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Claude Sonnet 5.5 vs GPT-6 Luna

Updated October 21, 2026. 92 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace Claude Sonnet 5.5 Replace GPT-6 Luna
Claude Sonnet 5.5Anthropic
Coding
88.9
Overall
56.0
Output $/M
$10.00
89
GPT-6 LunaOpenAI
Coding
71.4
Overall
38.1
Output $/M
$0.50
3
vs boards won of 92 shared

Decision reading

Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 71.4 for GPT-6 Luna.

Pick GPT-6 Luna when output tokens cost 20.0x less, or when the context window is larger, 1.05M against 1M tokens.

Model AClaude Sonnet 5.5Anthropic88.9/1002 independent benchmarksNo cost per solved taskModel BGPT-6 LunaOpenAI71.4/1002 independent benchmarksNo cost per solved task
Shared results
92
Claude Sonnet 5.5 only
3
GPT-6 Luna only
10
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.

At a glance

Coding index
Claude Sonnet 5.5 88.9 from 2 benchmarks, GPT-6 Luna 71.4 from 2 benchmarks.
Widest category
Agentic work, 20.5 points apart on average over 16 shared benchmarks.
Widest single gap
Mystery game puzzles: Claude Sonnet 5.5 65.0% against GPT-6 Luna 7.0%, 58.0 points apart on a 0 to 100 scale.
Output price
Claude Sonnet 5.5 $10.00 against GPT-6 Luna $0.50 per million output tokens, 20.0x apart.
Context window
Claude Sonnet 5.5 takes 1M tokens, GPT-6 Luna 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 5.5BarsGPT-6 LunaTies
Coding171
Intelligence20
Agentic work160
Reasoning110
Math60
Knowledge60
Web design70
General242
All shared boards893
CodingLike-for-likeFour of these boards feed the Vibe Coding Index171
Coding benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
LiveBench coding94.7%84.5%Claude Sonnet 5.5
LMArena WebDev17681578Claude Sonnet 5.5
Terminal-Bench 4 (Vals AI)64.1%13.6%Claude Sonnet 5.5
Vibe Code Bench (Vals AI)92.4%81.7%Claude Sonnet 5.5
Code migration (Vals AI)69.8%42.5%Claude Sonnet 5.5
ProgramBench (Vals AI)6.5%0.5%Claude Sonnet 5.5
IOI (Vals AI)83.1%55.6%Claude Sonnet 5.5
Terminal-Bench 2.1 (Vals AI)83.2%73.0%Claude Sonnet 5.5
SWE-bench Multimodal (Vals AI)58.3%37.5%Claude Sonnet 5.5
CyberBench (Vals AI)59.6%76.3%GPT-6 Luna
SciCode61.0%54.6%Claude Sonnet 5.5
FrontierCode52.1%42.4%Claude Sonnet 5.5
FrontierSWE61.9%Not measuredOnly Claude Sonnet 5.5 measured
ALE-Bench1819.11576.9Claude Sonnet 5.5
LMArena Text: coding15131437Claude Sonnet 5.5
LMArena Text: software and IT15041423Claude Sonnet 5.5
LMArena WebDev: React18171573Claude Sonnet 5.5
LMArena WebDev: HTML17411595Claude Sonnet 5.5
LMArena WebDev: from an image17371571Claude Sonnet 5.5
Neither model has a result on the other 19 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
AA Intelligence Index56.038.1Claude Sonnet 5.5
Epoch Capabilities Index166.2156.8Claude Sonnet 5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index160
Agentic work benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
Design Arena: agents building web apps13031189Claude Sonnet 5.5
Design Arena: agents building full-stack appsNot measured1158Only GPT-6 Luna measured
Design Arena: agents building mobile apps12651133Claude Sonnet 5.5
Design Arena: spreadsheets1245Not measuredOnly Claude Sonnet 5.5 measured
LiveBench research83.6%43.5%Claude Sonnet 5.5
LiveBench browser84.0%72.0%Claude Sonnet 5.5
LiveBench long agentic78.8%48.1%Claude Sonnet 5.5
SREBench (Vals AI)30.1%2.7%Claude Sonnet 5.5
Finance Agent (Vals AI)58.1%49.9%Claude Sonnet 5.5
Tax Agent Bench (Vals AI)42.0%19.9%Claude Sonnet 5.5
Legal Research Bench (Vals AI)48.1%30.3%Claude Sonnet 5.5
Harvey's Legal Agent Benchmark (Vals AI)10.4%4.2%Claude Sonnet 5.5
Excel Modeling Benchmark (Vals AI)75.7%68.5%Claude Sonnet 5.5
BioMysteryBench (Vals AI)81.1%61.5%Claude Sonnet 5.5
Terminal-Bench-Science (Vals AI)47.1%4.3%Claude Sonnet 5.5
Vals Science Index59.1%28.4%Claude Sonnet 5.5
APEX-Agents75.5%44.3%Claude Sonnet 5.5
SpireClimb1.3%0.0%Claude Sonnet 5.5
Vending-Bench 2$11,165Not measuredOnly Claude Sonnet 5.5 measured
Neither model has a result on the other 20 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index110
Reasoning benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
