STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Fledge Alpha vs Step 5 Preview

Step 5 Preview leads Fledge Alpha by 3.2 points on StealthMark, 39.0 to 35.8. Fledge Alpha leads on 5 of the 7 benchmarks with results for both and Step 5 Preview on 2. Step 5 Preview scores higher on Newton's Mirror, with its largest category advantage in reflections.

See the difference ↘
Model guide ↗
All results ↗

Overall StealthMark

35.8/100Overall rank 39/53
39.0/100Overall rank 36/53

General Intelligence

27.1/100
37.1/100

Visual Intelligence

45.2/100
41.9/100

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

  • Fledge AlphaMulti-step reasoning not measured

Open or local

BENCHMARK BY BENCHMARK

Where each model leads

  • Fledge Alpha
  • Step 5 Preview
  • Other models
  • Median

DATASHEET

Specs and pricing

  • Fledge Alpha
  • Step 5 Preview
  • Other models
  • Median
Context windowTokens per request, max output below
Fledge Alpha: Not publishedStep 5 Preview: 1M
Output speedTokens per second, our measurement
Fledge Alpha: 63tokens/sStep 5 Preview: Not measured
SizeTotal and active parameters
Fledge Alpha: Not disclosedStep 5 Preview: 600B27B active
Developer
Not publishedStepFun
Input → output
Not publishedText, image, video → text
Architecture
Not publishedSparse mixture-of-experts; 92 layers (88 MoE), 352 routed experts with 8 selected per token plus a shared expert; grouped-query attention with 512-token sliding windows and full attention every fourth layer; 3 multi-token-prediction layers; vision tower for image and video input

Full datasheets, every price and sourceStep 5 Preview ↗

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.

Step 5 Preview 59.9/100Rank 42/491 of 3 levels

1 of 3 played
Foresight: complete playing field
Level 122 ptsTurn 28 / 28

Points per level

LevelFledge AlphaStep 5 Preview
Level 1Second Thoughts
No run
22 ptsSurvived
Level 2Pressure Pot
No run
Pending
Level 3Hide or Flight
No run
Pending

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.

Step 5 Preview 40.7/100Rank 28/50

Cleared 4 of 5
Latch: complete playing field
Level 515 ptsTurn 35 / 40

Points per level

LevelFledge AlphaStep 5 Preview
Level 1Hold the door
No run
5.2 ptsCleared
Level 2Crossfeed
No run
9 ptsCleared
Level 3Relay vault
No run
18.6 ptsCleared
Level 4Passing bay
No run
15.6 ptsClearedFinished early · 3 beacons left
Level 5Second thoughts
No run
15 ptsFinished early

Newton's Mirror

Same task instructions

Physics, perspective and recursive reflections, tested together. Explore the test ↗

The judgment

Fledge Alpha

The candidate communicates a round metallic sphere, three paint colors and a separate airborne black blob. Its hovering support relationship, displaced framing and unresolved paint interaction limit physical credit. Sparse planar light ghosts and a soft sphere highlight provide little evidence for the required wall/floor repetitions and curved nested mirror imagery.

Step 5 Preview

The main sphere, airborne black and small colored features occupy broadly appropriate positions. Most of the defining mirror system is absent, and paint interaction remains only partially supported. The small paint features do not visibly establish a separate volume-scale violation.

Score breakdown

CategoryFledge AlphaStep 5 Preview
State at 600 ms9.0/2520.0/25
Camera and placement5.0/1513.5/15
Reflections7.5/12020.0/120
Materials and scale3.5/107.0/10
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

Fledge Alpha

A coherent, appealing mascot with expressive eyes, a cheerful beak and a readable swept-back silhouette. Its larger forward foot and trailing feathers suggest a running stride, but the upright body, stiff legs and minimally articulated feet limit convincing motion. Clean flat shapes suit the brief, while uneven feather junctions and incomplete cream accents reduce polish.

Step 5 Preview

A charming diagonal climber and warm palette communicate the central idea. Simple rounded construction, crowded limb counting, uncertain footholds and an unattached upper shelf limit its physical coherence. Growth bands and the yarn trail add specificity, but the requested material distinctions and unravelled bootie remain underdeveloped.

