Claude Sonnet 4.5 vs DeepSeek V4.1 Flash 1017
Updated October 21, 2026. 12 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick DeepSeek V4.1 Flash 1017 for coding: it scores 83.3 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5.
Claude Sonnet 4.5 is neither cheaper nor larger in context, and leads no benchmark both models were measured on.
- Shared results
- 12
- Claude Sonnet 4.5 only
- 80
- DeepSeek V4.1 Flash 1017 only
- 20
- Like-for-like categories
- 3 of 9
Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.
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, four public coding benchmarks
DeepSeek V4.1 Flash 1017
DeepSeek V4.1 Flash 1017 scores 83.3 against 59.1.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
DeepSeek V4.1 Flash 1017
DeepSeek V4.1 Flash 1017 leads, 39.5 against 20.7.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Claude Sonnet 4.5 has a AA Agentic Index result, 15.8.
Directional only
Reasoning
GPQA Diamond
No call
Only Claude Sonnet 4.5 has a GPQA Diamond result, 81.6%.
Directional only
Math
AIME
No call
Only Claude Sonnet 4.5 has a AIME result, 88.2%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Sonnet 4.5 has a MMLU Pro result, 87.4%.
Directional only
Web design
Design Arena: websites
DeepSeek V4.1 Flash 1017
DeepSeek V4.1 Flash 1017 leads, 1312 against 1190.
Same board, both measured
General
Vals Index
No call
Only DeepSeek V4.1 Flash 1017 has a Vals Index result, 61.3%.
Directional only
Long documents
Listed context window
DeepSeek V4.1 Flash 1017
DeepSeek V4.1 Flash 1017 takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
DeepSeek V4.1 Flash 1017
Claude Sonnet 4.5 $0.011, DeepSeek V4.1 Flash 1017 $0.0004 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Claude Sonnet 4.5 has the number, $1.16.
Directional only
At a glance
- Coding index
- Claude Sonnet 4.5 59.1 from 2 benchmarks, DeepSeek V4.1 Flash 1017 83.3 from 2 benchmarks.
- Widest category
- Coding, 43.2 points apart on average over 4 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Claude Sonnet 4.5 22.6% against DeepSeek V4.1 Flash 1017 87.7%, 65.1 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 4.5 $15.00 against DeepSeek V4.1 Flash 1017 $0.60 per million output tokens, 25.0x apart.
- Context window
- Claude Sonnet 4.5 takes 1M tokens, DeepSeek V4.1 Flash 1017 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 4.5 | Bars | DeepSeek V4.1 Flash 1017 | Ties |
|---|---|---|---|---|
| Coding | 0 | 4 | ||
| Intelligence | 0 | 1 | ||
| Web design | 0 | 7 | ||
| All shared boards | 0 | 12 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index04
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| SWE-bench Verified | 74.8% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Multilingual | 67.0% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveBench coding | Not measured | 96.0% | Only DeepSeek V4.1 Flash 1017 measured |
| LMArena WebDev | 1394 | 1664 | DeepSeek V4.1 Flash 1017 |
| AA Coding Index | 52.1 | Not measured | Only Claude Sonnet 4.5 measured |
| LiveCodeBench (Vals AI) | 73.0% | Not measured | Only Claude Sonnet 4.5 measured |
| SWE-bench Verified (Vals AI) | 70.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 31.8% | Only DeepSeek V4.1 Flash 1017 measured |
| Vibe Code Bench (Vals AI) | 22.6% | 87.7% | DeepSeek V4.1 Flash 1017 |
| Code migration (Vals AI) | Not measured | 44.2% | Only DeepSeek V4.1 Flash 1017 measured |
| SciCode | Not measured | 55.9% | Only DeepSeek V4.1 Flash 1017 measured |
| Terminal-Bench | 46.5% | Not measured | Only Claude Sonnet 4.5 measured |
| GSO-Bench | 14.7% | Not measured | Only Claude Sonnet 4.5 measured |
| WeirdML | 47.7% | Not measured | Only Claude Sonnet 4.5 measured |
| Cybench | 60.0% | Not measured | Only Claude Sonnet 4.5 measured |
| ALE-Bench | Not measured | 1622.0 | Only DeepSeek V4.1 Flash 1017 measured |
| LMArena Text: coding | 1488 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: software and IT | 1473 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena WebDev: React | 1386 | 1667 | DeepSeek V4.1 Flash 1017 |
| LMArena WebDev: HTML | 1399 | 1687 | DeepSeek V4.1 Flash 1017 |
| Neither model has a result on the other 18 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| AA Intelligence Index | 20.7 | 39.5 | DeepSeek V4.1 Flash 1017 |
| Epoch Capabilities Index | 146.7 | Not measured | Only Claude Sonnet 4.5 measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index19 boards, none shared
