Selector versus Closure: A Guardrail for Admissibility-Probability Separation and Record Compatibility in Model-Relative Candidate-History Frameworks

Paper B1 is a guardrail and bookkeeping working paper for complete-history-style candidate-history frameworks. It clarifies that selector language, where retained at all, should be treated only as legacy terminology for a possible model-relative closure/admissibility framing, not as a physical mechanism or within-world selection process. The paper separates five ledgers that are often conflated: candidate histories, closure/admissibility, probability or weighting structure, operational readout/record constraints, and diagnostic gates such as Born compatibility, no-signaling, and Bell-assumption bookkeeping. Its central formal point is that a closure condition C_closure may define an admissible set H_adm = {h in H_cand : C_closure(h)=1}, but this admissible set does not by itself define a probability law. B1 follows the reduced-history no-inference guardrail of Paper A and imports from D1 only the declared-access/readout/record discipline. It does not use D1 as evidence for a physical selector, closure law, probability principle, Born-rule derivation, Bell/no-signaling result, or experimental prediction. Decoherence, consistent histories, and Everettian branch language are discussed only to separate branch/record stability from admissibility, probability, and single-history actualization. The paper is not a physical model, not a replacement for quantum mechanics, not a Born-rule derivation, not a Bell/no-signaling solution, and not a prediction paper. It is a claim-control layer for later work.This is Paper B1 v0.3 in the Complete-History / Record-Capability working-paper sequence. It is a guardrail and bookkeeping paper only. It introduces no physical selector, no probability law, no Born-rule derivation, no Bell/no-signaling result, no quantum-mechanics replacement, and no experimental prediction. The uploaded source ZIP contains the LaTeX source for the working paper; SHA256SUMS.txt provides file-integrity hashes for the uploaded PDF and source archive.