Model comparison
Claude Sonnet 4.5 vs Step 3
Claude Sonnet 4.5 is the stronger model overall, scoring 44.1 to 40.5 on the Noometry Index.
Last verified . 16 shared benchmarks.
StepFunSummary
- They share 16 benchmarks with published results for both. Claude Sonnet 4.5 scores higher in 6 categories and Step 3 in 3 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in writing & preference, where Claude Sonnet 4.5 leads 66.5 to 54.3.
- Step 3 has downloadable open weights; the other is API-only.
Side by side
| Claude Sonnet 4.5 | Step 3 | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 44.1 | 40.5 |
| Released | 2025-09-29 | — |
| Weights | Proprietary | Open |
| Context window | 200K | — |
| Max output | 64K | — |
| Input $ / M tokens | $3 | — |
| Output $ / M tokens | $15 | — |
| Results tracked | 73 | 17 |
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Category by category
Coding Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 47.3 (#61), Step 3: 40.1 (#147)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Coding | 1489 | 1367 |
| SWE-bench Verified | 71.3% | — |
| SWE-bench Verified (bash only) | 71.4% | — |
| LMArena WebDev | 1393 | — |
| SWE-bench Multilingual | 67% | — |
| SciCode | 44.7% | — |
| GSO | 14.7% | — |
| WeirdML | 47.7% | — |
| ALE-Bench | 796.15 | — |
| AlgoTune | 1.52 | — |
Agentic & Tool Use Not comparable
Claude Sonnet 4.5: 38.3 (#32), Step 3: —
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| Terminal-Bench | 46.5% | — |
| Berkeley Function Calling Leaderboard | 73.2% | — |
| GDPval | 42.5% | — |
| Remote Labor Index | 2.1% | — |
| τ²-bench Airline | 72% | — |
| τ²-bench Banking | 25.3% | — |
| τ²-bench Retail | 72.4% | — |
| τ²-bench Telecom | 84.9% | — |
| Cybench | 60% | — |
| DeepResearch Bench | 52.6% | — |
| OSWorld | 62.9% | — |
| LMArena Search | 1159 | — |
| METR Time Horizons | 67.4% | — |
| Vending-Bench 2 | 3,839 | — |
Reasoning Step 3 leads
Claude Sonnet 4.5: 26.9 (#125), Step 3: 28.4 (#105)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| Kagi LLM Benchmark | 57.9% | 62.3% |
| LMArena Hard Prompts | 1462 | 1355 |
| ARC-AGI-2 | 13.6% | — |
| SimpleBench | 54.3% | — |
| NYT Connections (extended) | 37.3% | — |
| ARC-AGI-1 | 63.7% | — |
| CritPt | 1.1% | — |
| Chess Puzzles | 12% | — |
| EnigmaEval | 6% | — |
| EBR-Bench | 2.4% | — |
| Mystery Game Puzzles | 17% | — |
| DTBench | 83.2% | — |
| LMCA | 38.8% | — |
| Epoch Capabilities Index | 146.84 | — |
| ForecastBench | 61.9 | — |
Math Step 3 leads
Claude Sonnet 4.5: 32.3 (#216), Step 3: 37.6 (#148)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Math | 1449 | 1366 |
| FrontierMath (Tiers 1-3) | 23.9% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 77.8% | — |
| ProofBench | 19% | — |
| Omni-MATH | 55.3% | — |
| MATH Level 5 | 97.7% | — |
| FrontierMath (Feb 2025 set) | 15.2% | — |
| FrontierMath Tier 4 (v1) | 4.2% | — |
Knowledge Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 48.4 (#76), Step 3: 36.8 (#164)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Expert | 1482 | 1333 |
| GPQA Diamond | 82.3% | — |
| Humanity's Last Exam | 13.7% | — |
| SimpleQA Verified | 30.7% | — |
| MMLU-Pro | 86.9% | — |
| Vectara Hallucination Rate | 12% | — |
| GPQA (HELM) | 68.6% | — |
Multimodal Too close to call
Claude Sonnet 4.5: 34.8 (#89), Step 3: 35.5 (#86)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Vision | — | 1177 |
| VPCT | 39.8% | — |
| LMArena Document | 1450 | — |
Multilingual Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 53.4 (#69), Step 3: 46.3 (#159)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Non-English | 1425 | 1327 |
| LMArena Chinese | 1459 | 1397 |
| LMArena German | 1427 | 1371 |
| LMArena Korean | 1403 | 1269 |
| LMArena Russian | 1437 | 1331 |
| LMArena Spanish | 1457 | 1371 |
| LMArena French | 1458 | — |
| LMArena Japanese | 1390 | — |
Instruction Following Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 75.0 (#78), Step 3: 70.4 (#164)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Instruction Following | 1459 | 1332 |
| IFEval | 85% | — |
Long Context Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 45.2 (#46), Step 3: 40.3 (#157)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Longer Query | 1476 | 1326 |
Writing & Preference Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 66.5 (#34), Step 3: 54.3 (#151)
| Benchmark | Claude Sonnet 4.5 | Step 3 |
|---|---|---|
| LMArena Text | 1439 | 1350 |
| LMArena Creative Writing | 1442 | 1321 |
| LMArena Multi-Turn | 1465 | 1341 |
| EQ-Bench Creative Writing | 1678 | — |
| WildBench | 85.4% | — |
Frequently asked questions
Is Claude Sonnet 4.5 better than Step 3?
Claude Sonnet 4.5 is the stronger model overall, scoring 44.1 to 40.5 on the Noometry Index.
Is Claude Sonnet 4.5 or Step 3 better for coding?
Claude Sonnet 4.5 scores higher on coding benchmarks: 47.3 versus 40.1 in the Noometry coding category.
How many benchmarks do Claude Sonnet 4.5 and Step 3 share?
16 benchmarks have published results for both models. Claude Sonnet 4.5 has 73 scored results on Noometry and Step 3 has 17.