# GPT-5.1-Codex vs Nemotron 3.5 Lightning

> Nemotron 3.5 Lightning is the stronger model overall, scoring 39.3 to 38.2 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-nemotron-3-5-lightning
- Last updated: 2026-10-10
- Shared benchmarks: 0

## Summary

- The widest gap is in math, where Nemotron 3.5 Lightning leads 34.7 to 29.3.
- Nemotron 3.5 Lightning is cheaper at $0.06 / $0.16 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 262K.
- Nemotron 3.5 Lightning has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| Provider | OpenAI | NVIDIA |
| Noometry Index | 38.2 | 39.3 |
| Rank | 178 | 156 |
| Context | 400K | 262K |
| Input $/M | $1.25 | $0.06 |
| Output $/M | $10 | $0.16 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- Nemotron 3.5 Lightning: 39.6 (#143)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| LMArena Coding | — | 1370 |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- Nemotron 3.5 Lightning: —

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- Nemotron 3.5 Lightning: 25.7 (#128)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Hard Prompts | — | 1335 |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- Nemotron 3.5 Lightning: 34.7 (#156)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| ProofBench | 9% | — |
| LMArena Math | — | 1355 |

## Knowledge

- GPT-5.1-Codex: —
- Nemotron 3.5 Lightning: 36.9 (#154)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Expert | — | 1354 |

## Multilingual

- GPT-5.1-Codex: —
- Nemotron 3.5 Lightning: 44.0 (#175)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Non-English | — | 1292 |
| LMArena Chinese | — | 1356 |
| LMArena French | — | 1369 |
| LMArena German | — | 1280 |
| LMArena Japanese | — | 1213 |
| LMArena Korean | — | 1233 |
| LMArena Russian | — | 1257 |
| LMArena Spanish | — | 1321 |

## Instruction Following

- GPT-5.1-Codex: —
- Nemotron 3.5 Lightning: 69.8 (#166)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Instruction Following | — | 1317 |

## Long Context

- GPT-5.1-Codex: —
- Nemotron 3.5 Lightning: 39.9 (#160)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Longer Query | — | 1312 |

## Writing & Preference

- GPT-5.1-Codex: —
- Nemotron 3.5 Lightning: 48.5 (#198)

| Benchmark | GPT-5.1-Codex | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Text | — | 1324 |
| LMArena Creative Writing | — | 1254 |
| EQ-Bench Creative Writing | — | 1280 |
| LMArena Multi-Turn | — | 1327 |

## FAQ

### Is GPT-5.1-Codex better than Nemotron 3.5 Lightning?

Nemotron 3.5 Lightning is the stronger model overall, scoring 39.3 to 38.2 on the Noometry Index.

### Which is cheaper, GPT-5.1-Codex or Nemotron 3.5 Lightning?

Nemotron 3.5 Lightning is cheaper. It lists at $0.06 per million input tokens and $0.16 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.

### Is GPT-5.1-Codex or Nemotron 3.5 Lightning better for coding?

GPT-5.1-Codex scores higher on coding benchmarks: 41.7 versus 39.6 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.1-Codex does, with 400K tokens against 262K.

### How many benchmarks do GPT-5.1-Codex and Nemotron 3.5 Lightning share?

0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Nemotron 3.5 Lightning has 18.