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| AA Agentic Index | 15.8 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building web apps | 1060 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building full-stack apps | 1050 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: agents building mobile apps | 1137 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: spreadsheets | Not measured | 1238 | Only DeepSeek V4.1 Flash 1017 measured |
| LiveBench research | Not measured | 79.5% | Only DeepSeek V4.1 Flash 1017 measured |
| LiveBench browser | Not measured | 76.0% | Only DeepSeek V4.1 Flash 1017 measured |
| LiveBench long agentic | Not measured | 50.9% | Only DeepSeek V4.1 Flash 1017 measured |
| Finance Agent (Vals AI) | Not measured | 57.0% | Only DeepSeek V4.1 Flash 1017 measured |
| Tax Agent Bench (Vals AI) | Not measured | 44.4% | Only DeepSeek V4.1 Flash 1017 measured |
| Legal Research Bench (Vals AI) | Not measured | 45.2% | Only DeepSeek V4.1 Flash 1017 measured |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 14.2% | Only DeepSeek V4.1 Flash 1017 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 61.8% | Only DeepSeek V4.1 Flash 1017 measured |
| METR time horizons | 67.4% | Not measured | Only Claude Sonnet 4.5 measured |
| Remote Labor Index | 2.1% | Not measured | Only Claude Sonnet 4.5 measured |
| GDPval | 42.5% | Not measured | Only Claude Sonnet 4.5 measured |
| DeepResearch Bench | 52.6% | Not measured | Only Claude Sonnet 4.5 measured |
| OSWorld | 62.9% | Not measured | Only Claude Sonnet 4.5 measured |
| Vending-Bench 2 | $3,839 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 20 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index15 boards, none shared
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| GPQA Diamond | 81.6% | Not measured | Only Claude Sonnet 4.5 measured |
| LiveBench reasoning | Not measured | 89.1% | Only DeepSeek V4.1 Flash 1017 measured |
| MMMU Pro (Vals AI) | 79.3% | Not measured | Only Claude Sonnet 4.5 measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 43.3% | Only DeepSeek V4.1 Flash 1017 measured |
| GPQA Diamond (Epoch AI run) | 82.3% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI | 63.7% | Not measured | Only Claude Sonnet 4.5 measured |
| ARC-AGI-2 | 13.6% | Not measured | Only Claude Sonnet 4.5 measured |
| SimpleBench | 54.3% | Not measured | Only Claude Sonnet 4.5 measured |
| Chess puzzles | 10.0% | Not measured | Only Claude Sonnet 4.5 measured |
| Mystery game puzzles | 17.0% | Not measured | Only Claude Sonnet 4.5 measured |
| EBR-bench | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| VPCT | 39.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts | 1462 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: expert | 1483 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: hard prompts in English | 1471 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 6 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| AIME | 88.2% | Not measured | Only Claude Sonnet 4.5 measured |
| MGSM (Vals AI) | 94.3% | Not measured | Only Claude Sonnet 4.5 measured |
| OTIS Mock AIME | 77.8% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tiers 1 to 3 | 23.9% | Not measured | Only Claude Sonnet 4.5 measured |
| FrontierMath, tier 4 | 2.4% | Not measured | Only Claude Sonnet 4.5 measured |
| ProofBench | 19.0% | Not measured | Only Claude Sonnet 4.5 measured |
| MATH level 5 | 97.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: math | 1449 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: mathematical work | 1462 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 4 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index13 boards, none shared
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| MMLU Pro | 87.4% | Not measured | Only Claude Sonnet 4.5 measured |
| LegalBench (Vals AI) | 84.1% | Not measured | Only Claude Sonnet 4.5 measured |
| CaseLaw (Vals AI) | 62.2% | Not measured | Only Claude Sonnet 4.5 measured |
| CorpFin (Vals AI) | 62.0% | Not measured | Only Claude Sonnet 4.5 measured |
| TaxEval (Vals AI) | 73.3% | Not measured | Only Claude Sonnet 4.5 measured |
| MortgageTax (Vals AI) | 64.0% | Not measured | Only Claude Sonnet 4.5 measured |
| MedQA (Vals AI) | 94.7% | Not measured | Only Claude Sonnet 4.5 measured |
| MedCode (Vals AI) | 44.1% | Not measured | Only Claude Sonnet 4.5 measured |
| SimpleQA Verified | 30.7% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: science | 1448 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: medicine and healthcare | 1444 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: legal and government | 1451 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: business and finance | 1440 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 4 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index07
