The test, τ²-bench from Sierra, pairs an agent with a simulated customer and a policy it must follow, and only counts a task as solved if the end result is exactly right. With GPT-4.1, IBM’s agent ranked first in retail, ahead of a model fine-tuned for the benchmark. The playbook made conversations slightly shorter but prompts longer, raising retail cost from about 8 to 14 cents per conversation, much of which prompt caching can recover.
Why it matters
It points to a cheaper path to reliable agents: improve the instructions an existing model works from, rather than retraining it or paying for a bigger one. The results come from IBM’s own submissions to a public leaderboard, so how well such playbooks carry over to real customer conversations is still to be seen.
Original source
ALTK-Evolve: How learned memory tops the τ²-bench leaderboard on customer service tasks without a frontier model
Hugging Face
huggingface.co
Summary by Second Order AI. Full reporting is at the original source.