Model comparison
Solar Pro4 vs Step 3.5 Flash
Solar Pro4 and Step 3.5 Flash score almost the same on the Noometry Index (42.1 vs 42.3), so choose on price, context window or the category you care about most.
Last verified . 17 shared benchmarks.
Upstage
StepFunSummary
- They share 17 benchmarks with published results for both. Solar Pro4 scores higher in 2 categories and Step 3.5 Flash in 6 categories; 5 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Solar Pro4 leads 28.5 to 22.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $0.30 / $1.20 for Solar Pro4.
- Solar Pro4 accepts more context: 524K tokens versus 256K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.
Side by side
| Solar Pro4 | Step 3.5 Flash | |
|---|---|---|
| Provider | Upstage | StepFun |
| Noometry Index | 42.1 | 42.3 |
| Released | 2026-08-06 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 524K | 256K |
| Max output | 131K | 256K |
| Input $ / M tokens | $0.30 | $0.10 |
| Output $ / M tokens | $1.20 | $0.30 |
| Results tracked | 18 | 19 |
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Category by category
Coding Step 3.5 Flash leads
Solar Pro4: 40.1 (#149), Step 3.5 Flash: 42.4 (#105)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1437 | 1436 |
| LMArena WebDev | 1371 | — |
Reasoning Solar Pro4 leads
Solar Pro4: 28.5 (#104), Step 3.5 Flash: 22.2 (#202)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1411 |
| NYT Connections (extended) | — | 28.4% |
Math Step 3.5 Flash leads
Solar Pro4: 38.8 (#128), Step 3.5 Flash: 42.6 (#84)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1416 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |
Knowledge Too close to call
Solar Pro4: 39.8 (#129), Step 3.5 Flash: 39.6 (#132)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1427 | 1421 |
Multilingual Step 3.5 Flash leads
Solar Pro4: 48.7 (#139), Step 3.5 Flash: 50.5 (#119)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1361 | 1385 |
| LMArena Chinese | 1415 | 1447 |
| LMArena French | 1397 | 1421 |
| LMArena German | 1364 | 1405 |
| LMArena Japanese | 1309 | 1354 |
| LMArena Korean | 1382 | 1352 |
| LMArena Russian | 1360 | 1385 |
| LMArena Spanish | 1401 | 1419 |
Instruction Following Too close to call
Solar Pro4: 72.7 (#132), Step 3.5 Flash: 73.1 (#124)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1377 | 1385 |
Long Context Too close to call
Solar Pro4: 42.1 (#130), Step 3.5 Flash: 42.8 (#117)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1381 | 1402 |
Writing & Preference Step 3.5 Flash leads
Solar Pro4: 56.5 (#138), Step 3.5 Flash: 58.8 (#113)
| Benchmark | Solar Pro4 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1386 | 1403 |
| LMArena Creative Writing | 1316 | 1357 |
| LMArena Multi-Turn | 1385 | 1405 |
Frequently asked questions
Is Solar Pro4 better than Step 3.5 Flash?
Solar Pro4 and Step 3.5 Flash score almost the same on the Noometry Index (42.1 vs 42.3), so choose on price, context window or the category you care about most.
Which is cheaper, Solar Pro4 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; Solar Pro4 lists at $0.30 and $1.20.
Is Solar Pro4 or Step 3.5 Flash better for coding?
Step 3.5 Flash scores higher on coding benchmarks: 42.4 versus 40.1 in the Noometry coding category.
Which has the bigger context window?
Solar Pro4 does, with 524K tokens against 256K.
How many benchmarks do Solar Pro4 and Step 3.5 Flash share?
17 benchmarks have published results for both models. Solar Pro4 has 18 scored results on Noometry and Step 3.5 Flash has 19.