we can probably move the full name to a tooltip. However, this requires sorting by only builder name (not bulider id) and THAT would make it harder to distinguish Buildbot and LUCI builders with same names.

Still, we should show only one row for same builder on Buildbot and LUCI (and merge builds from both), and until that's done, we can simply hide LUCI builds.

We also threw around the idea of left aligning the "buildbot/master" portion, and right aligning the "buildername" portion.

Doesn't solve the small screen problem, but does make the buildername easier to parse.

is "buildbot/<master>" prefix necessary?

I think "buidlbot/" prefix should go away because, I think, users should not distinguish buildbot and LUCI builders. Specifically, I think we should provide one row for both linux_chromium_rel_ng builder and merge builds from both platforms in one row, filtered by whether the build is prod or not. Context: only one of Buildbot/LUCI can be "prod" for a builder at a time. This is consistent how transition is designed in console vie and API.

I believe builder names are unique enough so that master name is unnecessary. If a user is confused, they can hover the builder and see the full builder id.

Just showing the builder and requiring hover for disambiguation sounds fine to me.

Issue 791917 has been merged into this issue.