# Claude Sonnet 5.5 vs Step 3.7 Flash

> Side-by-side benchmark comparison for Claude Sonnet 5.5 and Step 3.7 Flash across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-sonnet-5-5-vs-step-3-7-flash
- Last updated: September 28, 2026

- Shared sourced benchmarks: 2
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

Evidence is too thin for a benchmark verdict: Claude Sonnet 5.5 and Step 3.7 Flash share only 2 sourced benchmark rows.

## Summary

- Only 2 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Step 3.7 Flash has the lower published output-token price.
- Claude Sonnet 5.5 has the larger published context window at 1M.

## Model Snapshot

| Property | Claude Sonnet 5.5 | Step 3.7 Flash |
|----------|----------|----------|
| Creator | Anthropic | StepFun |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 256K |
| Independent public score (not head-to-head) | 80.49 | 41.33 |
| Benchmarks Covered | 47 | 11 |
| Pricing (input/output) | $2.00 / $10.00 | $0.20 / $1.15 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: 66.1 (Supported · #10/111)
- Step 3.7 Flash public-lane score: 35.3 (Estimated · #60/111)

| Benchmark | Claude Sonnet 5.5 | Step 3.7 Flash | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 70.60% | Coming soon | Coming soon |
| HLE w/ tools | 64.5% | 47.2% | Claude Sonnet 5.5 |
| DRACO | 87.0% | Coming soon | Coming soon |
| Terminal-Bench-Science 0.1 | 59.9% | Coming soon | Coming soon |
| LAB all-pass (Harvey held-out) | 10.0% | Coming soon | Coming soon |
| LAB criterion-pass (Harvey held-out) | 93.1% | Coming soon | Coming soon |
| Toolathlon Verified Pass@3 | 85.2% | Coming soon | Coming soon |
| Toolathlon Verified Pass³ | 68.5% | Coming soon | Coming soon |
| Toolathlon Verified avg. turns | 31.6 turns | Coming soon | Coming soon |
| AutomationBench (Zapier 1.0.6) | 44.7% | Coming soon | Coming soon |
| Toolathlon-Verified | 77.8% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 59.5% | Coming soon |
| BrowseComp | Coming soon | 75.8% | Coming soon |
| DeepSearchQA | Coming soon | 92.8% | Coming soon |
| Toolathlon | Coming soon | 49.5% | Coming soon |
| Claw-Eval | Coming soon | 67.1% | Coming soon |
| Gert Labs | Coming soon | 51.57% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: 79.6 (Estimated · #3/136)
- Step 3.7 Flash public-lane score: 32 (Estimated · #82/136)

| Benchmark | Claude Sonnet 5.5 | Step 3.7 Flash | Winner |
|-----------|-----------|-----------|--------|
| FrontierCode 1.1 Main | 46.2% | Coming soon | Coming soon |
| cursorBench40 | 55.5% | Coming soon | Coming soon |
| SWE-bench Pro | 81.3% | 56.3% | Claude Sonnet 5.5 |
| SWE Multilingual | 90.3% | Coming soon | Coming soon |
| SWE Multimodal | 54.3% | Coming soon | Coming soon |
| DeepSWE | 71.0% | Coming soon | Coming soon |
| FrontierCode 1.1 Extended | 59.1% | Coming soon | Coming soon |
| ProgramBench | 79.7% | Coming soon | Coming soon |
| FrontierSWE v2 | 61.9% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 59.5% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: 79.2 (#7/27)
- Step 3.7 Flash public-lane score: 73 (Unranked · 2 rankable rows)

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: 83.3 (Unranked · 7 rankable rows)
- Step 3.7 Flash public-lane score: 72 (Unranked · 3 rankable rows)

| Benchmark | Claude Sonnet 5.5 | Step 3.7 Flash | Winner |
|-----------|-----------|-----------|--------|
| Chartography (no tools) | 61.6% | Coming soon | Coming soon |
| Chartography (tools) | 90.2% | Coming soon | Coming soon |
| BenchCAD Vision2Code (no tools) | 0.747 | Coming soon | Coming soon |
| BenchCAD Vision2Code (tools) | 0.963 | Coming soon | Coming soon |
| Biomedical image analysis | 72.2% | Coming soon | Coming soon |
| OfficeQA | 76.9% | Coming soon | Coming soon |
| OfficeQA Pro | 65.6% | Coming soon | Coming soon |
| SimpleVQA | Coming soon | 79.2% | Coming soon |
| V* | Coming soon | 95.3% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: 80.9 (Supported · #6/160)
- Step 3.7 Flash public-lane score: 43.2 (Estimated · #79/160)

| Benchmark | Claude Sonnet 5.5 | Step 3.7 Flash | Winner |
|-----------|-----------|-----------|--------|
| HealthBench (raw) | 69.4% | Coming soon | Coming soon |
| HealthBench (length-adjusted) | 65.4% | Coming soon | Coming soon |
| HealthBench Professional (raw) | 77.1% | Coming soon | Coming soon |
| HealthBench Professional | 69.2% | Coming soon | Coming soon |
| BioMysteryBench (human-solvable) | 89.2% | Coming soon | Coming soon |
| BioMysteryBench (human-difficult) | 44.7% | Coming soon | Coming soon |
| SpatialBench Verified | 72.5% | Coming soon | Coming soon |
| SingleCellBench | 59.1% | Coming soon | Coming soon |
| Protein Design | 51.0% | Coming soon | Coming soon |
| Morphology-to-molecule matching | 25.0% | Coming soon | Coming soon |
| Medicinal chemistry | 65.3% | Coming soon | Coming soon |
| Protein Design library ranking | 54.8% | Coming soon | Coming soon |
| De novo protein-binder design | 82.3% | Coming soon | Coming soon |
| Protocols (troubleshooting) | 67.3% | Coming soon | Coming soon |
| Protocols (understanding) | 66.6% | Coming soon | Coming soon |
| HLE w/o tools | 56.9% | Coming soon | Coming soon |

### Multilingual

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: Coming soon
- Step 3.7 Flash public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | Step 3.7 Flash | Winner |
|-----------|-----------|-----------|--------|
| GMMLU | 92.1% | Coming soon | Coming soon |
| MILU | 91.6% | Coming soon | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: Coming soon
- Step 3.7 Flash public-lane score: 80.6 (#53/124)

### Mathematics

- Winner: Insufficient shared evidence
- Claude Sonnet 5.5 public-lane score: Coming soon
- Step 3.7 Flash public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | Step 3.7 Flash | Winner |
|-----------|-----------|-----------|--------|
| ArXivMath Aug. 2026 (no tools) | 86.8% | Coming soon | Coming soon |
| ArXivMath Aug. 2026 (tools) | 95.2% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between Claude Sonnet 5.5 and Step 3.7 Flash?

Not yet. The models share only 2 sourced benchmark rows, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Claude Sonnet 5.5 vs GPT-6 Astra](/compare/claude-sonnet-5-5-vs-gpt-6-astra)
- [Step 3.7 Flash vs GPT-6 Astra](/compare/gpt-6-astra-vs-step-3-7-flash)
- [Claude Sonnet 5.5 vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-claude-sonnet-5-5)
- [Step 3.7 Flash vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-step-3-7-flash)

## Explore More

- [Claude Sonnet 5.5 profile](/models/claude-sonnet-5-5)
- [Step 3.7 Flash profile](/models/step-3-7-flash)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)