Hi Michael, Thanks for the review. To clarify: TLI 1 does not diverge — it is fully replicated to the standby before the timeline switch. The test then intentionally slows down replication on TLI 2 (e.g., by delaying WAL shipping), reproducing the scenario I illustrated. As far as I’m aware, `fsync` is `on` by default, and the test does not modify it — so no WAL records are lost due to unsafe flushing.
The core issue is that the new timeline’s segment is zero-initialized instead of copying the same segment from the previous timeline (as done in crash-recovery startup). As a result, startup cannot finish recovery due to non-replicated end of WAL causing failures like “invalid magic number”. --- Alena Vinter
