Model comparison
Claude Opus 5.5 vs Step 5 Preview
Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 47.9 on the Noometry Index. Step 5 Preview costs 5.6× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.
Last verified . 18 shared benchmarks.
StepFunSummary
- They share 18 benchmarks with published results for both. Claude Opus 5.5 scores higher in 9 categories and Step 5 Preview in 0 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Opus 5.5 leads 91.8 to 46.1.
- The biggest single-benchmark swing is ProofBench: 100% for Claude Opus 5.5 and 42% for Step 5 Preview.
- Step 5 Preview is cheaper at $1 / $2.70 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
- Step 5 Preview accepts more context: 1.02M tokens versus 1M.
Side by side
| Claude Opus 5.5 | Step 5 Preview | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 68.6 | 47.9 |
| Released | 2026-09-22 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.02M |
| Max output | 128K | 66K |
| Input $ / M tokens | $4 | $1 |
| Output $ / M tokens | $20 | $2.70 |
| Results tracked | 44 | 18 |
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Category by category
Coding Claude Opus 5.5 leads
Claude Opus 5.5: 71.9 (#3), Step 5 Preview: 51.8 (#36)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1813 | 1564 |
| SciCode | 66.9% | 58.9% |
| LMArena Coding | 1547 | 1480 |
| FrontierCode | 54.6% | — |
| CursorBench | 57.8% | — |
| FrontierSWE | 62.3% | — |
| MirrorCode | 77.4% | — |
| ALE-Bench | 2,147 | — |
Agentic & Tool Use Not comparable
Claude Opus 5.5: 45.3 (#15), Step 5 Preview: —
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| APEX-Agents | 73.5% | — |
| GDP.pdf | 30.6% | — |
| Vending-Bench 2 | 9,235 | — |
Reasoning Claude Opus 5.5 leads
Claude Opus 5.5: 80.2 (#3), Step 5 Preview: 40.0 (#57)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| CritPt | 31.7% | 20.9% |
| LMArena Hard Prompts | 1535 | 1465 |
| ARC-AGI-2 | 93.3% | — |
| NYT Connections (extended) | 88.5% | — |
| ARC-AGI-1 | 98.5% | — |
| EBR-Bench | 71.4% | — |
| Mystery Game Puzzles | 71% | — |
| DTBench | 98.9% | — |
| LMCA | 68.2% | — |
| Epoch Capabilities Index | 167.33 | — |
Math Claude Opus 5.5 leads
Claude Opus 5.5: 91.8 (#3), Step 5 Preview: 46.1 (#72)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| ProofBench | 100% | 42% |
| LMArena Math | 1506 | 1470 |
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| FrontierMath Erdős | 2.9% | — |
Knowledge Claude Opus 5.5 leads
Claude Opus 5.5: 66.4 (#10), Step 5 Preview: 41.2 (#112)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena Expert | 1547 | 1470 |
| GPQA Diamond | 90.6% | — |
| SimpleQA Verified | 72.2% | — |
Multimodal Claude Opus 5.5 leads
Claude Opus 5.5: 57.8 (#1), Step 5 Preview: 41.0 (#41)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena Vision | 1321 | 1267 |
| Blueprint-Bench 2 | 51.2% | — |
| Furniture Assembly | 83.3% | — |
Multilingual Claude Opus 5.5 leads
Claude Opus 5.5: 59.1 (#2), Step 5 Preview: 53.8 (#54)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena Non-English | 1507 | 1432 |
| LMArena Chinese | 1588 | 1519 |
| LMArena Russian | 1520 | 1436 |
| LMArena Spanish | 1507 | 1439 |
| LMArena French | 1514 | — |
Instruction Following Claude Opus 5.5 leads
Claude Opus 5.5: 80.0 (#3), Step 5 Preview: 76.0 (#50)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena Instruction Following | 1537 | 1444 |
Long Context Claude Opus 5.5 leads
Claude Opus 5.5: 47.1 (#19), Step 5 Preview: 44.5 (#64)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | 1532 | 1455 |
Writing & Preference Claude Opus 5.5 leads
Claude Opus 5.5: 78.2 (#3), Step 5 Preview: 62.8 (#71)
| Benchmark | Claude Opus 5.5 | Step 5 Preview |
|---|---|---|
| LMArena Text | 1515 | 1442 |
| LMArena Creative Writing | 1533 | 1410 |
| LMArena Multi-Turn | 1499 | 1447 |
| EQ-Bench Creative Writing | 2050 | — |
Frequently asked questions
Is Claude Opus 5.5 better than Step 5 Preview?
Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 47.9 on the Noometry Index. Step 5 Preview costs 5.6× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.
Which is cheaper, Claude Opus 5.5 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 Opus 5.5 lists at $4 and $20.
Is Claude Opus 5.5 or Step 5 Preview better for coding?
Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 51.8 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 Opus 5.5 and Step 5 Preview share?
18 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Step 5 Preview has 18.