The new Code Search tool on Replit allows users to search for comments, classes, or functions in their codebase using simple queries or regular expressions. The tool was built by a team of developers who worked together during a Hack Week in 2023 to improve the search experience in the workspace. The development process involved using existing tools and technologies such as ripgrep and crosis to stream results back to the client, while also employing techniques like virtualization and output limits to optimize performance. The resulting tool offers features like multiple panes, history, include/exclude filters, regular expressions, and keyboard navigation, making it more powerful and user-friendly than previous search tools.