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The initial CSS contains two font-family declarations. The source regex matches both and replaces each with one fixed system-font stack. Bars compare two matched strings with two replacements at one hundred fifty pixels per count. This is a case-insensitive string replacement, not a CSS parser. It can also match declaration-like text in comments and quoted content, so a replacement count is not proof the stylesheet is valid or that two visible elements changed font. The packager writes three named files: manifest dot JSON, content dot JS and styles dot CSS. Bars compare three populated package files with zero installed extensions at one hundred fifty pixels per file or installation. The manifest declares version three and two Claude-page match patterns; the content script is just a comment, and the stylesheet contains the transformed input. The page builds a ZIP using its pinned JSZip library, but it does not install it, change Claude, prove current DOM compatibility or cross iframe and shadow-root boundaries. A fixture with declaration-like text in a comment, a quoted string and a real declaration produces three matches. Bars compare three source-regex matches with the two default lines restored in the input after reload, at one hundred pixels per count. Reload restores the saved generated result but resets the textarea to its sample. A failed transform disables export while leaving the old result visible and stored. Reset removes that saved result. Actual ZIP contents are the output; no extension activation or backend model request occurs.