diff --git a/src-tauri/migrations/0008_calendar_dedup_cleanup.sql b/src-tauri/migrations/0008_calendar_dedup_cleanup.sql
new file mode 100644
index 0000000..695e335
--- /dev/null
+++ b/src-tauri/migrations/0008_calendar_dedup_cleanup.sql
@@ -0,0 +1,68 @@
+-- Bug fix: prior imports could accumulate many duplicate rows for the same
+-- real calendar event on every re-import -- either because the (source,
+-- raw_uid) unique index (added in 0005) never retroactively deduped rows
+-- that existed before it, or because an event with no UID in its source data
+-- got `raw_uid = NULL`, which that index's `WHERE raw_uid IS NOT NULL` clause
+-- explicitly exempts from uniqueness, so it duplicated on every single
+-- re-import forever. This collapses whatever's already in the table, then
+-- backfills a stable content-based key for anything still missing a UID so
+-- future re-imports resolve to the same row instead of minting a new one
+-- (see calendar::content_uid in src/calendar/mod.rs, which produces the
+-- identical 'content:subject|organizer|starts_at|ends_at' format used here).
+PRAGMA foreign_keys = ON;
+
+-- Drop the index first: the backfill below can momentarily produce rows that
+-- share a (source, raw_uid) pair before they're deduped a few statements
+-- later, which the index would reject mid-UPDATE.
+DROP INDEX IF EXISTS idx_calendar_events_source_uid;
+
+UPDATE calendar_events
+SET raw_uid = 'content:' || COALESCE(subject, '') || '|' || COALESCE(organizer, '')
+    || '|' || COALESCE(starts_at, 0) || '|' || COALESCE(ends_at, 0)
+WHERE raw_uid IS NULL;
+
+-- One survivor per (source, raw_uid) group: whichever row a meeting is
+-- already attached to (so `attach_meeting_to_event` links don't break), else
+-- the lexicographically-first id (arbitrary but deterministic).
+CREATE TEMP TABLE calendar_event_survivors AS
+SELECT source, raw_uid, MIN(id) AS keep_id
+FROM calendar_events
+GROUP BY source, raw_uid;
+
+UPDATE calendar_event_survivors
+SET keep_id = (
+    SELECT m.calendar_event_id FROM meetings m
+    JOIN calendar_events ce ON ce.id = m.calendar_event_id
+    WHERE ce.source = calendar_event_survivors.source
+      AND ce.raw_uid = calendar_event_survivors.raw_uid
+    LIMIT 1
+)
+WHERE EXISTS (
+    SELECT 1 FROM meetings m
+    JOIN calendar_events ce ON ce.id = m.calendar_event_id
+    WHERE ce.source = calendar_event_survivors.source
+      AND ce.raw_uid = calendar_event_survivors.raw_uid
+);
+
+-- Repoint any meeting attached to a duplicate that's about to be deleted
+-- onto the group's survivor instead.
+UPDATE meetings
+SET calendar_event_id = (
+    SELECT s.keep_id FROM calendar_event_survivors s
+    JOIN calendar_events ce ON ce.source = s.source AND ce.raw_uid = s.raw_uid
+    WHERE ce.id = meetings.calendar_event_id
+)
+WHERE calendar_event_id IN (
+    SELECT ce.id FROM calendar_events ce
+    JOIN calendar_event_survivors s ON ce.source = s.source AND ce.raw_uid = s.raw_uid
+    WHERE ce.id != s.keep_id
+);
+
+-- Drop the duplicates (cascades to calendar_event_participants).
+DELETE FROM calendar_events
+WHERE id NOT IN (SELECT keep_id FROM calendar_event_survivors);
+
+DROP TABLE calendar_event_survivors;
+
+CREATE UNIQUE INDEX idx_calendar_events_source_uid ON calendar_events(source, raw_uid)
+    WHERE raw_uid IS NOT NULL;