Claude Opus 5.5 vs DeepSeek V4.1 Flash 1017
Claude Opus 5.5 leads DeepSeek V4.1 Flash 1017 on coding, 88.8 to 70.3 on the Vibe Coding Index, and DeepSeek V4.1 Flash 1017 costs 33.3x less per output token ($0.60 vs $20.00 per million). Updated October 22, 2026; 38 benchmarks have a result for both.
Claude Opus 5.5 or DeepSeek V4.1 Flash 1017: which to pick
Pick Claude Opus 5.5 for coding: it scores 88.8 on the Vibe Coding Index against 70.3 for DeepSeek V4.1 Flash 1017.
Pick DeepSeek V4.1 Flash 1017 for output tokens 33.3x cheaper ($0.60 vs $20.00 per million) and a larger context window (1.05M against 1M tokens).
- Shared results
- 38
- Claude Opus 5.5 only
- 71
- DeepSeek V4.1 Flash 1017 only
- 1
- 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 Opus 5.5
Claude Opus 5.5 scores 88.8 against 70.3.
5 and 4 benchmarks behind the scores
Intelligence
AA Intelligence Index
Claude Opus 5.5
Claude Opus 5.5 leads, 57.6 against 39.5.
Same board, both measured
Web design
Design Arena: websites
Claude Opus 5.5
Claude Opus 5.5 leads, 1335 against 1311.
Same board, both measured
General
Vals Index
Claude Opus 5.5
Claude Opus 5.5 leads, 70.2% against 61.3%.
Same board, both measured
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 Opus 5.5 $0.014, DeepSeek V4.1 Flash 1017 $0.0004 per turn.
List prices
At a glance
- Coding index
- Claude Opus 5.5 88.8 from 5 benchmarks, DeepSeek V4.1 Flash 1017 70.3 from 4 benchmarks.
- Widest category
- Knowledge, 29.7 points apart on average over 1 shared benchmark.
- Widest single gap
- FrontierMath, tier 4: Claude Opus 5.5 95.0% against DeepSeek V4.1 Flash 1017 46.3%, 48.7 points apart on a 0 to 100 scale.
- Output price
- Claude Opus 5.5 $20.00 against DeepSeek V4.1 Flash 1017 $0.60 per million output tokens, 33.3x apart.
- Context window
- Claude Opus 5.5 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 Opus 5.5 | Bars | DeepSeek V4.1 Flash 1017 | Ties |
|---|---|---|---|---|
| Coding | 9 | 0 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 8 | 1 | ||
| Reasoning | 4 | 1 | ||
| Math | 3 | 0 | ||
| Knowledge | 1 | 0 | ||
| Web design | 7 | 0 | ||
| General | 3 | 0 | ||
| All shared boards | 36 | 2 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index90
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| LiveBench coding | 96.3% | 96.0% | Claude Opus 5.5 |
| LMArena WebDev | 1807 | 1664 | Claude Opus 5.5 |
| Terminal-Bench 4 (Vals AI) | 65.2% | 31.8% | Claude Opus 5.5 |
| Vibe Code Bench (Vals AI) | 90.3% | 87.7% | Claude Opus 5.5 |
| Code migration (Vals AI) | 66.7% | 44.2% | Claude Opus 5.5 |
| ProgramBench (Vals AI) | 18.5% | Not measured | Only Claude Opus 5.5 measured |
| IOI (Vals AI) | 95.1% | Not measured | Only Claude Opus 5.5 measured |
| Terminal-Bench 2.1 (Vals AI) | 87.6% | Not measured | Only Claude Opus 5.5 measured |
| SWE-bench Multimodal (Vals AI) | 70.2% | Not measured | Only Claude Opus 5.5 measured |
| Vibe Code Bench 1-100 (Vals AI) | 30.4% | Not measured | Only Claude Opus 5.5 measured |
| CyberBench (Vals AI) | 74.6% | Not measured | Only Claude Opus 5.5 measured |
| SciCode | 66.9% | 55.9% | Claude Opus 5.5 |
| FrontierCode | 54.6% | Not measured | Only Claude Opus 5.5 measured |
| FrontierSWE | 62.3% | Not measured | Only Claude Opus 5.5 measured |
| MirrorCode | 77.4% | Not measured | Only Claude Opus 5.5 measured |
| ALE-Bench | 2147.4 | 1622.0 | Claude Opus 5.5 |
| LMArena Text: coding | 1545 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: software and IT | 1538 | Not measured | Only Claude Opus 5.5 measured |
| LMArena WebDev: React | 1855 | 1667 | Claude Opus 5.5 |
| LMArena WebDev: HTML | 1753 | 1687 | Claude Opus 5.5 |
| LMArena WebDev: from an image | 1753 | Not measured | Only Claude Opus 5.5 measured |
| SciCode | 18.5% | Not measured | Only Claude Opus 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 index10
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| AA Intelligence Index | 57.6 | 39.5 | Claude Opus 5.5 |
| Epoch Capabilities Index | 168.8 | Not measured | Only Claude Opus 5.5 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index81
