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GPT-6 Luna vs Grok 4.5

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 GPT-6 Luna Replace Grok 4.5
GPT-6 LunaOpenAI
Coding
71.4
Overall
38.1
Output $/M
$0.50
32
Grok 4.5xAI
Coding
75.5
Overall
38.8
Output $/M
$6.00
60
vs boards won of 92 shared

Decision reading

Pick Grok 4.5 for coding: it scores 75.5 on the Vibe Coding Index against 71.4 for GPT-6 Luna.

Pick GPT-6 Luna when output tokens cost 12.0x less, or when the context window is larger, 1.05M against 500K tokens.

Model AGPT-6 LunaOpenAI71.4/1002 independent benchmarksNo cost per solved taskModel BGrok 4.5xAI75.5/1002 independent benchmarks$0.62 per solved task
Shared results
92
GPT-6 Luna only
10
Grok 4.5 only
28
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
GPT-6 Luna 71.4 from 2 benchmarks, Grok 4.5 75.5 from 2 benchmarks.
Widest category
Math, 17.5 points apart on average over 6 shared benchmarks.
Widest single gap
LiveBench research: GPT-6 Luna 43.5% against Grok 4.5 85.9%, 42.4 points apart on a 0 to 100 scale.
Output price
GPT-6 Luna $0.50 against Grok 4.5 $6.00 per million output tokens, 12.0x apart.
Context window
GPT-6 Luna takes 1.05M tokens, Grok 4.5 500K.

