High-velocity repositories may collect approved changes on a buffer (train) branch before merging into the protected branch, so the protected branch stays stable long enough for review; a failed train is abandoned and its changes re-applied to a new train. Because the revision created on the train was never itself pre-approved, the SCS and organization must protect the train like any artifact build pipeline, and at minimum the SCS must attest that the revision the train produces is identical to the protected branch with each approved change applied in order, with nothing added or removed.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.