsSource | 64.89% | — | Not comparable |
| ResearchClawBenchSource | 15.3% | — | Not comparable |
| JobBenchSource | 38.9% | — | Not comparable |
| ExploitGymSource | 6.0% | — | Not comparable |
| BFCL v4Source | — | 45.6% | Not comparable |
Coding6 benchmarks
Reasoning2 benchmarks
KnowledgeTie14 benchmarks
| Benchmark | GPT-5.4 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| GPQASource | 92.8% | 57.6% | GPT-5.4 leads |
| HLESource | 52.1% | — | Not comparable |
| HLE w/o toolsSource | 39.8% | — | Not comparable |
| GPQA-DSource | 92.8% | 57.6% | GPT-5.4 leads |
| HealthBench HardSource | 40.1% | — | Not comparable |
| MedXpertQA (Text)Source | 59.6% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | 51.4% | — | Not comparable |
| AA-GPQA DiamondSource | 92.0% | — | Not comparable |
| AA-HLESource | 41.6% | — | Not comparable |
| AA-Omniscience IndexSource | 5.7% | — | Not comparable |
| AA-Omniscience AccuracySource | 50.0% | — | Not comparable |
| AA-Omniscience Hallucination RateSource | 88.6% | — | Not comparable |
| HealthBench ProfessionalSource | 48.1% | — | Not comparable |
| MMLU-ReduxSource | — | 86.2% | Not comparable |
Math2 benchmarks
Multimodal11 benchmarks
| Benchmark | GPT-5.4 | Mellum2-12B-A2.5B-Thinking | Result |
|---|---|---|---|
| MMMU-ProSource | 81.2% | — | Not comparable |
| OfficeQA ProSource | 53.2% | — | Not comparable |
| MMMU-Pro w/ PythonSource | 82.1% | — | Not comparable |
| CharXivSource | 82.8% | — | Not comparable |
| ERQASource | 65.4% | — | Not comparable |
| SimpleVQASource | 61.1% | — | Not comparable |
| ScreenSpot ProSource | 85.4% | — | Not comparable |
| ZeroBenchSource | 41.0% | — | Not comparable |
| MedXpertQA (MM)Source | 77.1% | — | Not comparable |
| AA-MMMU-ProSource | 78.4% | — | Not comparable |
| Design Arena WebsiteSource | 1250 | — | Not comparable |
Frequently Asked Questions (2)
Which is better, GPT-5.4 or Mellum2-12B-A2.5B-Thinking?
GPT-5.4 and Mellum2-12B-A2.5B-Thinking 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 or Mellum2-12B-A2.5B-Thinking?
GPT-5.4 and Mellum2-12B-A2.5B-Thinking are effectively tied for knowledge tasks here, both landing at 57.6 on average.
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