Common geometric delay changes the fixed BF Dra phase contrast by <0.478 s for total companion mass ≤13 Jupiter masses, distances ≥0.5 au from each star, and binary line of sight speed ≤0.001 c

We test whether common geometric light travel delay can explain a known BF Draconis eclipse phase contrast. We reuse saved times from 38 public TESS light curves. Each local phase uses a secondary eclipse and the two primary eclipses that enclose it. A line fitted to 16 reference triplets in 2019–2022 predicts seven final triplets in 2024. Their mean phase lies 47.7949 seconds below that prediction. We hold the forecast weights fixed at the recorded dates. An exact interpolation bound covers all twice differentiable common delay maps that meet acceleration and speed limits. It includes the change to the phase denominator. Under Newtonian gravity, constant star masses, and a fixed line of sight, the delay changes this statistic by at most 0.477206 second if total companion mass is at most 13 nominal Jupiter masses, each companion stays at least 0.5 au from both stars during each included triplet, and the absolute line of sight speed of the binary center of mass is at most 0.001 c. This is about 1 percent of the measured contrast. All six source timing methods and both flux products give bounds below 0.478 second. They reuse the same data. An independent Decimal calculation and 4800 nonlinear inverse maps pass numerical checks. A clean run reproduces 18 numerical files exactly in the recorded environment. The result limits only the common geometric delay. It does not exclude gravitational changes to the binary orbit, prove a physical origin for the timing signal, or detect a planet. The package preserves the signed source data, proof, code, results, figures, and reproduction instructions.

BF Draconis · TIC 229776076 · TESS · eclipsing binaries · eclipse timing · light travel delay · companion acceleration · deterministic bound · local eclipse phase · reproducible astronomy