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 4.5Ties
Coding125
Intelligence11
Agentic work57
Reasoning29
Math42
Knowledge15
Web design36
General425
All shared boards3260
CodingLike-for-likeFour of these boards feed the Vibe Coding Index125
Coding benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
LiveBench coding84.5%94.3%Grok 4.5
LMArena WebDev15781553GPT-6 Luna
AA Coding IndexNot measured72.4Only Grok 4.5 measured
LiveCodeBench (Vals AI)Not measured87.3%Only Grok 4.5 measured
SWE-bench Verified (Vals AI)Not measured86.6%Only Grok 4.5 measured
Terminal-Bench 4 (Vals AI)13.6%8.6%GPT-6 Luna
Vibe Code Bench (Vals AI)81.7%69.0%GPT-6 Luna
Code migration (Vals AI)42.5%36.6%GPT-6 Luna
ProgramBench (Vals AI)0.5%0.0%GPT-6 Luna
IOI (Vals AI)55.6%40.6%GPT-6 Luna
Terminal-Bench 2.1 (Vals AI)73.0%67.8%GPT-6 Luna
SWE-bench Multimodal (Vals AI)37.5%Not measuredOnly GPT-6 Luna measured
SkillsBench (Vals AI)Not measured66.0%Only Grok 4.5 measured
CyberBench (Vals AI)76.3%71.0%GPT-6 Luna
SciCode54.6%55.0%Grok 4.5
FrontierCode42.4%42.4%Grok 4.5
WeirdMLNot measured46.4%Only Grok 4.5 measured
ALE-Bench1576.91309.3GPT-6 Luna
LMArena Text: coding14371474Grok 4.5
LMArena Text: software and IT14231471Grok 4.5
LMArena WebDev: React15731556GPT-6 Luna
LMArena WebDev: HTML15951567GPT-6 Luna
LMArena WebDev: from an image15711562GPT-6 Luna
Neither model has a result on the other 15 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index11
Intelligence benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
AA Intelligence Index38.138.8Grok 4.5
Epoch Capabilities Index156.8154.1GPT-6 Luna
Agentic workLike-for-likePublic boards, shown as published, kept out of the index57
Agentic work benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
AA Agentic IndexNot measured41.2Only Grok 4.5 measured
Design Arena: agents building web apps11891217Grok 4.5
Design Arena: agents building full-stack apps11581249Grok 4.5
Design Arena: agents building mobile apps11331221Grok 4.5
Design Arena: agents building Android appsNot measured1242Only Grok 4.5 measured
Design Arena: agents building Godot gamesNot measured1229Only Grok 4.5 measured
Design Arena: agents building gamesNot measured1235Only Grok 4.5 measured
Design Arena: HTML slidesNot measured1204Only Grok 4.5 measured
Design Arena: PowerPoint slidesNot measured1232Only Grok 4.5 measured
LiveBench research43.5%85.9%Grok 4.5
LiveBench browser72.0%44.0%GPT-6 Luna
LiveBench long agentic48.1%27.9%GPT-6 Luna
SREBench (Vals AI)2.7%0.8%GPT-6 Luna
Finance Agent (Vals AI)49.9%48.4%GPT-6 Luna
Tax Agent Bench (Vals AI)19.9%24.9%Grok 4.5
Legal Research Bench (Vals AI)30.3%38.0%Grok 4.5
Harvey's Legal Agent Benchmark (Vals AI)4.2%Not measuredOnly GPT-6 Luna measured
Excel Modeling Benchmark (Vals AI)68.5%52.9%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
Time Horizon Index (Vals AI)Not measured6.3%Only Grok 4.5 measured
APEX-Agents44.3%56.2%Grok 4.5
PostTrainBenchNot measured23.4%Only Grok 4.5 measured
SpireClimb0.0%Not measuredOnly GPT-6 Luna measured
Vending-Bench 2Not measured$3,887Only Grok 4.5 measured
LMArena SearchNot measured1216Only Grok 4.5 measured
Neither model has a result on the other 12 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index29
Reasoning benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
GPQA DiamondNot measured92.9%Only Grok 4.5 measured
LiveBench reasoning81.8%87.2%Grok 4.5
MysteryMechanism (Vals AI)19.4%Not measuredOnly GPT-6 Luna measured
MMMU Pro (Vals AI)Not measured61.8%Only Grok 4.5 measured
GPQA Diamond (Artificial Analysis run)Not measured93.1%Only Grok 4.5 measured
Humanity's Last Exam (Artificial Analysis run)38.5%42.7%Grok 4.5
GPQA Diamond (Epoch AI run)90.5%93.4%Grok 4.5
ARC-AGI86.7%87.2%Grok 4.5
ARC-AGI-259.3%52.6%GPT-6 Luna
SimpleBenchNot measured70.0%Only Grok 4.5 measured
Chess puzzles36.0%35.0%GPT-6 Luna
Mystery game puzzles7.0%Not measuredOnly GPT-6 Luna measured
LMArena Text: hard prompts14101462Grok 4.5
LMArena Text: expert14421465Grok 4.5
LMArena Text: hard prompts in English14101464Grok 4.5
LMArena Vision: diagrams12451304Grok 4.5
LMArena Vision: homework12611295Grok 4.5
Neither model has a result on the other 4 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index42
Math benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
OTIS Mock AIME98.9%97.8%GPT-6 Luna
FrontierMath, tiers 1 to 378.9%57.2%GPT-6 Luna
FrontierMath, tier 456.1%24.4%GPT-6 Luna
ProofBench64.0%31.0%GPT-6 Luna
LMArena Text: math14091460Grok 4.5
LMArena Text: mathematical work14271482Grok 4.5
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 GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
MMLU ProNot measured89.2%Only Grok 4.5 measured
LegalBench (Vals AI)Not measured86.0%Only Grok 4.5 measured
CorpFin (Vals AI)Not measured67.4%Only Grok 4.5 measured
TaxEval (Vals AI)Not measured71.7%Only Grok 4.5 measured
MortgageTax (Vals AI)Not measured61.8%Only Grok 4.5 measured
MedCode (Vals AI)44.7%43.3%GPT-6 Luna
SimpleQA Verified41.4%48.3%Grok 4.5
LMArena Text: science13861464Grok 4.5
LMArena Text: medicine and healthcare13521440Grok 4.5
LMArena Text: legal and government14001463Grok 4.5
LMArena Text: business and finance13881441Grok 4.5
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index36
Web design benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
Design Arena: websites12721281Grok 4.5
Design Arena: UI components12971279GPT-6 Luna
Design Arena: game dev12591263Grok 4.5
Design Arena: data viz12151267Grok 4.5
Design Arena: 3D12171257Grok 4.5
Design Arena: all code categories12711276Grok 4.5
Design Arena: SVG12531215GPT-6 Luna
Design Arena: ASCII art11561257Grok 4.5
LiveBench design82.5%78.1%GPT-6 Luna
GeneralLike-for-likePublic boards, shown as published, kept out of the index425
General benchmarks for GPT-6 Luna and Grok 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
Vals Index52.3%Not measuredOnly GPT-6 Luna measured
LiveBench data analysis73.4%73.0%GPT-6 Luna
Public Benefits Bench (Vals AI)57.6%Not measuredOnly GPT-6 Luna measured
SAGE (Vals AI)48.1%35.0%GPT-6 Luna
MedScribe (Vals AI)83.7%86.9%Grok 4.5
Vals Multimodal IndexNot measured63.4%Only Grok 4.5 measured
Long context reasoning (AA-LCR)83.3%79.3%GPT-6 Luna
DTBench90.1%96.5%Grok 4.5
LMCA44.5%45.2%Grok 4.5
Surface Evolver BenchNot measured74.4%Only Grok 4.5 measured
Furniture assembly44.2%22.5%GPT-6 Luna
LMArena Text13891448Grok 4.5
LMArena Text: instruction following14081445Grok 4.5
LMArena Text: creative writing13631442Grok 4.5
LMArena Vision12161287Grok 4.5
LMArena Text: English13931453Grok 4.5
LMArena Text: non-English13811440Grok 4.5
LMArena Text: Chinese14271495Grok 4.5
LMArena Text: German13761448Grok 4.5
LMArena Text: Japanese13691430Grok 4.5
LMArena Text: Korean13591406Grok 4.5
LMArena Text: French14081457Grok 4.5
LMArena Text: Spanish13911451Grok 4.5
LMArena Text: Russian13921449Grok 4.5
LMArena Text: Polish13831432Grok 4.5
LMArena Text: multi-turn13921456Grok 4.5
LMArena Text: longer queries14081462Grok 4.5
LMArena Text: writing and language13841445Grok 4.5
LMArena Text: entertainment and media13641434Grok 4.5
LMArena Vision: English12041285Grok 4.5
LMArena Vision: Chinese12661345Grok 4.5
LMArena Vision: reading text12251293Grok 4.5
LMArena Vision: humorNot measured1276Only Grok 4.5 measured
LMArena Vision: creative writing12051293Grok 4.5
LMArena DocumentNot measured1452Only Grok 4.5 measured
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 4.5
BenchmarkGPT-6 LunaGrok 4.5Leader
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 4.5$0.0050Fits in one request

