STEALTHMARK · HEAD TO HEAD

All comparisons ↗

GPT-6 Luna vs Step 5 Preview

GPT-6 Luna leads Step 5 Preview by 0.1 points on StealthMark, 39.1 to 39.0. It leads on 6 of 9 benchmarks, including both games, and Step 5 Preview on 3. Step 5 Preview scores higher on Newton's Mirror, with its largest category advantage in reflections.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

39.1/100Overall rank 35/53
39.0/100Overall rank 36/53

General Intelligence

31.3/100
37.1/100

Visual Intelligence

52.0/100
41.9/100

Reasoning efficiency

On every task, result quality and reasoning tokens are each compared with all measured models and weighed equally. Each dot is one model.

Single-step reasoning Result quality weighed against reasoning tokens on a single problem

Multi-step reasoning Result quality weighed against reasoning tokens across connected steps, as in agentic workflows

BENCHMARK BY BENCHMARK

Where each model leads

  • GPT-6 Luna
  • Step 5 Preview
  • Other models
  • Median

DATASHEET

Specs and pricing

Both take about 1.05M tokens of context.

  • GPT-6 Luna
  • Step 5 Preview
  • Other models
  • Median
PricePer 1M output tokens, input below
GPT-6 Luna: $0.50$0.10 inputStep 5 Preview: No list price
Context windowTokens per request, max output below
GPT-6 Luna: 1.05MTied128K max outputStep 5 Preview: 1MTied
Output speedTokens per second, our measurement
GPT-6 Luna: 131tokens/sStep 5 Preview: Not measured
SizeTotal and active parameters
GPT-6 Luna: Not disclosedStep 5 Preview: 600B27B active
Developer
OpenAIStepFun
Released
22 Sep 2026Not published
Origin
United StatesNot published
Input → output
Text, image → textText, image, video → text
Architecture
Not publishedSparse mixture-of-experts; 92 layers (88 MoE), 352 routed experts with 8 selected per token plus a shared expert; grouped-query attention with 512-token sliding windows and full attention every fourth layer; 3 multi-token-prediction layers; vision tower for image and video input

Full datasheets, every price and sourceGPT-6 Luna ↗Step 5 Preview ↗

Anticipating threats and planning ahead. Collect coins while avoiding ghosts. Ghosts move before the player each turn, and collisions cost a life. 3 levels in sequence, up to 66 turns in total. Earlier moves and outcomes carry forward, testing learning across levels.

GPT-6 Luna 29.8/100Rank 32/49

Survived 0 of 3
Foresight: complete playing field
Level 36 ptsTurn 7 / 20

Step 5 Preview 59.9/100Rank 42/491 of 3 levels

1 of 3 played
Foresight: complete playing field
Level 122 ptsTurn 28 / 28

Points per level

LevelGPT-6 LunaStep 5 Preview
Level 1Second Thoughts
15 ptsOut of lives
22 ptsSurvived
Level 2Pressure Pot
5 ptsOut of lives
Pending
Level 3Hide or Flight
6 ptsOut of lives
Pending

Cooperative planning and learning from experience. Coordinate two robots to push numbered cores onto matching sockets. Pressure plates hold doors open; moving either robot uses one turn. 5 levels in sequence, up to 152 turns in total. Earlier moves and outcomes carry forward, testing learning across levels.

GPT-6 Luna 44.0/100Rank 26/50

Cleared 4 of 5
Latch: complete playing field
Level 513 ptsTurn 15 / 40

Step 5 Preview 40.7/100Rank 28/50

Cleared 4 of 5
Latch: complete playing field
Level 515 ptsTurn 35 / 40

Points per level

LevelGPT-6 LunaStep 5 Preview
Level 1Hold the door
5.2 ptsCleared
5.2 ptsCleared
Level 2Crossfeed
8.8 ptsClearedFinished early · 1 beacon left
9 ptsCleared
Level 3Relay vault
17 ptsCleared1 beacon left
18.6 ptsCleared
Level 4Passing bay
15.8 ptsClearedFinished early · 3 beacons left
15.6 ptsClearedFinished early · 3 beacons left
Level 5Second thoughts
13 ptsFinished early
15 ptsFinished early

