The mirror keyed each event on (contact, type) only, and the read deduped on
that same pair from an unordered query. So a contact with two custom dates
('Wedding', 'Graduation') mirrored just one — and, the winner being
order-dependent, the single event could ping-pong between the two dates across
syncs. A Custom date's UID now carries a discriminator (its label, else its
month-day), the read dedups on the full UID, and the query is ordered by
Data._ID so a genuine duplicate resolves the same way every time.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Jean-Luc Makiola
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