Golden source builds publish their orcad + in-VM CLI as a commit-pinned bundle (R2, uploaded by the build VM over a signed PUT; the Worker computes the stored sha256). On every boot and wake, before orcad starts and inside the existing orcad phase, a sandbox whose /opt/orca/runtime/orcad/SOURCE_COMMIT differs from its region's active golden fetches that bundle from the control plane's own host (already on the egress allowlist) with a 10-minute signed URL, verifies the sha256 the control plane passes in, checks the commit and node runtime, and swaps orcad + orca-cli atomically. Any failure keeps the old orcad and boot continues; every outcome is logged (runtime_refresh: outcome, from, to, ms). RUNTIME_REFRESH=off is the kill switch. Dev R2 bucket orca-sandbox-runtime-dev.