Claude Opus 4.8 vs Kimi K3.1 Pro
Kimi K3.1 Pro leads Claude Opus 4.8 on coding, 82.2 to 62.8 on the Vibe Coding Index, and Kimi K3.1 Pro costs 2.5x less per output token ($10.00 vs $25.00 per million). Updated October 29, 2026; 20 benchmarks have a result for both.
vs boards won of 20 shared
Claude Opus 4.8 or Kimi K3.1 Pro: which to pick
Pick Kimi K3.1 Pro for coding: it scores 82.2 on the Vibe Coding Index against 62.8 for Claude Opus 4.8, though on 4 benchmarks against 5.
Pick Claude Opus 4.8 for work measured by Tax Agent Bench (Vals AI) or Legal Research Bench (Vals AI), where it leads.
Model AClaude Opus 4.8Anthropic62.8/1005 independent benchmarks$2.17 per solved taskModel BKimi K3.1 ProMoonshot AI82.2/1004 independent benchmarksNo cost per solved task
- Shared results
- 20
- Claude Opus 4.8 only
- 107
- Kimi K3.1 Pro only
- 15
- Like-for-like categories
- 6 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
Kimi K3.1 Pro
Kimi K3.1 Pro scores 82.2 against 62.8.
5 and 4 benchmarks behind the scores
Intelligence
AA Intelligence Index
No call
Only Kimi K3.1 Pro has a AA Intelligence Index result, 46.0.
Directional only
Agentic work
AA Agentic Index
No call
Only Claude Opus 4.8 has a AA Agentic Index result, 41.9.
Directional only
Reasoning
GPQA Diamond
No call
Only Claude Opus 4.8 has a GPQA Diamond result, 92.4%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Opus 4.8 has a MMLU Pro result, 89.6%.
Directional only
Web design
Design Arena: websites
Kimi K3.1 Pro
Kimi K3.1 Pro leads, 1325 against 1258.
Same board, both measured
General
Vals Index
No call
Only Kimi K3.1 Pro has a Vals Index result, 62.5%.
Directional only
Long documents
Listed context window
Kimi K3.1 Pro
Kimi K3.1 Pro takes 1.05M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Kimi K3.1 Pro
Claude Opus 4.8 $0.018, Kimi K3.1 Pro $0.0070 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Claude Opus 4.8 has the number, $2.17.
Directional only
At a glance
- Coding index
- Claude Opus 4.8 62.8 from 5 benchmarks, Kimi K3.1 Pro 82.2 from 4 benchmarks.
- Widest category
- Math, 20.8 points apart on average over 2 shared benchmarks.
- Widest single gap
- Terminal-Bench 4 (Vals AI): Claude Opus 4.8 23.2% against Kimi K3.1 Pro 63.6%, 53.9 points apart on a 0 to 100 scale.
- Output price
- Claude Opus 4.8 $25.00 against Kimi K3.1 Pro $10.00 per million output tokens, 2.5x apart.
- Context window
- Claude Opus 4.8 takes 1M tokens, Kimi K3.1 Pro 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 4.8 | Bars | Kimi K3.1 Pro | Ties |
|---|---|---|---|---|
| Coding | 0 | 6 | ||
| Agentic work | 2 | 1 | ||
| Reasoning | 0 | 1 | ||
| Math | 0 | 2 | ||
| Web design | 0 | 7 | ||
| General | 0 | 1 | ||
| All shared boards | 2 | 18 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index06
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| LiveBench coding | Not measured | 81.8% | Only Kimi K3.1 Pro measured |
| LMArena WebDev | 1556 | 1695 | Kimi K3.1 Pro |
| AA Coding Index | 74.3 | Not measured | Only Claude Opus 4.8 measured |
| LiveCodeBench (Vals AI) | 87.8% | Not measured | Only Claude Opus 4.8 measured |
| SWE-bench Verified (Vals AI) | 88.6% | Not measured | Only Claude Opus 4.8 measured |
| Terminal-Bench 4 (Vals AI) | 23.2% | 63.6% | Kimi K3.1 Pro |
| Vibe Code Bench (Vals AI) | 82.7% | 84.9% | Kimi K3.1 Pro |
| Code migration (Vals AI) | 47.3% | Not measured | Only Claude Opus 4.8 measured |
| ProgramBench (Vals AI) | 1.0% | Not measured | Only Claude Opus 4.8 measured |
| IOI (Vals AI) | Not measured | 81.9% | Only Kimi K3.1 Pro measured |
| Terminal-Bench 2.1 (Vals AI) | 71.9% | Not measured | Only Claude Opus 4.8 measured |
| SkillsBench (Vals AI) | 59.2% | Not measured | Only Claude Opus 4.8 measured |
| SciCode | 54.4% | 60.8% | Kimi K3.1 Pro |
| Terminal-Bench Hard (Artificial Analysis run) | 58.3% | Not measured | Only Claude Opus 4.8 measured |
| FrontierCode | 46.5% | Not measured | Only Claude Opus 4.8 measured |
| GSO-Bench | 47.1% | Not measured | Only Claude Opus 4.8 measured |
