huggingface.co/blog/ibm-research/altk-evolve-bc ALTK-Evolve: How learned memory tops the τ²-bench leaderboard on customer service tasks without a frontier model
A plain ReAct agent running GPT-4.1, an older non-reasoning model, solves 67.5% of τ²-bench retail tasks on all four attempts, beating every retail entry in an October 12, 2026 leaderboard snapshot. The gain comes from a short list of rules the same model wrote from its own past attempts and added to the system prompt, with no weight updates.
— via Hugging Face
