Hi mjs, no, there's no warning if the history chain will get broken by the current edit.

In order for history to do updates, it needs to find all the objects that were used as inputs to create the one to be updated, if any can't be found then that object will not be able to be recalculated.

When you do something like a boolean it's fairly different than a "move" or "rotate" - a boolean doesn't just transform an object keeping all its pieces in place, it basically deletes the current object and creates a new one that may have large chunks missing or added to it. The particular object from before the boolean is then no longer a part of the current model and so that will then break the history chain at that point.

In the future I want to overhaul the entire history mechanism to keep a continuous linear log of all objects and commands that have been used, so that it will be possible for updates to go into that repository and find previous inputs even if they are not in the current version of the model. I'm probably not going to be doing any more work on the current history mechanism by adding in warnings or additional UI for it as it currently works, since I think any work in that area will be largely wasted when it does come time to do the big overhaul.

- Michael