| WeirdML | 82.9% | Not measured | Only Claude Opus 4.8 measured |
| ALE-Bench | Not measured | 1932.8 | Only Kimi K3.1 Pro measured |
| LMArena Text: coding | 1491 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: software and IT | 1488 | Not measured | Only Claude Opus 4.8 measured |
| LMArena WebDev: React | 1557 | 1701 | Kimi K3.1 Pro |
| LMArena WebDev: HTML | 1543 | 1706 | Kimi K3.1 Pro |
| SciCode | 12.3% | Not measured | Only Claude Opus 4.8 measured |
| SWE Atlas: Codebase QnA | 57.3% | Not measured | Only Claude Opus 4.8 measured |
| SWE Atlas: Refactoring | 46.7% | Not measured | Only Claude Opus 4.8 measured |
| SWE Atlas: Test Writing | 49.6% | Not measured | Only Claude Opus 4.8 measured |
| Neither model has a result on the other 17 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| AA Intelligence Index | Not measured | 46.0 | Only Kimi K3.1 Pro measured |
| Epoch Capabilities Index | 159.0 | Not measured | Only Claude Opus 4.8 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index21
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| AA Agentic Index | 41.9 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: agents building web apps | 1234 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: agents building full-stack apps | 1249 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: agents building mobile apps | 1220 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: agents building Android apps | 1233 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: agents building Godot games | 1231 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: agents building games | 1200 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: HTML slides | 1117 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: PowerPoint slides | 1182 | Not measured | Only Claude Opus 4.8 measured |
| Design Arena: spreadsheets | 1217 | Not measured | Only Claude Opus 4.8 measured |
| LiveBench research | Not measured | 77.9% | Only Kimi K3.1 Pro measured |
| LiveBench browser | Not measured | 75.9% | Only Kimi K3.1 Pro measured |
| LiveBench long agentic | Not measured | 39.1% | Only Kimi K3.1 Pro measured |
| Finance Agent (Vals AI) | 53.9% | Not measured | Only Claude Opus 4.8 measured |
| Tax Agent Bench (Vals AI) | 30.0% | 24.9% | Claude Opus 4.8 |
| Legal Research Bench (Vals AI) | 43.8% | 37.5% | Claude Opus 4.8 |
| Harvey's Legal Agent Benchmark (Vals AI) | Not measured | 11.7% | Only Kimi K3.1 Pro measured |
| Excel Modeling Benchmark (Vals AI) | 69.4% | Not measured | Only Claude Opus 4.8 measured |
| BioMysteryBench (Vals AI) | Not measured | 75.6% | Only Kimi K3.1 Pro measured |
| Terminal-Bench-Science (Vals AI) | 4.3% | 31.4% | Kimi K3.1 Pro |
| Vals Science Index | Not measured | 44.4% | Only Kimi K3.1 Pro measured |
| Time Horizon Index (Vals AI) | 11.8% | Not measured | Only Claude Opus 4.8 measured |
| τ²-Bench Telecom | 94.4% | Not measured | Only Claude Opus 4.8 measured |
| APEX-Agents | 48.9% | Not measured | Only Claude Opus 4.8 measured |
| Remote Labor Index | 8.3% | Not measured | Only Claude Opus 4.8 measured |
| OSWorld 2.0 | 20.6% | Not measured | Only Claude Opus 4.8 measured |
| DeepResearch Bench | 50.2% | Not measured | Only Claude Opus 4.8 measured |
| PostTrainBench | 33.8% | Not measured | Only Claude Opus 4.8 measured |
| Vending-Bench 2 | $5,787 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Search | 1204 | Not measured | Only Claude Opus 4.8 measured |
| MCP Atlas | 82.2% | Not measured | Only Claude Opus 4.8 measured |
| Neither model has a result on the other 11 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| GPQA Diamond | 92.4% | Not measured | Only Claude Opus 4.8 measured |
| LiveBench reasoning | Not measured | 91.1% | Only Kimi K3.1 Pro measured |
| MysteryMechanism (Vals AI) | Not measured | 26.1% | Only Kimi K3.1 Pro measured |
| MMMU Pro (Vals AI) | 86.6% | Not measured | Only Claude Opus 4.8 measured |
| GPQA Diamond (Artificial Analysis run) | 92.0% | Not measured | Only Claude Opus 4.8 measured |
| Humanity's Last Exam (Artificial Analysis run) | 48.7% | 52.5% | Kimi K3.1 Pro |
