Function draw_fingerprint 

pub fn draw_fingerprint(conversations: &[Conversation]) -> String

2026-09-26: The draw fingerprint: SHA256 over the ordered conversations’ ids, tools, and each client turn’s number, messages and ground truth. Two runs with equal fingerprints replayed the same prompts, tools and ground truth in the same order; a differing fingerprint means the numbers are not comparable, whatever the sample counts say.