Always validate configuration values at runtime and provide clear, actionable error messages when invalid combinations are detected. This prevents runtime failures and guides users toward correct configuration. Key validation practices: - Check environment variables against allowed values before use - Validate configuration combinations that are mutually incompatible - Provide specific error messages that explain the problem and suggest solutions - Use runtime checks rather than relying on schema validation alone Example from environment variable validation: ```typescript if ( !args.outputStyle && process.env.NX_DEFAULT_OUTPUT_STYLE && choices.includes(process.env.NX_DEFAULT_OUTPUT_STYLE as OutputStyle) ) { args.outputStyle = process.env.NX_DEFAULT_OUTPUT_STYLE; } ``` Example from configuration combination validation: ```typescript if (usesVersionPlaceholder && hasSkipVersionActions) { throw new Error( `Release group "${groupName}" configures "skipVersionActions" but its docker version scheme contains the "{versionActionsVersion}" placeholder which cannot be resolved without version actions. Remove "skipVersionActions" or remove the placeholder from the scheme.` ); } ``` This approach catches configuration errors early, provides clear guidance for resolution, and prevents confusing runtime failures that are difficult to debug.