| GPQA Diamond (Epoch AI run) | 91.0% | Not measured | Only Claude Opus 4.8 measured |
| ARC-AGI | 92.5% | Not measured | Only Claude Opus 4.8 measured |
| ARC-AGI-2 | 72.1% | Not measured | Only Claude Opus 4.8 measured |
| SimpleBench | 64.8% | Not measured | Only Claude Opus 4.8 measured |
| Chess puzzles | 52.0% | Not measured | Only Claude Opus 4.8 measured |
| Mystery game puzzles | 36.0% | Not measured | Only Claude Opus 4.8 measured |
| EBR-bench | 28.6% | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: hard prompts | 1482 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: expert | 1503 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: hard prompts in English | 1487 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: diagrams | 1315 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: homework | 1337 | Not measured | Only Claude Opus 4.8 measured |
| Kagi LLM Benchmark | 88.8% | Not measured | Only Claude Opus 4.8 measured |
| Neither model has a result on the other 4 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| OTIS Mock AIME | 98.3% | Not measured | Only Claude Opus 4.8 measured |
| FrontierMath, tiers 1 to 3 | 80.0% | Not measured | Only Claude Opus 4.8 measured |
| FrontierMath, tier 4 | 56.1% | Not measured | Only Claude Opus 4.8 measured |
| ProofBench | 69.0% | 91.0% | Kimi K3.1 Pro |
| LMArena Text: math | 1485 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: mathematical work | 1497 | Not measured | Only Claude Opus 4.8 measured |
| MathArena | 39.9% | 59.6% | Kimi K3.1 Pro |
| Neither model has a result on the other 7 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| MMLU Pro | 89.6% | Not measured | Only Claude Opus 4.8 measured |
| LegalBench (Vals AI) | 83.6% | Not measured | Only Claude Opus 4.8 measured |
| CorpFin (Vals AI) | 66.7% | Not measured | Only Claude Opus 4.8 measured |
| TaxEval (Vals AI) | 75.6% | Not measured | Only Claude Opus 4.8 measured |
| MortgageTax (Vals AI) | 69.9% | Not measured | Only Claude Opus 4.8 measured |
| MedCode (Vals AI) | 53.2% | Not measured | Only Claude Opus 4.8 measured |
| SimpleQA Verified | 53.0% | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: science | 1477 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: medicine and healthcare | 1464 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: legal and government | 1477 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: business and finance | 1458 | Not measured | Only Claude Opus 4.8 measured |
| FACTS Benchmark Suite | 59.7% | Not measured | Only Claude Opus 4.8 measured |
| Neither model has a result on the other 8 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index07
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| Design Arena: websites | 1258 | 1325 | Kimi K3.1 Pro |
| Design Arena: UI components | 1254 | 1400 | Kimi K3.1 Pro |
| Design Arena: game dev | 1263 | 1410 | Kimi K3.1 Pro |
| Design Arena: data viz | 1240 | 1300 | Kimi K3.1 Pro |
| Design Arena: 3D | 1219 | 1451 | Kimi K3.1 Pro |
| Design Arena: all code categories | 1254 | 1354 | Kimi K3.1 Pro |
| Design Arena: SVG | 1193 | 1328 | Kimi K3.1 Pro |
| Design Arena: ASCII art | 1274 | Not measured | Only Claude Opus 4.8 measured |
| LiveBench design | Not measured | 77.8% | Only Kimi K3.1 Pro measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | Leader |
|---|---|---|---|
| Vals Index | Not measured | 62.5% | Only Kimi K3.1 Pro measured |
| LiveBench data analysis | Not measured | 79.1% | Only Kimi K3.1 Pro measured |
| Public Benefits Bench (Vals AI) | 68.1% | Not measured | Only Claude Opus 4.8 measured |
| MedScribe (Vals AI) | 85.8% | Not measured | Only Claude Opus 4.8 measured |
| Vals Multimodal Index | 70.9% | Not measured | Only Claude Opus 4.8 measured |
| IFBench | 62.2% | Not measured | Only Claude Opus 4.8 measured |
| Long context reasoning (AA-LCR) | 77.7% | 86.3% | Kimi K3.1 Pro |
| DTBench | 94.9% | Not measured | Only Claude Opus 4.8 measured |
| LMCA | 57.5% | Not measured | Only Claude Opus 4.8 measured |
