Cannot replicate anonymous transaction when AUTO_POSITION = 1

Root cause

GTID mode is enabled on the MySQL server (gtid_mode=ON) but the binlog contains anonymous transactions (without GTIDs) from before GTID was enabled. This happens after migrating from MySQL 5.7 to 8.0, or when enabling GTIDs on a running server without purging old binlogs.

How to fix

1. Purge the binlogs that contain anonymous transactions before enabling GTIDs:
   PURGE BINARY LOGS TO 'mysql-bin.XXXXXX';
2. Or temporarily bypass with snapshot.mode=initial to start fresh from a known GTID position.
3. Verify GTID consistency:
   SHOW MASTER STATUS; check that gtid_executed covers all servers.