STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Claude Sonnet 5.5 vs Kimi K3.1 Pro

Claude Sonnet 5.5 leads Kimi K3.1 Pro by 13.5 points on StealthMark, 70.2 to 56.7. It leads on 8 of 9 benchmarks, including Latch, and Kimi K3.1 Pro on 1, including Foresight. Claude Sonnet 5.5 scores higher on Ground Truth.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

70.2/100Overall rank 3/53
56.7/100Overall rank 11/53

General Intelligence

67.0/100
53.9/100

Visual Intelligence

76.1/100
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 Sonnet 5.5

BENCHMARK BY BENCHMARK

Where each model leads

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

DATASHEET

Specs and pricing

Claude Sonnet 5.5 scores higher on StealthMark and runs 2.1× faster in our speed test. Both take about 1M tokens of context.

  • Claude Sonnet 5.5
  • Kimi K3.1 Pro
  • Other models
  • Median
PricePer 1M output tokens, input below
Claude Sonnet 5.5: $10Tied$2 inputKimi K3.1 Pro: $10Tied$2 input
Context windowTokens per request, max output below
Claude Sonnet 5.5: 1MTied128K max outputKimi K3.1 Pro: 1MTied1M max output
Output speedTokens per second, our measurement
Claude Sonnet 5.5: 2492.1× fastertokens/sKimi K3.1 Pro: 117tokens/s
SizeTotal and active parameters
Claude Sonnet 5.5: Not disclosedKimi K3.1 Pro: 2.8T104B activeEstimated
Developer
AnthropicMoonshot AI
Released
28 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 Sonnet 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 Sonnet 5.5 59.6/100Rank 11/47

Survived 2 of 3
Foresight: complete playing field
Level 310 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 Sonnet 5.5Kimi K3.1 Pro
Level 1Second Thoughts
25 ptsSurvived
15 ptsOut of lives
Level 2Pressure Pot
10 ptsOut of lives
12 ptsOut of lives
Level 3Hide or Flight
10 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 Sonnet 5.5 83.9/100Rank 4/48

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 Sonnet 5.5Kimi K3.1 Pro
Level 1Hold the door
5.2 ptsCleared
5.2 ptsCleared
Level 2Crossfeed
10 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 Sonnet 5.5

The near-field silhouettes, broad perspective and paint contact order are recognizable. Missing outer chains, truncated repetitions and absent ordered imagery within the main and reflected spheres substantially limit the reflection system. Sparse spherical highlights leave much of the curved room and emitter mapping unsupported, despite some plausible planar light sequences.

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 Sonnet 5.5Kimi K3.1 Pro
State at 600 ms24.0/2523.5/25
Camera and placement15.0/1510.5/15
Reflections35.0/12026.0/120
Materials and scale10.0/107.0/10
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 Sonnet 5.5

The centered coral squid has a friendly, composed expression and a balanced flower-like silhouette. Eight thick arms and two slender tentacles remain visibly connected, with no inverted parts. The mantle is elongated rather than compact, and the arm spacing is uneven. Soft shading gives volume, but dense stippling weakens the requested smooth matte finish; the broad background halo makes depth less precise.

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 Sonnet 5.5Kimi K3.1 Pro
Task & likeness8.0/108.0/10
Anatomy & construction8.0/105.5/10
Space & placement8.0/106.5/10
Light & reflections7.5/106.5/10
Purposeful detail8.0/107.5/10
Artistry & character8.0/107.0/10
Materials & effects8.0/107.0/10
Visual integrity8.5/107.0/10

Benchmark task

Claude Sonnet 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

Different task instructions

Precise visual recall and portrait reconstruction.

The judgment

Claude Sonnet 5.5

The crossed hands, dark dress, restrained smile and winding landscape clearly recall the Mona Lisa. Replication is limited by the frontal symmetry, wide eyes, elongated neck and flattened fingers. Soft facial shading provides volume, but heavy darkness and pervasive crackle obscure forms. The composition is coherent; the landscape and fabric remain visibly schematic.

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 Sonnet 5.5Kimi K3.1 Pro
Task & likeness6.5/105.0/10
Anatomy & construction5.0/105.0/10
Space & placement6.0/105.5/10
Light & reflections6.5/106.0/10
Purposeful detail6.0/105.5/10
Artistry & character6.5/106.0/10
Materials & effects6.0/105.0/10
Visual integrity6.5/106.5/10

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 Sonnet 5.5

A richly designed beach illustration combines radiant sunset bands, intricate palm fans and playful silhouettes within a cohesive purple, coral and turquoise palette. Carefully varied accessories reward close inspection, while overlapping foreground forms and shoreline layers organize the abundant activity. Dense palm strokes compete with focal subjects; animal anatomy, relative scales and reflected silhouettes remain simplified.

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 Sonnet 5.5Kimi K3.1 Pro
Task & likeness9.0/108.5/10
Anatomy & construction8.0/105.5/10
Space & placement8.5/105.5/10
Light & reflections8.5/106.5/10
Purposeful detail9.5/106.5/10
Artistry & character9.5/105.5/10
Materials & effects8.5/106.5/10
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 Sonnet 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 Sonnet 5.5

The raccoon clearly rides on the dog's back while the dog grips the jet ski controls. Expressive faces, vivid colors and a sweeping wake make the scene appealing. Visible limbs connect coherently, but overlapping steering paws and an indistinct control mounting weaken construction. Flat character lighting and simplified water limit depth and material realism.

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 Sonnet 5.5Kimi K3.1 Pro
Task & likeness8.5/107.0/10
Anatomy & construction7.0/105.5/10
Space & placement8.0/106.0/10
Light & reflections6.5/105.5/10
Purposeful detail8.0/107.0/10
Artistry & character7.0/106.0/10
Materials & effects7.5/106.0/10
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 Sonnet 5.5

The pelican is immediately recognizable, with an expressive face, generous bill and appealing cycling pose. Spokes, chain, feathers and scarf provide purposeful detail. The bicycle largely holds together, though overlapping angular legs obscure the far foot’s pedal contact. Clean outlines and balanced composition succeed; flat surfaces and limited directional lighting constrain 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 Sonnet 5.5Kimi K3.1 Pro
Task & likeness9.0/108.5/10
Anatomy & construction7.5/107.5/10
Space & placement7.5/106.5/10
Light & reflections6.5/106.5/10
Purposeful detail8.0/107.5/10
Artistry & character7.5/107.5/10
Materials & effects6.5/106.5/10
Visual integrity8.0/107.5/10

Benchmark task

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