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GPT-6 Luna vs Grok 4.3

GPT-6 Luna leads Grok 4.3 on coding, 57.3 to 37.4 on the Vibe Coding Index, and GPT-6 Luna costs 5.0x less per output token ($0.50 vs $2.50 per million). Updated October 22, 2026; 76 benchmarks have a result for both.

Replace GPT-6 Luna Replace Grok 4.3
GPT-6 LunaOpenAI
Coding
57.3
Overall
59.7
Output $/M
$0.50
56
Grok 4.3xAI
Coding
37.4
Overall
53.1
Output $/M
$2.50
20
vs boards won of 76 shared

GPT-6 Luna or Grok 4.3: which to pick

Pick GPT-6 Luna for coding: it scores 57.3 on the Vibe Coding Index against 37.4 for Grok 4.3.

Pick Grok 4.3 for work measured by LMArena Text: science or LMArena Text: medicine and healthcare, where it leads.

Model AGPT-6 LunaOpenAI57.3/1005 independent benchmarksNo cost per solved taskModel BGrok 4.3xAI37.4/1003 independent benchmarks$0.31 per solved task
Shared results
76
GPT-6 Luna only
27
Grok 4.3 only
29
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
GPT-6 Luna 57.3 from 5 benchmarks, Grok 4.3 37.4 from 3 benchmarks.
Widest category
Coding, 25.1 points apart on average over 12 shared benchmarks.
Widest single gap
Vibe Code Bench (Vals AI): GPT-6 Luna 81.7% against Grok 4.3 19.4%, 62.3 points apart on a 0 to 100 scale.
Output price
GPT-6 Luna $0.50 against Grok 4.3 $2.50 per million output tokens, 5.0x apart.
Context window
GPT-6 Luna takes 1.05M tokens, Grok 4.3 1M.

