Claude Sonnet 5.5 vs Step 5 Preview
Updated October 21, 2026. 60 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 71.4 for Step 5 Preview.
Pick Step 5 Preview when output tokens cost 3.7x less, or when the context window is larger, 1.05M against 1M tokens.
- Shared results
- 60
- Claude Sonnet 5.5 only
- 35
- Step 5 Preview only
- 1
- Like-for-like categories
- 8 of 9
Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, four public coding benchmarks
Claude Sonnet 5.5
Claude Sonnet 5.5 scores 88.9 against 71.4.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 56.0 against 43.7.
Same board, both measured
Web design
Design Arena: websites
No call
Only Claude Sonnet 5.5 has a Design Arena: websites result, 1326.
Directional only
General
Vals Index
No call
Only Claude Sonnet 5.5 has a Vals Index result, 70.8%.
Directional only
Long documents
Listed context window
Step 5 Preview
Step 5 Preview takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 5 Preview
Claude Sonnet 5.5 $0.0070, Step 5 Preview $0.0024 per turn.
List prices
At a glance
- Coding index
- Claude Sonnet 5.5 88.9 from 2 benchmarks, Step 5 Preview 71.4 from 2 benchmarks.
- Widest category
- Agentic work, 26.2 points apart on average over 11 shared benchmarks.
- Widest single gap
- LiveBench browser: Claude Sonnet 5.5 84.0% against Step 5 Preview 24.0%, 60.0 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5.5 $10.00 against Step 5 Preview $2.70 per million output tokens, 3.7x apart.
- Context window
- Claude Sonnet 5.5 takes 1M tokens, Step 5 Preview 1.05M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Claude Sonnet 5.5 | Bars | Step 5 Preview | Ties |
|---|---|---|---|---|
| Coding | 13 | 0 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 11 | 0 | ||
| Reasoning | 8 | 0 | ||
| Math | 3 | 0 | ||
| Knowledge | 4 | 0 | ||
| Web design | 1 | 0 | ||
| General | 16 | 3 | ||
| All shared boards | 57 | 3 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index130
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench coding | 94.7% | 85.6% | Claude Sonnet 5.5 |
| LMArena WebDev | 1768 | 1567 | Claude Sonnet 5.5 |
| Terminal-Bench 4 (Vals AI) | 64.1% | 31.8% | Claude Sonnet 5.5 |
| Vibe Code Bench (Vals AI) | 92.4% | 70.4% | Claude Sonnet 5.5 |
| Code migration (Vals AI) | 69.8% | 39.0% | Claude Sonnet 5.5 |
| ProgramBench (Vals AI) | 6.5% | Not measured | Only Claude Sonnet 5.5 measured |
| IOI (Vals AI) | 83.1% | 38.1% | Claude Sonnet 5.5 |
| Terminal-Bench 2.1 (Vals AI) | 83.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SWE-bench Multimodal (Vals AI) | 58.3% | 40.8% | Claude Sonnet 5.5 |
| CyberBench (Vals AI) | 59.6% | Not measured | Only Claude Sonnet 5.5 measured |
| SciCode | 61.0% | 58.9% | Claude Sonnet 5.5 |
| FrontierCode | 52.1% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierSWE | 61.9% | Not measured | Only Claude Sonnet 5.5 measured |
| ALE-Bench | 1819.1 | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: coding | 1513 | 1485 | Claude Sonnet 5.5 |
| LMArena Text: software and IT | 1504 | 1473 | Claude Sonnet 5.5 |
| LMArena WebDev: React | 1817 | 1583 | Claude Sonnet 5.5 |
| LMArena WebDev: HTML | 1741 | 1556 | Claude Sonnet 5.5 |
| LMArena WebDev: from an image | 1737 | 1550 | Claude Sonnet 5.5 |
| Neither model has a result on the other 19 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| AA Intelligence Index | 56.0 | 43.7 | Claude Sonnet 5.5 |
| Epoch Capabilities Index | 166.2 | Not measured | Only Claude Sonnet 5.5 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index110
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1303 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: agents building mobile apps | 1265 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: spreadsheets | 1245 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench research | 83.6% | 72.8% | Claude Sonnet 5.5 |
| LiveBench browser | 84.0% | 24.0% | Claude Sonnet 5.5 |
| LiveBench long agentic | 78.8% | 27.5% | Claude Sonnet 5.5 |
| SREBench (Vals AI) | 30.1% | 0.4% | Claude Sonnet 5.5 |
| Finance Agent (Vals AI) | 58.1% | 50.7% | Claude Sonnet 5.5 |
| Tax Agent Bench (Vals AI) | 42.0% | 27.3% | Claude Sonnet 5.5 |
| Legal Research Bench (Vals AI) | 48.1% | 40.4% | Claude Sonnet 5.5 |
| Harvey's Legal Agent Benchmark (Vals AI) | 10.4% | Not measured | Only Claude Sonnet 5.5 measured |
| Excel Modeling Benchmark (Vals AI) | 75.7% | 57.1% | Claude Sonnet 5.5 |
| BioMysteryBench (Vals AI) | 81.1% | 67.4% | Claude Sonnet 5.5 |
| Terminal-Bench-Science (Vals AI) | 47.1% | 2.9% | Claude Sonnet 5.5 |
| Vals Science Index | 59.1% | 29.6% | Claude Sonnet 5.5 |
| APEX-Agents | 75.5% | Not measured | Only Claude Sonnet 5.5 measured |
| SpireClimb | 1.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Vending-Bench 2 | $11,165 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 21 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index80
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench reasoning | 91.6% | 83.8% | Claude Sonnet 5.5 |
| MysteryMechanism (Vals AI) | 49.1% | 18.5% | Claude Sonnet 5.5 |
| Humanity's Last Exam (Artificial Analysis run) | 55.0% | 46.5% | Claude Sonnet 5.5 |
| GPQA Diamond (Epoch AI run) | 95.6% | Not measured | Only Claude Sonnet 5.5 measured |
| Chess puzzles | 59.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Mystery game puzzles | 65.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: hard prompts | 1494 | 1461 | Claude Sonnet 5.5 |
