STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Claude Opus 5.5 vs Kimi K3.1 Pro

Claude Opus 5.5 leads Kimi K3.1 Pro by 15.9 points on StealthMark, 72.6 to 56.7. 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
56.7/100Overall rank 11/53

General Intelligence

71.3/100
53.9/100

Visual Intelligence

75.0/100
62.0/100

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

BENCHMARK BY BENCHMARK

Where each model leads

  • Claude Opus 5.5
  • Kimi K3.1 Pro
  • Other models
  • Median

DATASHEET

Specs and pricing

Claude Opus 5.5 scores higher on StealthMark and runs 42% faster in our speed test. Kimi K3.1 Pro is 2× cheaper per output token. Both take about 1M tokens of context.

  • Claude Opus 5.5
  • Kimi K3.1 Pro
  • Other models
  • Median
PricePer 1M output tokens, input below
Claude Opus 5.5: $20$4 inputKimi K3.1 Pro: $102× cheaper$2 input
Context windowTokens per request, max output below
Claude Opus 5.5: 1MTied128K max outputKimi K3.1 Pro: 1MTied1M max output
Output speedTokens per second, our measurement
Claude Opus 5.5: 16642% fastertokens/sKimi K3.1 Pro: 117tokens/s
SizeTotal and active parameters
Claude Opus 5.5: Not disclosedKimi K3.1 Pro: 2.8T104B activeEstimated
Developer
AnthropicMoonshot AI
Released
22 Sep 202623 Oct 2026
Origin
United StatesChina
Input → output
Text, image → textText, image, video → text
Architecture
Not publishedPost-trained version of Kimi K3, a Mixture-of-Experts model

Full datasheets, every price and sourceClaude Opus 5.5 ↗Kimi K3.1 Pro ↗

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

Kimi K3.1 Pro 61.1/100Rank 10/47

Survived 1 of 3
Foresight: complete playing field
Level 315 ptsTurn 20 / 20

Points per level

LevelClaude Opus 5.5Kimi K3.1 Pro
Level 1Second Thoughts
27 ptsSurvived
15 ptsOut of lives
Level 2Pressure Pot
11 ptsSurvived
12 ptsOut of lives
Level 3Hide or Flight
9 ptsSurvived
15 ptsSurvived

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

Kimi K3.1 Pro 81.8/100Rank 8/48

Cleared 5 of 5
Latch: complete playing field
Level 519.8 ptsTurn 31 / 40

Points per level

LevelClaude Opus 5.5Kimi K3.1 Pro
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
18.2 ptsClearedFinished early · 3 beacons left
Level 5Second thoughts
20.6 ptsCleared
19.8 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.

Kimi K3.1 Pro

The settled sphere, separate airborne black paint and crimson-before-cyan interaction are supported, with a modest crimson travel overshoot. A shared downward framing displacement remains after accounting for the square canvas. The principal limitation is the reflection system: sparse sphere copies and generic curved bands omit most of the ordered mirror-room structure. Materials receive a small upward revision because bounded bright images and dark bands visibly establish some polish, while soft shading and bulky paint remain separate weaknesses.

Score breakdown

CategoryClaude Opus 5.5Kimi K3.1 Pro
State at 600 ms24.0/2523.5/25
Camera and placement15.0/1510.5/15
Reflections55.0/12026.0/120
Materials and scale9.0/107.0/10
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

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.

Kimi K3.1 Pro

The transformed reflection, attentive pose and constellation anatomy clearly communicate introspection. Purposeful fine details enrich a coherent composition. Tubular limbs, crowded lower-body overlaps, shallow depth and limited cast lighting keep the overall execution within the competent range.

Score breakdown

CategoryClaude Opus 5.5Kimi K3.1 Pro
Task & likeness8.0/108.0/10
Anatomy & construction7.5/105.5/10
Space & placement8.0/106.5/10
Light & reflections7.5/106.5/10
Purposeful detail7.0/107.5/10
Artistry & character7.0/107.0/10
Materials & effects7.0/107.0/10
Visual integrity8.5/107.0/10

Benchmark task

Claude Opus 5.5

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

Kimi K3.1 Pro

An imagined creature encounters its reflection. The scene tests original character design, visual self-interpretation and the relationship between a subject and its reflected image.

Mona Lisa

Same 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.

Kimi K3.1 Pro

A coherent, recognizable interpretation with controlled color and readable landscape layers. Replication is limited by the frontal seated construction, elongated facial proportions and oversized, weakly articulated hands. Smooth shading supplies some volume but little of the reference's subtle expression, fabric structure or atmospheric transitions.

Score breakdown

CategoryClaude Opus 5.5Kimi K3.1 Pro
Task & likeness6.5/105.0/10
Anatomy & construction5.5/105.0/10
Space & placement6.5/105.5/10
Light & reflections6.5/106.0/10
Purposeful detail6.5/105.5/10
Artistry & character6.0/106.0/10
Materials & effects7.0/105.0/10
Visual integrity7.0/106.5/10

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

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.

Kimi K3.1 Pro

A coherent, playful beach illustration with readable animals, an organized composition and an aligned sunset reflection. Connected silhouettes, sand texture and atmospheric effects demonstrate controlled execution. Simplified joints, flattened foreground viewpoints and inconsistent shadows limit anatomical and spatial credibility.

Score breakdown

CategoryClaude Opus 5.5Kimi K3.1 Pro
Task & likeness8.5/108.5/10
Anatomy & construction7.5/105.5/10
Space & placement7.0/105.5/10
Light & reflections7.5/106.5/10
Purposeful detail7.5/106.5/10
Artistry & character8.0/105.5/10
Materials & effects6.5/106.5/10
Visual integrity8.0/107.5/10

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.

Kimi K3.1 Pro

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

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.

Kimi K3.1 Pro

The additional comparisons support retaining the assessment. Readable steering, shaped animal contours and purposeful details coexist with simplified joints, a frontal passenger whose seated weight is weakly conveyed, and limited physical lighting. The angled craft establishes more depth than the riding pose resolves.

Score breakdown

CategoryClaude Opus 5.5Kimi K3.1 Pro
Task & likeness8.5/107.0/10
Anatomy & construction7.5/105.5/10
Space & placement7.5/106.0/10
Light & reflections6.0/105.5/10
Purposeful detail8.5/107.0/10
Artistry & character7.0/106.0/10
Materials & effects7.0/106.0/10
Visual integrity8.0/107.0/10

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

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.

Kimi K3.1 Pro

A characterful coastal illustration with controlled contours and varied feather, accessory and bicycle detail. Layered scenery and subtle shading enrich the presentation. Soft leg articulation, unresolved riding contacts, shallow depth and generalized lighting limit physical precision.

Score breakdown

CategoryClaude Opus 5.5Kimi K3.1 Pro
Task & likeness8.5/108.5/10
Anatomy & construction8.0/107.5/10
Space & placement7.0/106.5/10
Light & reflections6.0/106.5/10
Purposeful detail8.0/107.5/10
Artistry & character7.5/107.5/10
Materials & effects6.0/106.5/10
Visual integrity8.5/107.5/10

Benchmark task

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