# Grok 4 Fast vs Yi-Lightning

> Grok 4 Fast is the stronger model overall, scoring 39.4 to 37.1 on the Noometry Index.

- Canonical page: https://noometry.com/compare/grok-4-fast-vs-yi-lightning
- Last updated: 2026-10-11
- Shared benchmarks: 17

## Summary

- They share 17 benchmarks with published results for both. Grok 4 Fast scores higher in 6 categories and Yi-Lightning in 2 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in long context, where Grok 4 Fast leads 63.2 to 39.4.

## Snapshot

| | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| Provider | xAI | 01.AI |
| Noometry Index | 39.4 | 37.1 |
| Rank | 167 | 209 |
| Context | — | — |
| Input $/M | — | — |
| Output $/M | — | — |
| Weights | Proprietary | Proprietary |

## Coding

- Grok 4 Fast: 32.5 (#271)
- Yi-Lightning: 27.4 (#320)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Coding | 1429 | 1312 |
| Aider Polyglot | — | 12.9% |
| LMArena WebDev | 1159 | — |
| WeirdML | 42.9% | — |

## Agentic & Tool Use

- Grok 4 Fast: 29.5 (#86)
- Yi-Lightning: —

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| τ²-bench Banking | 15.7% | — |
| Cybench | 30% | — |
| LMArena Search | 1171 | — |

## Reasoning

- Grok 4 Fast: 22.2 (#201)
- Yi-Lightning: 25.9 (#139)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Hard Prompts | 1412 | 1302 |
| ARC-AGI-2 | 5.3% | — |
| Kagi LLM Benchmark | 66.1% | — |
| ARC-AGI-1 | 48.5% | — |
| DTBench | 82.7% | — |
| Epoch Capabilities Index | 144.2 | — |
| ForecastBench | 60.5 | — |

## Math

- Grok 4 Fast: 38.9 (#123)
- Yi-Lightning: 36.2 (#172)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Math | 1419 | 1300 |

## Knowledge

- Grok 4 Fast: 32.0 (#214)
- Yi-Lightning: 35.4 (#185)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Expert | 1411 | 1286 |
| Vectara Hallucination Rate | 19.7% | — |

## Multilingual

- Grok 4 Fast: 51.3 (#111)
- Yi-Lightning: 42.2 (#196)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Non-English | 1396 | 1269 |
| LMArena Chinese | 1457 | 1320 |
| LMArena French | 1431 | 1305 |
| LMArena German | 1383 | 1267 |
| LMArena Japanese | 1352 | 1228 |
| LMArena Korean | 1357 | 1192 |
| LMArena Russian | 1389 | 1255 |
| LMArena Spanish | 1415 | 1315 |

## Instruction Following

- Grok 4 Fast: 73.2 (#121)
- Yi-Lightning: 67.4 (#196)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Instruction Following | 1387 | 1278 |

## Long Context

- Grok 4 Fast: 63.2 (#3)
- Yi-Lightning: 39.4 (#181)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Longer Query | 1415 | 1297 |
| Fiction.LiveBench | 94.4% | — |

## Writing & Preference

- Grok 4 Fast: 60.0 (#102)
- Yi-Lightning: 50.2 (#184)

| Benchmark | Grok 4 Fast | Yi-Lightning |
|---|---|---|
| LMArena Text | 1407 | 1302 |
| LMArena Creative Writing | 1387 | 1280 |
| LMArena Multi-Turn | 1414 | 1311 |

## FAQ

### Is Grok 4 Fast better than Yi-Lightning?

Grok 4 Fast is the stronger model overall, scoring 39.4 to 37.1 on the Noometry Index.

### Is Grok 4 Fast or Yi-Lightning better for coding?

Grok 4 Fast scores higher on coding benchmarks: 32.5 versus 27.4 in the Noometry coding category.

### How many benchmarks do Grok 4 Fast and Yi-Lightning share?

17 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Yi-Lightning has 18.