I’m using Linked Smart Objects to periodically update a file being modified outside of Photoshop (and refreshing, say, once every second), as sending pixels seems impossible for now.
This works just fine, except my history gets polluted. I’m interested in just about any hack possible to avoid spamming the history. This can include manually editing the history (if at all possible), or using another method altogether to update the pixels of a background layer.
Edit: Another annoying aspect of this solution is that the cursor flickers whenever the update happens (for instance, if a brush tool is selected, it reverts to a pointer for a few frames). I doubt this is possible but it would be really nice if this can be avoided in some way or another.