LiveBench reasoning91.6%81.8%Claude Sonnet 5.5
MysteryMechanism (Vals AI)49.1%19.4%Claude Sonnet 5.5
Humanity's Last Exam (Artificial Analysis run)55.0%38.5%Claude Sonnet 5.5
GPQA Diamond (Epoch AI run)95.6%90.5%Claude Sonnet 5.5
ARC-AGINot measured86.7%Only GPT-6 Luna measured
ARC-AGI-2Not measured59.3%Only GPT-6 Luna measured
Chess puzzles59.0%36.0%Claude Sonnet 5.5
Mystery game puzzles65.0%7.0%Claude Sonnet 5.5
LMArena Text: hard prompts14941410Claude Sonnet 5.5
LMArena Text: expert15311442Claude Sonnet 5.5
LMArena Text: hard prompts in English15021410Claude Sonnet 5.5
LMArena Vision: diagrams13291245Claude Sonnet 5.5
LMArena Vision: homework13311261Claude Sonnet 5.5
Neither model has a result on the other 8 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
OTIS Mock AIME100.0%98.9%Claude Sonnet 5.5
FrontierMath, tiers 1 to 388.8%78.9%Claude Sonnet 5.5
FrontierMath, tier 480.5%56.1%Claude Sonnet 5.5
ProofBench100.0%64.0%Claude Sonnet 5.5
LMArena Text: math14971409Claude Sonnet 5.5
LMArena Text: mathematical work15101427Claude 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 index60
Knowledge benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
MedCode (Vals AI)52.9%44.7%Claude Sonnet 5.5
SimpleQA Verified46.5%41.4%Claude Sonnet 5.5
LMArena Text: science14831386Claude Sonnet 5.5
LMArena Text: medicine and healthcare14641352Claude Sonnet 5.5
LMArena Text: legal and government14831400Claude Sonnet 5.5
LMArena Text: business and finance14681388Claude Sonnet 5.5
Neither model has a result on the other 11 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index70
Web design benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
Design Arena: websites13261272Claude Sonnet 5.5
Design Arena: UI components13671297Claude Sonnet 5.5
Design Arena: game dev14691259Claude Sonnet 5.5
Design Arena: data viz13891215Claude Sonnet 5.5
Design Arena: 3D14581217Claude Sonnet 5.5
Design Arena: all code categories13641271Claude Sonnet 5.5
Design Arena: SVGNot measured1253Only GPT-6 Luna measured
Design Arena: ASCII artNot measured1156Only GPT-6 Luna measured
LiveBench design85.0%82.5%Claude Sonnet 5.5
GeneralLike-for-likePublic boards, shown as published, kept out of the index242
General benchmarks for Claude Sonnet 5.5 and GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
Vals Index70.8%52.3%Claude Sonnet 5.5
LiveBench data analysis59.5%73.4%GPT-6 Luna
Public Benefits Bench (Vals AI)67.2%57.6%Claude Sonnet 5.5
SAGE (Vals AI)51.8%48.1%Claude Sonnet 5.5
MedScribe (Vals AI)91.1%83.7%Claude Sonnet 5.5
Long context reasoning (AA-LCR)82.7%83.3%GPT-6 Luna
DTBench97.3%90.1%Claude Sonnet 5.5
LMCA68.3%44.5%Claude Sonnet 5.5
Furniture assembly75.0%44.2%Claude Sonnet 5.5
LMArena Text14731389Claude Sonnet 5.5
LMArena Text: instruction following14921408Claude Sonnet 5.5
LMArena Text: creative writing14671363Claude Sonnet 5.5
LMArena Vision12871216Claude Sonnet 5.5
LMArena Text: English14841393Claude Sonnet 5.5
LMArena Text: non-English14561381Claude Sonnet 5.5
LMArena Text: Chinese15351427Claude Sonnet 5.5
LMArena Text: GermanNot measured1376Only GPT-6 Luna measured
LMArena Text: JapaneseNot measured1369Only GPT-6 Luna measured
LMArena Text: KoreanNot measured1359Only GPT-6 Luna measured
LMArena Text: French14991408Claude Sonnet 5.5
LMArena Text: Spanish14511391Claude Sonnet 5.5
LMArena Text: Russian14541392Claude Sonnet 5.5
LMArena Text: PolishNot measured1383Only GPT-6 Luna measured
LMArena Text: multi-turn14651392Claude Sonnet 5.5
LMArena Text: longer queries14951408Claude Sonnet 5.5
LMArena Text: writing and language14741384Claude Sonnet 5.5
LMArena Text: entertainment and media14611364Claude Sonnet 5.5
LMArena Vision: English12891204Claude Sonnet 5.5
LMArena Vision: ChineseNot measured1266Only GPT-6 Luna measured
LMArena Vision: reading text12971225Claude Sonnet 5.5
LMArena Vision: creative writing12421205Claude Sonnet 5.5
Neither model has a result on the other 15 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 GPT-6 Luna
BenchmarkClaude Sonnet 5.5GPT-6 LunaLeader
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
GPT-6 Luna$0.0003Fits in one request

