Model comparison
o3-pro vs Step 3.5 Flash
o3-pro and Step 3.5 Flash score almost the same on the Noometry Index (42.9 vs 42.3), so choose on price, context window or the category you care about most.
Last verified . 0 shared benchmarks.
StepFunSummary
- The widest gap is in long context, where o3-pro leads 72.2 to 42.8.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $20 / $80 for o3-pro.
- 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
| o3-pro | Step 3.5 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 42.9 | 42.3 |
| Released | 2025-06-10 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 200K | 256K |
| Max output | 100K | 256K |
| Input $ / M tokens | $20 | $0.10 |
| Output $ / M tokens | $80 | $0.30 |
| Results tracked | 12 | 19 |
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Category by category
Coding o3-pro leads
o3-pro: 55.5 (#24), Step 3.5 Flash: 42.4 (#105)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| Aider Polyglot | 84.9% | — |
| WeirdML | 58.2% | — |
| LMArena Coding | — | 1436 |
Reasoning o3-pro leads
o3-pro: 23.8 (#171), Step 3.5 Flash: 22.2 (#202)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| ARC-AGI-2 | 4.9% | — |
| Kagi LLM Benchmark | 72.1% | — |
| NYT Connections (extended) | — | 28.4% |
| ARC-AGI-1 | 59.3% | — |
| LMArena Hard Prompts | — | 1411 |
| DTBench | 86.9% | — |
| LMCA | 38.5% | — |
| Epoch Capabilities Index | 147.42 | — |
Math Not comparable
o3-pro: —, Step 3.5 Flash: 42.6 (#84)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| MathArena Final-Answer Competitions | — | 66.8% |
| LMArena Math | — | 1408 |
Knowledge Step 3.5 Flash leads
o3-pro: 29.5 (#238), Step 3.5 Flash: 39.6 (#132)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| Confabulations | 14.2% | — |
| Vectara Hallucination Rate | 23.3% | — |
| LMArena Expert | — | 1421 |
Multilingual Not comparable
o3-pro: —, Step 3.5 Flash: 50.5 (#119)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | — | 1385 |
| LMArena Chinese | — | 1447 |
| LMArena French | — | 1421 |
| LMArena German | — | 1405 |
| LMArena Japanese | — | 1354 |
| LMArena Korean | — | 1352 |
| LMArena Russian | — | 1385 |
| LMArena Spanish | — | 1419 |
Instruction Following Not comparable
o3-pro: —, Step 3.5 Flash: 73.1 (#124)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | — | 1385 |
Long Context o3-pro leads
o3-pro: 72.2 (#1), Step 3.5 Flash: 42.8 (#117)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| Fiction.LiveBench | 97.2% | — |
| LMArena Longer Query | — | 1402 |
Writing & Preference Step 3.5 Flash leads
o3-pro: 57.1 (#133), Step 3.5 Flash: 58.8 (#113)
| Benchmark | o3-pro | Step 3.5 Flash |
|---|---|---|
| LMArena Text | — | 1403 |
| LMArena Creative Writing | — | 1357 |
| Short-Story Creative Writing | 84.4% | — |
| LMArena Multi-Turn | — | 1405 |
Frequently asked questions
Is o3-pro better than Step 3.5 Flash?
o3-pro and Step 3.5 Flash score almost the same on the Noometry Index (42.9 vs 42.3), so choose on price, context window or the category you care about most.
Which is cheaper, o3-pro 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; o3-pro lists at $20 and $80.
Is o3-pro or Step 3.5 Flash better for coding?
o3-pro scores higher on coding benchmarks: 55.5 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 o3-pro and Step 3.5 Flash share?
0 benchmarks have published results for both models. o3-pro has 12 scored results on Noometry and Step 3.5 Flash has 19.