Cs (Formula presented) (Formula presented) AgBiBr (Formula presented) (Formula presented) have emerged as promising alternatives to Pb-based counterparts, though systematic exploration of front and back surface recombination is limited. In this study, a systematic numerical analysis was conducted to assess the effects of absorber thickness, bulk defect density, and surface recombination on device performance. The absorber thickness was optimized at 600 nm, ensuring a balance between optical absorption and charge extraction. Examination of back-surface recombination at the Cs (Formula presented) (Formula presented) AgBiBr (Formula presented) (Formula presented) /Spiro-OMeTAD interface revealed modest changes in (Formula presented) (Formula presented) and (Formula presented) (Formula presented), with efficiency increasing from 7.60% to 8.65% due to improvements in fill factor. By contrast, front-surface recombination at the Cs (Formula presented) (Formula presented) AgBiBr (Formula presented) (Formula presented) /SnO (Formula presented) (Formula presented) interface had a far stronger influence, boosting efficiency from 5.54% to 10.30% across the same defect density range. Variations in bulk defect density produced only minor effects, with a maximum efficiency of 10.35% at 10 (Formula presented) (Formula presented) cm (Formula presented) (Formula presented). Overall, the findings establish front-interface passivation as a key strategy for advancing efficient and stable lead-free perovskite photovoltaics.