Type Ia Supernova Distance Moduli in a Bounced Cosmology: Residuals Across Redshift and the Amplitude They Permit

Type Ia supernovae are the first distance-ladder rung that genuinely samples the redshifts where a bounce correction switches on, and their moduli bound the correction directly. Relative to the standard frame, the bounce frame at asymptotic amplitude epsilon = 0.10 changes distance moduli by -0.0021 mag at redshift 0.1, -0.0112 mag at redshift 0.5, -0.0221 mag at redshift 1.0, and -0.0376 mag at redshift 2.0. Published binned modulus uncertainties from the Pantheon+ compilation run from about 0.03 mag at low redshift to about 0.15 mag in the highest bins. A chi-squared comparison against those bin errors, treating the reference cosmology as the data centroid, returns a best amplitude of 0.000 and a 95 percent upper limit of epsilon = 0.430. Supernovae alone therefore permit only a modest early-time modification, and they locate its observable signature at redshift above 0.5, where the coming generation of surveys is most sensitive. This study is computed from stated assumptions, not measured.