Highlighting that seems ignored in CM6

FWIW, I ran into this same issue and the fix for me was disabling dependency injection in my vite.config.js for the @lezer/highlight package.

optimizeDeps: {
    exclude: [
      'codemirror',
      '@codemirror/commands',
      '@codemirror/language',
      '@codemirror/state',
      '@codemirror/view',
      '@codemirror/lang-sql',
      '@lezer/highlight'
    ]
  }