# Grok 4.1 Fast vs Step 3.5 Flash

> Grok 4.1 Fast and Step 3.5 Flash score almost the same on the Noometry Index (40.9 vs 41.7), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/grok-4-1-fast-vs-step-3-5-flash
- Last updated: 2026-10-10
- Shared benchmarks: 19

## Summary

- They share 19 benchmarks with published results for both. Grok 4.1 Fast scores higher in 2 categories and Step 3.5 Flash in 6 categories; 5 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Grok 4.1 Fast leads 42.3 to 21.2.
- The biggest single-benchmark swing is NYT Connections (extended): 87.4% for Grok 4.1 Fast and 28.4% for Step 3.5 Flash.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $0.20 / $0.50 for Grok 4.1 Fast.
- Step 3.5 Flash accepts more context: 256K tokens versus 128K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| Provider | xAI | StepFun |
| Noometry Index | 40.9 | 41.7 |
| Rank | 131 | 116 |
| Context | 128K | 256K |
| Input $/M | $0.20 | $0.10 |
| Output $/M | $0.50 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- Grok 4.1 Fast: 33.8 (#236)
- Step 3.5 Flash: 41.7 (#106)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1411 | 1436 |
| LMArena WebDev | 1241 | — |
| ALE-Bench | 394.93 | — |

## Agentic & Tool Use

- Grok 4.1 Fast: 36.1 (#35)
- Step 3.5 Flash: —

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| Berkeley Function Calling Leaderboard | 69.6% | — |
| τ²-bench Banking | 13.1% | — |
| LMArena Search | 1171 | — |
| Vending-Bench 2 | 1,107 | — |

## Reasoning

- Grok 4.1 Fast: 42.3 (#45)
- Step 3.5 Flash: 21.2 (#202)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| NYT Connections (extended) | 87.4% | 28.4% |
| LMArena Hard Prompts | 1407 | 1411 |
| SimpleBench | 56% | — |
| DTBench | 87.7% | — |
| ForecastBench | 61 | — |

## Math

- Grok 4.1 Fast: 30.9 (#201)
- Step 3.5 Flash: 40.6 (#77)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| MathArena Final-Answer Competitions | 60.9% | 66.8% |
| LMArena Math | 1408 | 1408 |
| ProofBench | 4% | — |

## Knowledge

- Grok 4.1 Fast: 32.6 (#203)
- Step 3.5 Flash: 39.0 (#127)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1398 | 1422 |
| Vectara Hallucination Rate | 17.8% | — |

## Multimodal

- Grok 4.1 Fast: 36.3 (#71)
- Step 3.5 Flash: —

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1201 | — |

## Multilingual

- Grok 4.1 Fast: 51.1 (#110)
- Step 3.5 Flash: 50.7 (#115)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1391 | 1386 |
| LMArena Chinese | 1441 | 1448 |
| LMArena French | 1416 | 1421 |
| LMArena German | 1404 | 1404 |
| LMArena Japanese | 1347 | 1353 |
| LMArena Korean | 1361 | 1350 |
| LMArena Russian | 1387 | 1385 |
| LMArena Spanish | 1411 | 1419 |

## Instruction Following

- Grok 4.1 Fast: 72.8 (#127)
- Step 3.5 Flash: 73.3 (#119)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1376 | 1385 |

## Long Context

- Grok 4.1 Fast: 42.4 (#121)
- Step 3.5 Flash: 42.8 (#112)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1390 | 1402 |

## Writing & Preference

- Grok 4.1 Fast: 57.4 (#126)
- Step 3.5 Flash: 59.0 (#108)

| Benchmark | Grok 4.1 Fast | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1408 | 1403 |
| LMArena Creative Writing | 1394 | 1357 |
| LMArena Multi-Turn | 1389 | 1405 |
| EQ-Bench Creative Writing | 1327 | — |

## FAQ

### Is Grok 4.1 Fast better than Step 3.5 Flash?

Grok 4.1 Fast and Step 3.5 Flash score almost the same on the Noometry Index (40.9 vs 41.7), so choose on price, context window or the category you care about most.

### Which is cheaper, Grok 4.1 Fast or Step 3.5 Flash?

Step 3.5 Flash is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; Grok 4.1 Fast lists at $0.20 and $0.50.

### Is Grok 4.1 Fast or Step 3.5 Flash better for coding?

Step 3.5 Flash scores higher on coding benchmarks: 41.7 versus 33.8 in the Noometry coding category.

### Which has the bigger context window?

Step 3.5 Flash does, with 256K tokens against 128K.

### How many benchmarks do Grok 4.1 Fast and Step 3.5 Flash share?

19 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Step 3.5 Flash has 19.