STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Beam 1.0 501B A23B vs Claude Fable 5.1

Claude Fable 5.1 leads Beam 1.0 501B A23B by 30.1 points on StealthMark, 62.0 to 31.9. It leads on 8 of 9 benchmarks, including Latch, and Beam 1.0 501B A23B on 1, including Foresight. Claude Fable 5.1 scores higher on Newton's Mirror, with its largest category advantage in reflections.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

31.9/100Overall rank 42/53
62.0/100Overall rank 8/53

General Intelligence

30.9/100
58.9/100

Visual Intelligence

33.8/100
67.1/100

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

Open or local

Open modelApache 2.0

BENCHMARK BY BENCHMARK

Where each model leads

  • Beam 1.0 501B A23B
  • Claude Fable 5.1
  • Other models
  • Median

DATASHEET

Specs and pricing

Beam 1.0 501B A23B is 50× cheaper per output token and runs 8× faster in our speed test. Claude Fable 5.1 scores higher on StealthMark. Both take about 1M tokens of context.

  • Beam 1.0 501B A23B
  • Claude Fable 5.1
  • Other models
  • Median
PricePer 1M output tokens, input below
Beam 1.0 501B A23B: $150× cheaper$0.25 inputClaude Fable 5.1: $50$10 input
Context windowTokens per request, max output below
Beam 1.0 501B A23B: 1MTied128K max outputClaude Fable 5.1: 1MTied128K max output
Output speedTokens per second, our measurement
Beam 1.0 501B A23B: 9728× fastertokens/sClaude Fable 5.1: 122tokens/s
SizeTotal and active parameters
Beam 1.0 501B A23B: 501B23.4B activeClaude Fable 5.1: Not disclosed
Developer
Reflection AIAnthropic
Released
16 Oct 20261 Sep 2026
Origin
United StatesBoth
Input → output
Text → textText, image → text
Architecture
Sparse mixture-of-experts transformer; 52 layers (3 dense, 49 MoE), 256 experts with 8 selected per token; gated GQA and sliding-window attentionNot published

Full datasheets, every price and sourceBeam 1.0 501B A23B ↗Claude Fable 5.1 ↗

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.

Beam 1.0 501B A23B 49.4/100Rank 18/47

Survived 1 of 3
Foresight: complete playing field
Level 39 ptsTurn 20 / 20

Claude Fable 5.1 34.2/100Rank 37/472 of 3 levels

2 of 3 played
Foresight: complete playing field
Level 38 ptsTurn 17 / 20

Points per level

LevelBeam 1.0 501B A23BClaude Fable 5.1
Level 1Second Thoughts
18 ptsOut of lives
21 ptsOut of lives
Level 2Pressure Pot
9 ptsOut of lives
Pending
Level 3Hide or Flight
9 ptsSurvived
8 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.

Beam 1.0 501B A23B 37.3/100Rank 29/48

Cleared 2 of 5
Latch: complete playing field
Level 55 ptsTurn 30 / 40

Claude Fable 5.1 80.2/100Rank 24/483 of 5 levels

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

Points per level

LevelBeam 1.0 501B A23BClaude Fable 5.1
Level 1Hold the door
5.2 ptsCleared
Pending
Level 2Crossfeed
9.6 ptsCleared
9.8 ptsCleared
Level 3Relay vault
11.2 ptsFinished early
Pending
Level 4Passing bay
3.6 ptsFinished early
18.2 ptsClearedFinished early · 3 beacons left
Level 5Second thoughts
5 ptsFinished early
20.6 ptsCleared

Newton's Mirror

Same task instructions

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

The judgment

Beam 1.0 501B A23B

Central object placement is fairly close, but the defining mirrored-room structure is missing. The paint colors suggest the required contact order without establishing their different interaction histories. The faint floor oval does not demonstrate valid reflection geometry, so it earns no reflection credit. Rounded volume and glossy paint provide limited material credit despite weak metallic finishes and oversized paint bodies.

Claude Fable 5.1

The broad paint sequence, bilateral near-field sphere arrangement, overlaps and diminishing panel repetitions are recognizable; crimson is slightly too low. Small paint scale and basic shading provide material cues, although the steel response remains soft. Inaccurate light projections, missing outer chains and incomplete nested room imagery remain the principal limitations.

Score breakdown

CategoryBeam 1.0 501B A23BClaude Fable 5.1
State at 600 ms20.5/2524.0/25
Camera and placement11.5/1514.0/15
Reflections2.0/12048.0/120
Materials and scale3.0/107.5/10
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

Beam 1.0 501B A23B

An appealing expression and warm palette support a coherent simple cartoon. The central polishing joke is not legible: the cloth is unresolved and the nose sits away from the fan. Pointed radial plates, uncertain limb attachments and weak ground contact limit construction, while restrained surface detail limits material richness.

Claude Fable 5.1

The coral palette, friendly face, matte shading and cream arch create a coherent emblem. However, the mantle is elongated rather than compact, and the appendages spread mostly sideways and downward instead of forming an evenly spaced, flower-like starburst. Two thin hanging appendages weaken the thick-arm motif. Clean contours and balanced framing support the simple design.

