Figure 1: PITCH (Proactive Intervention Timing in CHat) is the first benchmark for proactive inter-
vention timing built from unscripted human conversations and participants’ own judgments of when
proactive interjections should occur. We collected the benchmark data via a four-phrase protocol:
Conversation, Message Contribution, Timing Judgments, and Deliberation. We then evaluated 15
models across 28 configurations against the benchmark in three task setups that differ in their task
difficulty and realism for real-world deployment of agents in group conversations.