Newton's Mirror

Same task instructions

Physics, perspective and recursive reflections, tested together. Explore the test ↗

The judgment

GPT-6 Luna

The schematic scene supports the paint contact order and compact paint scale. Its low, undersized main sphere and incorrectly placed wall images depart from the reference geometry. A few shrinking wall images provide limited optical organization, while absent lateral recursion and outer chains, broad sphere ribbons and isolated panel highlights leave most nested room and emitter mapping undeveloped.

Step 5 Preview

The main sphere, airborne black and small colored features occupy broadly appropriate positions. Most of the defining mirror system is absent, and paint interaction remains only partially supported. The small paint features do not visibly establish a separate volume-scale violation.

Score breakdown

CategoryGPT-6 LunaStep 5 Preview
State at 600 ms22.0/2520.0/25
Camera and placement3.5/1513.5/15
Reflections5.0/12020.0/120
Materials and scale7.0/107.0/10
Floor-damage reward0.0/100.0/10

Benchmark task

A spinning metal sphere and paint in a mirrored room test physical reasoning, perspective and consistency across repeated reflections.

Selfie

Different task instructions

Visual construction and creative interpretation.

The judgment

GPT-6 Luna

Sixfold symmetry, pale coloring and six outward-facing heads establish the motif. However, every neck floats clear of the knot. Squared outer sections replace the required semicircular lobes, and the large stepped opening lacks a regular hexagonal contour. Repeated scales and soft shading suggest skin, but translucent crossings and doubled edges weaken the living, interwoven construction.

Step 5 Preview

A charming diagonal climber and warm palette communicate the central idea. Simple rounded construction, crowded limb counting, uncertain footholds and an unattached upper shelf limit its physical coherence. Growth bands and the yarn trail add specificity, but the requested material distinctions and unravelled bootie remain underdeveloped.

Score breakdown

CategoryGPT-6 LunaStep 5 Preview
Task & likeness4.5/106.0/10
Anatomy & construction3.5/104.5/10
Space & placement5.5/105.0/10
Light & reflections5.0/105.5/10
Purposeful detail5.0/105.5/10
Artistry & character5.0/105.0/10
Materials & effects5.0/106.0/10
Visual integrity4.5/105.0/10

Benchmark task

GPT-6 Luna

A pale serpent woven into an interlocking knot tests connected anatomy, repeated structure and readable overlaps. Organic surface detail must work with the overall geometry.

Step 5 Preview

Character scenes test expression, anatomy, materials and coherent visual construction.

Mona Lisa

Same task instructions

Precise visual recall and portrait reconstruction.

The judgment

GPT-6 Luna

The dark veil, crossed arms, restrained smile and layered landscape clearly evoke Mona Lisa. Clean contours and muted colors create a coherent illustration. Replication is limited by enlarged, outlined eyes, simplified facial volume, broad shoulders and indistinct overlapping hands. Gradients suggest depth, but lack the original's subtle painterly transitions.

Step 5 Preview

A recognizable, coherent simplification with purposeful facial contours and differentiated fingers. These provide more construction and detail than the broad silhouette alone suggests. The oversized face, frontal seated pose, unresolved wrists and sparse landscape still substantially limit likeness, depth and finish.

Score breakdown

CategoryGPT-6 LunaStep 5 Preview
Task & likeness4.5/104.0/10
Anatomy & construction4.0/104.0/10
Space & placement5.5/104.0/10
Light & reflections5.0/103.5/10
Purposeful detail5.0/104.0/10
Artistry & character4.5/104.0/10
Materials & effects5.0/103.0/10
Visual integrity6.0/103.5/10

Benchmark task

An SVG interpretation of the Mona Lisa tests facial likeness, anatomy and the composition of a familiar portrait.

