Comparing 2 models
Claude Sonnet 5.5 vs DeepSeek V4.1 Flash
Benchmarks through
Verdict
Claude Sonnet 5.5 places higher on 5 of the 5 tasks where both are ranked. DeepSeek V4.1 Flash costs 55.6x less per input token. DeepSeek V4.1 Flash accepts 1.0x more context. Only DeepSeek V4.1 Flash has open weights for self-hosting.
- Choose Claude Sonnet 5.5 for Debugging & Code Review (#1), Code Completion (#1), Autonomous Agents (#2).
- Choose DeepSeek V4.1 Flash for you need to self-host.
Built from the published task rankings below; ranks come from each task's own weighted benchmarks, so a win on one task says nothing about another.
Measured head to head
Benchmarks both models were run on
| Evaluation | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Source |
|---|---|---|---|
| FrontierMath Tiers 1-3 (Epoch AI) | 88.8% ± 1.9 | 67.4% ± 2.8 | source · 2026-09-29 |
| GPQA Diamond (Epoch AI) | 95.6% ± 1.4 | 89.8% ± 1.7 | source · 2026-09-29 |
| LiveBench Agentic Coding | 56.3% | 77.3% | source · 2026-10-16 |
| LiveBench Coding | 91.4% | 80.0% | source · 2026-10-16 |
| LiveBench Data Analysis | 59.5% | 79.3% | source · 2026-10-16 |
| LiveBench Instruction Following | 56.8% | 70.0% | source · 2026-10-16 |
| LiveBench Language | 78.0% | 81.2% | source · 2026-10-16 |
| LiveBench Math | 96.1% | 93.3% | source · 2026-10-16 |
| LiveBench Reasoning | 91.6% | 86.7% | source · 2026-10-16 |
| LMArena Agent | 12.5 | 3 | source · 2026-10-14 |
| LMArena Agent Bash Recovery | 15 | 7.9 | source · 2026-10-08 |
| LMArena Agent Steerability | 12.3 | 1.9 | source · 2026-10-14 |
| LMArena Agent Task Outcome | 20 | 7.5 | source · 2026-10-14 |
| LMArena Agent Tool Hallucination | 0.5 | 0.5 | source · 2026-10-14 |
| LMArena Creative Writing | 1467 Elo | 1437 Elo | source · 2026-10-15 |
| LMArena Instruction Following | 1488 Elo | 1473 Elo | source · 2026-10-15 |
| LMArena Long Query | 1494 Elo | 1474 Elo | source · 2026-10-15 |
| LMArena Math | 1499 Elo | 1478 Elo | source · 2026-10-15 |
| LMArena Text | 1475 Elo | 1475 Elo | source · 2026-10-15 |
| LMArena Text Factuality | 1474 Elo | 1468 Elo | source · 2026-10-15 |
| LMArena Vision | 1266 Elo | 1260 Elo | source · 2026-10-09 |
| LMArena Vision Diagrams | 1320 Elo | 1291 Elo | source · 2026-10-09 |
| LMArena Vision OCR | 1280 Elo | 1270 Elo | source · 2026-10-09 |
| LMArena WebDev | 1774 Elo | 1619 Elo | source · 2026-10-13 |
| LMArena WebDev Image-to-Web | 1740 Elo | 1609 Elo | source · 2026-10-09 |
| OTIS Mock AIME (Epoch AI) | 100% ± 0 | 98.3% ± 0.6 | source · 2026-09-29 |
| SimpleQA Verified (Epoch AI) | 46.5% ± 1.6 | 42.9% ± 1.6 | source · 2026-09-29 |
Values are as published by each evaluator, in its own units; rows from different evaluators are not on a common scale.
task evidence
How they place when the question changes
Lower ranks are better. “Best” marks the strongest option in this shortlist for that task.