---
id: "bug-1421"
status: "fixed"
status_updated: "2026-09-24"
status_note: ""
component: "controller"
severity: "unknown"
timestamp: "2026-07-08T06:55:15.000Z"
last_seen: "2026-09-19T09:00:00Z"
occurrences: 2
files: ["src/controller/ha.c"]
tags: ["ha", "raft", "term-desync", "liveness", "election-regression", "ae-reject", "replication"]
related: ["bug-1417", "bug-1418", "bug-851"]
legacy: true
---

# bug-1421: Sequential HA soak regression: no primary elected at term>8 by round 6 (initially suspected to…

## Description
Sequential HA soak regression: no primary elected at term>8 by round 6 (initially suspected to stem from the bug-1417 fix); root-caused 2026-07-09 as the primary never discovering a follower's higher term via AppendEntries-reject responses

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
ha_raft_on_repl_ack only routes AE-reply term-adoption for success=1 ACKs; AE rejects (success=0) never reach raft_on_append_entries_reply. That function additionally drops any reply with reply_term != s->term (raft.c:832-833, stale-term drop) before it can adopt a higher term. Net effect: once a follower is ahead in term (e.g. it steps down from PreVote to CTRL_STANDBY at a higher term while an existing primary keeps campaigning/replicating at its old term), every AppendEntries the stale primary sends is rejected with ae_reject_stale, the primary never learns the higher term, and it can never regain write-quorum (needs 2/3, only self-vote counts) — a permanent livelock. First surfaced as an election regression (sequential soak: no primary elected at term>8 by round 6, chaotic stalled at round 5) suspected to be caused by the bug-1417 vote-index-mapping fix; re-reproduced 2026-07-09 as a round-4 sequential stall (primary ctrl-2 term=6, follower ctrl-3 term=7, 490 ae_reject_stale events, primary writable_lsn stuck at 17), which pinned the exact mechanism above.

## Fix
Added two fallback term-discovery vectors that fire regardless of AE-reject outcome. (1) StateReport heartbeat-reply now carries the standby's current term (controller.capnp +term field @2, typemap.h state_report_t +term, ha_nop_reply_state_report populates it from ha->term) so the primary learns a higher term on every convergence cycle. (2) New library entry point raft_on_higher_term_observed(s, observed_term) mirrors UpdateTerm (strictly-greater-than only; touches term/voted_for/role; on_persist before on_become_follower for durability ordering) and is called from repl_ack_decode_and_dispatch on both the heartbeat state-report branch and the WAL-NACK branch (ha.c). Primary now steps down instead of retrying AppendEntries against a follower that rejects forever. Validated: 265 controller + 287 lib unit tests pass (zero regressions); 10-round sequential soak PASS (33 jobs, zero loss, all 3 nodes led ctrl-1/ctrl-2/ctrl-3); 10-round chaotic soak PASS (33 jobs, zero committed divergence, zero committed job loss).

## Verification
_Not recorded (migrated from buglog.json)._

## References
- Related: bug-1417, bug-1418, bug-851