STEALTHMARK · HEAD TO HEAD

All comparisons ↗

Inkling-Small vs Callstack Apex

Callstack Apex leads Inkling-Small by 21.9 points on StealthMark, 49.5 to 27.6. It leads on 7 of the 8 benchmarks with results for both and Inkling-Small on 1, including Latch. Pixel Canary scores higher on Newton's Mirror, with its largest category advantage in camera and placement.

See the difference ↘
All results ↗
Model guide ↗

Overall StealthMark

27.6/100Overall rank 43/53
49.5/100Overall rank 18/53

General Intelligence

25.5/100
40.4/100

Visual Intelligence

31.1/100
59.6/100

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

  • Inkling-Small

Open or local

Open modelApache 2.0

BENCHMARK BY BENCHMARK

Where each model leads

  • Inkling-Small
  • Callstack Apex
  • Other models
  • Median

DATASHEET

Specs and pricing

Inkling-Small takes 4× more context. Callstack Apex scores higher on StealthMark.

  • Inkling-Small
  • Callstack Apex
  • Other models
  • Median
PricePer 1M output tokens, input below
Inkling-Small: No list priceCallstack Apex: $3$0.50 input
Context windowTokens per request, max output below
Inkling-Small: 1M4× largerCallstack Apex: 256K
Output speedTokens per second, our measurement
Inkling-Small: Not measuredCallstack Apex: 255tokens/s
SizeTotal and active parameters
Inkling-Small: 276B12B activeCallstack Apex: Not disclosed
Developer
Thinking Machines LabCallstack
Released
Not published1 Oct 2026
Origin
Not publishedPoland
Input → output
Text, image, audio → textText → text
Architecture
42-layer decoder-only transformer with sparse mixture-of-experts feed-forward (6 of 256 routed experts plus 2 shared per token); hybrid local and global attention; natively multimodal with a hierarchical patch image encoder and discrete-token audioQwen foundation with Callstack domain post-training for React and React Native

Full datasheets, every price and sourceInkling-Small ↗Callstack Apex ↗

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.

Inkling-Small 30.2/100Rank 29/49

Survived 0 of 3
Foresight: complete playing field
Level 38 ptsTurn 17 / 20

Points per level

LevelInkling-SmallCallstack Apex
Level 1Second Thoughts
9 ptsOut of lives
No run
Level 2Pressure Pot
6 ptsOut of lives
No run
Level 3Hide or Flight
8 ptsOut of lives
No run

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.

Inkling-Small 34.7/100Rank 34/50

Cleared 3 of 5
Latch: complete playing field
Level 518 ptsTurn 40 / 40

Callstack Apex 100.0/100Rank 42/501 of 5 levels

1 of 5 played
Latch: complete playing field
Level 15.2 ptsTurn 6 / 12

Points per level

LevelInkling-SmallCallstack Apex
Level 1Hold the door
5.2 ptsCleared
5.2 ptsCleared
Level 2Crossfeed
9.8 ptsCleared
Pending
Level 3Relay vault
2.8 ptsFinished early
Pending
Level 4Passing bay
8 ptsFinished early
Not played
Level 5Second thoughts
18 ptsCleared
Not played

Newton's Mirror

Same task instructions

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

The judgment

Inkling-Small

The sphere's apparent floor support, separate dark feature and broad paint ordering justify partial state credit. The major weakness is the largely missing mirror system: isolated side images and faint floor echoes do not establish repeated virtual rooms or curved spherical mapping. Downward framing, the oversized frontal panel, unresolved paint transport and satin surface appearance remain distinct limitations.

Callstack Apex

The principal sphere placement and paint contact sequence are supported. Isolated sphere and panel images provide limited optical structure, but missing lateral chains and side-floor continuations prevent a coherent repeating mirror room. The main and reflected spheres lack ordered curved nested imagery, while sparse planar emitter images and incomplete spherical emitter mapping leave most of the reflection system unsupported.

Score breakdown

CategoryInkling-SmallCallstack Apex
State at 600 ms14.0/2520.0/25
Camera and placement3.0/1513.0/15
Reflections8.0/12010.0/120
Materials and scale2.5/107.0/10
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

Inkling-Small

The faces and dripping caps communicate a cute mushroom scene, but simple construction and weak spatial relationships limit the result. The defining foot-stamping action is unresolved, the flattering portrait is smaller than its painter, and the requested material contrasts are only partly conveyed.

Callstack Apex

The cheerful yellow bird, cream eyes, orange features and miniature teal console closely match the brief. Clean block edges, restrained colors and soft shadows create an appealing composition. The body reads more like a gridded disc than a fully cubic sphere, and the outlined left wing has limited volume. The right wing reaches the cyan block, though its grip is ambiguous.

