diff --git a/migrate/006_fix_uuid_defaults_and_draft_null.sql b/migrate/006_fix_uuid_defaults_and_draft_null.sql
new file mode 100644
index 0000000..d102372
--- /dev/null
+++ b/migrate/006_fix_uuid_defaults_and_draft_null.sql
@@ -0,0 +1,32 @@
+-- Align imks-managed IDs with application-generated UUID v7 values and
+-- make top-level drafts unique when thread_id is NULL.
+
+BEGIN;
+
+CREATE UNIQUE INDEX IF NOT EXISTS uq_message_draft_channel_user_no_thread
+    ON message_draft (channel_id, user_id)
+    WHERE thread_id IS NULL;
+
+ALTER TABLE message_attachment ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_embed ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_embed_field ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_poll ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_poll_option ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_poll_vote ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_pin ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_read_state ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_draft ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_edit ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_article ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_reaction ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_bookmark ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_mention ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_thread ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_thread_participant ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_notification ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_scheduled ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_sticker ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_forward ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE message_component ALTER COLUMN id DROP DEFAULT;
+
+COMMIT;