Claude Sonnet 5.5 vs Kimi K2.5
Updated October 21, 2026. 58 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
vs boards won of 58 shared
Decision reading
Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 58.5 for Kimi K2.5.
Pick Kimi K2.5 when output tokens cost 4.0x less, or when the benchmark that matters is LMArena Vision: creative writing, where it leads.
Model AClaude Sonnet 5.5Anthropic88.9/1002 independent benchmarksNo cost per solved taskModel BKimi K2.5Moonshot AI58.5/1002 independent benchmarks$0.24 per solved task
- Shared results
- 58
- Claude Sonnet 5.5 only
- 37
- Kimi K2.5 only
- 40
- Like-for-like categories
- 8 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
Claude Sonnet 5.5
Claude Sonnet 5.5 scores 88.9 against 58.5.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 56.0 against 23.5.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Kimi K2.5 has a GPQA Diamond result, 84.1%.
Directional only
Math
AIME
No call
Only Kimi K2.5 has a AIME result, 95.6%.
Directional only
Knowledge
MMLU Pro
No call
Only Kimi K2.5 has a MMLU Pro result, 85.9%.
Directional only
Web design
Design Arena: websites
Claude Sonnet 5.5
Claude Sonnet 5.5 leads, 1326 against 1249.
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
Claude Sonnet 5.5
Claude Sonnet 5.5 takes 1M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Kimi K2.5
Claude Sonnet 5.5 $0.0070, Kimi K2.5 $0.0018 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Kimi K2.5 has the number, $0.24.
Directional only
At a glance
- Coding index
- Claude Sonnet 5.5 88.9 from 2 benchmarks, Kimi K2.5 58.5 from 2 benchmarks.
- Widest category
- Coding, 35.4 points apart on average over 10 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Claude Sonnet 5.5 92.4% against Kimi K2.5 17.5%, 74.8 points apart on a 0 to 100 scale.
- Output price
- Claude Sonnet 5.5 $10.00 against Kimi K2.5 $2.50 per million output tokens, 4.0x apart.
- Context window
- Claude Sonnet 5.5 takes 1M tokens, Kimi K2.5 262K.
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 | Kimi K2.5 | Ties |
|---|---|---|---|---|
| Coding | 10 | 0 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 6 | 0 | ||
| Reasoning | 6 | 0 | ||
| Math | 2 | 0 | ||
| Knowledge | 6 | 0 | ||
| Web design | 6 | 0 | ||
| General | 19 | 1 | ||
| All shared boards | 57 | 1 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index100
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 70.8% | Only Kimi K2.5 measured |
| SWE-bench Multilingual | Not measured | 67.3% | Only Kimi K2.5 measured |
| LiveBench coding | 94.7% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena WebDev | 1768 | 1437 | Claude Sonnet 5.5 |
| AA Coding Index | Not measured | 46.8 | Only Kimi K2.5 measured |
| LiveCodeBench (Vals AI) | Not measured | 83.9% | Only Kimi K2.5 measured |
| SWE-bench Verified (Vals AI) | Not measured | 70.0% | Only Kimi K2.5 measured |
| Terminal-Bench 4 (Vals AI) | 64.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Vibe Code Bench (Vals AI) | 92.4% | 17.5% | Claude Sonnet 5.5 |
| Code migration (Vals AI) | 69.8% | 7.0% | Claude Sonnet 5.5 |
| ProgramBench (Vals AI) | 6.5% | Not measured | Only Claude Sonnet 5.5 measured |
| IOI (Vals AI) | 83.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench 2.1 (Vals AI) | 83.2% | 42.0% | Claude Sonnet 5.5 |
| SWE-bench Multimodal (Vals AI) | 58.3% | Not measured | Only Claude Sonnet 5.5 measured |
| CyberBench (Vals AI) | 59.6% | Not measured | Only Claude Sonnet 5.5 measured |
| SciCode | 61.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 34.8% | Only Kimi K2.5 measured |
