Supplementary material for "A Comprehensive Re-analysis of K2-18 b's JWST NIRISS+NIRSpec Transmission Spectrum" by Schmidt et al., submitted to AAS Journals (2025). This repository contains three categories of data products: Data reduction reproduction — Eureka! control files (.ecf) and parameter files (.epf) alongside saved Stage 3 output for the two reductions of the NIRSpec G395H visit. These allow replication of our data reduction, light curve fitting, and transmission spectra extraction using the open-source code Eureka! Transmission spectra — Reduced transmission spectra for NIRSpec G395H and NIRISS SOSS from Eureka!, FIREFLy, and exoTEDRF for different spectral resolutions. Retrievals — Corner plots from atmospheric retrievals applied to each combination of NIRISS SOSS + NIRSpec G395H data sets. The retrievals used the open-source code POSEIDON as well as the open-source code BeAR. For any additional data requests or questions, please contact: sschmi42@jh.edu