# Claude 3.5 Sonnet vs Step 3.5 Flash

> Step 3.5 Flash is the stronger model overall, scoring 41.7 to 34.4 on the Noometry Index.

- Canonical page: https://noometry.com/compare/claude-3-5-sonnet-vs-step-3-5-flash
- Last updated: 2026-10-10
- Shared benchmarks: 17

## Summary

- They share 17 benchmarks with published results for both. Claude 3.5 Sonnet scores higher in 1 category and Step 3.5 Flash in 7 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in math, where Step 3.5 Flash leads 40.6 to 18.0.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 34.4 | 41.7 |
| Rank | 225 | 116 |
| Context | — | 256K |
| Input $/M | — | $0.10 |
| Output $/M | — | $0.30 |
| Weights | Proprietary | Open |

## Coding

- Claude 3.5 Sonnet: 39.5 (#145)
- Step 3.5 Flash: 41.7 (#106)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1343 | 1436 |
| Aider Polyglot | 51.6% | — |
| GSO | 4.6% | — |
| WeirdML | 40% | — |
| BigCodeBench Instruct | 46.8% | — |
| LiveBench Coding | 67.1% | — |
| BigCodeBench Complete | 58.6% | — |
| CadEval | 48% | — |
| HumanEval+ | 81.7% | — |
| MBPP+ | 74.3% | — |

## Agentic & Tool Use

- Claude 3.5 Sonnet: 32.1 (#61)
- Step 3.5 Flash: —

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| TheAgentCompany | 24% | — |
| Cybench | 17.5% | — |
| BALROG | 32.6% | — |
| METR Time Horizons | 45.2% | — |

## Reasoning

- Claude 3.5 Sonnet: 22.5 (#176)
- Step 3.5 Flash: 21.2 (#202)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1305 | 1411 |
| SimpleBench | 41.4% | — |
| NYT Connections (extended) | — | 28.4% |
| EnigmaEval | 0.9% | — |
| LiveBench Reasoning | 56.7% | — |
| DTBench | 67.8% | — |
| LiveBench Data Analysis | 55% | — |
| Epoch Capabilities Index | 133.55 | — |
| ForecastBench | 60.7 | — |
| LiveBench | 59% | — |

## Math

- Claude 3.5 Sonnet: 18.0 (#282)
- Step 3.5 Flash: 40.6 (#77)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1306 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 8.5% | — |
| Omni-MATH | 27.6% | — |
| LiveBench Math | 52.3% | — |
| MATH Level 5 | 56.9% | — |
| FrontierMath (Feb 2025 set) | 2.1% | — |
| FrontierMath Tier 4 (v1) | 0% | — |

## Knowledge

- Claude 3.5 Sonnet: 28.5 (#236)
- Step 3.5 Flash: 39.0 (#127)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1264 | 1422 |
| GPQA Diamond | 55.3% | — |
| Humanity's Last Exam | 4.1% | — |
| MMLU-Pro | 77.7% | — |
| Confabulations | 19.9% | — |
| GPQA (HELM) | 56.5% | — |
| MMLU | 87.3% | — |

## Multimodal

- Claude 3.5 Sonnet: 26.0 (#115)
- Step 3.5 Flash: —

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1125 | — |
| Video-MME | 60% | — |
| GeoBench | 62% | — |
| VPCT | 33% | — |

## Multilingual

- Claude 3.5 Sonnet: 43.4 (#180)
- Step 3.5 Flash: 50.7 (#115)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1283 | 1386 |
| LMArena Chinese | 1271 | 1448 |
| LMArena French | 1304 | 1421 |
| LMArena German | 1297 | 1404 |
| LMArena Japanese | 1234 | 1353 |
| LMArena Korean | 1200 | 1350 |
| LMArena Russian | 1305 | 1385 |
| LMArena Spanish | 1289 | 1419 |

## Instruction Following

- Claude 3.5 Sonnet: 69.0 (#177)
- Step 3.5 Flash: 73.3 (#119)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1297 | 1385 |
| LiveBench Instruction Following | 69.3% | — |
| IFEval | 85.5% | — |

## Long Context

- Claude 3.5 Sonnet: 39.9 (#162)
- Step 3.5 Flash: 42.8 (#112)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1311 | 1402 |

## Writing & Preference

- Claude 3.5 Sonnet: 53.0 (#159)
- Step 3.5 Flash: 59.0 (#108)

| Benchmark | Claude 3.5 Sonnet | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1298 | 1403 |
| LMArena Creative Writing | 1292 | 1357 |
| LMArena Multi-Turn | 1326 | 1405 |
| Short-Story Creative Writing | 80.3% | — |
| EQ-Bench Creative Writing | 1451 | — |
| WildBench | 79.2% | — |
| LiveBench Language | 53.8% | — |

## FAQ

### Is Claude 3.5 Sonnet better than Step 3.5 Flash?

Step 3.5 Flash is the stronger model overall, scoring 41.7 to 34.4 on the Noometry Index.

### Is Claude 3.5 Sonnet or Step 3.5 Flash better for coding?

Step 3.5 Flash scores higher on coding benchmarks: 41.7 versus 39.5 in the Noometry coding category.

### How many benchmarks do Claude 3.5 Sonnet and Step 3.5 Flash share?

17 benchmarks have published results for both models. Claude 3.5 Sonnet has 60 scored results on Noometry and Step 3.5 Flash has 19.