Research Explainer · XiaoHu Explains

Same models, new shell: Opus 4.8 and Fable 5 hit 99% on ARC-AGI-3

A harness called Schema makes the model write each game's rules as a runnable program, verify them, then act. Self-reported 98.98% on the 25 public games — not independently verified by ARC Prize.
⚑This is Impossible Research's own harness release. Both scores are self-reported by the team, measured only on the 25 public games, and have not been independently verified by ARC Prize. How it would score on the semi-private set hasn't been measured yet.
Impossible Research × Berkeley × CMU

A game that won't tell you the rules

Impossible Research (working with UC Berkeley and Carnegie Mellon University) released Schema, a harness that lets frontier models play games like physicists. It targets a benchmark built specifically to trip up AI: ARC-AGI-3.

Primary source and reference