Comprehensive Statistical Validation of TOI-7701.01: A Sub-Saturn Companion at the Giant Planet Boundary

We present the formal statistical validation of TOI-7701.01 (TIC 122522333), a sub-Saturn transiting companion candidate orbiting a bright F-type subgiant host star (V=11.09). Initially detected via an automated machine-learning transit survey by Salinas et al. (2025), the planetary nature of this signal remained unclear. We implement an independent vetting and statistical pipeline leveraging multi-sector space kinematics and the triceratops Bayesian framework to compute false positive scenarios. A key methodological finding is the structural convergence of the companion's physical scale; despite utilizing un-detrended Simple Aperture Photometry (SAP) with a raw depth of 2417 ppm to preserve field dilution metrics, the triceratops MCMC engine naturally converges on a physical radius of 7.86,R under the dominant Target Planet scenario (P TP = 78.1%). This independent statistical derivation matches the geometric radius of 8.07,R inferred directly from the instrumentally corrected Pre-Search Data Conditioning (PDCSAP) data. By aggregating our multi-iteration ensemble to suppress MCMC stochasticity, we derive a robust global False Positive Probability (FPP = 0.00191) and a Nearby False Positive Probability (NFPP < 10-6), firmly validating the companion well below the rigorous 1.5% threshold established for this Bayesian framework. While the derived 7.8--8.1,R radius places the object at the boundary between giant planets and low-mass brown dwarfs, such a radius is highly atypical for a brown dwarf, pointing to a planetary nature. We report TOI-7701.01 as a validated companion and encourage prompt radial velocity characterization.