Noometry

Model comparison

GPT-5.6 Luna vs Grok 4 Fast

GPT-5.6 Luna is the stronger model overall, scoring 54.6 to 39.4 on the Noometry Index.

Last verified . 24 shared benchmarks.

GPT-5.6 Luna OpenAI

54.6

Rank #30 Confirmed

Grok 4 Fast xAI

39.4

Rank #167 Confirmed

Summary

  • They share 24 benchmarks with published results for both. GPT-5.6 Luna scores higher in 8 categories and Grok 4 Fast in 1 category; 9 gaps are clear of the uncertainty.
  • The widest gap is in math, where GPT-5.6 Luna leads 77.7 to 38.9.
  • The biggest single-benchmark swing is ARC-AGI-2: 59.5% for GPT-5.6 Luna and 5.3% for Grok 4 Fast.

Side by side

GPT-5.6 LunaGrok 4 Fast
ProviderOpenAIxAI
Noometry Index54.639.4
Released2026-07-092025-09-19
WeightsProprietaryProprietary
Context window1.05M—
Max output128K—
Input $ / M tokens$0.20—
Output $ / M tokens$1.20—
Results tracked5230

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Category by category

Coding GPT-5.6 Luna leads

GPT-5.6 Luna: 54.5 (#28), Grok 4 Fast: 32.5 (#271)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena WebDev15191159
WeirdML60.9%42.9%
LMArena Coding14661429
DeepSWE67.2%—
FrontierCode39.8%—
CursorBench35.9%—
SciCode53.6%—
ALE-Bench1,667—

Agentic & Tool Use GPT-5.6 Luna leads

GPT-5.6 Luna: 34.4 (#45), Grok 4 Fast: 29.5 (#86)

BenchmarkGPT-5.6 LunaGrok 4 Fast
APEX-Agents43%—
τ²-bench Banking—15.7%
Cybench—30%
BALROG45.6%—
GDP.pdf22.7%—
LMArena Search—1171
Vending-Bench 24,095—

Reasoning GPT-5.6 Luna leads

GPT-5.6 Luna: 47.6 (#43), Grok 4 Fast: 22.2 (#201)

BenchmarkGPT-5.6 LunaGrok 4 Fast
ARC-AGI-259.5%5.3%
Kagi LLM Benchmark49.1%66.1%
ARC-AGI-188%48.5%
LMArena Hard Prompts14511412
DTBench89.1%82.7%
Epoch Capabilities Index156.39144.2
SimpleBench46.8%—
NYT Connections (extended)69.4%—
CritPt20.6%—
Chess Puzzles40%—
Mystery Game Puzzles21%—
LMCA48.5%—
Surface Evolver Bench61.9%—
ForecastBench—60.5

Math GPT-5.6 Luna leads

GPT-5.6 Luna: 77.7 (#14), Grok 4 Fast: 38.9 (#123)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Math14581419
FrontierMath (Tiers 1-3)82.1%—
FrontierMath Tier 461%—
OTIS Mock AIME 2024-202598.3%—
ProofBench60%—

Knowledge GPT-5.6 Luna leads

GPT-5.6 Luna: 58.5 (#34), Grok 4 Fast: 32.0 (#214)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Expert14781411
GPQA Diamond91.6%—
SimpleQA Verified41%—
Vectara Hallucination Rate—19.7%

Multimodal Not comparable

GPT-5.6 Luna: 42.7 (#28), Grok 4 Fast: —

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Vision1258—
Blueprint-Bench 222.6%—
Furniture Assembly42.5%—
LMArena Document1457—

Multilingual GPT-5.6 Luna leads

GPT-5.6 Luna: 52.8 (#78), Grok 4 Fast: 51.3 (#111)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Non-English14171396
LMArena Chinese14701457
LMArena French14561431
LMArena German14541383
LMArena Japanese14111352
LMArena Korean14151357
LMArena Russian14281389
LMArena Spanish14481415

Instruction Following GPT-5.6 Luna leads

GPT-5.6 Luna: 75.6 (#57), Grok 4 Fast: 73.2 (#121)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Instruction Following14371387

Long Context Grok 4 Fast leads

GPT-5.6 Luna: 43.9 (#82), Grok 4 Fast: 63.2 (#3)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Longer Query14361415
Fiction.LiveBench—94.4%

Writing & Preference GPT-5.6 Luna leads

GPT-5.6 Luna: 68.0 (#29), Grok 4 Fast: 60.0 (#102)

BenchmarkGPT-5.6 LunaGrok 4 Fast
LMArena Text14311407
LMArena Creative Writing13961387
LMArena Multi-Turn14341414
EQ-Bench Creative Writing1829—
EQ-Bench 41156—

Frequently asked questions

Is GPT-5.6 Luna better than Grok 4 Fast?

GPT-5.6 Luna is the stronger model overall, scoring 54.6 to 39.4 on the Noometry Index.

Is GPT-5.6 Luna or Grok 4 Fast better for coding?

GPT-5.6 Luna scores higher on coding benchmarks: 54.5 versus 32.5 in the Noometry coding category.

How many benchmarks do GPT-5.6 Luna and Grok 4 Fast share?

24 benchmarks have published results for both models. GPT-5.6 Luna has 52 scored results on Noometry and Grok 4 Fast has 30.

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