Why: The dependency layer already existed in the backend, but service startup never passed it, so the sandbox could not import the packages the host already had.
Evidence: SELF go tests recorded on the backend commit. svc.sh only exports the env root after env ensure leaves a current base layer, and a failed download does not block startup.
Impact: Instances share runtime/envs. Existing exec= lines are left as stored. Proposal, backend, and frontend gitlinks move to this branch.
Refs: .task/feature-layered-python-env.md
Co-authored-by: Cursor <cursoragent@cursor.com>
