Seam is a lightweight site renderer for Markdown content and Twig templates. There isn’t nearly enough “managing” going on to call it CMS, but one prone to hyperbole could.
It is mostly writing Pico from scratch and differently. Powered by Silex, Composer, pjax, and other buzzwords.
There are a lot of previously invented wheels like it. But this one is mine.
Composer in WordPress is the one and only site this was made for. And even that one now runs on Jekyll instead.
Why would you even want to use this? Move along.