The LaunchDarkly CLI now supports a local development server feature that enables developers to create a local copy of their flags for testing in a local environment without an internet connection. This guide explains how to use the local development server with client-side and server-side flags in an Astro application. To set up the feature, users need to install the LaunchDarkly CLI, authenticate it with their account, create a project, and set up two feature flags for testing purposes. The guide also covers how to start the local development server and run the project using it.