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Claude Sonnet 5.5 vs Kimi K3

Claude Sonnet 5.5 leads Kimi K3 on coding, 87.3 to 62.3 on the Vibe Coding Index, and Claude Sonnet 5.5 costs 1.5x less per output token ($10.00 vs $15.00 per million). Updated October 22, 2026; 85 benchmarks have a result for both.

Replace Claude Sonnet 5.5 Replace Kimi K3
Claude Sonnet 5.5Anthropic
Coding
87.3
Overall
82.8
Output $/M
$10.00
66
Kimi K3Moonshot AI
Coding
62.3
Overall
66.5
Output $/M
$15.00
19
vs boards won of 85 shared

Claude Sonnet 5.5 or Kimi K3: which to pick

Pick Claude Sonnet 5.5 for coding: it scores 87.3 on the Vibe Coding Index against 62.3 for Kimi K3, though on 5 benchmarks against 6.

Pick Kimi K3 for a larger context window (1.05M against 1M tokens) and work measured by CyberBench (Vals AI) or Design Arena: agents building mobile apps, where it leads.

Model AClaude Sonnet 5.5Anthropic87.3/1005 independent benchmarksNo cost per solved taskModel BKimi K3Moonshot AI62.3/1006 independent benchmarks$0.81 per solved task
Shared results
85
Claude Sonnet 5.5 only
11
Kimi K3 only
32
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.

At a glance

Coding index
Claude Sonnet 5.5 87.3 from 5 benchmarks, Kimi K3 62.3 from 6 benchmarks.
Widest category
Agentic work, 18.7 points apart on average over 15 shared benchmarks.
Widest single gap
LiveBench browser: Claude Sonnet 5.5 84.0% against Kimi K3 16.0%, 68.0 points apart on a 0 to 100 scale.
Output price
Claude Sonnet 5.5 $10.00 against Kimi K3 $15.00 per million output tokens, 1.5x apart.
Context window
Claude Sonnet 5.5 takes 1M tokens, Kimi K3 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.