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| Design Arena: websites | 1190 | 1312 | DeepSeek V4.1 Flash 1017 |
| Design Arena: UI components | 1173 | 1305 | DeepSeek V4.1 Flash 1017 |
| Design Arena: game dev | 1166 | 1365 | DeepSeek V4.1 Flash 1017 |
| Design Arena: data viz | 1167 | 1330 | DeepSeek V4.1 Flash 1017 |
| Design Arena: 3D | 1158 | 1368 | DeepSeek V4.1 Flash 1017 |
| Design Arena: all code categories | 1183 | 1335 | DeepSeek V4.1 Flash 1017 |
| Design Arena: SVG | 1114 | Not measured | Only Claude Sonnet 4.5 measured |
| Design Arena: ASCII art | 1204 | 1244 | DeepSeek V4.1 Flash 1017 |
| LiveBench design | Not measured | 83.4% | Only DeepSeek V4.1 Flash 1017 measured |
GeneralDirectional onlyPublic boards, shown as published, kept out of the index25 boards, none shared
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| Vals Index | Not measured | 61.3% | Only DeepSeek V4.1 Flash 1017 measured |
| LiveBench data analysis | Not measured | 79.5% | Only DeepSeek V4.1 Flash 1017 measured |
| SAGE (Vals AI) | 36.1% | Not measured | Only Claude Sonnet 4.5 measured |
| MedScribe (Vals AI) | 84.5% | Not measured | Only Claude Sonnet 4.5 measured |
| Long context reasoning (AA-LCR) | Not measured | 82.7% | Only DeepSeek V4.1 Flash 1017 measured |
| DTBench | 83.2% | Not measured | Only Claude Sonnet 4.5 measured |
| LMCA | 38.8% | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text | 1438 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: instruction following | 1459 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: creative writing | 1442 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: English | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: non-English | 1425 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Chinese | 1460 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: German | 1427 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Japanese | 1390 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Korean | 1402 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: French | 1459 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Spanish | 1458 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Russian | 1437 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: Polish | 1423 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: multi-turn | 1465 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: longer queries | 1475 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: writing and language | 1442 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Text: entertainment and media | 1428 | Not measured | Only Claude Sonnet 4.5 measured |
| LMArena Document | 1450 | Not measured | Only Claude Sonnet 4.5 measured |
| Neither model has a result on the other 21 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 4.5 | DeepSeek V4.1 Flash 1017 | 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 1017 costs less
Repository review
50K input + 3K output tokens
DeepSeek V4.1 Flash 1017 costs less
Agent loop
200K input + 10K output tokens
DeepSeek V4.1 Flash 1017 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 4.5 | DeepSeek V4.1 Flash 1017 |
|---|---|---|
| Maker | Anthropic | DeepSeek |
| Weights | No public weights listed | Open weights |
| Released | September 29, 2025 | October 17, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $3.00 | $0.15 |
| Output $/Mtok | $15.00 | $0.60 |
| Coding index | 59.1 | 83.3 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | $1.16 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 4.5 better than DeepSeek V4.1 Flash 1017 for coding?
Pick DeepSeek V4.1 Flash 1017 for coding: it scores 83.3 on the Vibe Coding Index against 59.1 for Claude Sonnet 4.5. Claude Sonnet 4.5 is neither cheaper nor larger in context, and leads no benchmark both models were measured on.
Which is cheaper, Claude Sonnet 4.5 or DeepSeek V4.1 Flash 1017?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; DeepSeek V4.1 Flash 1017 costs $0.15 and $0.60. Cost per solved task is known for Claude Sonnet 4.5 only.
Which has the bigger context window, Claude Sonnet 4.5 or DeepSeek V4.1 Flash 1017?
DeepSeek V4.1 Flash 1017, with 1.05M tokens against 1M.
How many benchmarks is the Claude Sonnet 4.5 vs DeepSeek V4.1 Flash 1017 comparison based on?
12 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 4.5's coding index rests on 2 independent benchmarks and DeepSeek V4.1 Flash 1017's on 2. Where only one model has a result, the page says so instead of naming a winner.