Marks the enclosing scope as a HOST-originated parameter write.
Wrap every point where the host's value reaches the StateStore: the automation applied during process(), a setState/preset restore, a host-driven controller write. Without the mark, an edit bridge on the same thread cannot tell the host's own value from the user's and will echo it back — which hosts variously treat as a fight for control, a spurious automation write, or an undo-history entry the user never made.
Reentrant and thread-local: nesting is counted, and a mark on one thread never suppresses a genuine editor write on another.