Model comparison
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.
Last verified . 17 shared benchmarks.
StepFunSummary
- 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.
Side by side
| o4-mini | Step 3.5 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 41.6 | 42.3 |
| Released | 2025-04-16 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 200K | 256K |
| Max output | 100K | 256K |
| Input $ / M tokens | $1.10 | $0.10 |
| Output $ / M tokens | $4.40 | $0.30 |
| Results tracked | 60 | 19 |
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Category by category
Coding Step 3.5 Flash leads
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 Not comparable
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 leads
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 Step 3.5 Flash leads
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 leads
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 Not comparable
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 Step 3.5 Flash leads
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 leads
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 leads
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 Step 3.5 Flash leads
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% | — |
Frequently asked questions
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.