Claude Sonnet 5.5 vs DeepSeek V4.1 Flash
Claude Sonnet 5.5 leads DeepSeek V4.1 Flash on coding, 87.3 to 62.5 on the Vibe Coding Index, and DeepSeek V4.1 Flash costs 11.9x less per output token ($0.84 vs $10.00 per million). Updated October 22, 2026; 87 benchmarks have a result for both.
Claude Sonnet 5.5 or DeepSeek V4.1 Flash: which to pick
Pick Claude Sonnet 5.5 for coding: it scores 87.3 on the Vibe Coding Index against 62.5 for DeepSeek V4.1 Flash.
Pick DeepSeek V4.1 Flash for output tokens 11.9x cheaper ($0.84 vs $10.00 per million) and a larger context window (1.05M against 1M tokens).
- Shared results
- 87
- Claude Sonnet 5.5 only
- 9
- DeepSeek V4.1 Flash only
- 14
- Like-for-like categories
- 8 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
Claude Sonnet 5.5
Claude Sonnet 5.5 scores 87.3 against 62.5.
5 benchmarks behind each score
Intelligence
AA Intelligence Index
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 56.0 against 24.7.
Same board, both measured
Web design
Design Arena: websites
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 1326 against 1308.
Same board, both measured
General
Vals Index
No call
Only Claude Sonnet 5.5 has a Vals Index result, 70.8%.
Directional only
Long documents
Listed context window
DeepSeek V4.1 Flash
DeepSeek V4.1 Flash takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
DeepSeek V4.1 Flash
Claude Sonnet 5.5 $0.0070, DeepSeek V4.1 Flash $0.0006 per turn.
List prices
At a glance
- Coding index
- Claude Sonnet 5.5 87.3 from 5 benchmarks, DeepSeek V4.1 Flash 62.5 from 5 benchmarks.
- Widest category
- Intelligence, 22.1 points apart on average over 2 shared benchmarks.
- Widest single gap
- Terminal-Bench 4 (Vals AI): Claude Sonnet 5.5 64.1% against DeepSeek V4.1 Flash 19.7%, 59.3 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5.5 $10.00 against DeepSeek V4.1 Flash $0.84 per million output tokens, 11.9x apart.
- Context window
- Claude Sonnet 5.5 takes 1M tokens, DeepSeek V4.1 Flash 1.05M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Claude Sonnet 5.5 | Bars | DeepSeek V4.1 Flash | Ties |
|---|---|---|---|---|
| Coding | 17 | 1 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 10 | 1 | 1 tie | |
| Reasoning | 11 | 0 | ||
| Math | 6 | 0 | ||
| Knowledge | 5 | 1 | ||
| Web design | 7 | 0 | ||
| General | 20 | 5 | ||
| All shared boards | 78 | 8 | 1 tie |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index171
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| LiveBench coding | 94.7% | 90.2% | Claude Sonnet 5.5 |
| LMArena WebDev | 1768 | 1618 | Claude Sonnet 5.5 |
| Terminal-Bench 4 (Vals AI) | 64.1% | 19.7% | Claude Sonnet 5.5 |
| Vibe Code Bench (Vals AI) | 92.4% | 84.7% | Claude Sonnet 5.5 |
| Code migration (Vals AI) | 69.8% | 45.6% | Claude Sonnet 5.5 |
| ProgramBench (Vals AI) | 6.5% | 0.5% | Claude Sonnet 5.5 |
| IOI (Vals AI) | 83.1% | 40.3% | Claude Sonnet 5.5 |
| Terminal-Bench 2.1 (Vals AI) | 83.2% | 74.5% | Claude Sonnet 5.5 |
| SWE-bench Multimodal (Vals AI) | 58.3% | 46.5% | Claude Sonnet 5.5 |
| Vibe Code Bench 1-100 (Vals AI) | Not measured | 16.4% | Only DeepSeek V4.1 Flash measured |
| SkillsBench (Vals AI) | Not measured | 69.8% | Only DeepSeek V4.1 Flash measured |
| CyberBench (Vals AI) | 59.6% | 73.7% | DeepSeek V4.1 Flash |
| SciCode | 61.0% | 51.9% | Claude Sonnet 5.5 |
| FrontierCode | 52.1% | 43.9% | Claude Sonnet 5.5 |
| FrontierSWE | 61.9% | Not measured | Only Claude Sonnet 5.5 measured |
| ALE-Bench | 1819.1 | 1092.3 | Claude Sonnet 5.5 |
| LMArena Text: coding | 1513 | 1502 | Claude Sonnet 5.5 |
| LMArena Text: software and IT | 1504 | 1496 | Claude Sonnet 5.5 |
| LMArena WebDev: React | 1817 | 1628 | Claude Sonnet 5.5 |
| LMArena WebDev: HTML | 1741 | 1612 | Claude Sonnet 5.5 |
| LMArena WebDev: from an image | 1737 | 1606 | Claude Sonnet 5.5 |
| SciCode | 13.8% | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 17 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 56.0 | 24.7 | Claude Sonnet 5.5 |
| Epoch Capabilities Index | 166.2 | 155.9 | Claude Sonnet 5.5 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index101