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
CategoryGPT-6 LunaBarsGrok 4.3Ties
Coding120
Intelligence10
Agentic work70
Reasoning80
Math60
Knowledge42
Web design80
General1018
All shared boards5620
CodingLike-for-likeSix of these boards feed the Vibe Coding Index120
Coding benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
LiveBench coding84.5%Not measuredOnly GPT-6 Luna measured
LMArena WebDev15781358GPT-6 Luna
AA Coding IndexNot measured42.2Only Grok 4.3 measured
LiveCodeBench (Vals AI)Not measured84.5%Only Grok 4.3 measured
SWE-bench Verified (Vals AI)Not measured71.4%Only Grok 4.3 measured
Terminal-Bench 4 (Vals AI)13.6%Not measuredOnly GPT-6 Luna measured
Vibe Code Bench (Vals AI)81.7%19.4%GPT-6 Luna
Code migration (Vals AI)42.5%6.8%GPT-6 Luna
ProgramBench (Vals AI)0.5%0.0%GPT-6 Luna
IOI (Vals AI)55.6%Not measuredOnly GPT-6 Luna measured
Terminal-Bench 2.1 (Vals AI)73.0%42.0%GPT-6 Luna
SWE-bench Multimodal (Vals AI)37.5%Not measuredOnly GPT-6 Luna measured
SkillsBench (Vals AI)Not measured40.6%Only Grok 4.3 measured
CyberBench (Vals AI)76.3%Not measuredOnly GPT-6 Luna measured
SciCode54.6%48.3%GPT-6 Luna
Terminal-Bench Hard (Artificial Analysis run)Not measured37.9%Only Grok 4.3 measured
FrontierCode42.4%Not measuredOnly GPT-6 Luna measured
WeirdMLNot measured49.9%Only Grok 4.3 measured
ALE-Bench1576.9944.2GPT-6 Luna
LMArena Text: coding14371415GPT-6 Luna
LMArena Text: software and IT14231416GPT-6 Luna
LMArena WebDev: React15731353GPT-6 Luna
LMArena WebDev: HTML15951367GPT-6 Luna
LMArena WebDev: from an image15711375GPT-6 Luna
Neither model has a result on the other 15 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
AA Intelligence Index38.124.9GPT-6 Luna
Epoch Capabilities Index156.8Not measuredOnly GPT-6 Luna measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index70
Agentic work benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
AA Agentic IndexNot measured15.5Only Grok 4.3 measured
Design Arena: agents building web apps11911126GPT-6 Luna
Design Arena: agents building full-stack apps11581006GPT-6 Luna
Design Arena: agents building mobile apps11341058GPT-6 Luna
Design Arena: agents building Android appsNot measured962Only Grok 4.3 measured
Design Arena: agents building Godot gamesNot measured914Only Grok 4.3 measured
Design Arena: agents building gamesNot measured1007Only Grok 4.3 measured
Design Arena: HTML slidesNot measured959Only Grok 4.3 measured
Design Arena: PowerPoint slidesNot measured988Only Grok 4.3 measured
Design Arena: spreadsheetsNot measured879Only Grok 4.3 measured
LiveBench research43.5%Not measuredOnly GPT-6 Luna measured
LiveBench browser72.0%Not measuredOnly GPT-6 Luna measured
LiveBench long agentic48.1%Not measuredOnly GPT-6 Luna measured
SREBench (Vals AI)2.7%Not measuredOnly GPT-6 Luna measured
Finance Agent (Vals AI)49.9%37.7%GPT-6 Luna
Tax Agent Bench (Vals AI)19.9%6.2%GPT-6 Luna
Legal Research Bench (Vals AI)30.3%15.4%GPT-6 Luna
Harvey's Legal Agent Benchmark (Vals AI)4.2%Not measuredOnly GPT-6 Luna measured
Excel Modeling Benchmark (Vals AI)68.5%18.4%GPT-6 Luna
BioMysteryBench (Vals AI)61.5%Not measuredOnly GPT-6 Luna measured
Terminal-Bench-Science (Vals AI)4.3%Not measuredOnly GPT-6 Luna measured
Vals Science Index28.4%Not measuredOnly GPT-6 Luna measured
τ²-Bench TelecomNot measured97.7%Only Grok 4.3 measured
APEX-Agents44.3%Not measuredOnly GPT-6 Luna measured
SpireClimb0.0%Not measuredOnly GPT-6 Luna measured
Vending-Bench 2Not measured$35Only Grok 4.3 measured
LMArena SearchNot measured1166Only Grok 4.3 measured
Neither model has a result on the other 14 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index80
Reasoning benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
GPQA DiamondNot measured91.4%Only Grok 4.3 measured
LiveBench reasoning81.8%Not measuredOnly GPT-6 Luna measured
MysteryMechanism (Vals AI)19.4%Not measuredOnly GPT-6 Luna measured
MMMU Pro (Vals AI)Not measured83.1%Only Grok 4.3 measured
GPQA Diamond (Artificial Analysis run)Not measured90.1%Only Grok 4.3 measured
Humanity's Last Exam (Artificial Analysis run)38.5%37.2%GPT-6 Luna
GPQA Diamond (Epoch AI run)90.5%88.8%GPT-6 Luna
ARC-AGI86.7%Not measuredOnly GPT-6 Luna measured
ARC-AGI-259.3%Not measuredOnly GPT-6 Luna measured
Chess puzzles36.0%18.0%GPT-6 Luna
Mystery game puzzles7.0%Not measuredOnly GPT-6 Luna measured
LMArena Text: hard prompts14101396GPT-6 Luna
LMArena Text: expert14421384GPT-6 Luna
LMArena Text: hard prompts in English14101402GPT-6 Luna
LMArena Vision: diagrams12451241GPT-6 Luna
LMArena Vision: homework12611241GPT-6 Luna
Neither model has a result on the other 6 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
OTIS Mock AIME98.9%93.3%GPT-6 Luna
FrontierMath, tiers 1 to 378.9%42.8%GPT-6 Luna
FrontierMath, tier 456.1%14.6%GPT-6 Luna
ProofBench64.0%11.0%GPT-6 Luna
LMArena Text: math14091387GPT-6 Luna
LMArena Text: mathematical work14271396GPT-6 Luna
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index42
Knowledge benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
MMLU ProNot measured85.8%Only Grok 4.3 measured
LegalBench (Vals AI)Not measured84.5%Only Grok 4.3 measured
CaseLaw (Vals AI)Not measured79.3%Only Grok 4.3 measured
CorpFin (Vals AI)Not measured68.5%Only Grok 4.3 measured
TaxEval (Vals AI)Not measured70.8%Only Grok 4.3 measured
MortgageTax (Vals AI)Not measured48.3%Only Grok 4.3 measured
MedCode (Vals AI)44.7%38.1%GPT-6 Luna
SimpleQA Verified41.4%33.2%GPT-6 Luna
LMArena Text: science13861399Grok 4.3
LMArena Text: medicine and healthcare13521384Grok 4.3
LMArena Text: legal and government14001386GPT-6 Luna
LMArena Text: business and finance13881381GPT-6 Luna
FACTS Benchmark Suite63.3%Not measuredOnly GPT-6 Luna measured
Neither model has a result on the other 5 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index80
Web design benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
Design Arena: websites12711196GPT-6 Luna
Design Arena: UI components12951190GPT-6 Luna
Design Arena: game dev12571173GPT-6 Luna
Design Arena: data viz12161179GPT-6 Luna
Design Arena: 3D12181124GPT-6 Luna
Design Arena: all code categories12701186GPT-6 Luna
Design Arena: SVG12521080GPT-6 Luna
Design Arena: ASCII art11531125GPT-6 Luna
LiveBench design82.5%Not measuredOnly GPT-6 Luna measured
GeneralLike-for-likePublic boards, shown as published, kept out of the index1018
General benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
Vals Index52.3%Not measuredOnly GPT-6 Luna measured
LiveBench data analysis73.4%Not measuredOnly GPT-6 Luna measured
Public Benefits Bench (Vals AI)57.6%51.7%GPT-6 Luna
SAGE (Vals AI)48.1%19.7%GPT-6 Luna
MedScribe (Vals AI)83.7%74.4%GPT-6 Luna
Vals Multimodal IndexNot measured43.3%Only Grok 4.3 measured
IFBenchNot measured83.3%Only Grok 4.3 measured
Long context reasoning (AA-LCR)83.3%75.0%GPT-6 Luna
DTBench90.1%90.7%Grok 4.3
LMCA44.5%38.3%GPT-6 Luna
Furniture assembly44.2%Not measuredOnly GPT-6 Luna measured
LMArena Text13891397Grok 4.3
LMArena Text: instruction following14081366GPT-6 Luna
LMArena Text: creative writing13631380Grok 4.3
LMArena Vision12161229Grok 4.3
LMArena Text: English13931404Grok 4.3
LMArena Text: non-English13811385Grok 4.3
LMArena Text: Chinese14271422GPT-6 Luna
LMArena Text: German13761395Grok 4.3
LMArena Text: Japanese13691379Grok 4.3
LMArena Text: Korean13591354GPT-6 Luna
LMArena Text: French14081411Grok 4.3
LMArena Text: Spanish13911399Grok 4.3
LMArena Text: Russian13921399Grok 4.3
LMArena Text: Polish13831398Grok 4.3
LMArena Text: multi-turn13921406Grok 4.3
LMArena Text: longer queries14081393GPT-6 Luna
LMArena Text: writing and language13841385Grok 4.3
LMArena Text: entertainment and media13641370Grok 4.3
LMArena Vision: English12041235Grok 4.3
LMArena Vision: Chinese12661257GPT-6 Luna
LMArena Vision: reading text12251235Grok 4.3
LMArena Vision: humorNot measured1222Only Grok 4.3 measured
LMArena Vision: recognizing thingsNot measured1217Only Grok 4.3 measured
LMArena Vision: creative writing12051237Grok 4.3
Neither model has a result on the other 11 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-6 Luna and Grok 4.3
BenchmarkGPT-6 LunaGrok 4.3Leader
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

