# Claude Opus 4 vs Step 3.5 Flash

> Claude Opus 4 and Step 3.5 Flash score almost the same on the Noometry Index (43.1 vs 42.3), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/claude-opus-4-vs-step-3-5-flash
- Last updated: 2026-10-11
- Shared benchmarks: 17

## Summary

- They share 17 benchmarks with published results for both. Claude Opus 4 scores higher in 5 categories and Step 3.5 Flash in 3 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Opus 4 leads 27.3 to 22.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $15 / $75 for Claude Opus 4.
- Step 3.5 Flash accepts more context: 256K tokens versus 200K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.

## Snapshot

| | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 43.1 | 42.3 |
| Rank | 100 | 116 |
| Context | 200K | 256K |
| Input $/M | $15 | $0.10 |
| Output $/M | $75 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- Claude Opus 4: 47.2 (#62)
- Step 3.5 Flash: 42.4 (#105)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1442 | 1436 |
| SWE-bench Verified | 70.7% | — |
| SWE-bench Verified (bash only) | 67.6% | — |
| Aider Polyglot | 72% | — |
| GSO | 6.9% | — |
| WeirdML | 43.7% | — |
| AlgoTune | 1.33 | — |

## Agentic & Tool Use

- Claude Opus 4: 34.8 (#42)
- Step 3.5 Flash: —

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| Cybench | 38% | — |
| DeepResearch Bench | 46.8% | — |
| LMArena Search | 1127 | — |
| METR Time Horizons | 63.9% | — |

## Reasoning

- Claude Opus 4: 27.3 (#121)
- Step 3.5 Flash: 22.2 (#202)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1411 |
| ARC-AGI-2 | 8.6% | — |
| SimpleBench | 58.8% | — |
| Kagi LLM Benchmark | 74.3% | — |
| NYT Connections (extended) | — | 28.4% |
| ARC-AGI-1 | 35.7% | — |
| CritPt | 0.3% | — |
| EnigmaEval | 5.6% | — |
| DTBench | 81.6% | — |
| LMCA | 37.4% | — |
| Epoch Capabilities Index | 142.67 | — |
| ForecastBench | 61.1 | — |

## Math

- Claude Opus 4: 42.0 (#86)
- Step 3.5 Flash: 42.6 (#84)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1390 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 64.4% | — |
| Omni-MATH | 61.6% | — |
| MATH Level 5 | 85% | — |
| FrontierMath (Feb 2025 set) | 4.5% | — |
| FrontierMath Tier 4 (v1) | 4.2% | — |

## Knowledge

- Claude Opus 4: 44.0 (#88)
- Step 3.5 Flash: 39.6 (#132)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1386 | 1421 |
| GPQA Diamond | 76.3% | — |
| Humanity's Last Exam | 10.7% | — |
| MMLU-Pro | 87.5% | — |
| Confabulations | 15.9% | — |
| Vectara Hallucination Rate | 12% | — |
| GPQA (HELM) | 70.8% | — |

## Multimodal

- Claude Opus 4: 31.5 (#106)
- Step 3.5 Flash: —

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1192 | — |
| GeoBench | 49% | — |
| VPCT | 38% | — |

## Multilingual

- Claude Opus 4: 48.8 (#138)
- Step 3.5 Flash: 50.5 (#119)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1362 | 1385 |
| LMArena Chinese | 1386 | 1447 |
| LMArena French | 1372 | 1421 |
| LMArena German | 1391 | 1405 |
| LMArena Japanese | 1331 | 1354 |
| LMArena Korean | 1321 | 1352 |
| LMArena Russian | 1392 | 1385 |
| LMArena Spanish | 1389 | 1419 |

## Instruction Following

- Claude Opus 4: 77.1 (#28)
- Step 3.5 Flash: 73.1 (#124)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1406 | 1385 |
| IFEval | 91.8% | — |

## Long Context

- Claude Opus 4: 39.6 (#172)
- Step 3.5 Flash: 42.8 (#117)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1422 | 1402 |
| Fiction.LiveBench | 61.1% | — |

## Writing & Preference

- Claude Opus 4: 61.2 (#89)
- Step 3.5 Flash: 58.8 (#113)

| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1377 | 1403 |
| LMArena Creative Writing | 1387 | 1357 |
| LMArena Multi-Turn | 1396 | 1405 |
| Short-Story Creative Writing | 83.6% | — |
| EQ-Bench Creative Writing | 1580 | — |
| WildBench | 85.2% | — |

## FAQ

### Is Claude Opus 4 better than Step 3.5 Flash?

Claude Opus 4 and Step 3.5 Flash score almost the same on the Noometry Index (43.1 vs 42.3), so choose on price, context window or the category you care about most.

### Which is cheaper, Claude Opus 4 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; Claude Opus 4 lists at $15 and $75.

### Is Claude Opus 4 or Step 3.5 Flash better for coding?

Claude Opus 4 scores higher on coding benchmarks: 47.2 versus 42.4 in the Noometry coding category.

### Which has the bigger context window?

Step 3.5 Flash does, with 256K tokens against 200K.

### How many benchmarks do Claude Opus 4 and Step 3.5 Flash share?

17 benchmarks have published results for both models. Claude Opus 4 has 56 scored results on Noometry and Step 3.5 Flash has 19.