December 2025 monthly summary for argoproj/argo-workflows: Focused on strengthening the robustness of workflow specifications through type-safe defaults merging. Delivered Workflow Template Defaults Validation and Safe Merging, introducing type-aware default application and a validation method for template types. Merging logic was adjusted to prevent invalid defaults from being applied, reducing misconfigurations and runtime failures in workflows. This work is backed by the commit c8b66b244339803c16dbe78e43822fff085d040e ("fix: type-aware application of template defaults (#14899) (#15144)"). Major bugs fixed include correcting the handling of template defaults to ensure only valid, type-appropriate defaults are merged, thus preventing invalid defaults from being applied. Overall impact: increased reliability and correctness of workflow specifications, safer defaults for users, and improved maintainability of the workflow engine. This aligns with business value by reducing runtime errors, enabling faster authoring of robust workflows, and decreasing support overhead. Technologies/skills demonstrated: Go-based engine changes, type validation patterns, safer merging logic, code quality improvements, and contributor hygiene (Signed-off commits and issue-tracking alignment).