The 2026 transit of TOI-4603 b agrees with a 2021 and 2023 TESS clock under a shared symmetric shape

We test a transit clock for the known planet TOI-4603 b. The clock uses 14 TESS transits from 2021 and 2023. We test its prediction with one transit from January 2026. The later flux does not enter the earlier fit. We fit six public light curves with a shared symmetric shape. Each event has its own depth and baseline. The later transit is 1.33 minutes after the prediction. Its combined conditional standard error is 5.70 minutes. In 100 trials, shifted residuals give a wider timing spread of 6.6 minutes. Five changes to the analysis give residuals from 0.96 to 2.31 minutes. The full fit gives a period of 7.24560648 +/- 0.00001166 days. A quadratic clock gives no evidence for a period change. This is a retrospective test of public data. The archive already lists a revised period. The errors assume fixed noise estimates and the stated shape. The absolute time depends on the shape convention. We preserve native inputs, source hashes, queries, code, results, figures, and offline reproduction instructions. The result adds a later transit measurement and a tested clock. It does not detect a new planet or measure orbital decay.

TOI-4603 b · TIC 437856897 · TESS · transit timing · ephemeris · public data · reproducible astronomy · sector 1751