diff --git a/supabase/migrations/00013_reconcile_plot_counts.sql b/supabase/migrations/00013_reconcile_plot_counts.sql
new file mode 100644
index 00000000..b55c22a0
--- /dev/null
+++ b/supabase/migrations/00013_reconcile_plot_counts.sql
@@ -0,0 +1,16 @@
+-- Reconcile stale storylines.plot_count and last_plot_time from plots table.
+-- Idempotent: only updates rows where values differ from computed aggregates.
+-- Context: PR #258 fixed the code path; this migration fixes existing stale data.
+
+UPDATE storylines s
+SET plot_count = sub.cnt,
+    last_plot_time = sub.latest
+FROM (
+  SELECT storyline_id,
+         COUNT(*) AS cnt,
+         MAX(block_timestamp) AS latest
+  FROM plots
+  GROUP BY storyline_id
+) sub
+WHERE s.storyline_id = sub.storyline_id
+  AND (s.plot_count IS DISTINCT FROM sub.cnt OR s.last_plot_time IS DISTINCT FROM sub.latest);