Model comparison
Claude Sonnet 4.5 vs Step 5 Preview
Step 5 Preview is the stronger model overall, scoring 47.9 to 44.1 on the Noometry Index.
Last verified . 17 shared benchmarks.
StepFunSummary
- They share 17 benchmarks with published results for both. Claude Sonnet 4.5 scores higher in 3 categories and Step 5 Preview in 6 categories; 6 gaps are clear of the uncertainty.
- The widest gap is in math, where Step 5 Preview leads 46.1 to 32.3.
- The biggest single-benchmark swing is ProofBench: 19% for Claude Sonnet 4.5 and 42% for Step 5 Preview.
- Step 5 Preview is cheaper at $1 / $2.70 per million input/output tokens, against $3 / $15 for Claude Sonnet 4.5.
- Step 5 Preview accepts more context: 1.02M tokens versus 200K.
Side by side
| Claude Sonnet 4.5 | Step 5 Preview | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 44.1 | 47.9 |
| Released | 2025-09-29 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 200K | 1.02M |
| Max output | 64K | 66K |
| Input $ / M tokens | $3 | $1 |
| Output $ / M tokens | $15 | $2.70 |
| Results tracked | 73 | 18 |
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Category by category
Coding Step 5 Preview leads
Claude Sonnet 4.5: 47.3 (#61), Step 5 Preview: 51.8 (#36)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1393 | 1564 |
| SciCode | 44.7% | 58.9% |
| LMArena Coding | 1489 | 1480 |
| SWE-bench Verified | 71.3% | — |
| SWE-bench Verified (bash only) | 71.4% | — |
| SWE-bench Multilingual | 67% | — |
| 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 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| 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 5 Preview leads
Claude Sonnet 4.5: 26.9 (#125), Step 5 Preview: 40.0 (#57)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| CritPt | 1.1% | 20.9% |
| LMArena Hard Prompts | 1462 | 1465 |
| ARC-AGI-2 | 13.6% | — |
| SimpleBench | 54.3% | — |
| Kagi LLM Benchmark | 57.9% | — |
| NYT Connections (extended) | 37.3% | — |
| ARC-AGI-1 | 63.7% | — |
| 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 5 Preview leads
Claude Sonnet 4.5: 32.3 (#216), Step 5 Preview: 46.1 (#72)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| ProofBench | 19% | 42% |
| LMArena Math | 1449 | 1470 |
| FrontierMath (Tiers 1-3) | 23.9% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 77.8% | — |
| 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 5 Preview: 41.2 (#112)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Expert | 1482 | 1470 |
| 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 Step 5 Preview leads
Claude Sonnet 4.5: 34.8 (#89), Step 5 Preview: 41.0 (#41)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Vision | — | 1267 |
| VPCT | 39.8% | — |
| LMArena Document | 1450 | — |
Multilingual Too close to call
Claude Sonnet 4.5: 53.4 (#69), Step 5 Preview: 53.8 (#54)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Non-English | 1425 | 1432 |
| LMArena Chinese | 1459 | 1519 |
| LMArena Russian | 1437 | 1436 |
| LMArena Spanish | 1457 | 1439 |
| LMArena French | 1458 | — |
| LMArena German | 1427 | — |
| LMArena Japanese | 1390 | — |
| LMArena Korean | 1403 | — |
Instruction Following Too close to call
Claude Sonnet 4.5: 75.0 (#78), Step 5 Preview: 76.0 (#50)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Instruction Following | 1459 | 1444 |
| IFEval | 85% | — |
Long Context Too close to call
Claude Sonnet 4.5: 45.2 (#46), Step 5 Preview: 44.5 (#64)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | 1476 | 1455 |
Writing & Preference Claude Sonnet 4.5 leads
Claude Sonnet 4.5: 66.5 (#34), Step 5 Preview: 62.8 (#71)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Text | 1439 | 1442 |
| LMArena Creative Writing | 1442 | 1410 |
| LMArena Multi-Turn | 1465 | 1447 |
| EQ-Bench Creative Writing | 1678 | — |
| WildBench | 85.4% | — |
Frequently asked questions
Is Claude Sonnet 4.5 better than Step 5 Preview?
Step 5 Preview is the stronger model overall, scoring 47.9 to 44.1 on the Noometry Index.
Which is cheaper, Claude Sonnet 4.5 or Step 5 Preview?
Step 5 Preview is cheaper. It lists at $1 per million input tokens and $2.70 per million output tokens; Claude Sonnet 4.5 lists at $3 and $15.
Is Claude Sonnet 4.5 or Step 5 Preview better for coding?
Step 5 Preview scores higher on coding benchmarks: 51.8 versus 47.3 in the Noometry coding category.
Which has the bigger context window?
Step 5 Preview does, with 1.02M tokens against 200K.
How many benchmarks do Claude Sonnet 4.5 and Step 5 Preview share?
17 benchmarks have published results for both models. Claude Sonnet 4.5 has 73 scored results on Noometry and Step 5 Preview has 18.