The lifespan of halide perovskite solar cells (PSCs) is currently a major concern for the implementation and commercialization of the technology. Tensile and compressive strain alters the halide perovskite (HP) lattice under operando conditions, affecting PSC stability. However, the mechanisms governing strain responses are still unknown. In this work, we monitored the evolution of strain in PSCs during accelerated stability tests under continuous light irradiation and bias-voltage. Additive engineering led to the compression of the HP lattice improved PSC stability. The temporal evolution of the HP lattice, together with the electrical response of devices employing modified and reference HP, were tracked by in-situ X-ray diffraction, photoluminescence, and quasi in-situ electrochemical impedance spectroscopy. Our results demonstrate a good correlation between lattice expansion (strain) with the device’s current decay and stability. Additionally, and contrary to current understanding, we observed that lattice compression in HP was not sufficient to ensure protection against degradation.