@mpous it is our own open source delta server, which is based on ‘balena-engine’ as detailed here and here.
Could I ask it a different way - is the issue noted above still present in balena cloud? (i.e. if base images change, does that require devices to download new base images plus changed layers)? And if so, is there some kind of fundamental reason why this can’t be handled differently / can I help resolve it?
It feels like a fairly significant issue, because people who use delta updates rely on them being small, and I suspect most won’t appreciate that you need to leave 2x your fleet size in storage headroom on your device just in case base images change otherwise the update will get stuck. Especially when it seems that the base images do change from time to time, the debian one I noted above was just changed two weeks ago but retained the same tag - so even if you were “pinned” to that image, it would have changed, and would necessitate the storage headroom.