# Claude Sonnet 5.5 vs DeepSeek V4 Flash 0731

> Side-by-side benchmark comparison for Claude Sonnet 5.5 and DeepSeek V4 Flash 0731 across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-sonnet-5-5-vs-deepseek-v4-flash-0731
- Last updated: September 28, 2026

- Shared sourced benchmarks: 5
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

Pick Claude Sonnet 5.5 if you want the stronger benchmark profile. DeepSeek V4 Flash 0731 only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- Claude Sonnet 5.5 leads overall 80.49 to 57.
- The clearest category separation is in reasoning, where the averages are 79.2 for Claude Sonnet 5.5 and 57 for DeepSeek V4 Flash 0731.
- The biggest single benchmark swing is SWE-bench Pro in Coding, with scores of 81.3% and 52.6%.
- DeepSeek V4 Flash 0731 is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.

## Model Snapshot

| Property | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 |
|----------|----------|----------|
| Creator | Anthropic | DeepSeek |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1M |
| Overall Score | 80.49 | null |
| Benchmarks Covered | 47 | 42 |
| Pricing (input/output) | $2.00 / $10.00 | $0.14 / $0.28 |

## Category Breakdown

### Agentic

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: 66.1 (Supported · #10/111)
- DeepSeek V4 Flash 0731 public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 70.60% | Coming soon | Coming soon |
| HLE w/ tools | 64.5% | 45.1% | 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% | 70.3% | Claude Sonnet 5.5 |
| Terminal-Bench 2.0 | Coming soon | 56.9% | Coming soon |
| BrowseComp | Coming soon | 73.2% | Coming soon |
| MCP Atlas | Coming soon | 69% | Coming soon |
| Toolathlon | Coming soon | 47.8% | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 82.7% | Coming soon |
| CyberGym | Coming soon | 76.7% | Coming soon |
| Agents' Last Exam | Coming soon | 25.2% | Coming soon |
| AutomationBench | Coming soon | 25.1% | Coming soon |
| Terminal-Bench 2.1 (Vals) | Coming soon | 67.0% | Coming soon |

### Coding

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: 79.6 (Estimated · #3/136)
- DeepSeek V4 Flash 0731 public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | Winner |
|-----------|-----------|-----------|--------|
| FrontierCode 1.1 Main | 46.2% | Coming soon | Coming soon |
| cursorBench40 | 55.5% | Coming soon | Coming soon |
| SWE-bench Pro | 81.3% | 52.6% | Claude Sonnet 5.5 |
| SWE Multilingual | 90.3% | 73.3% | Claude Sonnet 5.5 |
| SWE Multimodal | 54.3% | Coming soon | Coming soon |
| DeepSWE | 71.0% | 54.4% | Claude Sonnet 5.5 |
| 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 |
| LiveCodeBench Pass@1-COT | Coming soon | 91.6% | Coming soon |
| Codeforces | Coming soon | 3052.0 | Coming soon |
| SWE-bench Verified | Coming soon | 79% | Coming soon |
| Terminal-Bench 2.0 | Coming soon | 56.9% | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 82.7% | Coming soon |
| NL2Repo | Coming soon | 54.2% | Coming soon |
| DSBench-FullStack | Coming soon | 68.7% | Coming soon |
| DSBench-Hard | Coming soon | 59.6% | Coming soon |
| VulcanBench v3 | Coming soon | 88.4% | Coming soon |
| OpenHarmony Bench | Coming soon | 53.8% | Coming soon |
| LiveCodeBench (Vals) | Coming soon | 87.3% | Coming soon |
| SWE-bench (Vals) | Coming soon | 88.8% | Coming soon |

### Reasoning

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: 79.2 (#7/27)
- DeepSeek V4 Flash 0731 public-lane score: 57 (Unranked · 4 rankable rows)

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | Winner |
|-----------|-----------|-----------|--------|
| MRCR 1M | Coming soon | 78.7% | Coming soon |
| CorpusQA 1M | Coming soon | 60.5% | Coming soon |
| ARC-AGI-1 | Coming soon | 89.00% | Coming soon |
| ARC-AGI-2 | Coming soon | 61.4% | Coming soon |

### Multimodal & Grounded

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: 83.3 (Unranked · 7 rankable rows)
- DeepSeek V4 Flash 0731 public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | 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 |

### Knowledge

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: 80.9 (Supported · #6/160)
- DeepSeek V4 Flash 0731 public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | 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 |
| MMLU-Pro | Coming soon | 86.2% | Coming soon |
| SimpleQA | Coming soon | 34.1% | Coming soon |
| Chinese-SimpleQA | Coming soon | 78.9% | Coming soon |
| GPQA | Coming soon | 88.1% | Coming soon |
| GPQA-D | Coming soon | 88.1% | Coming soon |
| HLE | Coming soon | 34.8% | Coming soon |
| GPQA Diamond (Vals) | Coming soon | 89.9% | Coming soon |
| MMLU-Pro (Vals) | Coming soon | 86.2% | Coming soon |

### Multilingual

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: Coming soon
- DeepSeek V4 Flash 0731 public-lane score: Coming soon

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | Winner |
|-----------|-----------|-----------|--------|
| GMMLU | 92.1% | Coming soon | Coming soon |
| MILU | 91.6% | Coming soon | Coming soon |

### Mathematics

- Winner: Not comparable
- Claude Sonnet 5.5 public-lane score: Coming soon
- DeepSeek V4 Flash 0731 public-lane score: 79.9 (Unranked · 4 rankable rows)

| Benchmark | Claude Sonnet 5.5 | DeepSeek V4 Flash 0731 | Winner |
|-----------|-----------|-----------|--------|
| ArXivMath Aug. 2026 (no tools) | 86.8% | Coming soon | Coming soon |
| ArXivMath Aug. 2026 (tools) | 95.2% | Coming soon | Coming soon |
| HMMT Feb 2026 | Coming soon | 94.8% | Coming soon |
| IMOAnswerBench | Coming soon | 88.4% | Coming soon |
| Apex | Coming soon | 33.0% | Coming soon |
| Apex Shortlist | Coming soon | 85.7% | Coming soon |

## FAQ

### Which is better overall, Claude Sonnet 5.5 or DeepSeek V4 Flash 0731?

Claude Sonnet 5.5 is ahead overall on BenchLM right now.

### Where is the biggest gap between Claude Sonnet 5.5 and DeepSeek V4 Flash 0731?

The widest category gap is in reasoning, where the averages are 79.2 for Claude Sonnet 5.5 and 57 for DeepSeek V4 Flash 0731.

### How many benchmarks does Claude Sonnet 5.5 cover on BenchLM?

Claude Sonnet 5.5 currently has 47 sourced benchmark scores on BenchLM.

### How many benchmarks does DeepSeek V4 Flash 0731 cover on BenchLM?

DeepSeek V4 Flash 0731 currently has 42 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Claude Sonnet 5.5 vs GPT-6 Astra](/compare/claude-sonnet-5-5-vs-gpt-6-astra)
- [DeepSeek V4 Flash 0731 vs GPT-6 Astra](/compare/deepseek-v4-flash-0731-vs-gpt-6-astra)
- [Claude Sonnet 5.5 vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-claude-sonnet-5-5)
- [DeepSeek V4 Flash 0731 vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-deepseek-v4-flash-0731)

## Explore More

- [Claude Sonnet 5.5 profile](/models/claude-sonnet-5-5)
- [DeepSeek V4 Flash 0731 profile](/models/deepseek-v4-flash-0731)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)