Associated software, manuscript, and indexing The software associated with the related manuscript is explicitly named DESI-RCA. DESI-RCA is a post-pipeline residual-covariance advisory and traceability tool for DESI spectral products. DESI-RCA is archived on Zenodo under DOI:https://doi.org/10.5281/zenodo.20740564 DESI-RCA is indexed in the Astrophysics Source Code Library as:ASCL identifier: ascl:2606.002ASCL code record: https://ascl.net/code/v/4759Bibcode: 2026ascl.soft06002M Preferred software citation:F. Javier Martínez Sánchez, DESI-RCA: Residual-covariance advisory and traceability tool for DESI spectral products, Zenodo, DOI: https://doi.org/10.5281/zenodo.20740564 Methodological background DESI-RCA is part of a broader residual-covariance diagnostic line developed from the methodological framework presented in the peer-reviewed article: F. Javier Martínez Sánchez, Forensic Characterization of Correlated Residuals in Large Spectroscopic Pipelines: A Case Study of SDSS/BOSS Data, Astronomy and Computing.DOI: https://doi.org/10.1016/j.ascom.2026.101155 Please use the DOI as the permanent citation link for the peer-reviewed methodological article. Description DESI-RCA is a local post-pipeline residual-covariance advisory and traceability tool for DESI spectral products. It provides an author- and reviewer-facing diagnostic workflow for inspecting residual independence, stacking, coaddition, simplified uncertainty propagation, and residual-covariance assumptions in selected DESI spectral subsets. Large spectroscopic surveys such as DESI produce highly processed data products that are often stacked, coadded, filtered, compared, or reused in downstream analyses. These workflows may rely, explicitly or implicitly, on assumptions that residual fluctuations are effectively independent or sufficiently well characterized. DESI-RCA provides a practical way to inspect those assumptions for selected DESI spectral products. The tool prepares controlled spectral matrices from DESI coadd products, constructs residual diagnostic products, computes spectrum-by-spectrum residual-correlation diagnostics, evaluates null controls, and issues conservative advisory decisions focused on stacking caution and residual-covariance risk. DESI-RCA does not replace the DESI pipeline, certify DESI data products, validate cosmological conclusions, claim pipeline failure, or perform astrophysical interpretation. Its purpose is narrower and methodological: to make residual-covariance structure visible, reproducible, and auditable for selected DESI spectral subsets. Release content This v0.2.0 beta-candidate release includes the DESI-RCA source code, documentation, configuration files, tests, common RCA command-line workflow, DESI-specific ingestion layer, guided workflow utilities, diagnostic routines, report-generation tools, file manifest, SHA-256 release checksums, and citation metadata. DESI-RCA provides: - controlled DESI coadd selection and local ingestion;- preparation of controlled spectral matrices from DESI products;- residual construction for statistical inspection;- residual-correlation diagnostics and eigenspectrum summaries;- null-test controls for residual-covariance context;- metadata-aware and fiber-aware group diagnostics;- conservative advisory decisions focused on stacking caution;- PDF reports, visual diagnostic summaries, machine-readable manifests, SHA-256 hashes, and report-package verification;- a common RCA command-line workflow aligned with the broader RCA software family;- a guided menu layer for scientist-facing operation without assembling long commands manually. Large DESI FITS products and heavy local run outputs are not included in the archived release. Scientific and operational boundaries DESI-RCA is not a replacement for the DESI reduction pipeline, not an official DESI certification system, and not a cosmological or astrophysical inference tool. It does not validate or invalidate DESI physical results, does not claim DESI pipeline failure, and does not redistribute DESI FITS products. The generated report packages may be useful as supplementary diagnostic material accompanying analyses that rely on stacked spectra, coadded products, or simplified independence assumptions. Such reports do not certify the scientific result; they provide a traceable record of one statistical diagnostic relevant to the analysis. RCA ecosystem DESI-RCA belongs to the broader FRANJAMAR-RCA residual-covariance advisor ecosystem, which collects related post-pipeline RCA tools for different astronomical surveys and instruments. The RCA family shares a common diagnostic philosophy, partially aligned command-line grammar, guided-menu design, traceability model, report-generation approach, and reviewer-facing interpretation boundary, while each tool keeps its own survey- or instrument-specific ingestion layer and validation examples. FRANJAMAR-RCA ecosystem DOI:https://doi.org/10.5281/zenodo.20525901 The FRANJAMAR-RCA umbrella record is cited to document software lineage, common RCA design principles, guided-menu and CLI alignment, and shared traceability philosophy. The DESI-RCA results and examples archived in this release are generated by the DESI-specific package. Related RCA software records ALMA-RCA https://doi.org/10.5281/zenodo.21322902 DESI-RCA — DOI: https://doi.org/10.5281/zenodo.20740564 — ASCL: ascl:2606.002 — Bibcode: 2026ascl.soft06002M — ASCL record: https://ascl.net/code/v/4759 SDSS/BOSS-RCA — DOI: https://doi.org/10.5281/zenodo.20832322 IRAM30M-RCA — DOI: https://doi.org/10.5281/zenodo.20808446 JWST-RCA — DOI: https://doi.org/10.5281/zenodo.20367489 RUBIN-RCA — DOI: https://doi.org/10.5281/zenodo.20406707 EUCLID-RCA — DOI: https://doi.org/10.5281/zenodo.20427939 FRANJAMAR-RCA — DOI: https://doi.org/10.5281/zenodo.20525901