The conditions were joined with " AND " and nothing else, so a smart playlist could only ever narrow: "jazz released after 1960" was expressible and "jazz or blues" was not, which is most of what anyone reaches for a second rule to say. `RuleSet.Match` is "all" or "any", and an empty match is "all" — which is what every playlist saved before the field existed carries, so an upgrade cannot silently widen one. ParseRuleSet rejects anything else rather than falling through to AND, since a playlist quietly returning the wrong tracks is worse than one that refuses to be saved. Under OR each condition is parenthesised and under AND it is not: AND is the tighter operator, so an OR-join has to protect a condition carrying a top-level AND of its own — `days_since_played less_than` is two predicates belonging to one rule. The editor shows the choice as a sentence with the control in the middle, and hides it while there is one rule: with nothing to combine, all and any are the same query. Closes #35 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>