STEALTHMARK · HEAD TO HEAD

All comparisons ↗

GPT-5.5 vs MiMo-V2.6-Pro

MiMo-V2.6-Pro leads GPT-5.5 by 16.6 points on StealthMark, 47.9 to 31.3. It leads on 6 of the 7 benchmarks with results for both and GPT-5.5 on 1. MiMo-V2.6-Pro scores higher on Newton's Mirror, with its largest category advantage in reflections.

See the difference ↘
All results ↗
All results ↗

Overall StealthMark

31.3/100Overall rank 43/53
47.9/100Overall rank 21/53

General Intelligence

26.8/100
44.3/100

Visual Intelligence

36.3/100
54.3/100

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

  • GPT-5.5Multi-step reasoning not measured

Open or local

Open modelMIT

BENCHMARK BY BENCHMARK

Where each model leads

  • GPT-5.5
  • MiMo-V2.6-Pro
  • Other models
  • Median

DATASHEET

Specs and pricing

GPT-5.5 runs 1.7× faster in our speed test. MiMo-V2.6-Pro scores higher on StealthMark and is 34× cheaper per output token. Both take about 1.05M tokens of context.

  • GPT-5.5
  • MiMo-V2.6-Pro
  • Other models
  • Median
PricePer 1M output tokens, input below
GPT-5.5: $30$5 inputMiMo-V2.6-Pro: $0.8734× cheaper$0.43 input
Context windowTokens per request, max output below
GPT-5.5: 1.05MTied128K max outputMiMo-V2.6-Pro: 1MTied128K max output
Output speedTokens per second, our measurement
GPT-5.5: 1931.7× fastertokens/sMiMo-V2.6-Pro: 116tokens/s
SizeTotal and active parameters
GPT-5.5: Not disclosedMiMo-V2.6-Pro: 1.02T42B active
Developer
OpenAIXiaomi
Released
23 Apr 202621 Sep 2026
Origin
United StatesChina
Input → output
Text, image → textText, image, video, audio → text
Architecture
Not publishedSparse Mixture-of-Experts; OpenRouter maps the route to the released Pro-RL checkpoint. The UltraSpeed edition is a separate route

Full datasheets, every price and sourceGPT-5.5 ↗MiMo-V2.6-Pro ↗

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.

MiMo-V2.6-Pro 54.6/100Rank 13/47

Survived 1 of 3
Foresight: complete playing field
Level 319 ptsTurn 20 / 20

Points per level

LevelGPT-5.5MiMo-V2.6-Pro
Level 1Second Thoughts
No run
4 ptsOut of lives
Level 2Pressure Pot
No run
9 ptsOut of lives
Level 3Hide or Flight
No run
19 ptsSurvived

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.

MiMo-V2.6-Pro 52.6/100Rank 22/48

Cleared 5 of 5
Latch: complete playing field
Level 520.4 ptsTurn 28 / 40

Points per level

LevelGPT-5.5MiMo-V2.6-Pro
Level 1Hold the door
No run
5.2 ptsCleared
Level 2Crossfeed
No run
9 ptsClearedFinished early · 1 beacon left
Level 3Relay vault
No run
17.2 ptsClearedFinished early · 1 beacon left
Level 4Passing bay
No run
16 ptsClearedFinished early · 3 beacons left
Level 5Second thoughts
No run
20.4 ptsCleared

Newton's Mirror

Same task instructions

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

The judgment

GPT-5.5

The paint ordering and separate black bead support part of the physical state, but adhesion and rotational transport remain only partly established. The sweeping cyan arc and long crimson lobes do not clearly communicate the limited time since their respective impacts. The main sphere is too large and too low, and the black bead is below its required projected position. Displaced isolated sphere images, a flattened floor echo and missing recursive, nested and emitter reflections provide little coherent optical structure. The colored paint is excessively bulky for the specified quantities.

MiMo-V2.6-Pro

The main framing and visible paint-contact story are well supported. Major optical omissions dominate the result: sparse repetitions, undersized first images, missing outer chains and absent curved nested imagery prevent a coherent mirror-room system. The metallic forms remain convincing in volume but have a soft illustrative finish.

Score breakdown

CategoryGPT-5.5MiMo-V2.6-Pro
State at 600 ms15.0/2523.0/25
Camera and placement6.0/1512.0/15
Reflections5.0/12019.0/120
Materials and scale6.0/107.5/10
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

GPT-5.5

Six pale, scaled lobes form a balanced radial arrangement, but they remain separate capsules rather than an interlocking serpent knot. There are no crossings, alternating overlaps, or crisp inner bends; the central hexagon is an isolated outline. Small outward-facing heads sit within the lobes without integrated necks. Soft shading and tidy contours provide some finish, while repetitive oval scales and cartoon faces limit organic credibility.

MiMo-V2.6-Pro

An appealing rabbit with balanced framing, expressive eyes and purposeful costume accents. Simple frontal construction limits anatomical and spatial accomplishment. The orange orb provides an effective luminous focal point, but unreadable wrist connections weaken the requested gestures and prevent stronger integrity credit.

