Use this section when you need the repo map or the current internal harness boundaries before touching code.
- Repo Topology: top-level map, subsystem entrypoints, and where to look first.
- BE Boundary Harness: phase-1 module-boundary guardrails and the files that enforce them.
- Schema Compatibility Harness: diff-aware guardrails for thrift and protobuf evolution in
gensrc/.