Loop the Loopies!

Loopie: Looped MoE Transformer achieves gold-medal performance at IMO and IPhO

Researchers introduce Loopie, a looped Transformer series using Mixture-of-Experts architecture in two sizes (20B/2B active and 6B/0.6B active parameters). The work directly addresses the longstanding challenge that scaling parameters outperforms looping under equal compute budgets, demonstrating that Loopie substantially outperforms vanilla Transformer baselines at the same compute. A novel post-training pipeline yields strong reasoning capabilities, with Loopie achieving gold-medal performance at the 2025 IMO and IPhO competitions without tool use.