The install guard catches an unsupported OS/architecture pair when the machine's architecture is already known, but a machine queued before it was ever discovered reaches dispatch with nothing having checked. Serving it the x86-only Ubuntu kernel is exactly the failure this work exists to fix, so stop with a legible reason on the console instead -- a machine handed a kernel it cannot execute fails later and far less clearly. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_015nRFZXpKwUVE4SRSHw6GjF