Model comparison
GPT-5.5 Instant vs Step 3.5 Flash
GPT-5.5 Instant and Step 3.5 Flash score almost the same on the Noometry Index (42.7 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. GPT-5.5 Instant scores higher in 7 categories and Step 3.5 Flash in 1 category; 7 gaps are clear of the uncertainty.
- The widest gap is in math, where Step 3.5 Flash leads 42.6 to 26.5.
- Step 3.5 Flash has downloadable open weights; the other is API-only.
Side by side
| GPT-5.5 Instant | Step 3.5 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 42.7 | 42.3 |
| Released | 2026-05-05 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | — | 256K |
| Max output | — | 256K |
| Input $ / M tokens | — | $0.10 |
| Output $ / M tokens | — | $0.30 |
| Results tracked | 27 | 19 |
Sponsored placements are available on pages like this one. Advertise on Noometry
Category by category
Coding GPT-5.5 Instant leads
GPT-5.5 Instant: 44.3 (#74), Step 3.5 Flash: 42.4 (#105)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1433 | 1436 |
| SciCode | 48.6% | — |
Reasoning GPT-5.5 Instant leads
GPT-5.5 Instant: 24.9 (#155), Step 3.5 Flash: 22.2 (#202)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1426 | 1411 |
| NYT Connections (extended) | — | 28.4% |
| CritPt | 0% | — |
| Chess Puzzles | 12% | — |
| Epoch Capabilities Index | 142.52 | — |
Math Step 3.5 Flash leads
GPT-5.5 Instant: 26.5 (#259), Step 3.5 Flash: 42.6 (#84)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1420 | 1408 |
| FrontierMath (Tiers 1-3) | 26.3% | — |
| FrontierMath Tier 4 | 2.4% | — |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 68.1% | — |
Knowledge GPT-5.5 Instant leads
GPT-5.5 Instant: 48.9 (#74), Step 3.5 Flash: 39.6 (#132)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1409 | 1421 |
| GPQA Diamond | 82.5% | — |
Multimodal Not comparable
GPT-5.5 Instant: 40.0 (#52), Step 3.5 Flash: —
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1250 | — |
| LMArena Document | 1403 | — |
Multilingual GPT-5.5 Instant leads
GPT-5.5 Instant: 52.8 (#80), Step 3.5 Flash: 50.5 (#119)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1417 | 1385 |
| LMArena Chinese | 1456 | 1447 |
| LMArena French | 1428 | 1421 |
| LMArena German | 1411 | 1405 |
| LMArena Japanese | 1408 | 1354 |
| LMArena Korean | 1392 | 1352 |
| LMArena Russian | 1431 | 1385 |
| LMArena Spanish | 1429 | 1419 |
Instruction Following GPT-5.5 Instant leads
GPT-5.5 Instant: 74.2 (#100), Step 3.5 Flash: 73.1 (#124)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1406 | 1385 |
Long Context Too close to call
GPT-5.5 Instant: 43.4 (#96), Step 3.5 Flash: 42.8 (#117)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1422 | 1402 |
Writing & Preference GPT-5.5 Instant leads
GPT-5.5 Instant: 61.8 (#85), Step 3.5 Flash: 58.8 (#113)
| Benchmark | GPT-5.5 Instant | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1419 | 1403 |
| LMArena Creative Writing | 1419 | 1357 |
| LMArena Multi-Turn | 1433 | 1405 |
Frequently asked questions
Is GPT-5.5 Instant better than Step 3.5 Flash?
GPT-5.5 Instant and Step 3.5 Flash score almost the same on the Noometry Index (42.7 vs 42.3), so choose on price, context window or the category you care about most.
Is GPT-5.5 Instant or Step 3.5 Flash better for coding?
GPT-5.5 Instant scores higher on coding benchmarks: 44.3 versus 42.4 in the Noometry coding category.
How many benchmarks do GPT-5.5 Instant and Step 3.5 Flash share?
17 benchmarks have published results for both models. GPT-5.5 Instant has 27 scored results on Noometry and Step 3.5 Flash has 19.