Metal halide perovskites have recently gained attention as materials for memristive devices due to their mixed ionic-electronic transport, low‑voltage operation, and cost-effective fabrication methods. However, the reliability of these devices remains limited by environmental stability. Several resistive‑switching (RS) mechanisms have been proposed to explain the hysteresis observed in halide perovskites, including models based on conductive filament formation, interface‑governed switching processes, and charge trapping–detrapping dynamics1. In this work, we investigate the influence of interfacial layers on the resistive switching behaviour of MAPbBr₃‑based memristors by comparing three device architectures: FTO/MAPbBr₃/PMMA/Ag, FTO/MAPbBr₃/PMMA/AgI/Ag, and FTO/MAPbBr₃/AgI/Ag. Figure 1 shows electrical characterization of the device with structure FTO/MAPbBr₃/PMMA/Ag. I-V exhibits non‑volatile switching behaviour under inert conditions. Previous works propose that the switching mechanism is likely governed by halide vacancies within the perovskite layer and the migration of Ag atoms into the PMMA layer2. Transition to volatile behaviour occurs after ambient exposure, indicating strong susceptibility of the PMMA/perovskite interface to moisture and oxygen induced degradation. A previously employed strategy has been to introduce preoxidized metal in the form of a AgI layer3-4. Figure 2 shows that the structures including preoxidized Ag show a polarity inversion of the SET voltage, pointing to a dominant electrochemical metallization mechanism governed by Ag filament formation. For both devices containing AgI the I-V evolves similarly, showing highly stable characteristics with good cycle‑to‑cycle reproducibility over the first 50 cycles, validating AgI as an effective ion regulating interlayer. The device containing both PMMA and AgI requires an initial electroforming step, while the PMMA‑free configuration operates without electroforming, demonstrating that PMMA primarily acts as an initial barrier to Ag⁺ migration. Neuromorphic measurements show that devices with PMMA can emulate potentiation and depression but suffer rapid endurance degradation, whereas AgI‑based devices exhibit limited dynamic range and volatile behaviour under pulsed operation.