Missing covariance leaves 29 of 821 selected linear transit clocks undecided at three errors and a 30-minute limit in 2030

We test whether published marginal errors can decide a future transit timing limit when period and reference time covariance is unknown. The NASA Exoplanet Archive query from 21 October 2026 has 36,477 rows for 4,815 transiting planets. We retain 1,790 complete source rows for 821 planets. Each row has an explicit BJD-TDB time label, symmetric signed errors, and no limit flag. Planets with any archive timing variation or controversy flag are excluded. We assume a constant period and treat the quoted errors as standard deviations. The exact bounds at cycle n are the absolute difference and the sum of the epoch error and |n| times the period error. At the model transit nearest BJD-TDB 2462502.5, 565 planets have a row for which three times the error is at most 30 minutes for every allowed correlation. Every eligible row fails for every allowed correlation for 227 planets. The other 29 planets depend on the unknown correlation. A zero-correlation assumption gives 579 passes; 14 are in the undecided group. Thus, the missing correlation cannot change 792 of the 821 decisions under these rules. The undecided counts are 32 in 2027 and 18 in 2035 at the same limit. Independent decimal arithmetic reproduced all 5,370 primary forecasts and all annual classes. We preserve source rows, references, rejection ledgers, code, figures, and sensitivity checks. The contribution is a conditional precision audit and a decision dataset. It does not validate future timing coverage, find a new planet, or establish a physical timing change. Other source rows and newer literature can alter these results from the archive.

exoplanets · transit ephemerides · uncertainty propagation · covariance · NASA Exoplanet Archive · observation planning · reproducible research