| Surface Evolver Bench | 87.5% | Not measured | Only Claude Opus 4.8 measured |
| Furniture assembly | 42.5% | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text | 1461 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: instruction following | 1477 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: creative writing | 1455 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision | 1294 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: English | 1469 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: non-English | 1450 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: Chinese | 1507 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: German | 1471 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: Japanese | 1442 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: Korean | 1431 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: French | 1480 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: Spanish | 1465 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: Russian | 1475 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: Polish | 1458 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: multi-turn | 1476 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: longer queries | 1484 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: writing and language | 1462 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Text: entertainment and media | 1441 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: English | 1293 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: Chinese | 1346 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: reading text | 1303 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: humor | 1282 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Vision: creative writing | 1301 | Not measured | Only Claude Opus 4.8 measured |
| LMArena Document | 1475 | Not measured | Only Claude Opus 4.8 measured |
| EQ-Bench 4 | 1268 | Not measured | Only Claude Opus 4.8 measured |
| Neither model has a result on the other 12 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Opus 4.8 | Kimi K3.1 Pro | 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
Claude Opus 4.8$0.018Fits in one request
Kimi K3.1 Pro$0.0070Fits in one request
Kimi K3.1 Pro costs less
Repository review
50K input + 3K output tokens
Claude Opus 4.8$0.325Fits in one request
Kimi K3.1 Pro$0.130Fits in one request
Kimi K3.1 Pro costs less
Agent loop
200K input + 10K output tokens
Claude Opus 4.8$1.25Fits in one request
Kimi K3.1 Pro$0.500Fits in one request
Kimi K3.1 Pro 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 4.8 | MoonshotAI Kimi K3.1 Pro |
|---|---|---|
| Maker | Anthropic | Moonshot AI |
| Weights | No public weights listed | No public weights listed |
| Released | May 27, 2026 | October 23, 2026 |
| Context window | 1M | 1.05M |
| Input $/Mtok | $5.00 | $2.00 |
| Output $/Mtok | $25.00 | $10.00 |
| Coding index | 62.8 | 82.2 |
| Independent measurements behind it | 5 | 4 |
| Cost per solved task | $2.17 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Opus 4.8 better than Kimi K3.1 Pro for coding?
Pick Kimi K3.1 Pro for coding: it scores 82.2 on the Vibe Coding Index against 62.8 for Claude Opus 4.8, though on 4 benchmarks against 5. Pick Claude Opus 4.8 for work measured by Tax Agent Bench (Vals AI) or Legal Research Bench (Vals AI), where it leads.
Which is cheaper, Claude Opus 4.8 or Kimi K3.1 Pro?
Claude Opus 4.8 costs $5.00 per million input tokens and $25.00 per million output tokens; Kimi K3.1 Pro costs $2.00 and $10.00. Cost per solved task is known for Claude Opus 4.8 only.
Which has the bigger context window, Claude Opus 4.8 or Kimi K3.1 Pro?
Kimi K3.1 Pro, with 1.05M tokens against 1M.
How many benchmarks is the Claude Opus 4.8 vs Kimi K3.1 Pro comparison based on?
20 benchmarks have a result for both models as of October 29, 2026. Claude Opus 4.8's coding index rests on 5 independent benchmarks and Kimi K3.1 Pro's on 4. Where only one model has a result, the page says so instead of naming a winner.