Yep! I worked on moving to codemirror 6 today, and it took me like an hour and I was able to strip like over half the code 
. I do need to build a syntax highlighter, but the cursor and styling is done. Here’s the branch: GitHub - moonrise-tk/gem at codemirror
Lezer is exactly what I am looking for as well! Thanks! I was thinking of using tree-sitter and compile to wasm for syntax highlighting (I know, overkill, but I’m just playing and wanted to learn rust/wasm anyway). I might do both and see if there are performance benefits…