Boards won, where both have a result
CategoryClaude Sonnet 5.5BarsKimi K3Ties
Coding181
Intelligence20
Agentic work132
Reasoning71
Math60
Knowledge15
Web design61
General139
All shared boards6619
CodingLike-for-likeSix of these boards feed the Vibe Coding Index181
Coding benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
LiveBench coding94.7%59.3%Claude Sonnet 5.5
LMArena WebDev17681655Claude Sonnet 5.5
AA Coding IndexNot measured76.2Only Kimi K3 measured
LiveCodeBench (Vals AI)Not measured87.2%Only Kimi K3 measured
SWE-bench Verified (Vals AI)Not measured93.4%Only Kimi K3 measured
Terminal-Bench 4 (Vals AI)64.1%17.2%Claude Sonnet 5.5
Vibe Code Bench (Vals AI)92.4%85.0%Claude Sonnet 5.5
Code migration (Vals AI)69.8%16.1%Claude Sonnet 5.5
ProgramBench (Vals AI)6.5%2.0%Claude Sonnet 5.5
IOI (Vals AI)83.1%48.9%Claude Sonnet 5.5
Terminal-Bench 2.1 (Vals AI)83.2%80.9%Claude Sonnet 5.5
SWE-bench Multimodal (Vals AI)58.3%44.2%Claude Sonnet 5.5
Vibe Code Bench 1-100 (Vals AI)Not measured18.2%Only Kimi K3 measured
CyberBench (Vals AI)59.6%75.2%Kimi K3
SciCode61.0%59.5%Claude Sonnet 5.5
FrontierCode52.1%44.2%Claude Sonnet 5.5
FrontierSWE61.9%25.9%Claude Sonnet 5.5
WeirdMLNot measured82.6%Only Kimi K3 measured
ALE-Bench1819.11524.5Claude Sonnet 5.5
LMArena Text: coding15131508Claude Sonnet 5.5
LMArena Text: software and IT15041499Claude Sonnet 5.5
LMArena WebDev: React18171670Claude Sonnet 5.5
LMArena WebDev: HTML17411644Claude Sonnet 5.5
LMArena WebDev: from an image17371579Claude Sonnet 5.5
SciCode13.8%Not measuredOnly Claude Sonnet 5.5 measured
Neither model has a result on the other 14 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
AA Intelligence Index56.043.6Claude Sonnet 5.5
Epoch Capabilities Index166.2157.9Claude Sonnet 5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index132
Agentic work benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
AA Agentic IndexNot measured50.0Only Kimi K3 measured
Design Arena: agents building web apps13051295Claude Sonnet 5.5
Design Arena: agents building full-stack appsNot measured1315Only Kimi K3 measured
Design Arena: agents building mobile apps12601269Kimi K3
Design Arena: agents building Android appsNot measured1253Only Kimi K3 measured
Design Arena: agents building Godot gamesNot measured1223Only Kimi K3 measured
Design Arena: agents building gamesNot measured1252Only Kimi K3 measured
Design Arena: HTML slidesNot measured1206Only Kimi K3 measured
Design Arena: PowerPoint slidesNot measured1247Only Kimi K3 measured
Design Arena: spreadsheets12601070Claude Sonnet 5.5
LiveBench research83.6%79.0%Claude Sonnet 5.5
LiveBench browser84.0%16.0%Claude Sonnet 5.5
LiveBench long agentic78.8%42.8%Claude Sonnet 5.5
SREBench (Vals AI)30.1%Not measuredOnly Claude Sonnet 5.5 measured
Finance Agent (Vals AI)58.1%53.1%Claude Sonnet 5.5
Tax Agent Bench (Vals AI)42.0%33.4%Claude Sonnet 5.5
Legal Research Bench (Vals AI)48.1%46.1%Claude Sonnet 5.5
Harvey's Legal Agent Benchmark (Vals AI)10.4%12.9%Kimi K3
Excel Modeling Benchmark (Vals AI)75.7%66.7%Claude Sonnet 5.5
BioMysteryBench (Vals AI)81.1%72.6%Claude Sonnet 5.5
Terminal-Bench-Science (Vals AI)47.1%1.4%Claude Sonnet 5.5
Vals Science Index59.1%Not measuredOnly Claude Sonnet 5.5 measured
Time Horizon Index (Vals AI)Not measured10.5%Only Kimi K3 measured
APEX-Agents75.5%47.8%Claude Sonnet 5.5
PostTrainBenchNot measured32.0%Only Kimi K3 measured
SpireClimb1.3%Not measuredOnly Claude Sonnet 5.5 measured
Vending-Bench 2$11,165$5,165Claude Sonnet 5.5
Neither model has a result on the other 14 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index71
Reasoning benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
GPQA DiamondNot measured92.9%Only Kimi K3 measured
LiveBench reasoning91.6%90.7%Claude Sonnet 5.5
MysteryMechanism (Vals AI)49.1%Not measuredOnly Claude Sonnet 5.5 measured
MMMU Pro (Vals AI)Not measured88.2%Only Kimi K3 measured
GPQA Diamond (Artificial Analysis run)Not measured93.5%Only Kimi K3 measured
Humanity's Last Exam (Artificial Analysis run)55.0%46.9%Claude Sonnet 5.5
GPQA Diamond (Epoch AI run)95.6%93.1%Claude Sonnet 5.5
ARC-AGINot measured94.5%Only Kimi K3 measured
ARC-AGI-2Not measured60.4%Only Kimi K3 measured
SimpleBenchNot measured60.7%Only Kimi K3 measured
Chess puzzles59.0%37.0%Claude Sonnet 5.5
Mystery game puzzles65.0%26.0%Claude Sonnet 5.5
LMArena Text: hard prompts14941495Kimi K3
LMArena Text: expert15311520Claude Sonnet 5.5
LMArena Text: hard prompts in English15021496Claude Sonnet 5.5
LMArena Vision: diagrams1329Not measuredOnly Claude Sonnet 5.5 measured
LMArena Vision: homework1331Not measuredOnly Claude Sonnet 5.5 measured
Neither model has a result on the other 5 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
OTIS Mock AIME100.0%97.2%Claude Sonnet 5.5
FrontierMath, tiers 1 to 388.8%72.2%Claude Sonnet 5.5
FrontierMath, tier 480.5%39.0%Claude Sonnet 5.5
ProofBench100.0%87.0%Claude Sonnet 5.5
LMArena Text: math14971494Claude Sonnet 5.5
LMArena Text: mathematical work15101505Claude 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 index15
Knowledge benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
MMLU ProNot measured88.0%Only Kimi K3 measured
LegalBench (Vals AI)Not measured86.2%Only Kimi K3 measured
CorpFin (Vals AI)Not measured71.6%Only Kimi K3 measured
TaxEval (Vals AI)Not measured75.7%Only Kimi K3 measured
MortgageTax (Vals AI)Not measured66.3%Only Kimi K3 measured
MedCode (Vals AI)52.9%49.4%Claude Sonnet 5.5
SimpleQA Verified46.5%50.6%Kimi K3
LMArena Text: science14831508Kimi K3
LMArena Text: medicine and healthcare14641489Kimi K3
LMArena Text: legal and government14831503Kimi K3
LMArena Text: business and finance14681470Kimi K3
Neither model has a result on the other 7 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index61
Web design benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
Design Arena: websites13261334Kimi K3
Design Arena: UI components13681341Claude Sonnet 5.5
Design Arena: game dev14711358Claude Sonnet 5.5
Design Arena: data viz13921351Claude Sonnet 5.5
Design Arena: 3D14451387Claude Sonnet 5.5
Design Arena: all code categories13641360Claude Sonnet 5.5
Design Arena: SVGNot measured1302Only Kimi K3 measured
LiveBench design85.0%77.2%Claude Sonnet 5.5
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index139
General benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
Vals Index70.8%53.0%Claude Sonnet 5.5
LiveBench data analysis59.5%78.7%Kimi K3
Public Benefits Bench (Vals AI)67.2%68.2%Kimi K3
SAGE (Vals AI)51.8%52.8%Kimi K3
MedScribe (Vals AI)91.1%88.0%Claude Sonnet 5.5
Vals Multimodal IndexNot measured73.4%Only Kimi K3 measured
Long context reasoning (AA-LCR)82.7%88.7%Kimi K3
DTBench97.3%91.2%Claude Sonnet 5.5
LMCA68.3%52.7%Claude Sonnet 5.5
Surface Evolver BenchNot measured95.0%Only Kimi K3 measured
Furniture assembly75.0%34.2%Claude Sonnet 5.5
LMArena Text14731476Kimi K3
LMArena Text: instruction following14921485Claude Sonnet 5.5
LMArena Text: creative writing14671457Claude Sonnet 5.5
LMArena Vision1287Not measuredOnly Claude Sonnet 5.5 measured
LMArena Text: English14841481Claude Sonnet 5.5
LMArena Text: non-English14561466Kimi K3
LMArena Text: Chinese15351529Claude Sonnet 5.5
LMArena Text: GermanNot measured1490Only Kimi K3 measured
LMArena Text: JapaneseNot measured1494Only Kimi K3 measured
LMArena Text: KoreanNot measured1460Only Kimi K3 measured
LMArena Text: French14991492Claude Sonnet 5.5
LMArena Text: Spanish14511472Kimi K3
LMArena Text: Russian14541485Kimi K3
LMArena Text: PolishNot measured1458Only Kimi K3 measured
LMArena Text: multi-turn14651489Kimi K3
LMArena Text: longer queries14951494Claude Sonnet 5.5
LMArena Text: writing and language14741471Claude Sonnet 5.5
LMArena Text: entertainment and media14611453Claude Sonnet 5.5
LMArena Vision: English1289Not measuredOnly Claude Sonnet 5.5 measured
LMArena Vision: reading text1297Not measuredOnly Claude Sonnet 5.5 measured
LMArena Vision: creative writing1242Not measuredOnly Claude Sonnet 5.5 measured
Neither model has a result on the other 14 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Claude Sonnet 5.5 and Kimi K3
BenchmarkClaude Sonnet 5.5Kimi K3Leader
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 K3$0.011Fits in one request

