STEALTHMARK · HEAD TO HEAD

All comparisons ↗

GPT-5.6 Terra vs Muse Spark Open

GPT-5.6 Terra leads Muse Spark Open by 1.7 points on StealthMark, 45.8 to 44.1. It leads on 7 of 9 benchmarks, including both games, and Muse Spark Open on 2. GPT-5.6 Terra scores higher on Newton's Mirror, with its largest category advantage in state at 600 ms.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

45.8/100Overall rank 25/53
44.1/100Overall rank 29/53

General Intelligence

41.9/100
42.6/100

Visual Intelligence

52.7/100
46.6/100

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 Terra
  • Muse Spark Open

Open or local

BENCHMARK BY BENCHMARK

Where each model leads

  • GPT-5.6 Terra
  • Muse Spark Open
  • Other models
  • Median

DATASHEET

Specs and pricing

GPT-5.6 Terra scores higher on StealthMark. Muse Spark Open is 2.8× cheaper per output token and runs 3.6× faster in our speed test. Both take about 1.05M tokens of context.

  • GPT-5.6 Terra
  • Muse Spark Open
  • Other models
  • Median
PricePer 1M output tokens, input below
GPT-5.6 Terra: $12$2 inputMuse Spark Open: $4.252.8× cheaper$1.25 input
Context windowTokens per request, max output below
GPT-5.6 Terra: 1.05MTied128K max outputMuse Spark Open: 1MTied1M max output
Output speedTokens per second, our measurement
GPT-5.6 Terra: 102tokens/sMuse Spark Open: 3613.6× fastertokens/s
SizeTotal and active parameters
GPT-5.6 Terra: Not disclosedMuse Spark Open: 816B42B active
Developer
OpenAIMeta
Released
9 Jul 202615 Oct 2026
Origin
United StatesBoth
Input → output
Text, image → textText, image, audio, video → text
Architecture
Not publishedSparse mixture-of-experts Transformer with perception encoders; 62 decoder layers, 256 experts with 8 selected per token, grouped-query attention and sliding-window/full-attention layers.

Full datasheets, every price and sourceGPT-5.6 Terra ↗Muse Spark Open ↗

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 Terra 30.1/100Rank 31/47

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

Muse Spark Open 29.4/100Rank 34/47

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

Points per level

LevelGPT-5.6 TerraMuse Spark Open
Level 1Second Thoughts
5 ptsOut of lives
4 ptsOut of lives
Level 2Pressure Pot
9 ptsOut of lives
9 ptsOut of lives
Level 3Hide or Flight
6 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 Terra 80.0/100Rank 9/48

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

Muse Spark Open 75.7/100Rank 12/48

Cleared 5 of 5
Latch: complete playing field
Level 519.6 ptsTurn 32 / 40

Points per level

LevelGPT-5.6 TerraMuse Spark Open
Level 1Hold the door
5.2 ptsCleared
5.2 ptsCleared
Level 2Crossfeed
9.6 ptsCleared
9.8 ptsCleared
Level 3Relay vault
19.2 ptsCleared
19.2 ptsCleared
Level 4Passing bay
18.2 ptsClearedFinished early · 3 beacons left
17.8 ptsClearedFinished early · 1 beacon left
Level 5Second thoughts
20.6 ptsCleared
19.6 ptsCleared

Newton's Mirror

Same task instructions

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

The judgment

GPT-5.6 Terra

The real sphere and airborne black blob are substantially too low in the complete frame after accounting for aspect ratio. The first wall and floor reflections have incompatible placement, relative size or silhouette. Both lateral regions lack the references' receding lane-and-chain organization. The few recognizable mirror images provide limited optical structure. The main, side and floor spheres replace nested mirror imagery with smooth bands, while sparse planar light patches and broad spherical highlights fail to establish coherent repeated emitter mapping.

Muse Spark Open

The airborne black blob and deformed paint support the broad contact sequence, although cyan attachment and wheel-directed transport remain partial. The sphere and black blob have substantial framing errors. The dominant limitation is the largely absent mirror system: faint wall circles and isolated highlights provide little evidence of recursive room geometry or curved nested reflections. Oversized compact paint features and diffuse material treatment further limit credit.

Score breakdown

CategoryGPT-5.6 TerraMuse Spark Open
State at 600 ms24.0/2514.0/25
Camera and placement6.0/156.0/15
Reflections7.0/1208.0/120
Materials and scale5.5/103.5/10
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 Terra

Six ivory heads and rounded lobes create a striking radial emblem around a clear hexagonal opening. Soft shading gives the bodies volume, but abrupt rectangular and diagonal band endings make the continuous alternating weave ambiguous. Repetitive scale lines and simplified faces convey an ornamental serpent more convincingly than living anatomy.

Muse Spark Open

The rounded silhouette and asymmetric expression make an appealing baby elephant, supported by a quiet background and grounding shadow. The protective action remains difficult to read: forefeet cannot be confidently traced into a grip, and seed contact is crowded by fine lines. Controlled simple shapes provide charm, but limited anatomical clarity, shading and surface detail leave the execution uneven.

