Model comparison
Claude Sonnet 5.5 vs Step 3
Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 40.5 on the Noometry Index.
Last verified . 13 shared benchmarks.
StepFunSummary
- They share 13 benchmarks with published results for both. Claude Sonnet 5.5 scores higher in 9 categories and Step 3 in 0 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Sonnet 5.5 leads 87.9 to 37.6.
- Step 3 has downloadable open weights; the other is API-only.
Side by side
| Claude Sonnet 5.5 | Step 3 | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 61.9 | 40.5 |
| Released | 2026-09-28 | — |
| Weights | Proprietary | Open |
| Context window | 1M | — |
| Max output | 128K | — |
| Input $ / M tokens | $2 | — |
| Output $ / M tokens | $10 | — |
| Results tracked | 32 | 17 |
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Category by category
Coding Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 67.3 (#6), Step 3: 40.1 (#147)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Coding | 1513 | 1367 |
| FrontierCode | 52.1% | — |
| CursorBench | 55.5% | — |
| LMArena WebDev | 1774 | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
| ALE-Bench | 1,819 | — |
Agentic & Tool Use Not comparable
Claude Sonnet 5.5: 45.0 (#16), Step 3: —
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| APEX-Agents | 75.5% | — |
Reasoning Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 54.0 (#28), Step 3: 28.4 (#105)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Hard Prompts | 1495 | 1355 |
| Kagi LLM Benchmark | — | 62.3% |
| NYT Connections (extended) | 80.5% | — |
| CritPt | 31.4% | — |
| Mystery Game Puzzles | 65% | — |
| Epoch Capabilities Index | 165.03 | — |
Math Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 87.9 (#6), Step 3: 37.6 (#148)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Math | 1510 | 1366 |
| FrontierMath (Tiers 1-3) | 88.8% | — |
| FrontierMath Tier 4 | 80.5% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| FrontierMath Erdős | 2.9% | — |
Knowledge Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 66.0 (#12), Step 3: 36.8 (#164)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Expert | 1540 | 1333 |
| GPQA Diamond | 95.6% | — |
| SimpleQA Verified | 46.5% | — |
Multimodal Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 51.5 (#6), Step 3: 35.5 (#86)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Vision | 1289 | 1177 |
| Furniture Assembly | 75% | — |
Multilingual Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 55.3 (#30), Step 3: 46.3 (#159)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Non-English | 1452 | 1327 |
| LMArena Chinese | 1522 | 1397 |
| LMArena Russian | 1451 | 1331 |
| LMArena German | — | 1371 |
| LMArena Korean | — | 1269 |
| LMArena Spanish | — | 1371 |
Instruction Following Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 78.3 (#11), Step 3: 70.4 (#164)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Instruction Following | 1495 | 1332 |
Long Context Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 45.9 (#28), Step 3: 40.3 (#157)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Longer Query | 1498 | 1326 |
Writing & Preference Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 66.0 (#40), Step 3: 54.3 (#151)
| Benchmark | Claude Sonnet 5.5 | Step 3 |
|---|---|---|
| LMArena Text | 1471 | 1350 |
| LMArena Creative Writing | 1465 | 1321 |
| LMArena Multi-Turn | 1474 | 1341 |
Frequently asked questions
Is Claude Sonnet 5.5 better than Step 3?
Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 40.5 on the Noometry Index.
Is Claude Sonnet 5.5 or Step 3 better for coding?
Claude Sonnet 5.5 scores higher on coding benchmarks: 67.3 versus 40.1 in the Noometry coding category.
How many benchmarks do Claude Sonnet 5.5 and Step 3 share?
13 benchmarks have published results for both models. Claude Sonnet 5.5 has 32 scored results on Noometry and Step 3 has 17.