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Gas-phase metallicity is a fundamental tracer of galaxy evolution, yet strong-line calibrations derived from local galaxies become biased at high redshift due to evolving interstellar medium (ISM) conditions. With JWST now enabling direct metallicity measurements via auroral lines at z>2, a consistent theoretical framework for interpreting strong-line diagnostics across cosmic time is urgently needed. We present a first-principles framework to derive redshift-dependent metallicity calibrations for galaxies at z=2-7. Our approach combines the cosmological simulation ASTRID with stellar population synthesis and MAPPINGS V photoionization modeling. HII region properties are computed self-consistently for young star clusters using an analytic feedback model, capturing the coupled evolution of stellar feedback, ionization parameter, and local ISM density. The resulting emission-line predictions are validated against observed star-formation rate indicators and the [OIII] luminosity function. From this model, we derive calibrations for common optical (R23, O3N2, N2, O32) and UV (C3O3, N3O3) diagnostics. We find significant redshift evolution in these relations, driven primarily by changing ionization conditions. A Bayesian analysis quantifies calibration performance under varying signal-to-noise, enabling diagnostic recommendations as a function of redshift and data quality. The R23 calibration has the lowest scatter, lowest sensitivity to S/N, and weakest redshift evolution. These results provide a practical framework for interpreting JWST spectroscopy and tracing chemical evolution from cosmic noon to the epoch of reionization.
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