Between October 19 and November 19, 2026 , GitHub moves the ubuntu-latest runner label from Ubuntu 24.04 to Ubuntu 26.04. Nothing in your repository changes — the machine underneath your CI does. I diffed the official actions/runner-images toolsets ( toolset-2404.json vs toolset-2604.json ) on 2026-10-10 and found 22 differences . These are the ones most likely to break or silently change a build: Removed outright mercurial ( hg ) , mediainfo , sphinxsearch , ha...