Model comparison
GPT-5.4 Pro vs Step 3.5 Flash
GPT-5.4 Pro is the stronger model overall, scoring 58.9 to 42.3 on the Noometry Index. Step 3.5 Flash costs 450× less per token, which makes it the better buy when GPT-5.4 Pro's lead doesn't matter for your workload.
Last verified . 0 shared benchmarks.
StepFunSummary
- The widest gap is in reasoning, where GPT-5.4 Pro leads 70.7 to 22.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $30 / $180 for GPT-5.4 Pro.
- GPT-5.4 Pro accepts more context: 1.05M tokens versus 256K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.
Side by side
| GPT-5.4 Pro | Step 3.5 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 58.9 | 42.3 |
| Released | 2026-03-05 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 1.05M | 256K |
| Max output | 128K | 256K |
| Input $ / M tokens | $30 | $0.10 |
| Output $ / M tokens | $180 | $0.30 |
| Results tracked | 16 | 19 |
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Category by category
Coding Too close to call
GPT-5.4 Pro: 43.2 (#90), Step 3.5 Flash: 42.4 (#105)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| WeirdML | 57.4% | — |
| LMArena Coding | — | 1436 |
Reasoning GPT-5.4 Pro leads
GPT-5.4 Pro: 70.7 (#13), Step 3.5 Flash: 22.2 (#202)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| ARC-AGI-2 | 83.3% | — |
| SimpleBench | 74.1% | — |
| NYT Connections (extended) | — | 28.4% |
| ARC-AGI-1 | 94.5% | — |
| CritPt | 30% | — |
| Chess Puzzles | 58.6% | — |
| EnigmaEval | 23.8% | — |
| LMArena Hard Prompts | — | 1411 |
| Epoch Capabilities Index | 158.93 | — |
Math GPT-5.4 Pro leads
GPT-5.4 Pro: 72.4 (#22), Step 3.5 Flash: 42.6 (#84)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| FrontierMath (Tiers 1-3) | 82.5% | — |
| FrontierMath Tier 4 | 58.5% | — |
| MathArena Final-Answer Competitions | — | 66.8% |
| LMArena Math | — | 1408 |
| FrontierMath (Feb 2025 set) | 50% | — |
| FrontierMath Tier 4 (v1) | 37.5% | — |
Knowledge GPT-5.4 Pro leads
GPT-5.4 Pro: 68.3 (#7), Step 3.5 Flash: 39.6 (#132)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| GPQA Diamond | 94.6% | — |
| Humanity's Last Exam | 44.3% | — |
| SimpleQA Verified | 46.3% | — |
| Vectara Hallucination Rate | 8.3% | — |
| LMArena Expert | — | 1421 |
Multilingual Not comparable
GPT-5.4 Pro: —, Step 3.5 Flash: 50.5 (#119)
| Benchmark | GPT-5.4 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
GPT-5.4 Pro: —, Step 3.5 Flash: 73.1 (#124)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | — | 1385 |
Long Context Not comparable
GPT-5.4 Pro: —, Step 3.5 Flash: 42.8 (#117)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | — | 1402 |
Writing & Preference Not comparable
GPT-5.4 Pro: —, Step 3.5 Flash: 58.8 (#113)
| Benchmark | GPT-5.4 Pro | Step 3.5 Flash |
|---|---|---|
| LMArena Text | — | 1403 |
| LMArena Creative Writing | — | 1357 |
| LMArena Multi-Turn | — | 1405 |
Frequently asked questions
Is GPT-5.4 Pro better than Step 3.5 Flash?
GPT-5.4 Pro is the stronger model overall, scoring 58.9 to 42.3 on the Noometry Index. Step 3.5 Flash costs 450× less per token, which makes it the better buy when GPT-5.4 Pro's lead doesn't matter for your workload.
Which is cheaper, GPT-5.4 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; GPT-5.4 Pro lists at $30 and $180.
Is GPT-5.4 Pro or Step 3.5 Flash better for coding?
They score almost the same on coding (43.2 vs 42.4); test both on your own repository before choosing.
Which has the bigger context window?
GPT-5.4 Pro does, with 1.05M tokens against 256K.
How many benchmarks do GPT-5.4 Pro and Step 3.5 Flash share?
0 benchmarks have published results for both models. GPT-5.4 Pro has 16 scored results on Noometry and Step 3.5 Flash has 19.