| LMArena Text: expert | 1531 | 1485 | Claude Sonnet 5.5 |
| LMArena Text: hard prompts in English | 1502 | 1454 | Claude Sonnet 5.5 |
| LMArena Vision: diagrams | 1329 | 1308 | Claude Sonnet 5.5 |
| LMArena Vision: homework | 1331 | 1265 | Claude Sonnet 5.5 |
| Neither model has a result on the other 10 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| OTIS Mock AIME | 100.0% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tiers 1 to 3 | 88.8% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tier 4 | 80.5% | Not measured | Only Claude Sonnet 5.5 measured |
| ProofBench | 100.0% | 42.0% | Claude Sonnet 5.5 |
| LMArena Text: math | 1497 | 1458 | Claude Sonnet 5.5 |
| LMArena Text: mathematical work | 1510 | 1460 | Claude Sonnet 5.5 |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index40
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| MedCode (Vals AI) | 52.9% | Not measured | Only Claude Sonnet 5.5 measured |
| SimpleQA Verified | 46.5% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: science | 1483 | 1454 | Claude Sonnet 5.5 |
| LMArena Text: medicine and healthcare | 1464 | 1439 | Claude Sonnet 5.5 |
| LMArena Text: legal and government | 1483 | 1437 | Claude Sonnet 5.5 |
| LMArena Text: business and finance | 1468 | 1435 | Claude Sonnet 5.5 |
| Neither model has a result on the other 11 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| Design Arena: websites | 1326 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: UI components | 1367 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: game dev | 1469 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: data viz | 1389 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: 3D | 1458 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: all code categories | 1364 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench design | 85.0% | 76.9% | Claude Sonnet 5.5 |
| Neither model has a result on the other 2 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index163
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| Vals Index | 70.8% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench data analysis | 59.5% | 63.5% | Step 5 Preview |
| Public Benefits Bench (Vals AI) | 67.2% | 58.1% | Claude Sonnet 5.5 |
| SAGE (Vals AI) | 51.8% | Not measured | Only Claude Sonnet 5.5 measured |
| MedScribe (Vals AI) | 91.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Long context reasoning (AA-LCR) | 82.7% | 88.3% | Step 5 Preview |
| DTBench | 97.3% | Not measured | Only Claude Sonnet 5.5 measured |
| LMCA | 68.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Furniture assembly | 75.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text | 1473 | 1440 | Claude Sonnet 5.5 |
| LMArena Text: instruction following | 1492 | 1438 | Claude Sonnet 5.5 |
| LMArena Text: creative writing | 1467 | 1409 | Claude Sonnet 5.5 |
| LMArena Vision | 1287 | 1265 | Claude Sonnet 5.5 |
| LMArena Text: English | 1484 | 1447 | Claude Sonnet 5.5 |
| LMArena Text: non-English | 1456 | 1428 | Claude Sonnet 5.5 |
| LMArena Text: Chinese | 1535 | 1500 | Claude Sonnet 5.5 |
| LMArena Text: Japanese | Not measured | 1383 | Only Step 5 Preview measured |
| LMArena Text: French | 1499 | 1438 | Claude Sonnet 5.5 |
| LMArena Text: Spanish | 1451 | 1441 | Claude Sonnet 5.5 |
| LMArena Text: Russian | 1454 | 1433 | Claude Sonnet 5.5 |
| LMArena Text: multi-turn | 1465 | 1437 | Claude Sonnet 5.5 |
| LMArena Text: longer queries | 1495 | 1449 | Claude Sonnet 5.5 |
| LMArena Text: writing and language | 1474 | 1425 | Claude Sonnet 5.5 |
| LMArena Text: entertainment and media | 1461 | 1412 | Claude Sonnet 5.5 |
| LMArena Vision: English | 1289 | 1290 | Step 5 Preview |
| LMArena Vision: reading text | 1297 | 1282 | Claude Sonnet 5.5 |
| LMArena Vision: creative writing | 1242 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 19 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 5.5 | Step 5 Preview | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Step 5 Preview costs less
Repository review
50K input + 3K output tokens
Step 5 Preview costs less
Agent loop
200K input + 10K output tokens
Step 5 Preview costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Anthropic Claude Sonnet 5.5 | StepFun Step 5 Preview |
|---|---|---|
| Maker | Anthropic | StepFun |
| Weights | No public weights listed | Open weights |
| Released | September 28, 2026 | October 8, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $2.00 | $1.00 |
| Output $/Mtok | $10.00 | $2.70 |
| Coding index | 88.9 | 71.4 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5.5 better than Step 5 Preview for coding?
Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 71.4 for Step 5 Preview. Pick Step 5 Preview when output tokens cost 3.7x less, or when the context window is larger, 1.05M against 1M tokens.
Which is cheaper, Claude Sonnet 5.5 or Step 5 Preview?
Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; Step 5 Preview costs $1.00 and $2.70. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Sonnet 5.5 or Step 5 Preview?
Step 5 Preview, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 5.5 vs Step 5 Preview comparison based on?
60 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5.5's coding index rests on 2 independent benchmarks and Step 5 Preview's on 2. Where only one model has a result, the page says so instead of naming a winner.