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1316 | Not measured | Only Claude Opus 5.5 measured |
| Design Arena: agents building mobile apps | 1308 | Not measured | Only Claude Opus 5.5 measured |
| Design Arena: spreadsheets | 1368 | 1245 | Claude Opus 5.5 |
| LiveBench research | 85.0% | 79.5% | Claude Opus 5.5 |
| LiveBench browser | 80.0% | 76.0% | Claude Opus 5.5 |
| LiveBench long agentic | 85.0% | 50.9% | Claude Opus 5.5 |
| SREBench (Vals AI) | 33.6% | Not measured | Only Claude Opus 5.5 measured |
| Finance Agent (Vals AI) | 58.6% | 57.0% | Claude Opus 5.5 |
| Tax Agent Bench (Vals AI) | 45.6% | 44.4% | Claude Opus 5.5 |
| Legal Research Bench (Vals AI) | 50.5% | 45.2% | Claude Opus 5.5 |
| Harvey's Legal Agent Benchmark (Vals AI) | 9.2% | 14.2% | DeepSeek V4.1 Flash 1017 |
| Excel Modeling Benchmark (Vals AI) | 75.9% | 61.8% | Claude Opus 5.5 |
| BioMysteryBench (Vals AI) | 79.3% | Not measured | Only Claude Opus 5.5 measured |
| Terminal-Bench-Science (Vals AI) | 47.1% | Not measured | Only Claude Opus 5.5 measured |
| Vals Science Index | 58.7% | Not measured | Only Claude Opus 5.5 measured |
| Time Horizon Index (Vals AI) | 91.3% | Not measured | Only Claude Opus 5.5 measured |
| CUA-bench (Vals AI) | 14.0% | Not measured | Only Claude Opus 5.5 measured |
| Robo-bench (Vals AI) | 14.6% | Not measured | Only Claude Opus 5.5 measured |
| APEX-Agents | 73.5% | Not measured | Only Claude Opus 5.5 measured |
| Remote Labor Index | 21.3% | Not measured | Only Claude Opus 5.5 measured |
| SpireClimb | 3.3% | Not measured | Only Claude Opus 5.5 measured |
| Vending-Bench 2 | $9,235 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Search | 1213 | Not measured | Only Claude Opus 5.5 measured |
| Neither model has a result on the other 18 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index41
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| LiveBench reasoning | 92.2% | 89.1% | Claude Opus 5.5 |
| MysteryMechanism (Vals AI) | 49.5% | Not measured | Only Claude Opus 5.5 measured |
| Humanity's Last Exam (Artificial Analysis run) | 61.4% | 43.3% | Claude Opus 5.5 |
| GPQA Diamond (Epoch AI run) | 90.6% | 93.2% | DeepSeek V4.1 Flash 1017 |
| ARC-AGI | 98.5% | Not measured | Only Claude Opus 5.5 measured |
| ARC-AGI-2 | 93.3% | Not measured | Only Claude Opus 5.5 measured |
| Chess puzzles | 67.0% | 46.0% | Claude Opus 5.5 |
| Mystery game puzzles | 71.0% | 49.0% | Claude Opus 5.5 |
| EBR-bench | 71.4% | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: hard prompts | 1536 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: expert | 1549 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: hard prompts in English | 1535 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Vision: diagrams | 1345 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Vision: homework | 1362 | Not measured | Only Claude Opus 5.5 measured |
| Neither model has a result on the other 8 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| OTIS Mock AIME | 100.0% | 99.4% | Claude Opus 5.5 |
| FrontierMath, tiers 1 to 3 | 91.2% | 71.2% | Claude Opus 5.5 |
| FrontierMath, tier 4 | 95.0% | 46.3% | Claude Opus 5.5 |
| ProofBench | 100.0% | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: math | 1518 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: mathematical work | 1516 | Not measured | Only Claude Opus 5.5 measured |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| MedCode (Vals AI) | 49.8% | Not measured | Only Claude Opus 5.5 measured |
| SimpleQA Verified | 72.2% | 42.5% | Claude Opus 5.5 |
| LMArena Text: science | 1524 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: medicine and healthcare | 1509 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: legal and government | 1518 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: business and finance | 1494 | Not measured | Only Claude Opus 5.5 measured |
| FACTS Benchmark Suite | 65.3% | Not measured | Only Claude Opus 5.5 measured |
| 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 Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| Design Arena: websites | 1335 | 1311 | Claude Opus 5.5 |
| Design Arena: UI components | 1385 | 1303 | Claude Opus 5.5 |