| Terminal-Bench | Not measured | 43.2% | Only Kimi K2.5 measured |
| FrontierCode | 52.1% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierSWE | 61.9% | Not measured | Only Claude Sonnet 5.5 measured |
| WeirdML | Not measured | 45.6% | Only Kimi K2.5 measured |
| ALE-Bench | 1819.1 | 821.6 | Claude Sonnet 5.5 |
| LMArena Text: coding | 1513 | 1483 | Claude Sonnet 5.5 |
| LMArena Text: software and IT | 1504 | 1471 | Claude Sonnet 5.5 |
| LMArena WebDev: React | 1817 | 1429 | Claude Sonnet 5.5 |
| LMArena WebDev: HTML | 1741 | 1426 | Claude Sonnet 5.5 |
| LMArena WebDev: from an image | 1737 | 1439 | Claude Sonnet 5.5 |
| Neither model has a result on the other 11 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 56.0 | 23.5 | Claude Sonnet 5.5 |
| Epoch Capabilities Index | 166.2 | 148.1 | Claude Sonnet 5.5 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1303 | 1136 | Claude Sonnet 5.5 |
| Design Arena: agents building full-stack apps | Not measured | 1114 | Only Kimi K2.5 measured |
| Design Arena: agents building mobile apps | 1265 | 1147 | Claude Sonnet 5.5 |
| Design Arena: agents building Android apps | Not measured | 1124 | Only Kimi K2.5 measured |
| Design Arena: agents building Godot games | Not measured | 1219 | Only Kimi K2.5 measured |
| Design Arena: spreadsheets | 1245 | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench research | 83.6% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench browser | 84.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench long agentic | 78.8% | Not measured | Only Claude Sonnet 5.5 measured |
| SREBench (Vals AI) | 30.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Finance Agent (Vals AI) | 58.1% | 35.8% | Claude Sonnet 5.5 |
| Tax Agent Bench (Vals AI) | 42.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Legal Research Bench (Vals AI) | 48.1% | 15.9% | 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% | 28.5% | Claude Sonnet 5.5 |
| BioMysteryBench (Vals AI) | 81.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Terminal-Bench-Science (Vals AI) | 47.1% | Not measured | Only Claude Sonnet 5.5 measured |
| Vals Science Index | 59.1% | Not measured | Only Claude Sonnet 5.5 measured |
| τ²-Bench Telecom | Not measured | 95.9% | Only Kimi K2.5 measured |
| APEX-Agents | 75.5% | Not measured | Only Claude Sonnet 5.5 measured |
| OSWorld | Not measured | 63.3% | Only Kimi K2.5 measured |
| SpireClimb | 1.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Vending-Bench 2 | $11,165 | $1,198 | Claude Sonnet 5.5 |
| Neither model has a result on the other 16 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 84.1% | Only Kimi K2.5 measured |
| LiveBench reasoning | 91.6% | Not measured | Only Claude Sonnet 5.5 measured |
| MysteryMechanism (Vals AI) | 49.1% | Not measured | Only Claude Sonnet 5.5 measured |
| MMMU Pro (Vals AI) | Not measured | 84.3% | Only Kimi K2.5 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 87.9% | Only Kimi K2.5 measured |
| Humanity's Last Exam (Artificial Analysis run) | 55.0% | 30.7% | Claude Sonnet 5.5 |
| GPQA Diamond (Epoch AI run) | 95.6% | Not measured | Only Claude Sonnet 5.5 measured |
| ARC-AGI | Not measured | 65.3% | Only Kimi K2.5 measured |
| ARC-AGI-2 | Not measured | 11.8% | Only Kimi K2.5 measured |
| SimpleBench | Not measured | 46.8% | Only Kimi K2.5 measured |
| Chess puzzles | 59.0% | Not measured | Only Claude Sonnet 5.5 measured |
| Mystery game puzzles | 65.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: hard prompts | 1494 | 1453 | Claude Sonnet 5.5 |
