Measurement and Record Channels: Operational Guardrails for Candidate-History Frameworks

Paper C0 is a measurement- and record-channel guardrail working paper in the Complete-History / Record-Capability sequence. It clarifies the operational vocabulary needed when candidate-history frameworks use measurement, record, readout, decoder, and downstream-architecture language. The central C0 guardrail is that decohered alternatives, accessible records, single-outcome actualization, and Born-compatible probability laws are distinct notions. C0 represents the record-channel layer of measurement claims using standard quantum instruments, open-system record formation, environmental decoherence, storage/noise dynamics, decoder classes, access frames, time windows, error tolerances, and provenance conditions. A record is treated as a decodable physical carrier relative to a declared outcome alphabet, access frame, decoder convention, tolerance, time window, and noise or storage model. The main negative result is that sectorwise record consistency underdetermines sector weights. Even perfect records inside each sector do not by themselves determine external sector weights, Born weights, or a probability law. Born compatibility remains a separate probability/ensemble/protocol constraint. C0 follows Paper A, D1, and B1 as a guardrail dependency, not as an evidential chain. It does not solve the measurement problem, derive the Born rule, introduce a new probability law, provide a single-outcome actualization rule, replace quantum mechanics, solve Bell/no-signaling, or make an experimental prediction. Downstream architecture, final-boundary, photonic-loop, null-test, and chaotic-amplification motifs are treated only as future guardrails, not as C0 results.This is Paper C0 v0.2c in the Complete-History / Record-Capability working-paper sequence. It is a measurement- and record-channel guardrail paper only. It introduces no physical selector, no single-outcome actualization rule, 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.