This result delivers new developments and diagnostics implemented in ESMValTool within the ESM2025 project. ESMValTool is a widely adopted, community-driven software framework for the evaluation and analysis of Earth System Model (ESM) simulations. ESM2025 contributed to a new version of ESMValTool and developed a substantial set of new diagnostics targeting key Earth system processes and policy-relevant questions addressed in the project. These diagnostics span multiple components and themes, including carbon cycle processes, land–atmosphere interactions, methane-related processes, ocean and cryosphere behaviour, and emission-driven simulations. The developments are fully integrated into the ESMValTool framework, enabling consistent evaluation against observations and reference datasets, systematic comparison across models and experiments, and reproducible analysis workflows. Together, these contributions strengthen ESMValTool as a core infrastructure for ESM development, model evaluation and intercomparison in the European and international climate modelling community.