GPT-6 Luna costs less

Repository review

50K input + 3K output tokens

Claude Sonnet 5.5$0.130Fits in one request
GPT-6 Luna$0.0065Fits in one request

GPT-6 Luna costs less

Agent loop

200K input + 10K output tokens

Claude Sonnet 5.5$0.500Fits in one request
GPT-6 Luna$0.025Fits in one request

GPT-6 Luna 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 GPT-6 Luna
SpecificationAnthropic Claude Sonnet 5.5OpenAI GPT-6 Luna
MakerAnthropicOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 28, 2026September 22, 2026
Context window1M1.05M
Input $/Mtok$2.00$0.10
Output $/Mtok$10.00$0.50
Coding index88.971.4
Independent measurements behind it22
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Sonnet 5.5 better than GPT-6 Luna for coding?

Pick Claude Sonnet 5.5 for coding: it scores 88.9 on the Vibe Coding Index against 71.4 for GPT-6 Luna. Pick GPT-6 Luna when output tokens cost 20.0x less, or when the context window is larger, 1.05M against 1M tokens.

Which is cheaper, Claude Sonnet 5.5 or GPT-6 Luna?

Claude Sonnet 5.5 costs $2.00 per million input tokens and $10.00 per million output tokens; GPT-6 Luna costs $0.10 and $0.50. Cost per solved task is known for neither of them.

Which has the bigger context window, Claude Sonnet 5.5 or GPT-6 Luna?

GPT-6 Luna, with 1.05M tokens against 1M.

How many benchmarks is the Claude Sonnet 5.5 vs GPT-6 Luna comparison based on?

92 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 GPT-6 Luna's on 2. Where only one model has a result, the page says so instead of naming a winner.

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