Liquid AI Open-Sources Antidoom: A Final Token Preference Optimization (FTPO) Method that Reduces Doom Loops in Reasoning Models

Liquid AI released Antidoom, an open-source method that targets doom loops in reasoning models. A doom loop repeats a span until the context window is exhausted. Antidoom finds the token that starts the loop and retrains only that position using Final Token Preference Optimization (FTPO). On LFM2.5-2.6B, doom-loop rates fell from 10.2% to 1.4%; on Qwen3.5-4B, from 22.9% to 1%. Generation, detection, and the FTPO trainer are open source.