Model comparison
Claude Opus 4 vs Step 3.5 Flash
Claude Opus 4 is the stronger model overall, scoring 42.9 to 41.7 on the Noometry Index. Step 3.5 Flash costs 200× less per token, which makes it the better buy when Claude Opus 4's lead doesn't matter for your workload.
Last verified . 17 shared benchmarks.
StepFunSummary
- They share 17 benchmarks with published results for both. Claude Opus 4 scores higher in 5 categories and Step 3.5 Flash in 3 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Opus 4 leads 27.4 to 21.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $15 / $75 for Claude Opus 4.
- 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
| Claude Opus 4 | Step 3.5 Flash | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 42.9 | 41.7 |
| Released | 2025-05-22 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 200K | 256K |
| Max output | 32K | 256K |
| Input $ / M tokens | $15 | $0.10 |
| Output $ / M tokens | $75 | $0.30 |
| Results tracked | 56 | 19 |
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Category by category
Coding Claude Opus 4 leads
Claude Opus 4: 47.8 (#55), Step 3.5 Flash: 41.7 (#106)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1442 | 1436 |
| SWE-bench Verified | 70.7% | — |
| SWE-bench Verified (bash only) | 67.6% | — |
| Aider Polyglot | 72% | — |
| GSO | 6.9% | — |
| WeirdML | 43.7% | — |
| AlgoTune | 1.33 | — |
Agentic & Tool Use Not comparable
Claude Opus 4: 34.5 (#39), Step 3.5 Flash: —
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| Cybench | 38% | — |
| DeepResearch Bench | 46.8% | — |
| LMArena Search | 1127 | — |
| METR Time Horizons | 63.9% | — |
Reasoning Claude Opus 4 leads
Claude Opus 4: 27.4 (#104), Step 3.5 Flash: 21.2 (#202)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1411 |
| ARC-AGI-2 | 8.6% | — |
| SimpleBench | 58.8% | — |
| Kagi LLM Benchmark | 74.3% | — |
| NYT Connections (extended) | — | 28.4% |
| ARC-AGI-1 | 35.7% | — |
| CritPt | 0.3% | — |
| EnigmaEval | 5.6% | — |
| DTBench | 81.6% | — |
| LMCA | 37.4% | — |
| Epoch Capabilities Index | 142.67 | — |
| ForecastBench | 61.1 | — |
Math Too close to call
Claude Opus 4: 40.2 (#80), Step 3.5 Flash: 40.6 (#77)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1391 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |
| OTIS Mock AIME 2024-2025 | 64.4% | — |
| Omni-MATH | 61.6% | — |
| MATH Level 5 | 85% | — |
| FrontierMath (Feb 2025 set) | 4.5% | — |
| FrontierMath Tier 4 (v1) | 4.2% | — |
Knowledge Claude Opus 4 leads
Claude Opus 4: 43.9 (#82), Step 3.5 Flash: 39.0 (#127)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1384 | 1422 |
| GPQA Diamond | 76.3% | — |
| Humanity's Last Exam | 10.7% | — |
| MMLU-Pro | 87.5% | — |
| Confabulations | 15.9% | — |
| Vectara Hallucination Rate | 12% | — |
| GPQA (HELM) | 70.8% | — |
Multimodal Not comparable
Claude Opus 4: 30.9 (#101), Step 3.5 Flash: —
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1192 | — |
| GeoBench | 49% | — |
| VPCT | 38% | — |
Multilingual Step 3.5 Flash leads
Claude Opus 4: 49.0 (#133), Step 3.5 Flash: 50.7 (#115)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1362 | 1386 |
| LMArena Chinese | 1386 | 1448 |
| LMArena French | 1370 | 1421 |
| LMArena German | 1391 | 1404 |
| LMArena Japanese | 1332 | 1353 |
| LMArena Korean | 1318 | 1350 |
| LMArena Russian | 1392 | 1385 |
| LMArena Spanish | 1388 | 1419 |
Instruction Following Claude Opus 4 leads
Claude Opus 4: 77.3 (#26), Step 3.5 Flash: 73.3 (#119)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1406 | 1385 |
| IFEval | 91.8% | — |
Long Context Step 3.5 Flash leads
Claude Opus 4: 39.5 (#167), Step 3.5 Flash: 42.8 (#112)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1422 | 1402 |
| Fiction.LiveBench | 61.1% | — |
Writing & Preference Claude Opus 4 leads
Claude Opus 4: 61.4 (#85), Step 3.5 Flash: 59.0 (#108)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1377 | 1403 |
| LMArena Creative Writing | 1386 | 1357 |
| LMArena Multi-Turn | 1396 | 1405 |
| Short-Story Creative Writing | 83.6% | — |
| EQ-Bench Creative Writing | 1580 | — |
| WildBench | 85.2% | — |
Frequently asked questions
Is Claude Opus 4 better than Step 3.5 Flash?
Claude Opus 4 is the stronger model overall, scoring 42.9 to 41.7 on the Noometry Index. Step 3.5 Flash costs 200× less per token, which makes it the better buy when Claude Opus 4's lead doesn't matter for your workload.
Which is cheaper, Claude Opus 4 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; Claude Opus 4 lists at $15 and $75.
Is Claude Opus 4 or Step 3.5 Flash better for coding?
Claude Opus 4 scores higher on coding benchmarks: 47.8 versus 41.7 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 Claude Opus 4 and Step 3.5 Flash share?
17 benchmarks have published results for both models. Claude Opus 4 has 56 scored results on Noometry and Step 3.5 Flash has 19.