Pebbles is Guidewire's enterprise UI framework. It is loosely based on the Java Server Faces spec; pages are configured by defining widget trees in XML files. Pebbles integrates with the open type system of Gosu, Guidewire's programming language, so composition of and navigation between UI components is strongly typed. As a result, Pebbles provides extensive design-time error checking.

My contributions to Pebbles included a rewrite of the rendering layer to allow more look-and-feel customization by customers via CSS, new widgets for AJAX-based notification of the progress of asynchronous server tasks and display of hierarchical data, and a quasi-WYSIWYG page configuration editor with rapid error feedback and code completion facilities.