Model comparison
Claude Sonnet 4.5 vs Step 5 Preview
Claude Sonnet 4.5 and Step 5 Preview score almost the same on the Noometry Index (44.0 vs 43.8), so choose on price, context window or the category you care about most.
Last verified . 3 shared benchmarks.
StepFunSummary
- They share 3 benchmarks with published results for both. Claude Sonnet 4.5 scores higher in 0 categories and Step 5 Preview in 2 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Step 5 Preview leads 38.0 to 26.9.
- The biggest single-benchmark swing is CritPt: 1.1% for Claude Sonnet 4.5 and 20.9% 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 1M.
Side by side
| Claude Sonnet 4.5 | Step 5 Preview | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 44.0 | 43.8 |
| Released | 2025-09-29 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.02M |
| Max output | 64K | 66K |
| Input $ / M tokens | $3 | $1 |
| Output $ / M tokens | $15 | $2.70 |
| Results tracked | 73 | 3 |
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Category by category
Coding Step 5 Preview leads
Claude Sonnet 4.5: 47.8 (#54), Step 5 Preview: 50.6 (#40)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1393 | 1569 |
| SciCode | 44.7% | 58.9% |
| SWE-bench Verified | 71.3% | — |
| SWE-bench Verified (bash only) | 71.4% | — |
| SWE-bench Multilingual | 67% | — |
| GSO | 14.7% | — |
| WeirdML | 47.7% | — |
| LMArena Coding | 1489 | — |
| ALE-Bench | 796.15 | — |
| AlgoTune | 1.52 | — |
Agentic & Tool Use Not comparable
Claude Sonnet 4.5: 38.1 (#30), 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 (#113), Step 5 Preview: 38.0 (#58)
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| CritPt | 1.1% | 20.9% |
| 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% | — |
| LMArena Hard Prompts | 1462 | — |
| Mystery Game Puzzles | 17% | — |
| DTBench | 83.2% | — |
| LMCA | 38.8% | — |
| Epoch Capabilities Index | 146.84 | — |
| ForecastBench | 61.9 | — |
Math Not comparable
Claude Sonnet 4.5: 31.9 (#190), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| FrontierMath (Tiers 1-3) | 23.9% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 77.8% | — |
| ProofBench | 19% | — |
| Omni-MATH | 55.3% | — |
| LMArena Math | 1448 | — |
| MATH Level 5 | 97.7% | — |
| FrontierMath (Feb 2025 set) | 15.2% | — |
| FrontierMath Tier 4 (v1) | 4.2% | — |
Knowledge Not comparable
Claude Sonnet 4.5: 48.4 (#70), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| 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% | — |
| LMArena Expert | 1483 | — |
Multimodal Not comparable
Claude Sonnet 4.5: 34.1 (#84), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| VPCT | 39.8% | — |
| LMArena Document | 1450 | — |
Multilingual Not comparable
Claude Sonnet 4.5: 53.6 (#65), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Non-English | 1425 | — |
| LMArena Chinese | 1459 | — |
| LMArena French | 1459 | — |
| LMArena German | 1427 | — |
| LMArena Japanese | 1390 | — |
| LMArena Korean | 1403 | — |
| LMArena Russian | 1436 | — |
| LMArena Spanish | 1457 | — |
Instruction Following Not comparable
Claude Sonnet 4.5: 75.2 (#74), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| IFEval | 85% | — |
| LMArena Instruction Following | 1459 | — |
Long Context Not comparable
Claude Sonnet 4.5: 45.2 (#45), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | 1476 | — |
Writing & Preference Not comparable
Claude Sonnet 4.5: 66.7 (#33), Step 5 Preview: —
| Benchmark | Claude Sonnet 4.5 | Step 5 Preview |
|---|---|---|
| LMArena Text | 1439 | — |
| LMArena Creative Writing | 1442 | — |
| EQ-Bench Creative Writing | 1678 | — |
| WildBench | 85.4% | — |
| LMArena Multi-Turn | 1465 | — |
Frequently asked questions
Is Claude Sonnet 4.5 better than Step 5 Preview?
Claude Sonnet 4.5 and Step 5 Preview score almost the same on the Noometry Index (44.0 vs 43.8), so choose on price, context window or the category you care about most.
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: 50.6 versus 47.8 in the Noometry coding category.
Which has the bigger context window?
Step 5 Preview does, with 1.02M tokens against 1M.
How many benchmarks do Claude Sonnet 4.5 and Step 5 Preview share?
3 benchmarks have published results for both models. Claude Sonnet 4.5 has 73 scored results on Noometry and Step 5 Preview has 3.