We recently pushed a change that updates Vitepress (used for the Codex docs site) to v1.0.0-alpha.47. It looks like this latest version of Vitepress requires Node v16.6.0 or greater due to use of Array.prototype.at in its internals (parsing filenames). See the compatibility table for this method here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at#browser_compatibility
PatchDemo is still running Node 14. This means that all attempts to build Codex inside of a PatchDemo instance now fail with the following error:
build error: TypeError: filename.split(...).at is not a function
There are also a lot of "unsupported engine" warnings in the console output.
Short-term solution
We should revert the Vitepress update in our code to preserve PatchDemo functionality.
Long-term solution
PatchDemo should be updated to use Node LTS version 16.
Alternate solution
Looks like Vitepress fixed this problem themselves upstream, and it's been included in the alpha 48 release which came out yesterday. See https://github.com/vuejs/vitepress/commit/fd995906f61e5181ca8e1116dcd93eec65075056 (included in the latest release).