A pattern (phrases, a severity, a source, a window) is counted every minute into plugin_metrics as lines_matching_<key> per added source, zero included, so an ordinary alert rule fires on a match and clears once the window passes. Each count reads only the lines stored since the last, by line id; a new or changed pattern reads its window once. Patterns page with ready-made storage-trouble presets and "Alert on it", which opens the rule form aimed at the count. Source names are kept unique, and a rename moves its counts and the rules on them. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>