Beach

Same task instructions

Creativity, perspective and visual beauty.

The judgment

GPT-6 Luna

The warm sky, layered sea and framing palms create an appealing beach composition. Animals, birds, toys and reflected sunlight fulfill the brief. Human anatomy remains schematic, and simplified figures offer limited expression. Missing shadows and the dolphin's splashless jump weaken physical grounding, while clean silhouettes and readable small details support the illustration.

Step 5 Preview

A recognizable sunset beach with clear warm-cool contrast and playful accessories. Basic animal construction, shallow foreground placement and schematic reflections limit spatial and physical credibility. Sparse descriptive detail and abruptly ended sky bands constrain the finish.

Score breakdown

CategoryGPT-6 LunaStep 5 Preview
Task & likeness7.5/104.0/10
Anatomy & construction5.0/103.0/10
Space & placement7.5/103.5/10
Light & reflections5.0/103.5/10
Purposeful detail7.0/103.0/10
Artistry & character5.0/103.0/10
Materials & effects6.5/103.5/10
Visual integrity6.0/104.0/10

Benchmark task

A busy shoreline at sunset tests scene composition, animal forms and the relationship between light and water reflections.

Ground Truth

Same task instructions

Physical reasoning, light and visual reconstruction.

The judgment

GPT-6 Luna

This benchmark has not been assessed yet.

Step 5 Preview

This benchmark has not been assessed yet.

Benchmark task

A plank, computer mouse and blueberry in a steel room test physical stability, spatial relationships, materials and lighting.

Raccoon

Same task instructions

Scene composition and interacting subjects.

The judgment

GPT-6 Luna

Expressive faces, warm sunset colors and clean silhouettes create an appealing illustration. The raccoon sits on the dog's back, but the dog's grip and steering linkage remain unclear. The broad hull resembles a speedboat, and flat shading, absent sun reflections and modest water displacement limit depth and motion.

Step 5 Preview

Recognizable animals, a bright palette and identifying accessories support a basic cartoon. Primitive anatomy, partial seated support, unresolved steering and weak hull-water contact limit the central action. Lighting and spray provide atmosphere without establishing convincing physical depth.

Score breakdown

CategoryGPT-6 LunaStep 5 Preview
Task & likeness8.0/104.0/10
Anatomy & construction5.5/104.5/10
Space & placement7.5/103.0/10
Light & reflections6.0/103.5/10
Purposeful detail7.0/104.0/10
Artistry & character5.5/103.5/10
Materials & effects6.5/103.0/10
Visual integrity5.0/103.0/10

Benchmark task

A jet-ski scene pairs a canine driver with a raccoon passenger. It tests the placement and contact of interacting subjects, along with vehicle construction.

Pelican

Same task instructions

Subject construction and spatial relationships.

The judgment

GPT-6 Luna

The pelican’s distinctive bill and the coordinated vintage poster palette make an appealing illustration. Circular wheels, orderly spokes and clean lettering strengthen the design. Riding mechanics are less convincing: neither wing reaches the handlebars, pedal contact is ambiguous, and the drivetrain is incomplete. The wheels sit against water without a clear supporting surface. Flat lighting limits volume.

Step 5 Preview

The pelican and bicycle are recognizable, with a pleasant palette and basic diffuse shading. The riding relationship fails physically: the bird is unsupported, the front wheel is unmounted, and pedalling is unresolved. Simple geometric construction and sparse material treatment further limit the drawing.

Score breakdown

CategoryGPT-6 LunaStep 5 Preview
Task & likeness8.0/103.0/10
Anatomy & construction5.0/103.0/10
Space & placement6.5/103.0/10
Light & reflections6.5/103.0/10
Purposeful detail7.5/104.0/10
Artistry & character6.5/103.0/10
Materials & effects6.5/103.0/10
Visual integrity7.0/102.0/10

Benchmark task

A cycling pelican tests anatomy, riding posture and contact between the bird and the bicycle.