5.6's RDHUP-no-preempt guard (81cb09a) is unit-verified and slows the round-4 term
churn, but the soak still stalls — a 5th layer (task 5.7). The freshest survivor
ctrl-2 (15@t5) wins PreVote, enters the real election, and ctrl-3 GRANTS it
(vote_granted) — but ctrl-2 never tallies a majority: every grant arrives as
vote_reply_stale_drop (reply term < ctrl-2's current term). ctrl-2's term
escalates via repeated election timeouts faster than ctrl-3 (cold peer
connection, fresh SSL connect per vote, plus dead-ctrl-1 connect timeouts) can
reply, so each grant is one term stale -> dropped -> timeout -> term++.
Self-perpetuating; DropStaleResponse itself is correct Raft.
Adds task 5.7 (don't re-escalate the term while a vote RTT is outstanding /
warm-reuse the peer vote connection / wider jitter). 5 layers of the round-4
stall now peeled, 4 fixed (deadlock, segfault, advertised-term, RDHUP-preempt);
the cold-connection term-lag remains. Consensus SAFETY intact throughout.
Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019dbTHR9CsEYK9RsqmQpQpC
Rongsong Shen
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