GPT-6 Luna$0.0003Fits in one request
Grok 4.3$0.0025Fits in one request

GPT-6 Luna costs less

Repository review

50K input + 3K output tokens

GPT-6 Luna$0.0065Fits in one request
Grok 4.3$0.070Fits in one request

GPT-6 Luna costs less

Agent loop

200K input + 10K output tokens

GPT-6 Luna$0.025Fits in one request
Grok 4.3$0.275Fits 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 GPT-6 Luna and Grok 4.3
SpecificationOpenAI GPT-6 LunaSpaceXAI Grok 4.3
MakerOpenAIxAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 22, 2026April 30, 2026
Context window1.05M1M
Input $/Mtok$0.10$1.25
Output $/Mtok$0.50$2.50
Coding index57.337.4
Independent measurements behind it53
Cost per solved taskNot computable$0.31
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-6 Luna better than Grok 4.3 for coding?

Pick GPT-6 Luna for coding: it scores 57.3 on the Vibe Coding Index against 37.4 for Grok 4.3. Pick Grok 4.3 for work measured by LMArena Text: science or LMArena Text: medicine and healthcare, where it leads.

Which is cheaper, GPT-6 Luna or Grok 4.3?

GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens; Grok 4.3 costs $1.25 and $2.50. Cost per solved task is known for Grok 4.3 only.

Which has the bigger context window, GPT-6 Luna or Grok 4.3?

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

How many benchmarks is the GPT-6 Luna vs Grok 4.3 comparison based on?

76 benchmarks have a result for both models as of October 22, 2026. GPT-6 Luna's coding index rests on 5 independent benchmarks and Grok 4.3's on 3. Where only one model has a result, the page says so instead of naming a winner.

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<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/gpt-6-luna-vs-grok-4-3">LLMBenchmark.ai, GPT-6 Luna vs Grok 4.3</a></p>