With two Operators, the frozen feature tree is split into disjoint subtrees — computed from the dependency graph and ownership index, root-balanced by node count. Disjointness is the safety property: no two Operators ever write the same file, so the write-boundary guarantee survives parallelism untouched.
Parallel wall-clock speedup comes from independent nodes, never from simultaneous edits to a shared surface — twenty concurrent writers on one interface file fight each other, which is exactly the oscillation the serial resolver exists to prevent. Partition is deterministic: same tree, same split, reproducible from the ledger.