Deterministic bidirectional diffusion with role-aware quotas is the controlled test-case graph-RAG method studied in this paper. From a query concept, the procedure deterministically diffuses along prerequisite edges in both directions of the prerequisite graph (toward ancestors/parents and toward descendants/children), collecting candidate concepts. A role-aware quota caps how many slots are allocated to each role (e.g., prerequisite parents vs. dependent children), preventing one direction from monopolizing the top-$k$ output. The method is deterministic given the graph, so its behavior is reproducible and auditable, which is why the paper uses it as a controlled probe of where graph structure helps rather than as a new headline retriever.