Noometry

Model comparison

GPT-6 Luna vs Step 3.5 Flash

GPT-6 Luna is the stronger model overall, scoring 53.3 to 42.3 on the Noometry Index.

Last verified . 18 shared benchmarks.

GPT-6 Luna OpenAI

53.3

Rank #36 Confirmed

Step 3.5 Flash StepFun

42.3

Rank #116 Confirmed

Summary

  • They share 18 benchmarks with published results for both. GPT-6 Luna scores higher in 7 categories and Step 3.5 Flash in 1 category; 5 gaps are clear of the uncertainty.
  • The widest gap is in math, where GPT-6 Luna leads 76.1 to 42.6.
  • The biggest single-benchmark swing is NYT Connections (extended): 68.7% for GPT-6 Luna and 28.4% for Step 3.5 Flash.
  • Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $0.10 / $0.50 for GPT-6 Luna.
  • GPT-6 Luna accepts more context: 1.05M tokens versus 256K.
  • Step 3.5 Flash has downloadable open weights; the other is API-only.

Side by side

GPT-6 LunaStep 3.5 Flash
ProviderOpenAIStepFun
Noometry Index53.342.3
Released2026-09-222026-01-29
WeightsProprietaryOpen
Context window1.05M256K
Max output128K256K
Input $ / M tokens$0.10$0.10
Output $ / M tokens$0.50$0.30
Results tracked4219

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Category by category

Coding GPT-6 Luna leads

GPT-6 Luna: 55.5 (#25), Step 3.5 Flash: 42.4 (#105)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Coding14391436
DeepSWE66.6%—
FrontierCode42.4%—
LMArena WebDev1581—
SciCode54.6%—
ALE-Bench1,577—

Agentic & Tool Use Not comparable

GPT-6 Luna: 33.3 (#54), Step 3.5 Flash: —

BenchmarkGPT-6 LunaStep 3.5 Flash
APEX-Agents44.3%—
GDP.pdf23%—

Reasoning GPT-6 Luna leads

GPT-6 Luna: 48.2 (#41), Step 3.5 Flash: 22.2 (#202)

BenchmarkGPT-6 LunaStep 3.5 Flash
NYT Connections (extended)68.7%28.4%
LMArena Hard Prompts14111411
ARC-AGI-259.3%—
ARC-AGI-186.7%—
CritPt19.4%—
Chess Puzzles31%—
Mystery Game Puzzles7%—
DTBench90.1%—
LMCA44.5%—
Epoch Capabilities Index156.28—

Math GPT-6 Luna leads

GPT-6 Luna: 76.1 (#15), Step 3.5 Flash: 42.6 (#84)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Math14161408
FrontierMath (Tiers 1-3)78.9%—
FrontierMath Tier 456.1%—
MathArena Final-Answer Competitions—66.8%
OTIS Mock AIME 2024-202598.9%—
ProofBench64%—

Knowledge GPT-6 Luna leads

GPT-6 Luna: 57.0 (#41), Step 3.5 Flash: 39.6 (#132)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Expert14441421
GPQA Diamond90.5%—
SimpleQA Verified41.4%—

Multimodal Not comparable

GPT-6 Luna: 42.4 (#30), Step 3.5 Flash: —

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Vision1217—
Blueprint-Bench 231.2%—
Furniture Assembly44.2%—

Multilingual Too close to call

GPT-6 Luna: 50.5 (#117), Step 3.5 Flash: 50.5 (#119)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Non-English13861385
LMArena Chinese14331447
LMArena French14201421
LMArena German13691405
LMArena Japanese13691354
LMArena Korean13601352
LMArena Russian13941385
LMArena Spanish13931419

Instruction Following GPT-6 Luna leads

GPT-6 Luna: 74.3 (#99), Step 3.5 Flash: 73.1 (#124)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Instruction Following14091385

Long Context Too close to call

GPT-6 Luna: 43.0 (#111), Step 3.5 Flash: 42.8 (#117)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Longer Query14091402

Writing & Preference Too close to call

GPT-6 Luna: 58.3 (#119), Step 3.5 Flash: 58.8 (#113)

BenchmarkGPT-6 LunaStep 3.5 Flash
LMArena Text13911403
LMArena Creative Writing13631357
LMArena Multi-Turn13961405

Frequently asked questions

Is GPT-6 Luna better than Step 3.5 Flash?

GPT-6 Luna is the stronger model overall, scoring 53.3 to 42.3 on the Noometry Index.

Which is cheaper, GPT-6 Luna or Step 3.5 Flash?

Step 3.5 Flash is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; GPT-6 Luna lists at $0.10 and $0.50.

Is GPT-6 Luna or Step 3.5 Flash better for coding?

GPT-6 Luna scores higher on coding benchmarks: 55.5 versus 42.4 in the Noometry coding category.

Which has the bigger context window?

GPT-6 Luna does, with 1.05M tokens against 256K.

How many benchmarks do GPT-6 Luna and Step 3.5 Flash share?

18 benchmarks have published results for both models. GPT-6 Luna has 42 scored results on Noometry and Step 3.5 Flash has 19.

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