Model comparison
GPT-5.1-Codex-Max vs Nemotron Ultra 253B
Head-to-head evidence from 11 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.1-Codex-Max #90 (Estimated); Nemotron Ultra 253B #150 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex-Max and Nemotron Ultra 253B share 11 comparable benchmark results. 0 of 8 categories are comparable. 2 results are unique to GPT-5.1-Codex-Max; 0 to Nemotron Ultra 253B.
Updated July 20, 2026- Shared results
- 11
- GPT-5.1-Codex-Max only
- 2
- Nemotron Ultra 253B only
- 0
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex-Max and Nemotron Ultra 253B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 11 shared benchmark results across 5 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-Max is priced at $1.25 input / $10.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for Nemotron Ultra 253B. GPT-5.1-Codex-Max has the larger context window at 400K, compared with 32K for Nemotron Ultra 253B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1-Codex-Max | Nemotron Ultra 253B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-Codex-Max$1.25 input / $10 output | Nemotron Ultra 253B$0 input / $0 output | Nemotron Ultra 253B has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.1-Codex-MaxNot available | Nemotron Ultra 253BNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-Codex-MaxNot available | Nemotron Ultra 253BNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex-Max400K | Nemotron Ultra 253B32K | GPT-5.1-Codex-Max lists the larger context window. |
Benchmark Deep Dive
Agentic1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Nemotron Ultra 253B | Result |
|---|---|---|---|
| τ²-bench resultsSource | 83% | 11.4% | GPT-5.1-Codex-Max leads |
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Nemotron Ultra 253B | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | 9.1% | GPT-5.1-Codex-Max leads |
| AA-GPQA DiamondSource | 86.0% | 72.8% | GPT-5.1-Codex-Max leads |
| AA-HLESource | 23.4% | 8.1% | GPT-5.1-Codex-Max leads |
| AA-Omniscience IndexSource | -6.0% | -45.5% | GPT-5.1-Codex-Max leads |
| AA-Omniscience AccuracySource | 39.2% | 19.9% | GPT-5.1-Codex-Max leads |
| AA-Omniscience Hallucination RateSource | 74.4% | 81.7% | GPT-5.1-Codex-Max leads |
Multimodal1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Nemotron Ultra 253B | Result |
|---|---|---|---|
| AA-MMMU-ProSource | 72.5% | — | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Nemotron Ultra 253B | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | 38.2% | GPT-5.1-Codex-Max leads |
Frequently Asked Questions (3)
Can I compare GPT-5.1-Codex-Max and Nemotron Ultra 253B 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.
What data is available for GPT-5.1-Codex-Max and Nemotron Ultra 253B today?
GPT-5.1-Codex-Max: $1.25 input / $10.00 output per 1M tokens Nemotron Ultra 253B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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