unsafe or unknown mutation action policy

Why this fires¶

TE752 rejects an unknown action policy or a superseding/cancellation policy such as .Latest. A mutation already accepted by the server may still commit even if its response is no longer interesting, so hiding or cancelling only the client continuation would make the UI lie about the effect.

let save = Document::save.lane(policy: .Latest)
// error[TE752]: mutation actions cannot use supersession

Fix it¶

Choose the concurrency contract explicitly:

• .Drop ignores accidental duplicate submits while one run is active (the default).
• .Queue preserves every intent in FIFO order.
• .Parallel starts every run and exposes them through pending_count and runs.

The editor offers a safe .Drop replacement. Cancelable reads and autocomplete belong in a task/loader abstraction rather than a mutation action.