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1305 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: agents building mobile apps | 1260 | Not measured | Only Claude Sonnet 5.5 measured |
| Design Arena: spreadsheets | 1260 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench research | 83.6% | 86.8% | DeepSeek V4.1 Flash |
| LiveBench browser | 84.0% | 84.0% | Tie |
| LiveBench long agentic | 78.8% | 40.1% | Claude Sonnet 5.5 |
| SREBench (Vals AI) | 30.1% | 0.8% | Claude Sonnet 5.5 |
| Finance Agent (Vals AI) | 58.1% | 53.5% | Claude Sonnet 5.5 |
| Tax Agent Bench (Vals AI) | 42.0% | 26.6% | Claude Sonnet 5.5 |
| Legal Research Bench (Vals AI) | 48.1% | 41.4% | Claude Sonnet 5.5 |
| Harvey's Legal Agent Benchmark (Vals AI) | 10.4% | Not measured | Only Claude Sonnet 5.5 measured |
| Excel Modeling Benchmark (Vals AI) | 75.7% | 57.2% | Claude Sonnet 5.5 |
| BioMysteryBench (Vals AI) | 81.1% | 67.8% | Claude Sonnet 5.5 |
| Terminal-Bench-Science (Vals AI) | 47.1% | 0.0% | Claude Sonnet 5.5 |
| Vals Science Index | 59.1% | 29.6% | Claude Sonnet 5.5 |
| APEX-Agents | 75.5% | 39.5% | Claude Sonnet 5.5 |
| SpireClimb | 1.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Vending-Bench 2 | $11,165 | Not measured | Only Claude Sonnet 5.5 measured |
| Neither model has a result on the other 23 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index110
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| LiveBench reasoning | 91.6% | 86.7% | Claude Sonnet 5.5 |
| MysteryMechanism (Vals AI) | 49.1% | 21.2% | Claude Sonnet 5.5 |
| Humanity's Last Exam (Artificial Analysis run) | 55.0% | 39.2% | Claude Sonnet 5.5 |
| GPQA Diamond (Epoch AI run) | 95.6% | 89.8% | Claude Sonnet 5.5 |
| ARC-AGI | Not measured | 94.5% | Only DeepSeek V4.1 Flash measured |
| ARC-AGI-2 | Not measured | 72.9% | Only DeepSeek V4.1 Flash measured |
| Chess puzzles | 59.0% | 48.0% | Claude Sonnet 5.5 |
| Mystery game puzzles | 65.0% | 43.0% | Claude Sonnet 5.5 |
| LMArena Text: hard prompts | 1494 | 1483 | Claude Sonnet 5.5 |
| LMArena Text: expert | 1531 | 1501 | Claude Sonnet 5.5 |
| LMArena Text: hard prompts in English | 1502 | 1488 | Claude Sonnet 5.5 |
| LMArena Vision: diagrams | 1329 | 1297 | Claude Sonnet 5.5 |
| LMArena Vision: homework | 1331 | 1307 | Claude Sonnet 5.5 |
| Neither model has a result on the other 9 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| OTIS Mock AIME | 100.0% | 98.3% | Claude Sonnet 5.5 |
| FrontierMath, tiers 1 to 3 | 88.8% | 67.4% | Claude Sonnet 5.5 |
| FrontierMath, tier 4 | 80.5% | 26.8% | Claude Sonnet 5.5 |
| ProofBench | 100.0% | 54.0% | Claude Sonnet 5.5 |
| LMArena Text: math | 1497 | 1478 | Claude Sonnet 5.5 |
| LMArena Text: mathematical work | 1510 | 1485 | Claude Sonnet 5.5 |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index51
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| LegalBench (Vals AI) | Not measured | 83.3% | Only DeepSeek V4.1 Flash measured |
| MedCode (Vals AI) | 52.9% | 41.2% | Claude Sonnet 5.5 |
| SimpleQA Verified | 46.5% | 42.9% | Claude Sonnet 5.5 |
| LMArena Text: science | 1483 | 1469 | Claude Sonnet 5.5 |
| LMArena Text: medicine and healthcare | 1464 | 1484 | DeepSeek V4.1 Flash |
| LMArena Text: legal and government | 1483 | 1443 | Claude Sonnet 5.5 |
| LMArena Text: business and finance | 1468 | 1461 | Claude Sonnet 5.5 |
| Neither model has a result on the other 11 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index70
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1326 | 1308 | Claude Sonnet 5.5 |
| Design Arena: UI components | 1368 | 1312 | Claude Sonnet 5.5 |
| Design Arena: game dev | 1471 | 1330 | Claude Sonnet 5.5 |
| Design Arena: data viz | 1392 | 1291 | Claude Sonnet 5.5 |
| Design Arena: 3D | 1445 | 1355 | Claude Sonnet 5.5 |
| Design Arena: all code categories | 1364 | 1320 | Claude Sonnet 5.5 |
| Design Arena: SVG | Not measured | 1245 | Only DeepSeek V4.1 Flash measured |
| Design Arena: ASCII art | Not measured | 1265 | Only DeepSeek V4.1 Flash measured |
