Specs a second concrete BottleBackend selectable via
CLAUDE_BOTTLE_BACKEND=smolmachines: per-agent libkrun microVM on
macOS, sidecars relocated to host-side loopback ports plumbed via
Smolfile env, PRD 0022's sandbox-escape suite as the acceptance
gate (the env-var flip is the only change required). Docker
backend ships unchanged and remains default.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