Score breakdown

CategoryInkling-SmallCallstack Apex
Task & likeness2.5/108.5/10
Anatomy & construction1.5/107.0/10
Space & placement3.5/107.5/10
Light & reflections3.0/107.5/10
Purposeful detail4.5/107.5/10
Artistry & character3.0/107.0/10
Materials & effects3.5/107.0/10
Visual integrity2.0/107.5/10

Benchmark task

Inkling-Small

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

Callstack Apex

A rounded bird built from small cubes explores a miniature machine. The scene tests block construction, expressive proportions, contact and soft lighting.

Mona Lisa

Different task instructions

Precise visual recall and portrait reconstruction.

The judgment

Inkling-Small

A recognizable but rudimentary Mona Lisa interpretation. Facial shading and subdued colors provide coherence, while the frontal blocklike torso, unresolved wrists, fingerless hands and shallow landscape substantially limit likeness, construction and finish.

Callstack Apex

The framed portrait recalls Mona Lisa through dark hair, folded arms and a hazy landscape. Replication is limited by wide, staring eyes, an elongated neck and a downturned mouth. The overlapping hands lack convincing finger and wrist construction. Soft tonal shading suggests volume, but pervasive blur obscures clothing, landscape and anatomical detail.

Score breakdown

CategoryInkling-SmallCallstack Apex
Task & likeness2.5/103.5/10
Anatomy & construction2.5/104.0/10
Space & placement3.0/104.5/10
Light & reflections2.5/106.0/10
Purposeful detail2.0/104.5/10
Artistry & character2.5/104.5/10
Materials & effects2.0/105.5/10
Visual integrity3.0/105.5/10

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

Inkling-Small

A recognizable sunset beach with a clear focal sun and appealing color transitions. Connected fish silhouettes and layered scenery establish basic coherence. Primitive figures, ambiguous recreation, sparse descriptive detail and weak grounding limit construction and depth. The aligned reflection supplies a useful lighting cue, but shadows and material effects remain underdeveloped.

Callstack Apex

A cohesive sunset beach illustration with lively wildlife, playful accents, and an appealing warm-to-purple palette. Palm framing and the aligned sun reflection organize the scene, while connected silhouettes keep the activities readable. Schematic joints, ambiguous dolphin junctions, loosely matched reflections, and repetitive surface marks limit construction, lighting coherence, and material depth.

Score breakdown

CategoryInkling-SmallCallstack Apex
Task & likeness3.5/108.5/10
Anatomy & construction3.0/104.5/10
Space & placement3.0/107.5/10
Light & reflections3.0/105.5/10
Purposeful detail3.0/107.5/10
Artistry & character3.0/106.5/10
Materials & effects2.5/107.0/10
Visual integrity2.0/104.0/10

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

Inkling-Small

This benchmark has not been assessed yet.

Callstack Apex

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

Multiple instruction versions

Scene composition and interacting subjects.

The judgment

Inkling-Small

Recognizable animals, readable accessories and an appealing sunset support a coherent basic cartoon. Rounded construction leaves joints, riding support and steering unresolved. Decorative gradients contribute atmosphere, but directional lighting, distinct materials and convincing water displacement are weakly demonstrated.

Callstack Apex

The raccoon clearly rides the dog's back, and the dog's paws reach the jet ski controls. Expressive faces, a sweeping tail and a strong sunset composition give the illustration character. Limbs remain connected, but the dog's foreleg joints and vehicle seating are loosely constructed. Angular splashes convey speed more successfully than convincing water displacement; lighting and reflections remain decorative.

Score breakdown

CategoryInkling-SmallCallstack Apex
Task & likeness4.0/109.0/10
Anatomy & construction3.0/107.0/10
Space & placement4.0/107.5/10
Light & reflections5.0/107.0/10
Purposeful detail5.5/108.5/10
Artistry & character4.0/107.5/10
Materials & effects5.0/107.0/10
Visual integrity5.0/108.0/10

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

Different task instructions

Subject construction and spatial relationships.

The judgment

Inkling-Small

The pelican is immediately recognizable, and its sweeping neck, shaped bill and orderly spokes provide character. Riding remains only partially realized: legs, pedal engagement, steering and seat support cannot be read confidently. Controlled graphic effects add atmosphere, but simplified construction and weak grounding keep the result basic.

Callstack Apex

An appealing cartoon with a distinctive pelican, expressive eye, warm bill and carefully drawn bicycle wheels. The wing reaches the handlebar, but the feet do not clearly engage the pedals, weakening the riding mechanics. Layered hills create depth; limited ground shadows weaken contact. Clean curves and purposeful feather details give the illustration polish.

Score breakdown

CategoryInkling-SmallCallstack Apex
Task & likeness4.0/108.5/10
Anatomy & construction3.0/106.5/10
Space & placement3.0/107.5/10
Light & reflections3.0/107.5/10
Purposeful detail4.5/108.0/10
Artistry & character5.0/108.0/10
Materials & effects4.5/107.5/10
Visual integrity3.0/108.0/10

Benchmark task

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