Dev reads the dev and stable manifests and offers the newer by semver; a test build stores Dev on its first start, so the release that updates it keeps the channel. Switching to Stable in a test build asks before going back to an older release. tool/dev_release.sh's one-time command also writes the update-channel file that sets Dev. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>