Prospective testing of CLEO with Euclid data

The ability to test a cosmological theory with a new survey depends on the correspondence betweenpreviously specified predictions and the observational products actually available. We investigate thiscorrespondence for the CLEO–LOP–COUT programme and the Euclid telescope releases, focusingon DR1 Foundation, scheduled for 12 November 2026, and complete DR1, scheduled for mid-2027.The study combines analysis of two reference manuscripts from the programme, retrieval of an earlierclosure-comparison protocol, an audit of historical forecasts, and verification against primary missiondocumentation. No images are reprocessed, cosmological catalogues fitted, or new observationalparameters estimated. The principal result is an explicit formulation of the test of two competingclosures in the coefficient plane of 𝒞𝐻 = −𝑢′𝐻 /[𝑢𝐻 (3−𝑢𝐻 )], with 𝑢𝐻 = −𝑑 ln 𝐻2/𝑑 ln 𝑎. The hypothesesimpose 𝛽0 = 1 and 𝛽0 + 3𝛽1 = 1, respectively, and intersect at (1, 0). We derive their distinct jerksignatures, demonstrate the loss of discrimination when an independent clock normalization is allowed,and formulate the comparison using the joint covariance. The audit establishes that predictions alreadyexist, but that some earlier growth forecasts lack sufficient operational definition and consistency forconfirmatory use. The November release can support methodological applications and independentanalyses conditional on product validation; it does not, by itself, guarantee the reconstructions requiredfor the principal cosmological test. We conclude that Euclid can test specified realizations of CLEO,while observational agreement would not automatically establish either the physical origin of theclosure or the microscopic COUT–CLEO bridge.