Explicit host-owned delta conversion. No xdelta runner is bundled.

Requests carry a unique call identity, absolute monotonic deadline, verified connection/context, opaque host base source and native delta/rootfs manifests. download_delta accepts an acknowledged sink and downloads the verified delta once. Call it synchronously before emitting converted rootfs chunks. Stop on any failed acknowledgement. All callbacks execute in one bounded worker.

The host owns tools, credentials, base files and conversion state. Idempotent cleanup/3 must release per-call external resources even if conversion was killed mid-creation. Fixture success is not installed-converter acceptance.