- Remove background thread mutation of logbook.logs during merge to prevent ConcurrentModificationException crashes - Cancel ongoing timer when user enters manual duration to prevent orphaned ongoing events - Prevent duplicate timer dialogs when tapping ongoing event in list - Block starting a second timer while another is already running - Track old fingerprint on event edit to prevent merge re-adding the old version Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>