Understanding and predicting the coupled effects of chemical composition, mechanical stresses, and microstructural evolution during phase transformations is a fundamental challenge in materials modeling. In many technologically relevant systems, such as metals and battery materials, composition-dependent stresses and stress-driven diffusion play a decisive role, requiring a fully coupled chemo-mechanical description. The phase-field method provides a numerically efficient framework for modeling microstructural evolution, enabling the treatment of moving interfaces within a diffuse interface formulation without explicit interface tracking. This approach naturally accommodates multiple physical driving forces for interfacial motion, including chemical and mechanical contributions [1]. In this work, a fully coupled chemo-mechanical multiphase-field model is presented with a particular emphasis on analytical consistency and model verification [2]. The formulation is validated against analytical sharp-interface solutions derived from the generalized Gibbs–Thomson equation, explicitly accounting for balance laws on singular surfaces and the Hadamard jump conditions. These comparisons serve as benchmarks to validate the coupling strategy and its numerical implementation. The impact of the chosen coupling approach on equilibrium states, diffusion, and phase evolution is systematically analyzed, revealing significant deviations from alternative coupling formulations and highlighting the necessity of a fully coupled chemomechanical treatment. [1] Svendsen B., Shanthraj P., Raabe D., Finite-deformation phase-field chemomechanics for multiphase, multicomponent solids. J. Mech. Phys. Solids, 112, 619-636, 2018. [2] Kannenberg T., Prahs A., Svendsen B., Nestler B., Schneider D., Coupling Approaches in Chemo-Mechanical Multiphase-Field Models. Int J Mech Sci, 303, 110569, 2025.