Model comparison
Claude Opus 4 vs Step 3.5 Flash
Claude Opus 4 and Step 3.5 Flash score almost the same on the Noometry Index (43.1 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. 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 27.3 to 22.2.
- 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 | 43.1 | 42.3 |
| 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: 47.2 (#62), Step 3.5 Flash: 42.4 (#105)
| 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: 34.8 (#42), 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: 27.3 (#121), Step 3.5 Flash: 22.2 (#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: 42.0 (#86), Step 3.5 Flash: 42.6 (#84)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1390 | 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: 44.0 (#88), Step 3.5 Flash: 39.6 (#132)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1386 | 1421 |
| 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: 31.5 (#106), 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: 48.8 (#138), Step 3.5 Flash: 50.5 (#119)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1362 | 1385 |
| LMArena Chinese | 1386 | 1447 |
| LMArena French | 1372 | 1421 |
| LMArena German | 1391 | 1405 |
| LMArena Japanese | 1331 | 1354 |
| LMArena Korean | 1321 | 1352 |
| LMArena Russian | 1392 | 1385 |
| LMArena Spanish | 1389 | 1419 |
Instruction Following Claude Opus 4 leads
Claude Opus 4: 77.1 (#28), Step 3.5 Flash: 73.1 (#124)
| 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: 39.6 (#172), Step 3.5 Flash: 42.8 (#117)
| 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: 61.2 (#89), Step 3.5 Flash: 58.8 (#113)
| Benchmark | Claude Opus 4 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1377 | 1403 |
| LMArena Creative Writing | 1387 | 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 and Step 3.5 Flash score almost the same on the Noometry Index (43.1 vs 42.3), so choose on price, context window or the category you care about most.
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: 47.2 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 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.