> For the complete documentation index, see [llms.txt](https://angel3-docs.dukefirehawk.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://angel3-docs.dukefirehawk.com/angel-framework-migration/angel-2.x.x-to-angel3/rationale.md).

# Rationale - Why a new Version?

Starting with Dart SDK 2.12.0, NNBD support becomes mandatory in most of the packages. In order to keep up, Angel3 framework has to undergo a major refactoring to support NNBD.