A key component of DFAs for E DFT c is its well-studied spatially resolved counterpart, the correlation energy density denoted by e DFT c (r). By contrast, the wavefunction-based e c (r) has received far less attention, since wavefunction methods traditionally bypass it by directly obtaining E c from correlated wavefunctions. Although correlation energy densities are not uniquely defined, several well-founded gauge choices exist in KS DFT (see e.g., Ref. 19). In particular, the conventional DFT gauge for e DFT c (r), based on the electrostatic potential of the correlation hole , has been extensively studied. It provides a physically meaningful definition of e DFT c (r), transparently arising from the correlated wavefunction and has demonstrated advantages for DFAs construction . On the wavefunction side, existing definitions of e c (r) are largely ad hoc, in the sense of being tied to specific approximate wavefunction methods (see, e.g., the work of Nakai and Reuter and coworkers ). Therefore, a universal framework for extracting e c (r) from arbitrary correlated wavefunctions is lacking. This prompts the question: If wavefunction methods directly construct E c , is e c (r) necessary? The growing interest in methods at the interface of wavefunction and DFA-based approaches, where HF-densitybased features are mapped by approximate functionals to wavefunction-based E c , suggests that it is . These methods, which map HF-density-based features to E c , offer specific advantages over KS DFAs as alternative correlation energy approximations. They typically achieve significantly higher accuracy for systems involving charge transfer (or cases where DFAs yield spurious charge transfer), simplify functional optimization , reduce error-cancellation issues that affect transferability , and avoid certain technical complications linked to self-consistency , albeit at the cost of making analytical gradients more challenging to implement .