5.5's real root cause was a stale advertised lastLogTerm (c->persist.term vs
persist_entry_term), not the last_activity hypothesis — fixed in b8453b2 and
VERIFIED: with it, the freshest survivor now wins PreVote and enters the real
election (it could not before). But round 4 still does not complete: a deeper
layer (task 5.6) — under the dead-primary RDHUP cadence (~15s) the two survivors
duel in lockstep and the term escalates unbounded (21->25->28->29...) without
reaching majority. Adds task 5.6 (randomized failover backoff to desync the duel
/ don't re-trigger failover mid-real-election). Consensus SAFETY intact; this is
election LIVENESS under sustained churn. 4 layers of the round-4 stall now peeled
(deadlock, segfault, advertised-term fixed; dueling-candidate remains).
Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019dbTHR9CsEYK9RsqmQpQpC
Rongsong Shen
fa53feaf62