We report the discovery and characterization of a close subdwarf B (sdB) + white dwarf binary system—TYC 3135-86-1. By combining spectroscopy, spectral energy distribution fitting, and light curve modeling, we determine that the sdB component has an effective temperature of Teff = 22597.10 ± 413.06 K, a surface gravity of , and a mass of . The system has a short orbital period of P = 0.248895435(65) days, and the white dwarf companion has a mass of . The compact configuration of the system is consistent with formation through common-envelope (CE) ejection. Within this framework, our MESA models suggest a possible scenario in which the sdB component retains a relatively thick hydrogen envelope at the onset of the post-CE phase, in contrast to the typically thinner envelopes of CE-formed sdB stars.

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