Score breakdown

CategoryBeam 1.0 501B A23BClaude Fable 5.1
Task & likeness4.0/106.5/10
Anatomy & construction3.5/107.0/10
Space & placement5.5/107.5/10
Light & reflections5.5/106.5/10
Purposeful detail4.5/106.0/10
Artistry & character4.0/107.0/10
Materials & effects4.5/106.5/10
Visual integrity7.0/108.0/10

Benchmark task

Beam 1.0 501B A23B

A golden pangolin polishes its oversized amber tail while its nose smudges the same scale. The scene tests expressive anatomy, physical contact and contrasting translucent, polished and soft materials.

Claude Fable 5.1

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

Mona Lisa

Different task instructions

Precise visual recall and portrait reconstruction.

The judgment

Beam 1.0 501B A23B

The candidate shows a faint warm oval against an almost entirely black field. Minimal placement and smooth tonal variation are visible, but the portrait, anatomy, crossed hands and landscape remain unreadable. The saved comparisons provide no specific evidence supporting a change to the baseline categories.

Claude Fable 5.1

The dark clothing, crossed hands and hazy landscape establish the Mona Lisa composition. Replication is limited by the frontal, elongated face, wide eyes and simplified smile. Rounded, parallel fingers and unclear wrist transitions weaken the hands. Warm facial shading gives some volume, but broad garment shapes and scattered crack marks substitute for convincing folds and painterly detail.

Score breakdown

CategoryBeam 1.0 501B A23BClaude Fable 5.1
Task & likeness0.0/105.5/10
Anatomy & construction0.0/106.0/10
Space & placement0.0/106.0/10
Light & reflections0.5/106.0/10
Purposeful detail0.0/105.0/10
Artistry & character0.0/105.5/10
Materials & effects0.0/106.0/10
Visual integrity0.0/106.5/10

Benchmark task

An SVG interpretation of the Mona Lisa tests facial likeness, anatomy and the composition of a familiar portrait.

Beach

Different task instructions

Creativity, perspective and visual beauty.

The judgment

Beam 1.0 501B A23B

A coherent, cheerful beach illustration fulfills the main subjects with clean shapes and a strong sunset focal point. Its basic geometric construction, ambiguous animal anatomy, shallow depth and schematic lighting limit its accomplishment. Decorative details provide interest without developing intricate forms or convincing physical surfaces.

Claude Fable 5.1

The colorful sunset, layered shoreline, animals, kite and beach toys fulfill the lively beach brief. Clean silhouettes and a balanced composition give the illustration character. Construction is simplified: the umbrella resembles a segmented fan, dolphins have weak water interaction, and the sun’s reflection forms a rigid widening wedge. Flat surfaces and sparse contact shadows limit depth.

Score breakdown

CategoryBeam 1.0 501B A23BClaude Fable 5.1
Task & likeness7.0/108.5/10
Anatomy & construction5.0/107.0/10
Space & placement6.0/107.0/10
Light & reflections5.0/107.0/10
Purposeful detail5.5/107.5/10
Artistry & character4.0/107.5/10
Materials & effects5.0/106.5/10
Visual integrity5.0/107.5/10

Benchmark task

A busy shoreline at sunset tests scene composition, animal forms and the relationship between light and water reflections.

Ground Truth

Different task instructions

Physical reasoning, light and visual reconstruction.

The judgment

Beam 1.0 501B A23B

This benchmark has not been assessed yet.

Claude Fable 5.1

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

Beam 1.0 501B A23B

A cheerful, readable illustration with recognizable animals, expressive faces and useful accessories. Simple rounded construction limits complexity, while ambiguous steering attachments and weak hull-to-water contact reduce physical coherence. Lighting and surface effects establish the setting without convincing environmental interaction.

Claude Fable 5.1

The raccoon rides on the dog's back, and the dog's extended foreleg reaches the jet ski controls. Expressive faces, a clear silhouette and sweeping spray make the action readable. Limb and handlebar overlaps weaken construction; broad shading provides limited volume, and the glowing sun has little corresponding reflection on the water. Clean vector shapes support an appealing but simplified illustration.

Score breakdown

CategoryBeam 1.0 501B A23BClaude Fable 5.1
Task & likeness5.0/108.5/10
Anatomy & construction3.5/106.5/10
Space & placement5.5/107.0/10
Light & reflections4.0/105.5/10
Purposeful detail6.5/107.0/10
Artistry & character3.5/107.0/10
Materials & effects5.0/106.5/10
Visual integrity6.5/107.5/10

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

Beam 1.0 501B A23B

A cheerful, clearly readable pelican-and-bicycle illustration with clean contours and balanced composition. Simple geometric construction limits artistic complexity, while ambiguous neck and steering overlaps, merged pedal contacts and an incomplete drivetrain weaken physical coherence.

Claude Fable 5.1

The pelican reads clearly, with an expressive face, prominent bill and appealing composition. Both legs connect to the body, but the far foot's pedal contact and the wing's steering grip remain unclear. Wheel alignment and background layers are coherent. Clean contours and feather lines give polish, while schematic machinery, limited surface texture and weak directional lighting constrain the finish.

Score breakdown

CategoryBeam 1.0 501B A23BClaude Fable 5.1
Task & likeness5.5/108.5/10
Anatomy & construction4.5/107.0/10
Space & placement5.0/107.5/10
Light & reflections4.0/106.0/10
Purposeful detail4.0/107.0/10
Artistry & character4.0/107.0/10
Materials & effects4.0/106.0/10
Visual integrity5.5/108.0/10

Benchmark task

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