2026-08-17 · paper-digest
Pereira & Zuidema: Reasoning Models Build a Map of the Tower of Hanoi, Then Lose It — Fukai Reads
An arXiv preprint by Devin Pereira and Willem Zuidema (University of Amsterdam). On the flat-to-flat Tower of Hanoi, reasoning models encode the board almost perfectly at the end of the prompt (rank correlation 0.935, nearest-state retrieval 1.00), yet that representation decays while they write out the moves — shown with linear probes and activation patching. Re-injecting the prompt-time representation lifted Qwen3.6-27B from 33/81 (41%) to 59/81 (73%) optimal solutions.
