I'm trying to debug a couple of action groups that don't execute reliably.

Are individual actions in a group all launched immediately, in the order they are listed, or are there situations where an action's execution is delayed until a previous step has completed?

Specifically, does Indigo wait for an embedded AppleScript (or Python code) to finish before executing the next action in the group?

Thanks.

In general, they are scheduled to run in parallel (unless they have a delay specified). Embedded AppleScripts are the exception because they have to run on the main thread of the Indigo Server so there is a little serialization. Fundamentally, however, you shouldn't assume that the order of the actions means anything. If you need something to happen serially, then you should add delays to guarantee one finishes before the next.