interrupt

Requests that a blocking call another lane is stuck inside return promptly with a typed failure, and that every later blocking call on this source fail fast.

One-way: an interrupted source is being abandoned, and the session that owns it is on its way down. The engine calls this from the actor while the demux lane is wedged inside a read or seek, which is the ONE concurrency this contract permits; it never runs concurrently with, or after, the backend session's close.