ReadonlykindReadonlycodeMachine-readable block code (e.g., "COMMAND_NOT_ALLOWED", "TICKET_REQUIRED").
ReadonlyreasonHuman-readable explanation.
Optional ReadonlyrecoveryOrdered recovery steps for the user (from reason registry).
Optional ReadonlyquickOptional command that fixes the issue (from reason registry).
Optional ReadonlyoverflowStructured auto-advance overflow context (#428). Present only when this
block was produced from an AutoAdvanceOverflow. Carried as typed
data (not parsed from reason) so the plugin boundary can detect and log
the overflow structurally.
Rail was blocked — precondition failed, state is UNCHANGED.