Score breakdown

CategoryGPT-5.6 TerraMuse Spark Open
Task & likeness7.5/105.0/10
Anatomy & construction5.5/104.5/10
Space & placement7.0/106.0/10
Light & reflections7.5/105.0/10
Purposeful detail6.5/106.0/10
Artistry & character5.5/105.0/10
Materials & effects6.5/105.0/10
Visual integrity5.0/106.5/10

Benchmark task

GPT-5.6 Terra

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.

Muse Spark Open

A small elephant protecting a delicate seed tests expressive anatomy, physical contact and contrasting organic materials.

Mona Lisa

Different task instructions

Precise visual recall and portrait reconstruction.

The judgment

GPT-5.6 Terra

The dark clothing, central portrait and restrained smile evoke the Mona Lisa, but replication is limited by the broad face, elongated neck, nearly frontal pose and indistinct landscape. Soft gradients give the face some volume. Crossed arms become rounded masses without readable fingers or wrists, and the expression lacks the original's subtlety. Clean framing and curves support an otherwise basic, uneven portrait.

Muse Spark Open

A recognizable, orderly interpretation with clean major contours, connected body forms and modest facial shading. Wide eyes, frontal symmetry and schematic hands limit likeness and expression. Layered scenery establishes basic depth, but shallow arm overlaps, flat clothing and sparse fine detail keep the execution basic and uneven.

Score breakdown

CategoryGPT-5.6 TerraMuse Spark Open
Task & likeness4.0/103.0/10
Anatomy & construction3.0/103.0/10
Space & placement4.5/105.0/10
Light & reflections5.0/104.5/10
Purposeful detail4.0/104.0/10
Artistry & character4.0/103.0/10
Materials & effects4.0/104.0/10
Visual integrity6.0/106.0/10

Benchmark task

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

Beach

Different task instructions

Creativity, perspective and visual beauty.

The judgment

GPT-5.6 Terra

Warm sunset gradients, framing palms and colorful beach activities create an appealing scene. Animals, birds and a sun reflection fulfill the brief. The dog and turtle remain schematic, foreground depth is shallow, and the reflection forms rigid bands. Clean silhouettes and readable accessories support a competent illustration, but limited anatomy, material variation and lighting keep it below exceptional.

Muse Spark Open

A coherent sunset beach with readable activities, balanced framing and controlled colour transitions. Small accessories add interest, but schematic anatomy, limited surface detail, weak directional shadows and a geometric reflection constrain its finish. Most shapes and overlaps remain clean.

Score breakdown

CategoryGPT-5.6 TerraMuse Spark Open
Task & likeness7.5/108.0/10
Anatomy & construction5.0/106.0/10
Space & placement6.0/106.5/10
Light & reflections5.0/105.5/10
Purposeful detail6.5/106.5/10
Artistry & character5.0/105.5/10
Materials & effects5.5/106.0/10
Visual integrity5.0/108.0/10

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 Terra

This benchmark has not been assessed yet.

Muse Spark Open

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

Different task instructions

Scene composition and interacting subjects.

The judgment

GPT-5.6 Terra

Expressive faces, a recognizable raccoon perched on the dog, and a sweeping wake make an appealing cartoon. The principal weakness is the steering interaction: the dog's paw sits beside the control assembly without a convincing handlebar grip. Bold outlines and coherent layering provide polish, while simplified shading, compressed seating geometry and angular splashes limit depth and physical credibility.

Muse Spark Open

Expressive faces, distinct accessories and clean color separation make the scene appealing and recognizable. Character detail is stronger than the functional construction: steering contact, limb overlaps and seating remain ambiguous. The readable hull and lively spray establish motion, while limited directional shading and simplified surfaces constrain depth and physical coherence.

Score breakdown

CategoryGPT-5.6 TerraMuse Spark Open
Task & likeness7.5/104.0/10
Anatomy & construction5.0/103.0/10
Space & placement7.0/106.0/10
Light & reflections6.0/104.5/10
Purposeful detail7.0/107.0/10
Artistry & character5.0/103.5/10
Materials & effects7.0/105.0/10
Visual integrity7.5/105.0/10

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

Different task instructions

Subject construction and spatial relationships.

The judgment

GPT-5.6 Terra

The oversized bill, expressive eye and balanced twilight palette make the cyclist immediately readable. Clean contours and wheel details support the illustration, but the rabbit-like head tufts weaken pelican likeness. The wing does not clearly grip the handlebar, pedal contact is uneven, and the drivetrain is incomplete. Lighting remains mostly decorative.

Muse Spark Open

A controlled, appealing cartoon with a recognizable pelican, expressive face and clean curved forms. Feather lines, spokes and bill shading provide useful complexity. Aligned wheels and a ground shadow establish placement, but uncertain pedal contacts and obscured mechanical connections weaken support and riding action. Lighting remains loosely coordinated with the sun.

Score breakdown

CategoryGPT-5.6 TerraMuse Spark Open
Task & likeness6.0/107.5/10
Anatomy & construction6.0/105.0/10
Space & placement7.0/106.0/10
Light & reflections6.5/105.0/10
Purposeful detail7.0/106.5/10
Artistry & character6.5/105.5/10
Materials & effects6.5/106.0/10
Visual integrity7.0/107.5/10

Benchmark task

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