STEALTHMARK · HEAD TO HEAD

All comparisons ↗

GPT-5.6 Luna vs Inkling-Small

GPT-5.6 Luna leads Inkling-Small by 10.2 points on StealthMark, 37.8 to 27.6. It leads on 8 of 9 benchmarks, including Latch, and Inkling-Small on 1, including Foresight. GPT-5.6 Luna scores higher on Beach, with its largest category advantage in prompt & likeness.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

37.8/100Overall rank 37/53
27.6/100Overall rank 43/53

General Intelligence

30.4/100
25.5/100

Visual Intelligence

50.2/100
31.1/100

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

  • GPT-5.6 Luna
  • Inkling-Small

Open or local

Open modelApache 2.0

BENCHMARK BY BENCHMARK

Where each model leads

  • GPT-5.6 Luna
  • Inkling-Small
  • Other models
  • Median

DATASHEET

Specs and pricing

Both take about 1.05M tokens of context.

  • GPT-5.6 Luna
  • Inkling-Small
  • Other models
  • Median
PricePer 1M output tokens, input below
GPT-5.6 Luna: $1.20$0.20 inputInkling-Small: No list price
Context windowTokens per request, max output below
GPT-5.6 Luna: 1.05MTied128K max outputInkling-Small: 1MTied
Output speedTokens per second, our measurement
GPT-5.6 Luna: 181tokens/sInkling-Small: Not measured
SizeTotal and active parameters
GPT-5.6 Luna: Not disclosedInkling-Small: 276B12B active
Developer
OpenAIThinking Machines Lab
Released
9 Jul 2026Not published
Origin
United StatesNot published
Input → output
Text, image → textText, image, audio → text
Architecture
Not published42-layer decoder-only transformer with sparse mixture-of-experts feed-forward (6 of 256 routed experts plus 2 shared per token); hybrid local and global attention; natively multimodal with a hierarchical patch image encoder and discrete-token audio

Full datasheets, every price and sourceGPT-5.6 Luna ↗Inkling-Small ↗

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-5.6 Luna 25.1/100Rank 36/49

Survived 0 of 3
Foresight: complete playing field
Level 38 ptsTurn 15 / 20

Inkling-Small 30.2/100Rank 29/49

Survived 0 of 3
Foresight: complete playing field
Level 38 ptsTurn 17 / 20

Points per level

LevelGPT-5.6 LunaInkling-Small
Level 1Second Thoughts
4 ptsOut of lives
9 ptsOut of lives
Level 2Pressure Pot
6 ptsOut of lives
6 ptsOut of lives
Level 3Hide or Flight
8 ptsOut of lives
8 ptsOut of lives

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-5.6 Luna 52.9/100Rank 23/50

Cleared 5 of 5
Latch: complete playing field
Level 520.6 ptsTurn 27 / 40

Inkling-Small 34.7/100Rank 34/50

Cleared 3 of 5
Latch: complete playing field
Level 518 ptsTurn 40 / 40

Points per level

LevelGPT-5.6 LunaInkling-Small
Level 1Hold the door
5.2 ptsCleared
5.2 ptsCleared
Level 2Crossfeed
8.6 ptsClearedFinished early · 1 beacon left
9.8 ptsCleared
Level 3Relay vault
18 ptsCleared
2.8 ptsFinished early
Level 4Passing bay
17 ptsClearedFinished early · 3 beacons left
8 ptsFinished early
Level 5Second thoughts
20.6 ptsCleared
18 ptsCleared

Newton's Mirror

Same task instructions

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

The judgment

GPT-5.6 Luna

The room enclosure has coherent symmetric perspective, with the overhead panel, sphere and black aligned centrally. The sphere and airborne black occupy substantially lower positions than the reference framing, inconsistent with the prescribed camera aim. The diagonal crimson streak does not establish the required surface transport. Faint wall sphere images provide limited mirrored correspondence, but the shallow floor image, missing receding chains, absent nested sphere imagery and sparse emitter mapping leave most reflection structure unsupported.

Inkling-Small

The sphere's apparent floor support, separate dark feature and broad paint ordering justify partial state credit. The major weakness is the largely missing mirror system: isolated side images and faint floor echoes do not establish repeated virtual rooms or curved spherical mapping. Downward framing, the oversized frontal panel, unresolved paint transport and satin surface appearance remain distinct limitations.

Score breakdown

CategoryGPT-5.6 LunaInkling-Small
State at 600 ms15.0/2514.0/25
Camera and placement4.0/153.0/15
Reflections3.5/1208.0/120
Materials and scale6.5/102.5/10
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-5.6 Luna

Six pale, outward-facing heads and six rounded lobes make the knot recognizable. The central hexagonal opening remains clear. However, broad gray crossing panels flatten the weave, several inner joins resemble capped strips, and sparse oversized scale marks leave the bodies looking more like decorated ribbons than living snakes.

