We’ve been working on this behind the scenes, but should’ve reached out earlier. The short answer is: new Sprites will start shipping Ubuntu 25.10 “soon” (some time this week, depends on the other release schedules and how fast your region’s pool cycles).
The two main blockers with 25.10 were uutils compatibility and upstream moving to Rockcraft for building the base Ubuntu images. While each Sprite gets its own VM, the user environment lives in a lightweight container. Those containers init using tini, which we bundle with the parent Machine’s Pilot. To ship 25.10, we’ve reworked our image pipeline. We now build images directly from the rootfs tarballs provided by Canonical. This will give us more flexibility with Ubuntu updates and should simplify the transition to 26.04 LTS. Initially shipping with 25.04 instead of 24.04 LTS was probably a short-sighted decision, but that’s in the past. When 26.04 LTS releases, we plan to stick with that.
For your current Sprites: once created, we don’t modify them. When 25.10 rolls out, I would create a new Sprite and copy the necessary files. I usually do this by proxying an SSH connection and using rsync. If this is impractical, the do-release-upgrade tool “works” (slowly). You will need to install ubuntu-release-upgrader-core first.
I’ve updated the docs to fix this!
There was some mixed messaging in the past, but sprite upgrade upgrades the client. sprite v0.0.1-rc40 will include slightly tweaked wording to make this less confusing.