Claude Sonnet 5.5 vs DeepSeek V4.1 Flash
Claude Sonnet 5.5 
DeepSeek V4.1 Flash Verdict
- Claude Sonnet 5.5 (max) leads on quality: 67.6 vs 61.8.
- Claude Sonnet 5.5 (max) is stronger in agents & tools, coding, composite, knowledge, maths, reasoning.
- DeepSeek V4.1 Flash (max) is stronger in long context, human preference, multimodal.
- DeepSeek V4.1 Flash (max) is 7.6× cheaper ($0.525 vs $4.00 per 1M blended).
- DeepSeek V4.1 Flash (max) streams 1.5× faster (217 vs 141 tokens per second).
| Metric | Claude Sonnet 5.5 (max) | DeepSeek V4.1 Flash (max) |
|---|---|---|
| BenchLeader Index | 67.6 | 61.8 |
| Agents & tools score | 69.5 | 55.5 |
| Coding score | 69.8 | 64.0 |
| Composite score | 72.6 | 71.2 |
| Knowledge score | 65.4 | 59.3 |
| Long context score | 66.6 | 67.3 |
| Maths score | 72.9 | 61.9 |
| Reasoning score | 81.1 | 65.2 |
| Human preference score | – | 66.9 |
| Multimodal score | – | 60.9 |
| Blended price $/M | $4.00 | $0.525 |
| Output speed | 141 tok/s | 217 tok/s |
| Time to first answer | 487.1 s | 10.4 s |
| Context window | 1M | 1M |
| GPQA Diamond | 95.6% | 89.8% |
| FrontierMath Tiers 1–3 | 88.8% | 67.4% |
| FrontierMath Tier 4 | 80.5% | 26.8% |
| OTIS Mock AIME | 100.0% | 98.3% |
| SimpleQA Verified | 46.5% | – |
| Terminal-Bench | 61.8% | – |
| SciCode | 61.0% | 51.9% |
| APEX-Agents | 75.5% | – |
| ProofBench | 100.0% | – |
| LMArena Text | – | 1475 |
| LMArena Hard Prompts | – | 1499 |
| LMArena Coding | – | 1528 |
| LMArena WebDev | – | 1619 |
| LMArena Vision | – | 1277 |
| LMArena Agent | 12 | 3.8 |
| LiveBench | 75.7% | 81.1% |
| LiveBench Reasoning | 91.6% | 86.7% |
| LiveBench Coding | 91.4% | 80.0% |
| LiveBench Agentic Coding | 56.3% | 77.3% |
| LiveBench Mathematics | 96.1% | 93.3% |
| LiveBench Data Analysis | 59.5% | 79.3% |
| LiveBench Language | 78.0% | 81.2% |
| LiveBench Instruction Following | 56.8% | 70.0% |
| AA Intelligence Index v4.3.2 | 56 | 39.5 |
| AA-LCR | 82.7% | 84.0% |
| MMMU-Pro | – | 77.0% |
| AA-Omniscience | 32.3 | -5.3 |
| Humanity's Last Exam (AA) | 55.0% | 39.3% |
| SciCode (AA) | 61.0% | 51.9% |
| ARC-AGI-1 | – | 94.5% |
| ARC-AGI-2 | – | 72.9% |
| CritPt | 31.4% | 14.3% |
| GDPval-AA v2.1 | 67.0% | 55.0% |
| ITBench SRE (AA) | – | 46.9% |
| Analyst Agent (AA) | 57.5% | – |
| Harvey's Legal Agent Benchmark | – | 6.7% |
| Public Benefits Bench | – | 64.3% |
| SREBench | – | 0.8% |
| LMArena Maths | – | 1493 |
| LMArena Creative Writing | – | 1439 |
| LMArena Instruction Following | – | 1477 |
| LMArena Multi-turn | – | 1466 |
| LMArena Longer Queries | – | 1482 |
| Mystery Game Puzzles | 65.0% | 43.0% |
| CursorBench | 55.5% | – |
| ALE-Bench | – | 1092.3 |
| GDP.pdf | – | 19.8% |
| FrontierSWE | 61.9% | – |
| Terminal-Bench 4.0 (AA) | 63.6% | 26.8% |
| AutomationBench | 71.8% | 68.9% |
| GDP.pdf | 25.8% | 12.8% |
| MLCR | 75.0% | 22.8% |
| Harvey LAB | 2.8% | 1.7% |
| AA-Omniscience: accuracy | 54.0% | 46.4% |
| AA-Omniscience: non-hallucination | 53.0% | 3.5% |
| AA-Briefcase v1.1 | 1823 | 1422 |
| AA Openness Index | – | 44.4 |
Data as of 2026-10-11. Best configuration of each model; every score links to its source on the model pages.
Claude Sonnet 5.5 vs DeepSeek V4.1 Flash: questions
- Is Claude Sonnet 5.5 better than DeepSeek V4.1 Flash?
- Claude Sonnet 5.5 (max) leads on quality: 67.6 vs 61.8. The BenchLeader Index combines every independent quality benchmark; Claude Sonnet 5.5 (max) is ahead overall as of 2026-10-11, but check the category scores for your use.
- Is Claude Sonnet 5.5 better than DeepSeek V4.1 Flash for coding?
- Claude Sonnet 5.5 scores higher in coding (70 vs 64 on the category index, where 50 is average).
- Is Claude Sonnet 5.5 better than DeepSeek V4.1 Flash for agentic tasks?
- Claude Sonnet 5.5 scores higher in agentic tasks (70 vs 56 on the category index, where 50 is average).
- Which is cheaper, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?
- DeepSeek V4.1 Flash is cheaper: $0.525 against $4.00 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?
- DeepSeek V4.1 Flash streams faster: 217 against 141 output tokens per second.
- Which has the larger context window?
- Both accept 1M tokens of context.