I am aware of the Convex Helpers package, which allows us to write custom context objects on queries, mutations, and actions, but that only allows us to write the CTX object before the request happens and not after a response is returned.
My biggest use for this would be to enable convex compatibility with the evlog (https://www.evlog.dev/getting-started/installation) package, which allows us to use wide logging on our events. That integration usually requires us to call .flush() on the object after the response is returned, to emit the log event. And I don't see a clean way to do this in convex.