1 · The derivation
Read top to bottom: sources, the DFT chain, harmonic quantities, scattering channels, and transport. Observable nodes carry no gauge freedom. Hidden nodes depend on a gauge choice: the eigenvectors, group velocities, and linewidths are intermediates, and the QHGK thermal conductivity at the bottom is an approximation. The dashed edge illustrates a learned shortcut: a surrogate model that produces the same linewidth node without computing the third-order force constants. The same derivation is live in the tracer.
This screen is too narrow for the diagram; the tracer link above opens the same derivation.
2 · The lineage record
The map stores the quantity and its value; the lineage record pins how the number was made and where the bulk data lives. This is an example record; open it in the playground. Raw artifacts never enter the store: the record carries pointers, and the files stay with their provider.