R–03 · Security
Fast patches, app-wide testing, rollback, and a clear end to old runtime lines.
Conclusion
Runtime sharing reduces duplicated Chromium copies only if each runtime line has an owner, bounded dependants, a full retest path, a rollback package, and an explicit retirement rule.
A runtime update changes a dependency shared by several applications. The unit of security work is therefore the runtime plus every package bound to that line—not the runtime artifact alone.
Repository metadata and the previous known-good runtime must remain recoverable during promotion. An application should not be forced onto an untested Electron major merely because a newer runtime exists. Exact lower and upper dependency bounds make that constraint visible to APT.
Co-installable majors are a compatibility tool, not permission to preserve obsolete Chromium indefinitely. A runtime line leaves when its applications have moved to a supported line or when it can no longer be maintained safely. Packages that cannot move must be reported honestly and may need removal.