Score breakdown

CategoryGPT-5.5MiMo-V2.6-Pro
Task & likeness3.0/106.5/10
Anatomy & construction3.0/105.0/10
Space & placement5.0/105.5/10
Light & reflections5.0/106.5/10
Purposeful detail4.5/106.5/10
Artistry & character4.0/105.0/10
Materials & effects4.5/106.5/10
Visual integrity7.0/106.0/10

Benchmark task

GPT-5.5

A pale serpent woven into an interlocking knot tests connected anatomy, repeated structure and readable overlaps. Organic surface detail must work with the overall geometry.

MiMo-V2.6-Pro

A small rabbit in an explorer outfit floats with a luminous orb. The scene tests character anatomy, pose and the placement of geometric forms around it.

Mona Lisa

Different task instructions

Precise visual recall and portrait reconstruction.

The judgment

GPT-5.5

The veil, restrained smile, crossed hands and muted landscape establish Mona Lisa references. The oversized frontal face and schematic features weaken likeness and expression, while fingerless tapered hand shapes leave anatomy unresolved. Clean contours and balanced framing provide coherence, but sparse garment detail, broad landscape bands and shallow shading limit the portrait's sophistication.

MiMo-V2.6-Pro

The portrait is recognizable through its dark silhouette, slight smile and muted landscape, but replication is weak. A frontal, oversized head and symmetric torso replace the reference's turned seated pose; angular, separated hands omit its central gesture. Smooth shading maintains coherence while anatomical detail, depth and material rendering remain basic.

Score breakdown

CategoryGPT-5.5MiMo-V2.6-Pro
Task & likeness1.5/103.5/10
Anatomy & construction1.5/103.5/10
Space & placement1.5/104.0/10
Light & reflections2.0/105.0/10
Purposeful detail2.5/103.0/10
Artistry & character1.5/104.0/10
Materials & effects2.0/104.0/10
Visual integrity1.5/106.0/10

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

GPT-5.5

The sunset, palms, birds, playful animals and ball clearly establish the requested beach scene. Warm sky gradients and clean silhouettes make it appealing. Animal construction is underdeveloped: torso and limb connections are unclear, especially in the round-eared foreground figure. The dolphin lacks a convincing splash, and broad reflection bands suggest sunset light without resolving its behavior on water.

MiMo-V2.6-Pro

A readable sunset beach with clear requested subjects, appealing framing and purposeful accessories. Schematic anatomy, flattened foreground objects, repetitive water highlights and sparse directional shadows limit construction and physical depth. The kite's unresolved anchor also constrains integrity.

Score breakdown

CategoryGPT-5.5MiMo-V2.6-Pro
Task & likeness7.0/108.5/10
Anatomy & construction2.5/105.0/10
Space & placement3.0/106.0/10
Light & reflections3.0/106.5/10
Purposeful detail3.0/106.5/10
Artistry & character3.0/105.0/10
Materials & effects3.0/106.0/10
Visual integrity3.5/106.0/10

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

GPT-5.5

This benchmark has not been assessed yet.

MiMo-V2.6-Pro

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

GPT-5.5

The raccoon's masked face, bright hull and sweeping wake make the scene readable and lively. The dog is much less resolved: its head is ambiguous, overlapping brown forms obscure its anatomy, and its paws do not visibly grip the controls. Smooth shapes and cheerful colors provide appeal, but weak steering construction and limited depth keep the drawing uneven.

MiMo-V2.6-Pro

A coherent, cheerful cartoon with recognizable animals, readable steering contact and useful small details. The dog's orientation follows the craft more successfully than a wholly frontal pose would. Simple anatomy, weak raccoon grip and compressed seating contacts still limit physical credibility. Gradients and spray provide polish without resolving complex construction.

Score breakdown

CategoryGPT-5.5MiMo-V2.6-Pro
Task & likeness3.5/107.0/10
Anatomy & construction3.0/105.0/10
Space & placement4.5/105.5/10
Light & reflections5.0/105.5/10
Purposeful detail3.5/106.0/10
Artistry & character3.0/104.0/10
Materials & effects5.0/105.5/10
Visual integrity3.0/104.5/10

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

Same task instructions

Subject construction and spatial relationships.

The judgment

GPT-5.5

The oversized bill, bright bicycle and sunset create an appealing, recognizable cartoon. Riding mechanics are less convincing: the wing has no clear steering contact, leg attachments are uneven, and feet do not visibly engage pedals. A dark notch complicates the rear neck junction. Clean contours and orderly spokes provide polish, while simplified anatomy and lighting limit depth.

MiMo-V2.6-Pro

The distinctive bill, continuous silhouette and detailed wheels establish a readable pelican cyclist. Shaped feathers and soft shading add character, but jointless legs, crowded pedal contacts, absent steering contact and loosely directional lighting limit the construction. The comparisons support retaining the baseline category scores.

Score breakdown

CategoryGPT-5.5MiMo-V2.6-Pro
Task & likeness7.5/106.5/10
Anatomy & construction4.5/105.0/10
Space & placement6.5/106.0/10
Light & reflections6.5/105.5/10
Purposeful detail5.5/106.0/10
Artistry & character5.0/106.0/10
Materials & effects6.0/105.5/10
Visual integrity7.5/106.0/10

Benchmark task

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