stealthmodels.

MODEL FIELD GUIDE

Claude Sonnet 5.5: Mona Lisa

Pairs high-end Claude reasoning with faster measured output and lower token rates than Opus 5.5 and Fable 5.1.

Drawn by this model01 / 01
Mona Lisa benchmark result generated by this model
SVG BENCHMARKMona LisaView result

A good fit for

Everyday production coding, document analysis and agents that need strong reasoning at a lower cost than Claude's premium tiers.

Context window
1,000,000tokens[1]
Model factsArchitecture, context & capabilities
First available
2026-09-28[1]
Developer
Anthropic[1]
Origin
United States[2]
Family
Claude 5.5[1]
Context window
1,000,000 tokens[1]
Maximum output
128,000 tokens[1]
Input
text, image[1]
Output
text[1]
API access & pricingOpenRouter · $2 input / $10 output · per 1M tokens

Anthropic API; input 2 USD/1M; cached read 0.2/1M; output 10/1M; 1-hour cache write $4/M; batch 50% discount.

[1]
  • OpenRouterObserved 2026-10-06
    Input $2Output $10Cached read $0.2Cached write $2.5

    per 1M tokens

    anthropic/claude-sonnet-5.5[3]
  • Anthropic APIObserved 2026-10-06
    Input $2Output $10Cached read $0.2Cached write $2.5Batch input $1Batch output $5

    per 1M tokens

    Available

    claude-sonnet-5-5[1]
Measurements & sources4 primary references · Speed & serving conditions

StealthMark score

StealthMark measures fluid and visual intelligence of AI models.

General and Visual

General Intelligence

Perspective, anatomy, correct shadows, purposeful detail and physical consistency.

Visual Intelligence

Likeness, anatomy, detail, light, materials, composition and artistic expression.

Judging

Frontier Models blindly judge the AI generation unbiased through an intricate process. Our researchers control for mistakes.

Overall score

Overall combines weighted task scores on a scale from 0 to 100. Repeating a task does not increase its weight. Estimated means the total includes an estimate for one missing scene.

Benchmaxxing

Benchmaxx flags models that score unusually well on the familiar Pelican task compared with their other benchmark results. The percentage measures that imbalance, not the probability of training contamination. Flagged Pelican scores are excluded from Overall. Pelican never counts toward General or Visual.

We keep some prompts private to discourage test-specific optimization.

Scoring categories

Prompt & likeness

Subjects, actions and likeness.

Anatomy & construction

Coherent bodies, joints and machinery.

Space & placement

Perspective, scale and contact.

Light & reflections

Lighting, shadows and reflections.

Purposeful detail

Clear, purposeful small features.

Artistry & character

Composition, expression and drawing skill.

Materials & effects

Surfaces, texture and movement.

Visual integrity

Clean shapes, layers and edges.

BENCHMARK RESULTS

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StealthMark benchmark results

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