# o4-mini vs Step 3.5 Flash

> o4-mini and Step 3.5 Flash score almost the same on the Noometry Index (41.6 vs 42.3), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/o4-mini-vs-step-3-5-flash
- Last updated: 2026-10-11
- Shared benchmarks: 17

## Summary

- They share 17 benchmarks with published results for both. o4-mini scores higher in 4 categories and Step 3.5 Flash in 4 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in writing & preference, where Step 3.5 Flash leads 58.8 to 54.0.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $1.10 / $4.40 for o4-mini.
- 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

| | o4-mini | Step 3.5 Flash |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 41.6 | 42.3 |
| Rank | 132 | 116 |
| Context | 200K | 256K |
| Input $/M | $1.10 | $0.10 |
| Output $/M | $4.40 | $0.30 |
| Weights | Proprietary | Open |

## Coding

- o4-mini: 40.9 (#127)
- Step 3.5 Flash: 42.4 (#105)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1368 | 1436 |
| SWE-bench Verified (bash only) | 45% | — |
| Aider Polyglot | 72% | — |
| GSO | 3.6% | — |
| WeirdML | 52.6% | — |
| CadEval | 62% | — |
| ALE-Bench | 826.17 | — |
| AlgoTune | 1.72 | — |

## Agentic & Tool Use

- o4-mini: 32.6 (#61)
- Step 3.5 Flash: —

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| Berkeley Function Calling Leaderboard | 53.2% | — |
| GDPval | 25.3% | — |
| METR Time Horizons | 63.9% | — |

## Reasoning

- o4-mini: 24.6 (#162)
- Step 3.5 Flash: 22.2 (#202)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1351 | 1411 |
| ARC-AGI-2 | 6.1% | — |
| SimpleBench | 38.7% | — |
| Kagi LLM Benchmark | 67.6% | — |
| NYT Connections (extended) | — | 28.4% |
| ARC-AGI-1 | 58.7% | — |
| CritPt | 0.6% | — |
| Chess Puzzles | 26% | — |
| EnigmaEval | 9.2% | — |
| Mystery Game Puzzles | 5% | — |
| DTBench | 77.6% | — |
| LMCA | 26.5% | — |
| Epoch Capabilities Index | 145.64 | — |
| ForecastBench | 61.8 | — |

## Math

- o4-mini: 40.8 (#89)
- Step 3.5 Flash: 42.6 (#84)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1389 | 1408 |
| FrontierMath (Tiers 1-3) | 36.1% | — |
| FrontierMath Tier 4 | 4.9% | — |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 81.7% | — |
| Omni-MATH | 72% | — |
| MATH Level 5 | 97.8% | — |
| FrontierMath (Feb 2025 set) | 24.8% | — |
| FrontierMath Tier 4 (v1) | 6.3% | — |

## Knowledge

- o4-mini: 43.6 (#91)
- Step 3.5 Flash: 39.6 (#132)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1343 | 1421 |
| GPQA Diamond | 79.6% | — |
| Humanity's Last Exam | 18.1% | — |
| SimpleQA Verified | 19.6% | — |
| MMLU-Pro | 82% | — |
| Confabulations | 15.8% | — |
| Vectara Hallucination Rate | 18.6% | — |
| GPQA (HELM) | 73.5% | — |

## Multimodal

- o4-mini: 40.2 (#49)
- Step 3.5 Flash: —

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1194 | — |
| GeoBench | 64% | — |
| VPCT | 57.5% | — |

## Multilingual

- o4-mini: 47.0 (#154)
- Step 3.5 Flash: 50.5 (#119)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1337 | 1385 |
| LMArena Chinese | 1354 | 1447 |
| LMArena French | 1364 | 1421 |
| LMArena German | 1336 | 1405 |
| LMArena Japanese | 1308 | 1354 |
| LMArena Korean | 1312 | 1352 |
| LMArena Russian | 1334 | 1385 |
| LMArena Spanish | 1347 | 1419 |

## Instruction Following

- o4-mini: 75.2 (#68)
- Step 3.5 Flash: 73.1 (#124)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1321 | 1385 |
| IFEval | 92.8% | — |

## Long Context

- o4-mini: 45.5 (#33)
- Step 3.5 Flash: 42.8 (#117)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1315 | 1402 |
| Fiction.LiveBench | 77.8% | — |

## Writing & Preference

- o4-mini: 54.0 (#152)
- Step 3.5 Flash: 58.8 (#113)

| Benchmark | o4-mini | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1353 | 1403 |
| LMArena Creative Writing | 1294 | 1357 |
| LMArena Multi-Turn | 1350 | 1405 |
| Short-Story Creative Writing | 75% | — |
| WildBench | 85.4% | — |

## FAQ

### Is o4-mini better than Step 3.5 Flash?

o4-mini and Step 3.5 Flash score almost the same on the Noometry Index (41.6 vs 42.3), so choose on price, context window or the category you care about most.

### Which is cheaper, o4-mini 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; o4-mini lists at $1.10 and $4.40.

### Is o4-mini or Step 3.5 Flash better for coding?

Step 3.5 Flash scores higher on coding benchmarks: 42.4 versus 40.9 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 o4-mini and Step 3.5 Flash share?

17 benchmarks have published results for both models. o4-mini has 60 scored results on Noometry and Step 3.5 Flash has 19.