I want to invoke

pulumi up

using another application, but I want that application to know about the success of the stack creation/deletion/etc. Possible?

You definitely can use webooks, yes, but the Pulumi CLI will exit with a status of

0

on success, and non-zero on failure, if you’re calling it synchronously, you could use that, too.

But does that mean I have to wait for the whole stack to be created first? and then it returns a

0

thereafter?

Sorry for the delay! Yes, Pulumi will wait until the stack is completely created or updated, then exit, just like when you run it locally.