Abstract: Silicate weathering regulates atmospheric CO₂ and planetary habitability on geological timescales. While marine carbonate strontium (⁸⁷Sr/⁸⁶Sr) and lithium (δ⁷Li) isotopes are widely acknowledged weathering proxies, they are subject to distinct biogeochemical controls. Consequently, their combined analysis offers orthogonal constraints that resolve the non-uniqueness inherent in single-proxy reconstructions. The COPSE biogeochemical model has successfully simulated Phanerozoic trends in carbon-sulfur-strontium isotopes, yet its representation of the lithium cycle remains rudimentary and inconsistent with geological records. This study integrates a comprehensive lithium cycle into the COPSE framework. We aim to reproduce the major trends of Phanerozoic δ⁷Li, revealing that the rise of the land plants significantly changed the Li cycle, resulting in a sharp increase in marine δ⁷Li values. This new mode configuration refines our understanding of long-term carbon cycle dynamics.