Model comparison
GPT-5.1-Codex 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-5.1-Codex #99 (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-5.1-Codex and Mellum2-12B-A2.5B-Instruct share 0 comparable benchmark results. 0 of 8 categories are comparable. 16 results are unique to GPT-5.1-Codex; 5 to Mellum2-12B-A2.5B-Instruct.
Updated July 23, 2026- Shared results
- 0
- GPT-5.1-Codex only
- 16
- Mellum2-12B-A2.5B-Instruct only
- 5
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex and Mellum2-12B-A2.5B-Instruct is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 0 shared benchmark results across 0 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
GPT-5.1-Codex has the larger context window at 400K, 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-5.1-Codex | Mellum2-12B-A2.5B-Instruct | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-CodexNot available | Mellum2-12B-A2.5B-InstructNot available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.1-CodexNot available | Mellum2-12B-A2.5B-InstructNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-CodexNot available | Mellum2-12B-A2.5B-InstructNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex400K | Mellum2-12B-A2.5B-Instruct128K | GPT-5.1-Codex lists the larger context window. |
Benchmark Deep Dive
Agentic4 benchmarks
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge9 benchmarks
| Benchmark | GPT-5.1-Codex | Mellum2-12B-A2.5B-Instruct | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | — | Not comparable |
| AA-GPQA DiamondSource | 86.0% | — | Not comparable |
| AA-HLESource | 23.4% | — | Not comparable |
| AA-Omniscience IndexSource | -6.0% | — | Not comparable |
| AA-Omniscience AccuracySource | 39.2% | — | Not comparable |
| AA-Omniscience Hallucination RateSource | 74.4% | — | Not comparable |
| MMLU-ReduxSource | — | 78.1% | Not comparable |
| GPQASource | — | 40.9% | Not comparable |
| GPQA-DSource | — | 40.9% | Not comparable |
Multimodal2 benchmarks
Frequently Asked Questions (2)
Can I compare GPT-5.1-Codex and Mellum2-12B-A2.5B-Instruct on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
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