z_listsentbyaddress re-walks the whole wallet when there's no usable
watermark, which the daemon does under cs_main for every send -- hundreds
of seconds, 400+ s and ~19 GB RSS on a large wallet. The watermark lived
only in memory, so every relaunch, reconnect or daemon restart paid for a
full sweep. This persists it so those cases run a bounded windowed sweep
([z, 0, 2, tip - W + margin]) instead (SENT-HISTORY-SWEEP Part 1).
- The watermark (W = last swept tip), its anchor (A = W - margin) and anchor
hash (H_A = getblockhash(A)), plus the enrichment backlog and the full-
sweep backoff, ride in the encrypted history snapshot as an optional
`sent_sweep` object (schema stays v1; a missing/inconsistent one reads as
"no watermark" = today's behaviour, so older builds and payloads are safe).
- Before the first windowed sweep after a load, the anchor is verified
(getblockhash(A) == H_A). A match means any fork is inside the window; a
mismatch (reorg deeper than the margin, different chain/datadir) or an
inability to check drops the watermark and sweeps the whole wallet.
- The first sweep after a load uses a bigger margin (absorbs notifier lag),
and a watermark older than 2400 blocks uses the long timeout (callLong).
- The backlog is persisted WITH W: a pure z->z send's txid lives only in a
sweep result and would be lost if the window moved past an un-enriched one.
- Watermark changes reach disk (folded into the store signature), and every
hard case still forces a full sweep: reorg (anchor verify), GUI rescan /
zap / import / address change, restoreOriginalWallet, and disconnect.
Deferred (follow-ups, each only turns a correct-but-slow case faster, never a
correctness risk): the banded full sweep for seeding on a pre-note-cache
daemon, the external-import tripwire, and the weekly safety-net re-sweep.
Part 2 (the daemon's decrypt cost) is already on the daemon's
perf/sapling-note-cache branch.
Pure helpers + cache round-trip + anchor-verify/large-window covered by
tests; the getblockhash-after-sweep updates the pinned RPC sequences.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
