At previous jobs I was building iOS apps with an embedded code editor. The only solution at the time was Highlightr, a Swift wrapper around highlight.js. It worked, but you paid for a JS bridge.
Over winter break I had time to revisit the problem. On iOS that gap is now closed. There are working tree-sitter Swift bindings, dedicated syntax-highlighting libraries, and full code-editor components. I assumed Android was the same, but it wasn't. The Kotlin tree-sitter bindings weren't usable at the time (may have changed since), and there were no real grammar engines. What I saw was ad-hoc regex per language or a few natively-supported languages.
So I wrote one, a pure-Kotlin port of Microsoft's vscode-textmate. Real .tmLanguage grammar support (600+ grammars the VS Code ecosystem already maintains) and Compose AnnotatedString renderer for Android.
Repo, architecture notes, and benchmarks all in the link.