Access-scale inversion of public quantum records in a microscopic critical-spin-bath model

Quantum Darwinism identifies objectivity with redundant environmental records of system information. A complementary question arises when more than one finite-strength diagnostic record is available to an observer with a declared access rule: which record is selected at a given fragment size? We formulate this question as a context-indexed public-record selector and derive a microscopic asymptotic mechanism for access-scale inversion. The model contains a central qubit coupled simultaneously to a local spin-meter bath that records a σz diagnostic and to a critical transverse-field Ising bath that records a σx diagnostic through the Ising order parameter. For contiguous fragments of length ℓ, the local meter gives trace-distance evidence Fz (ℓ, t) =Cz (t) ℓ+o (ℓ), whereas the critical bath gives Fx (ℓ, t) =Cx (t) ℓ^7/4+o (ℓ^7/4) in the Ising scaling regime. With public amplitude Aᵢᵖub (ℓ) =R (ℓ) Fᵢ (ℓ) ^1/2 and block redundancy R (ℓ) =N/ℓ, the local record is selected at small access scales but the critical record is selected for ℓ>ℓc, with ℓc=Cz (t) /Cx (t) ^4/3 up to sector-size and scaling corrections. The crossover is not simultaneous perfect broadcasting of incompatible observables; it is a context-indexed finite-record selection rule. An exact free-fermion/Toeplitz scaling check of the critical bath gives a block-susceptibility exponent consistent with 7/4, while exact diagonalization of a small noncommuting Hamiltonian and parameter scans are included as finite-size pilots of the selector mechanism. This record is a public preprint/manuscript version and has not been peer-reviewed as a journal publication.