STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Claude Opus 5.5 vs Muse Spark Open

Claude Opus 5.5 leads Muse Spark Open by 28.5 points on StealthMark, 72.6 to 44.1. It leads on all 9 benchmarks. Claude Opus 5.5 scores higher on Newton's Mirror, with its largest category advantage in reflections.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

72.6/100Overall rank 2/53
44.1/100Overall rank 29/53

General Intelligence

71.3/100
42.6/100

Visual Intelligence

75.0/100
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

  • Claude Opus 5.5
  • Muse Spark Open

Open or local

BENCHMARK BY BENCHMARK

Where each model leads

  • Claude Opus 5.5
  • Muse Spark Open
  • Other models
  • Median

DATASHEET

Specs and pricing

Claude Opus 5.5 scores higher on StealthMark. Muse Spark Open is 4.7× cheaper per output token and runs 2.2× faster in our speed test. Both take about 1M tokens of context.

  • Claude Opus 5.5
  • Muse Spark Open
  • Other models
  • Median
PricePer 1M output tokens, input below
Claude Opus 5.5: $20$4 inputMuse Spark Open: $4.254.7× cheaper$1.25 input
Context windowTokens per request, max output below
Claude Opus 5.5: 1MTied128K max outputMuse Spark Open: 1MTied1M max output
Output speedTokens per second, our measurement
Claude Opus 5.5: 166tokens/sMuse Spark Open: 3612.2× fastertokens/s
SizeTotal and active parameters
Claude Opus 5.5: Not disclosedMuse Spark Open: 816B42B active
Developer
AnthropicMeta
Released
22 Sep 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 sourceClaude Opus 5.5 ↗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.

Claude Opus 5.5 66.3/100Rank 5/47

Survived 3 of 3
Foresight: complete playing field
Level 39 ptsTurn 20 / 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

LevelClaude Opus 5.5Muse Spark Open
Level 1Second Thoughts
27 ptsSurvived
4 ptsOut of lives
Level 2Pressure Pot
11 ptsSurvived
9 ptsOut of lives
Level 3Hide or Flight
9 ptsSurvived
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.

Claude Opus 5.5 87.6/100Rank 1/48

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

LevelClaude Opus 5.5Muse Spark Open
Level 1Hold the door
5.2 ptsCleared
5.2 ptsCleared
Level 2Crossfeed
10.2 ptsClearedFinished early · 1 beacon left
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

Claude Opus 5.5

Open lateral sightlines, first reflected silhouettes and near-field planar panel placement are convincing. Missing outer chains, truncated repetitions and absent nested spherical room and emitter imagery remain the main weaknesses.

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

CategoryClaude Opus 5.5Muse Spark Open
State at 600 ms24.0/2514.0/25
Camera and placement15.0/156.0/15
Reflections55.0/1208.0/120
Materials and scale9.0/103.5/10
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

Claude Opus 5.5

The centered coral squid has a friendly, restrained expression and a balanced radial silhouette within a cream arch. Smooth curves and soft shading give it an appealing matte finish. The mantle is more elongated than compact, the upper arms are visually ambiguous, and the two hanging tentacles read somewhat like legs. Clean execution supports a strong stylized illustration.

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

CategoryClaude Opus 5.5Muse Spark Open
Task & likeness8.0/105.0/10
Anatomy & construction7.5/104.5/10
Space & placement8.0/106.0/10
Light & reflections7.5/105.0/10
Purposeful detail7.0/106.0/10
Artistry & character7.0/105.0/10
Materials & effects7.0/105.0/10
Visual integrity8.5/106.5/10

Benchmark task

Claude Opus 5.5

A coral squid with spreading arms tests connected anatomy, balanced composition and soft surface shading.

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

Claude Opus 5.5

The portrait preserves the recognizable composition, dark veil, folded hands and distant landscape. Replication is limited by the elongated face and neck, conspicuous eyes and simplified smile. Hands remain connected but their rounded fingers and wrists lack convincing anatomy. Restrained colors create cohesion; shallow modeling and pervasive mottling weaken volume and painterly subtlety.

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

CategoryClaude Opus 5.5Muse Spark Open
Task & likeness6.5/103.0/10
Anatomy & construction5.5/103.0/10
Space & placement6.5/105.0/10
Light & reflections6.5/104.5/10
Purposeful detail6.5/104.0/10
Artistry & character6.0/103.0/10
Materials & effects7.0/104.0/10
Visual integrity7.0/106.0/10

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

Claude Opus 5.5

A lively, well-composed beach illustration with rich sunset colors, recognizable animals and appealing accessories. The sun reflection establishes a strong central focus. Clean silhouettes and small details reward inspection, though simplified animal construction, uneven contact shadows and mostly flat materials limit depth and realism.

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

CategoryClaude Opus 5.5Muse Spark Open
Task & likeness8.5/108.0/10
Anatomy & construction7.5/106.0/10
Space & placement7.0/106.5/10
Light & reflections7.5/105.5/10
Purposeful detail7.5/106.5/10
Artistry & character8.0/105.5/10
Materials & effects6.5/106.0/10
Visual integrity8.0/108.0/10

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

Claude Opus 5.5

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

Claude Opus 5.5

The masked raccoon clearly rides the dog's back, and the dog's forward paw reaches the steering grip. Expressive faces, vivid colors and sweeping wakes create an appealing illustration. Connected limbs remain schematic, as does the small steering assembly. The broad hull and flat foam weaken water contact; the glowing sun lacks a corresponding reflection or convincing cast shadows.

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

CategoryClaude Opus 5.5Muse Spark Open
Task & likeness8.5/104.0/10
Anatomy & construction7.5/103.0/10
Space & placement7.5/106.0/10
Light & reflections6.0/104.5/10
Purposeful detail8.5/107.0/10
Artistry & character7.0/103.5/10
Materials & effects7.0/105.0/10
Visual integrity8.0/105.0/10

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

Different task instructions

Subject construction and spatial relationships.

The judgment

Claude Opus 5.5

The recognizable pelican, orderly bicycle wheels and harmonious sunset create an appealing illustration. Both legs connect to the body and reach pedals; no clear detached or inverted parts appear. Steering contact and seating support are less convincing, while the drivetrain remains schematic. Crisp outlines give a clean finish, but limited shading and flat surfaces leave the scene with modest depth.

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

CategoryClaude Opus 5.5Muse Spark Open
Task & likeness8.5/107.5/10
Anatomy & construction8.0/105.0/10
Space & placement7.0/106.0/10
Light & reflections6.0/105.0/10
Purposeful detail8.0/106.5/10
Artistry & character7.5/105.5/10
Materials & effects6.0/106.0/10
Visual integrity8.5/107.5/10

Benchmark task

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