As far as I understand, the current behaviour of treesit-parser-set-included-ranges is that the concatenation of text from different regions in the same range set is considered as one program. This means that for this html program treesitter would consider "alert('hello');" to be inside a comment and the second script tag would contain an error about missing comment end. However, testing this in Firefox, it seems that the first script tag is the erroneous one here and the alert function call isn't inside a comment. So I guess the correct way to parse this html document would be to have two instances of javascript parser, one for each region. On the other hand, we should consider if this is worth the added complexity and performance degradation. Thanks and best regards.