| LMArena Text: expert | 1531 | 1466 | Claude Sonnet 5.5 |
| LMArena Text: hard prompts in English | 1502 | 1460 | Claude Sonnet 5.5 |
| LMArena Vision: diagrams | 1329 | 1282 | Claude Sonnet 5.5 |
| LMArena Vision: homework | 1331 | 1297 | Claude Sonnet 5.5 |
| Neither model has a result on the other 4 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| AIME | Not measured | 95.6% | Only Kimi K2.5 measured |
| OTIS Mock AIME | 100.0% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tiers 1 to 3 | 88.8% | Not measured | Only Claude Sonnet 5.5 measured |
| FrontierMath, tier 4 | 80.5% | Not measured | Only Claude Sonnet 5.5 measured |
| ProofBench | 100.0% | Not measured | Only Claude Sonnet 5.5 measured |
| LMArena Text: math | 1497 | 1470 | Claude Sonnet 5.5 |
| LMArena Text: mathematical work | 1510 | 1473 | Claude Sonnet 5.5 |
| Neither model has a result on the other 6 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 85.9% | Only Kimi K2.5 measured |
| CaseLaw (Vals AI) | Not measured | 58.7% | Only Kimi K2.5 measured |
| CorpFin (Vals AI) | Not measured | 68.3% | Only Kimi K2.5 measured |
| TaxEval (Vals AI) | Not measured | 74.2% | Only Kimi K2.5 measured |
| MortgageTax (Vals AI) | Not measured | 66.5% | Only Kimi K2.5 measured |
| MedQA (Vals AI) | Not measured | 94.4% | Only Kimi K2.5 measured |
| MedCode (Vals AI) | 52.9% | 39.3% | Claude Sonnet 5.5 |
| SimpleQA Verified | 46.5% | 34.3% | Claude Sonnet 5.5 |
| LMArena Text: science | 1483 | 1459 | Claude Sonnet 5.5 |
| LMArena Text: medicine and healthcare | 1464 | 1448 | Claude Sonnet 5.5 |
| LMArena Text: legal and government | 1483 | 1441 | Claude Sonnet 5.5 |
| LMArena Text: business and finance | 1468 | 1427 | Claude Sonnet 5.5 |
| Neither model has a result on the other 5 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index60
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1326 | 1249 | Claude Sonnet 5.5 |
| Design Arena: UI components | 1367 | 1236 | Claude Sonnet 5.5 |
| Design Arena: game dev | 1469 | 1207 | Claude Sonnet 5.5 |
| Design Arena: data viz | 1389 | 1219 | Claude Sonnet 5.5 |
| Design Arena: 3D | 1458 | 1205 | Claude Sonnet 5.5 |
| Design Arena: all code categories | 1364 | 1236 | Claude Sonnet 5.5 |
| Design Arena: SVG | Not measured | 1149 | Only Kimi K2.5 measured |
| Design Arena: ASCII art | Not measured | 1165 | Only Kimi K2.5 measured |
| LiveBench design | 85.0% | Not measured | Only Claude Sonnet 5.5 measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index191
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | Leader |
|---|---|---|---|
| Vals Index | 70.8% | Not measured | Only Claude Sonnet 5.5 measured |
| LiveBench data analysis | 59.5% | Not measured | Only Claude Sonnet 5.5 measured |
| Public Benefits Bench (Vals AI) | 67.2% | Not measured | Only Claude Sonnet 5.5 measured |
| SAGE (Vals AI) | 51.8% | 49.9% | Claude Sonnet 5.5 |
| MedScribe (Vals AI) | 91.1% | 76.4% | Claude Sonnet 5.5 |
| IFBench | Not measured | 70.2% | Only Kimi K2.5 measured |
| Long context reasoning (AA-LCR) | 82.7% | 78.0% | Claude Sonnet 5.5 |
| DTBench | 97.3% | Not measured | Only Claude Sonnet 5.5 measured |
| LMCA | 68.3% | Not measured | Only Claude Sonnet 5.5 measured |
| Fiction.LiveBench | Not measured | 86.1% | Only Kimi K2.5 measured |
| CL-bench | Not measured | 19.3% | Only Kimi K2.5 measured |
| Furniture assembly | 75.0% | Not measured | Only Claude Sonnet 5.5 measured |
| CL-bench Life | Not measured | 13.2% | Only Kimi K2.5 measured |
| LMArena Text | 1473 | 1445 | Claude Sonnet 5.5 |