Claude Sonnet 5.5 costs less

Repository review

50K input + 3K output tokens

Claude Sonnet 5.5$0.130Fits in one request
Kimi K3$0.195Fits in one request

Claude Sonnet 5.5 costs less

Agent loop

200K input + 10K output tokens

Claude Sonnet 5.5$0.500Fits in one request
Kimi K3$0.750Fits in one request

Claude Sonnet 5.5 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.

Specifications of Claude Sonnet 5.5 and Kimi K3
SpecificationAnthropic Claude Sonnet 5.5MoonshotAI Kimi K3
MakerAnthropicMoonshot AI
WeightsNo public weights listedOpen weights
ReleasedSeptember 28, 2026July 16, 2026
Context window1M1.05M
Input $/Mtok$2.00$3.00
Output $/Mtok$10.00$15.00
Coding index87.362.3
Independent measurements behind it56
Cost per solved taskNot computable$0.81
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Sonnet 5.5 better than Kimi K3 for coding?

Pick Claude Sonnet 5.5 for coding: it scores 87.3 on the Vibe Coding Index against 62.3 for Kimi K3, though on 5 benchmarks against 6. Pick Kimi K3 for a larger context window (1.05M against 1M tokens) and work measured by CyberBench (Vals AI) or Design Arena: agents building mobile apps, where it leads.

Which is cheaper, Claude Sonnet 5.5 or Kimi K3?

Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; Kimi K3 costs $3.00 and $15.00. Cost per solved task is known for Kimi K3 only.

Which has the bigger context window, Claude Sonnet 5.5 or Kimi K3?

Kimi K3, with 1.05M tokens against 1M.

How many benchmarks is the Claude Sonnet 5.5 vs Kimi K3 comparison based on?

85 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 Kimi K3's on 6. Where only one model has a result, the page says so instead of naming a winner.

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