| LiveBench design | 85.0% | 79.2% | Claude Sonnet 5.5 |
GeneralLike-for-likePublic boards, shown as published, kept out of the index205
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| Vals Index | 70.8% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench data analysis | 59.5% | 79.3% | DeepSeek V4.1 Flash |
| Public Benefits Bench (Vals AI) | 67.2% | 64.3% | Claude Sonnet 5.5 |
| SAGE (Vals AI) | 51.8% | 47.9% | Claude Sonnet 5.5 |
| MedScribe (Vals AI) | 91.1% | 85.5% | Claude Sonnet 5.5 |
| Long context reasoning (AA-LCR) | 82.7% | 84.0% | DeepSeek V4.1 Flash |
| DTBench | 97.3% | 89.9% | Claude Sonnet 5.5 |
| LMCA | 68.3% | 47.0% | Claude Sonnet 5.5 |
| Surface Evolver Bench | Not measured | 46.3% | Only DeepSeek V4.1 Flash measured |
| Furniture assembly | 75.0% | 34.2% | Claude Sonnet 5.5 |
| LMArena Text | 1473 | 1464 | Claude Sonnet 5.5 |
| LMArena Text: instruction following | 1492 | 1473 | Claude Sonnet 5.5 |
| LMArena Text: creative writing | 1467 | 1437 | Claude Sonnet 5.5 |
| LMArena Vision | 1287 | 1278 | Claude Sonnet 5.5 |
| LMArena Text: English | 1484 | 1473 | Claude Sonnet 5.5 |
| LMArena Text: non-English | 1456 | 1449 | Claude Sonnet 5.5 |
| LMArena Text: Chinese | 1535 | 1501 | Claude Sonnet 5.5 |
| LMArena Text: German | Not measured | 1470 | Only DeepSeek V4.1 Flash measured |
| LMArena Text: Japanese | Not measured | 1432 | Only DeepSeek V4.1 Flash measured |
| LMArena Text: Korean | Not measured | 1436 | Only DeepSeek V4.1 Flash measured |
| LMArena Text: French | 1499 | 1465 | Claude Sonnet 5.5 |
| LMArena Text: Spanish | 1451 | 1459 | DeepSeek V4.1 Flash |
| LMArena Text: Russian | 1454 | 1467 | DeepSeek V4.1 Flash |
| LMArena Text: Polish | Not measured | 1457 | Only DeepSeek V4.1 Flash measured |
| LMArena Text: multi-turn | 1465 | 1461 | Claude Sonnet 5.5 |
| LMArena Text: longer queries | 1495 | 1473 | Claude Sonnet 5.5 |
| LMArena Text: writing and language | 1474 | 1450 | Claude Sonnet 5.5 |
| LMArena Text: entertainment and media | 1461 | 1445 | Claude Sonnet 5.5 |
| LMArena Vision: English | 1289 | 1288 | Claude Sonnet 5.5 |
| LMArena Vision: Chinese | Not measured | 1327 | Only DeepSeek V4.1 Flash measured |
| LMArena Vision: reading text | 1297 | 1282 | Claude Sonnet 5.5 |
| LMArena Vision: humor | Not measured | 1260 | Only DeepSeek V4.1 Flash measured |
| LMArena Vision: creative writing | 1242 | 1275 | DeepSeek V4.1 Flash |
| Neither model has a result on the other 13 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
DeepSeek V4.1 Flash costs less
Repository review
50K input + 3K output tokens
DeepSeek V4.1 Flash costs less
Agent loop
200K input + 10K output tokens
DeepSeek V4.1 Flash costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Anthropic Claude Sonnet 5.5 | DeepSeek V4.1 Flash |
|---|---|---|
| Maker | Anthropic | DeepSeek |
| Weights | No public weights listed | Open weights |
| Released | September 28, 2026 | September 10, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $2.00 | $0.2225 |
| Output $/Mtok | $10.00 | $0.84 |
| Coding index | 87.3 | 62.5 |
| Independent measurements behind it | 5 | 5 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5.5 better than DeepSeek V4.1 Flash for coding?
Pick Claude Sonnet 5.5 for coding: it scores 87.3 on the Vibe Coding Index against 62.5 for DeepSeek V4.1 Flash. Pick DeepSeek V4.1 Flash for output tokens 11.9x cheaper ($0.84 vs $10.00 per million) and a larger context window (1.05M against 1M tokens).
Which is cheaper, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?
Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; DeepSeek V4.1 Flash costs $0.2225 and $0.84. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?
DeepSeek V4.1 Flash, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 5.5 vs DeepSeek V4.1 Flash comparison based on?
87 benchmarks have a result for both models as of October 22, 2026. Claude Sonnet 5.5's coding index rests on 5 independent benchmarks and DeepSeek V4.1 Flash's on 5. Where only one model has a result, the page says so instead of naming a winner.