Function idle_probe_backoff_secs 

fn idle_probe_backoff_secs(consecutive_failures: u32) -> u64

Seconds to wait before the next idle probe after consecutive_failures failures in a row. Doubles from 2 s and saturates at IDLE_PROBE_BACKOFF_MAX_SECS; the first failure alone already stops the per-tick hammering. consecutive_failures is always >= 1 at the call site (it’s incremented before this runs), but 0 is handled defensively and yields the same first-step delay.