Score breakdown

CategoryFledge AlphaStep 5 Preview
Task & likeness7.5/106.0/10
Anatomy & construction6.5/104.5/10
Space & placement7.0/105.0/10
Light & reflections5.5/105.5/10
Purposeful detail6.5/105.5/10
Artistry & character4.0/105.0/10
Materials & effects6.0/106.0/10
Visual integrity6.5/105.0/10

Benchmark task

Fledge Alpha

An eager young seabird running toward the viewer tests expressive anatomy, balance and a convincing forward-moving pose.

Step 5 Preview

Character scenes test expression, anatomy, materials and coherent visual construction.

Mona Lisa

Different task instructions

Precise visual recall and portrait reconstruction.

The judgment

Fledge Alpha

A recognizable but basic Mona Lisa reinterpretation with a coherent silhouette and subdued palette. Curtain-like hair obscures much of the face, while elongated facial construction and oversized, minimally articulated hands substantially weaken replication. Soft shading supplies modest volume, but anatomy, landscape depth and purposeful detail remain underdeveloped.

Step 5 Preview

A recognizable, coherent simplification with purposeful facial contours and differentiated fingers. These provide more construction and detail than the broad silhouette alone suggests. The oversized face, frontal seated pose, unresolved wrists and sparse landscape still substantially limit likeness, depth and finish.

Score breakdown

CategoryFledge AlphaStep 5 Preview
Task & likeness3.0/104.0/10
Anatomy & construction3.0/104.0/10
Space & placement2.5/104.0/10
Light & reflections2.5/103.5/10
Purposeful detail3.0/104.0/10
Artistry & character3.0/104.0/10
Materials & effects2.5/103.0/10
Visual integrity2.5/103.5/10

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

Fledge Alpha

A cheerful, recognizable sunset beach with a cohesive warm palette and clear accessories. Simple construction, uncertain palm support, an ambiguous upper boundary and schematic reflections limit depth and finish. The scene communicates its subject successfully but lacks the developed forms, lighting and detail of exceptional illustration.

Step 5 Preview

A recognizable sunset beach with clear warm-cool contrast and playful accessories. Basic animal construction, shallow foreground placement and schematic reflections limit spatial and physical credibility. Sparse descriptive detail and abruptly ended sky bands constrain the finish.

Score breakdown

CategoryFledge AlphaStep 5 Preview
Task & likeness7.5/104.0/10
Anatomy & construction4.0/103.0/10
Space & placement5.5/103.5/10
Light & reflections5.0/103.5/10
Purposeful detail3.0/103.0/10
Artistry & character3.0/103.0/10
Materials & effects2.5/103.5/10
Visual integrity4.0/104.0/10

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

Fledge Alpha

This benchmark has not been assessed yet.

Step 5 Preview

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

Fledge Alpha

An appealing sunset illustration with recognizable characters and a clear riding action. Color, expression and silhouette are stronger than anatomical construction: overlapping paws obscure support, the dog's steering limb is simplified, and the vehicle controls lack definition. The wake conveys movement, while lighting and water reflections remain decorative.

Step 5 Preview

Recognizable animals, a bright palette and identifying accessories support a basic cartoon. Primitive anatomy, partial seated support, unresolved steering and weak hull-water contact limit the central action. Lighting and spray provide atmosphere without establishing convincing physical depth.

Score breakdown

CategoryFledge AlphaStep 5 Preview
Task & likeness8.5/104.0/10
Anatomy & construction5.5/104.5/10
Space & placement7.5/103.0/10
Light & reflections6.5/103.5/10
Purposeful detail7.0/104.0/10
Artistry & character5.5/103.5/10
Materials & effects7.0/103.0/10
Visual integrity4.5/103.0/10

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

Fledge Alpha

A clear, cheerful illustration with a recognizable pelican, coherent bicycle silhouette and tidy composition. Simplified leg articulation, steering contact, mechanical detail and lighting keep it at a competent illustrative level.

Step 5 Preview

The pelican and bicycle are recognizable, with a pleasant palette and basic diffuse shading. The riding relationship fails physically: the bird is unsupported, the front wheel is unmounted, and pedalling is unresolved. Simple geometric construction and sparse material treatment further limit the drawing.

Score breakdown

CategoryFledge AlphaStep 5 Preview
Task & likeness8.0/103.0/10
Anatomy & construction6.0/103.0/10
Space & placement6.5/103.0/10
Light & reflections4.5/103.0/10
Purposeful detail5.5/104.0/10
Artistry & character5.0/103.0/10
Materials & effects5.5/103.0/10
Visual integrity6.5/102.0/10

Benchmark task

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