This erratum corrects two presentation-level points in the Informational Theory ofPhysics (ITP) monograph (Zenodo DOI: 10.5281/zenodo.17780098) and in the companionmonograph Informational Quantum Gravity (Zenodo DOI: 10.5281/zenodo.17808321).Erratum A refines the interferometric “path–coherence” relation stated in Appendix Q.2(Prediction 1): fringe visibility is an intrinsically bi-path quantity and cannot be fixed bythe two single-path purities alone in the presence of which-path markers. The correctedformula introduces the required cross-arm overlap functional, and clarifies how SWAP-testobservables relate to visibility (notably, in the standard pure-marker scenario SWAP yieldsthe square of the visibility). Erratum B updates the early coherence-evolution expressionlabelled as an “ansatz” (Eq. (2.16) in the ITP monograph): it is reclassified and replaced byan identity derived from standard completely-positive trace-preserving (CPTP) dynamics(Lindblad form) in regimes where an effective Markovian description is appropriate. Thesecorrections do not modify the strong-field compact-object branch, the horizon-shell entropycounting, or the evaporation/Page-curve construction; they sharpen one laboratory test andone derived dynamical statement. The corrections apply to:• ITP monograph (DOI: 10.5281/zenodo.17780098): Appendix Q.2 (Prediction 1), andthe associated double-slit/interferometry discussion (including the visibility prefactor usedin Section 10.3); plus Eq. (2.16) in the coherence-dynamics discussion.• Informational Quantum Gravity (DOI: 10.5281/zenodo.17808321): any passages thatrestate Prediction 1 as an unconditional identity in interferometric settings with which-pathmarking.