With the increasing demand for high-precision and long-lead-time seamless weather-climate prediction, the development of a cost-effective and dynamically coordinated seamless forecasting workflow, together with a scientific and systematic evaluation framework, has become a key challenge for next-generation integrated weather-climate prediction systems. Building on the achievements of the National Key Research and Development Program of China, “Integration and Application of Weather-Climate Integrated Model Based on Unstructured Grid” (hereafter referred to as “the program”), this study takes the Global-Regional Integrated Forecast System with Modular Ocean Model (GRISTMOM) as an example to construct a 0—90-day seamless forecasting workflow spanning weather, subseasonal, and seasonal timescales. A variable-resolution seamless forecasting strategy that balances computational efficiency and forecast skill is proposed, and a systematic quantitative evaluation framework is developed to assess the continuity and smoothness of the workflow during resolution transitions. Specifically, building upon the project-integrated GRISTMOM seamless forecasting system, variable-resolution forecast experiments are conducted as an application case. Through comprehensive analyses of key large-scale background fields, typical weather systems such as tropical cyclones (TCs), and the Madden-Julian Oscillation (MJO) across multiple scales, the continuity and stability of the variable-resolution transition process are quantitatively evaluated. The results demonstrated that 1) during the transition from 10 km to 100 km resolution, forecast errors of large-scale circulation fields evolve smoothly without abrupt changes during the transition episode, indicating that the seamless workflow maintains excellent continuity and stability in large-scale fields; and 2) in validations using multi-scale objects, the tracks, intensity, precipitation area and circulation structures of TCs exhibit temporally and spatially consistent across resolution transition, and the phase-space evolution and associated convection-wind propagation characteristics of the MJO maintain continuous and coherent behavior. These results confirm the excellent physical integrity of the seamless workflow in transmitting weather-climate signals across scales. Overall, this study establishes a comprehensive framework encompassing seamless workflow construction and execution, quantitative design for continuity and smoothness assessment, and comprehensive evaluation, providing critical scientific support for the operational development of integrated seamless weather-climate forecasting systems in China.