GPT-6 Luna costs less

Repository review

50K input + 3K output tokens

GPT-6 Luna$0.0065Fits in one request
Grok 4.5$0.118Fits in one request

GPT-6 Luna costs less

Agent loop

200K input + 10K output tokens

GPT-6 Luna$0.025Fits in one request
Grok 4.5$0.460Fits 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 4.5
SpecificationOpenAI GPT-6 LunaSpaceXAI Grok 4.5
MakerOpenAIxAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 22, 2026July 8, 2026
Context window1.05M500K
Input $/Mtok$0.10$2.00
Output $/Mtok$0.50$6.00
Coding index71.475.5
Independent measurements behind it22
Cost per solved taskNot computable$0.62
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-6 Luna better than Grok 4.5 for coding?

Pick Grok 4.5 for coding: it scores 75.5 on the Vibe Coding Index against 71.4 for GPT-6 Luna. Pick GPT-6 Luna when output tokens cost 12.0x less, or when the context window is larger, 1.05M against 500K tokens.

Which is cheaper, GPT-6 Luna or Grok 4.5?

GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens; Grok 4.5 costs $2.00 and $6.00. Cost per solved task is known for Grok 4.5 only.

Which has the bigger context window, GPT-6 Luna or Grok 4.5?

GPT-6 Luna, with 1.05M tokens against 500K.

How many benchmarks is the GPT-6 Luna vs Grok 4.5 comparison based on?

92 benchmarks have a result for both models as of October 21, 2026. GPT-6 Luna's coding index rests on 2 independent benchmarks and Grok 4.5's on 2. 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-4-5">LLMBenchmark.ai, GPT-6 Luna vs Grok 4.5</a></p>