| Design Arena: game dev | 1461 | 1357 | Claude Opus 5.5 |
| Design Arena: data viz | 1397 | 1330 | Claude Opus 5.5 |
| Design Arena: 3D | 1476 | 1358 | Claude Opus 5.5 |
| Design Arena: all code categories | 1390 | 1332 | Claude Opus 5.5 |
| Design Arena: SVG | 1329 | Not measured | Only Claude Opus 5.5 measured |
| Design Arena: ASCII art | Not measured | 1242 | Only DeepSeek V4.1 Flash 1017 measured |
| LiveBench design | 86.9% | 83.4% | Claude Opus 5.5 |
GeneralLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Opus 5.5 | DeepSeek V4.1 Flash 1017 | Leader |
|---|---|---|---|
| Vals Index | 70.2% | 61.3% | Claude Opus 5.5 |
| LiveBench data analysis | 80.3% | 79.5% | Claude Opus 5.5 |
| Public Benefits Bench (Vals AI) | 70.6% | Not measured | Only Claude Opus 5.5 measured |
| SAGE (Vals AI) | 45.8% | Not measured | Only Claude Opus 5.5 measured |
| MedScribe (Vals AI) | 91.4% | Not measured | Only Claude Opus 5.5 measured |
| Long context reasoning (AA-LCR) | 84.7% | 82.7% | Claude Opus 5.5 |
| DTBench | 98.9% | Not measured | Only Claude Opus 5.5 measured |
| LMCA | 68.2% | Not measured | Only Claude Opus 5.5 measured |
| Furniture assembly | 83.3% | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text | 1516 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: instruction following | 1537 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: creative writing | 1535 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Vision | 1321 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: English | 1519 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: non-English | 1507 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: Chinese | 1582 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: Japanese | 1534 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: French | 1493 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: Spanish | 1508 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: Russian | 1517 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: multi-turn | 1501 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: longer queries | 1532 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: writing and language | 1532 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Text: entertainment and media | 1515 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Vision: English | 1317 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Vision: reading text | 1326 | Not measured | Only Claude Opus 5.5 measured |
| LMArena Vision: creative writing | 1320 | Not measured | Only Claude Opus 5.5 measured |
| Neither model has a result on the other 19 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Opus 5.5 | 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 Opus 5.5 | DeepSeek V4.1 Flash 1017 |
|---|---|---|
| Maker | Anthropic | DeepSeek |
| Weights | No public weights listed | Open weights |
| Released | September 22, 2026 | October 17, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $4.00 | $0.15 |
| Output $/Mtok | $20.00 | $0.60 |
| Coding index | 88.8 | 70.3 |
| Independent measurements behind it | 5 | 4 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Opus 5.5 better than DeepSeek V4.1 Flash 1017 for coding?
Pick Claude Opus 5.5 for coding: it scores 88.8 on the Vibe Coding Index against 70.3 for DeepSeek V4.1 Flash 1017. Pick DeepSeek V4.1 Flash 1017 for output tokens 33.3x cheaper ($0.60 vs $20.00 per million) and a larger context window (1.05M against 1M tokens).
Which is cheaper, Claude Opus 5.5 or DeepSeek V4.1 Flash 1017?
Claude Opus 5.5 costs $4.00 per million input tokens and $20.00 per million output tokens; DeepSeek V4.1 Flash 1017 costs $0.15 and $0.60. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Opus 5.5 or DeepSeek V4.1 Flash 1017?
DeepSeek V4.1 Flash 1017, with 1.05M tokens against 1M.
How many benchmarks is the Claude Opus 5.5 vs DeepSeek V4.1 Flash 1017 comparison based on?
38 benchmarks have a result for both models as of October 22, 2026. Claude Opus 5.5's coding index rests on 5 independent benchmarks and DeepSeek V4.1 Flash 1017's on 4. Where only one model has a result, the page says so instead of naming a winner.