STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Claude Sonnet 5.5 vs DeepSeek-V4.1-Flash-1017

Claude Sonnet 5.5 leads DeepSeek-V4.1-Flash-1017 by 11.0 points on StealthMark, 70.2 to 59.2. It leads on all 9 benchmarks. Claude Sonnet 5.5 scores higher on Beach, with its largest category advantage in artistry & character.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

70.2/100Overall rank 3/53
59.2/100Overall rank 9/53

General Intelligence

67.0/100
56.8/100

Visual Intelligence

76.1/100
63.5/100

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

Open or local

Open modelMIT

BENCHMARK BY BENCHMARK

Where each model leads

  • Claude Sonnet 5.5
  • DeepSeek-V4.1-Flash-1017
  • Other models
  • Median

DATASHEET

Specs and pricing

Claude Sonnet 5.5 scores higher on StealthMark. DeepSeek-V4.1-Flash-1017 is 8.3× cheaper per output token and runs 25% faster in our speed test. Both take about 1M tokens of context.

  • Claude Sonnet 5.5
  • DeepSeek-V4.1-Flash-1017
  • Other models
  • Median
PricePer 1M output tokens, input below
Claude Sonnet 5.5: $10$2 inputDeepSeek-V4.1-Flash-1017: $1.208.3× cheaper$0.30 input
Context windowTokens per request, max output below
Claude Sonnet 5.5: 1MTied128K max outputDeepSeek-V4.1-Flash-1017: 1MTied384K max output
Output speedTokens per second, our measurement
Claude Sonnet 5.5: 249tokens/sDeepSeek-V4.1-Flash-1017: 31025% fastertokens/s
SizeTotal and active parameters
Claude Sonnet 5.5: Not disclosedDeepSeek-V4.1-Flash-1017: 763B16B activeEstimated
Developer
AnthropicDeepSeek-AI
Released
28 Sep 202617 Oct 2026
Origin
United StatesChina
Input → output
Text, image → textBoth
Architecture
Not publishedSparse mixture-of-experts with a causal encoder-decoder design and native image understanding.

Full datasheets, every price and sourceClaude Sonnet 5.5 ↗DeepSeek-V4.1-Flash-1017 ↗

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

DeepSeek-V4.1-Flash-1017 52.9/100Rank 15/47

Survived 1 of 3
Foresight: complete playing field
Level 310 ptsTurn 15 / 20

Points per level

LevelClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
Level 1Second Thoughts
25 ptsSurvived
26 ptsSurvived
Level 2Pressure Pot
10 ptsOut of lives
7 ptsOut of lives
Level 3Hide or Flight
10 ptsSurvived
10 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 Sonnet 5.5 83.9/100Rank 4/48

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

DeepSeek-V4.1-Flash-1017 73.9/100Rank 13/48

Cleared 5 of 5
Latch: complete playing field
Level 520 ptsTurn 30 / 40

Points per level

LevelClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
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
16.4 ptsClearedFinished early · 3 beacons left
Level 5Second thoughts
20.6 ptsCleared
20 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.

DeepSeek-V4.1-Flash-1017

Principal sphere and airborne-black placements are supported, and diminishing bilateral chains provide limited optical structure. Missing nested imagery, incomplete outer chains, distorted first images and sparse emitter recurrence remain the dominant weaknesses. Oversized paint bodies and unresolved cyan contact impose separate limitations.

Score breakdown

CategoryClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
State at 600 ms24.0/2523.0/25
Camera and placement15.0/1513.5/15
Reflections35.0/12034.0/120
Materials and scale10.0/108.5/10
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 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.

DeepSeek-V4.1-Flash-1017

An expressive, intricately drawn storybook scene with a complete flowing silhouette and differentiated glossy materials. The supported main lens and continuous shrimp body make the central interaction readable, but reciprocal eye lines, facial magnification and the smaller lens grip remain ambiguous. Bright granular fringes and crowded accessory lines limit the finish.

Score breakdown

CategoryClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
Task & likeness8.0/107.5/10
Anatomy & construction8.0/107.5/10
Space & placement8.0/108.0/10
Light & reflections7.5/107.0/10
Purposeful detail8.0/107.5/10
Artistry & character8.0/108.0/10
Materials & effects8.0/107.5/10
Visual integrity8.5/106.5/10

Benchmark task

Claude Sonnet 5.5

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

DeepSeek-V4.1-Flash-1017

A whale and a tiny shrimp examine one another through bubble lenses, with an octopus nearby. The scene tests interacting characters, differences in scale and transparent materials.

Mona Lisa

Same 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.

DeepSeek-V4.1-Flash-1017

A coherent graphic interpretation with controlled contours, modeled facial volume and purposeful portrait details. Replication remains limited by the frontal pose, enlarged face, altered expression and ambiguous crossed hands. Landscape layering provides depth, while schematic fabric, smooth surfaces and tonal bands constrain the finish.

Score breakdown

CategoryClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
Task & likeness6.5/105.0/10
Anatomy & construction5.0/105.0/10
Space & placement6.0/106.0/10
Light & reflections6.5/106.0/10
Purposeful detail6.0/105.5/10
Artistry & character6.5/105.5/10
Materials & effects6.0/105.5/10
Visual integrity6.5/106.0/10

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

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.

DeepSeek-V4.1-Flash-1017

A coherent, colorful beach illustration with controlled curves, clean layering and varied readable accessories. Castle details and small animal features strengthen its finish. Schematic airborne animals, uncertain board support, shallow architectural depth and decorative reflections limit physical coherence and drawing sophistication.

Score breakdown

CategoryClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
Task & likeness9.0/107.0/10
Anatomy & construction8.0/105.5/10
Space & placement8.5/105.5/10
Light & reflections8.5/106.0/10
Purposeful detail9.5/106.5/10
Artistry & character9.5/105.0/10
Materials & effects8.5/105.5/10
Visual integrity8.0/104.5/10

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.

DeepSeek-V4.1-Flash-1017

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 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.

DeepSeek-V4.1-Flash-1017

An appealing cartoon with recognizable riders, expressive faces and a cohesive twilight palette. Clean shapes support the composition, but ambiguous limb overlaps, weak seat contact and loosely resolved steering limit physical coherence. Lighting and water effects are decorative, with modest material differentiation and drawing complexity.

Score breakdown

CategoryClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
Task & likeness8.5/108.0/10
Anatomy & construction7.0/107.0/10
Space & placement8.0/107.0/10
Light & reflections6.5/106.5/10
Purposeful detail8.0/107.0/10
Artistry & character7.0/107.0/10
Materials & effects7.5/106.5/10
Visual integrity8.0/108.0/10

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.

DeepSeek-V4.1-Flash-1017

An expressive, controlled illustration with continuous body construction, substantial bicycle detail and effective landscape depth. Unclear foot-to-pedal and wing-to-handlebar contacts limit physical conviction and local readability. Purposeful detail and composition are stronger than directional lighting and material treatment.

Score breakdown

CategoryClaude Sonnet 5.5DeepSeek-V4.1-Flash-1017
Task & likeness9.0/108.5/10
Anatomy & construction7.5/107.0/10
Space & placement7.5/107.5/10
Light & reflections6.5/106.5/10
Purposeful detail8.0/107.5/10
Artistry & character7.5/107.0/10
Materials & effects6.5/107.0/10
Visual integrity8.0/107.5/10

Benchmark task

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