Function chain_depth 

pub fn chain_depth(lps: &[f32], ln_tau: f32) -> usize

2026-10-02: How many leading drafts of a chain to verify, from each draft’s top-1 log-probability lps[j] (in draft order): drafting continues past draft j only while lps[j] >= ln_tau, so the chain ends with the first draft below the threshold, which is still verified. An empty chain is 0.