| LMArena Text: instruction following | 1492 | 1431 | Claude Sonnet 5.5 |
| LMArena Text: creative writing | 1467 | 1422 | Claude Sonnet 5.5 |
| LMArena Vision | 1287 | 1269 | Claude Sonnet 5.5 |
| LMArena Text: English | 1484 | 1453 | Claude Sonnet 5.5 |
| LMArena Text: non-English | 1456 | 1433 | Claude Sonnet 5.5 |
| LMArena Text: Chinese | 1535 | 1494 | Claude Sonnet 5.5 |
| LMArena Text: German | Not measured | 1441 | Only Kimi K2.5 measured |
| LMArena Text: Japanese | Not measured | 1423 | Only Kimi K2.5 measured |
| LMArena Text: Korean | Not measured | 1412 | Only Kimi K2.5 measured |
| LMArena Text: French | 1499 | 1454 | Claude Sonnet 5.5 |
| LMArena Text: Spanish | 1451 | 1450 | Claude Sonnet 5.5 |
| LMArena Text: Russian | 1454 | 1435 | Claude Sonnet 5.5 |
| LMArena Text: Polish | Not measured | 1445 | Only Kimi K2.5 measured |
| LMArena Text: multi-turn | 1465 | 1444 | Claude Sonnet 5.5 |
| LMArena Text: longer queries | 1495 | 1445 | Claude Sonnet 5.5 |
| LMArena Text: writing and language | 1474 | 1425 | Claude Sonnet 5.5 |
| LMArena Text: entertainment and media | 1461 | 1417 | Claude Sonnet 5.5 |
| LMArena Vision: English | 1289 | 1274 | Claude Sonnet 5.5 |
| LMArena Vision: Chinese | Not measured | 1328 | Only Kimi K2.5 measured |
| LMArena Vision: reading text | 1297 | 1276 | Claude Sonnet 5.5 |
| LMArena Vision: humor | Not measured | 1284 | Only Kimi K2.5 measured |
| LMArena Vision: captioning | Not measured | 1257 | Only Kimi K2.5 measured |
| LMArena Vision: recognizing things | Not measured | 1285 | Only Kimi K2.5 measured |
| LMArena Vision: creative writing | 1242 | 1269 | Kimi K2.5 |
| Neither model has a result on the other 8 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Sonnet 5.5 | Kimi K2.5 | 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 Sonnet 5.5$0.0070Fits in one request
Kimi K2.5$0.0018Fits in one request
Kimi K2.5 costs less
Repository review
50K input + 3K output tokens
Claude Sonnet 5.5$0.130Fits in one request
Kimi K2.5$0.033Fits in one request
Kimi K2.5 costs less
Agent loop
200K input + 10K output tokens
Claude Sonnet 5.5$0.500Fits in one request
Kimi K2.5$0.125Fits in one request
Kimi K2.5 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 | MoonshotAI Kimi K2.5 |
|---|---|---|
| Maker | Anthropic | Moonshot AI |
| Weights | No public weights listed | Open weights |
| Released | September 28, 2026 | January 27, 2026 |
| Context window | 1M | 262K |
| Input $/Mtok | $2.00 | $0.50 |
| Output $/Mtok | $10.00 | $2.50 |
| Coding index | 88.9 | 58.5 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | Not computable | $0.24 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Sonnet 5.5 better than Kimi K2.5 for coding?
Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 58.5 for Kimi K2.5. Pick Kimi K2.5 when output tokens cost 4.0x less, or when the benchmark that matters is LMArena Vision: creative writing, where it leads.
Which is cheaper, Claude Sonnet 5.5 or Kimi K2.5?
Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; Kimi K2.5 costs $0.50 and $2.50. Cost per solved task is known for Kimi K2.5 only.
Which has the bigger context window, Claude Sonnet 5.5 or Kimi K2.5?
Claude Sonnet 5.5, with 1M tokens against 262K.
How many benchmarks is the Claude Sonnet 5.5 vs Kimi K2.5 comparison based on?
58 benchmarks have a result for both models as of October 21, 2026. Claude Sonnet 5.5's coding index rests on 2 independent benchmarks and Kimi K2.5's on 2. Where only one model has a result, the page says so instead of naming a winner.