Inkling-Small

The faces and dripping caps communicate a cute mushroom scene, but simple construction and weak spatial relationships limit the result. The defining foot-stamping action is unresolved, the flattering portrait is smaller than its painter, and the requested material contrasts are only partly conveyed.

Score breakdown

CategoryGPT-5.6 LunaInkling-Small
Task & likeness7.5/102.5/10
Anatomy & construction6.0/101.5/10
Space & placement6.5/103.5/10
Light & reflections5.0/103.0/10
Purposeful detail5.5/104.5/10
Artistry & character6.0/103.0/10
Materials & effects5.0/103.5/10
Visual integrity6.0/102.0/10

Benchmark task

GPT-5.6 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.

Inkling-Small

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

Mona Lisa

Same task instructions

Precise visual recall and portrait reconstruction.

The judgment

GPT-5.6 Luna

The central portrait, dark clothing, crossed hands and muted landscape clearly evoke Mona Lisa. Replication is limited by the elongated face, conspicuous eyes and simplified smile. Overlapping fingers have uncertain anatomy, while broad gradients and heavy outlines flatten the portrait. The composition and restrained palette remain coherent.

Inkling-Small

A recognizable but rudimentary Mona Lisa interpretation. Facial shading and subdued colors provide coherence, while the frontal blocklike torso, unresolved wrists, fingerless hands and shallow landscape substantially limit likeness, construction and finish.

Score breakdown

CategoryGPT-5.6 LunaInkling-Small
Task & likeness3.5/102.5/10
Anatomy & construction3.5/102.5/10
Space & placement4.0/103.0/10
Light & reflections4.5/102.5/10
Purposeful detail4.0/102.0/10
Artistry & character4.0/102.5/10
Materials & effects3.5/102.0/10
Visual integrity4.5/103.0/10

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-5.6 Luna

The warm sunset, palm silhouette and varied beach activities create an appealing, readable composition. Animals, birds and a broad sun reflection satisfy the brief. Drawing remains elementary: angular airborne sea animals lack splash or convincing motion, the crab's claws are awkwardly constructed, and repeated reflection bands suggest a stepped platform. Clean outlines and pleasant colors exceed the anatomical and spatial sophistication.

Inkling-Small

A recognizable sunset beach with a clear focal sun and appealing color transitions. Connected fish silhouettes and layered scenery establish basic coherence. Primitive figures, ambiguous recreation, sparse descriptive detail and weak grounding limit construction and depth. The aligned reflection supplies a useful lighting cue, but shadows and material effects remain underdeveloped.

Score breakdown

CategoryGPT-5.6 LunaInkling-Small
Task & likeness7.5/103.5/10
Anatomy & construction4.0/103.0/10
Space & placement5.5/103.0/10
Light & reflections4.0/103.0/10
Purposeful detail6.5/103.0/10
Artistry & character3.5/103.0/10
Materials & effects4.0/102.5/10
Visual integrity3.5/102.0/10

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-5.6 Luna

This benchmark has not been assessed yet.

Inkling-Small

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-5.6 Luna

Expressive animals, a striped tail and clean outlines make the scene appealing and readable. The raccoon sits convincingly on the dog's back, but the overlapping steering paws are ambiguous and the control stem stops above the hull. Broad wake shapes suggest motion; the glowing sun lacks a corresponding water reflection.

Inkling-Small

Recognizable animals, readable accessories and an appealing sunset support a coherent basic cartoon. Rounded construction leaves joints, riding support and steering unresolved. Decorative gradients contribute atmosphere, but directional lighting, distinct materials and convincing water displacement are weakly demonstrated.

Score breakdown

CategoryGPT-5.6 LunaInkling-Small
Task & likeness7.0/104.0/10
Anatomy & construction5.0/103.0/10
Space & placement6.5/104.0/10
Light & reflections6.0/105.0/10
Purposeful detail6.5/105.5/10
Artistry & character4.5/104.0/10
Materials & effects5.5/105.0/10
Visual integrity5.0/105.0/10

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-5.6 Luna

A recognizable pelican cyclist with an expressive profile, balanced composition and controlled outlines. Head, neck and torso connect coherently. The bicycle wheels and frame are convincing, but overlapping feet obscure pedal contact, the drivetrain lacks a clear chain, and the wing's handlebar grip is schematic. Atmospheric color succeeds more strongly than directional lighting or material depth.

Inkling-Small

The pelican is immediately recognizable, and its sweeping neck, shaped bill and orderly spokes provide character. Riding remains only partially realized: legs, pedal engagement, steering and seat support cannot be read confidently. Controlled graphic effects add atmosphere, but simplified construction and weak grounding keep the result basic.

Score breakdown

CategoryGPT-5.6 LunaInkling-Small
Task & likeness8.5/104.0/10
Anatomy & construction5.5/103.0/10
Space & placement7.5/103.0/10
Light & reflections6.5/103.0/10
Purposeful detail6.5/104.5/10
Artistry & character5.5/105.0/10
Materials & effects7.0/104.5/10
Visual integrity6.5/103.0/10

Benchmark task

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