Scheme Request for Implementation 173,
by Amirouche Boubekki,
has gone into "final" status.
The document and an archive of the discussion are available at https://srfi.schemers.org/srfi-173/.
Here's the abstract:
This library describes a mechanism known as hooks. Hooks are a certain kind of extension point in a program that allows interleaving the execution of arbitrary code with the execution of the program without introducing any coupling between the two.
Many thanks to Amirouche and to everyone who contributed to the discussion of this SRFI.