Claude Fable 5 and GPT-5.6 Sol High are fighting for the crown

I wanted to see if "just letting the AI do it" actually works for high-fidelity UI, so I ran a stress test. The goal was a Robinhood clone using React Native and Expo. This wasn't about basic features; it was a test of motion fidelity. We're talking Reanimated, Gesture Handler, and Skia for charts—matching easing, timing, and haptics frame-for-frame against a reference video.

The constraints were strict to keep the benchmark honest: one single prompt, no follow-up corrections, and a completely blank Expo project. If the code didn't run on a physical device, it was a fail. I tested GPT-5.6 Sol High, Claude Fable 5, and Kimi K3 High.

Here is the exact prompt used for the deep dive:

Recreate the Robinhood app screens shown in the attached video as a React Native
(Expo) app. Build three screens: Discover, Token detail (scrubbable chart with
price + Buy reveal), and the Swap/amount keypad screen.
Priority is fidelity of motion and feel, not features — match the real app's
easing, timing, gesture response, haptics, and typography (numbers should
animate digit-by-digit). Use Reanimated + Gesture Handler, and Skia for the
chart. Mock all data locally; no backend.
Watch the video closely and match what you see frame for frame. Tell me which
interactions you couldn't reproduce and why.

The Performance Breakdown

GPT-5.6 Sol High took the win here. It was the only model that truly understood a "motion brief" as a requirement for feel rather than just layout.

• Tokens used: 2.0M
• Estimated cost: ~$15
• Time to first render: 32 minutes
• Dependencies added: 3

The result was surprisingly accurate. It nailed the odometer-style rolling digits on the price ticker—a detail most LLMs fail at by defaulting to a simple cross-fade. The Skia chart was actually scrubbable, and the layout was nearly identical to the reference.

However, there is a technical caveat. Like the other models, GPT-5.6 handled the ticker and chart redraws via React state instead of utilizing UI-thread worklets. This introduces a "JS-thread tax," meaning the interactions aren't as buttery smooth as the actual Robinhood app. If you're looking for a professional deployment, you'll still need to manually optimize those animations to move them off the main thread.

Despite that, it outperformed the others in speed and cost, hitting the mark in half the time of the runner-up. For anyone building a complex AI workflow for mobile UI, this proves that the latest reasoning models are getting significantly better at interpreting visual timing and easing from video references.