Anthropic’s Excel skill stops LibreOffice from rewriting your workbook

In Anthropic's skills repository, the Excel skill no longer lets LibreOffice rewrite your spreadsheet when it checks the formulas. LibreOffice now calculates on a copy, and only the computed values go back into your file. If Claude edits workbooks for you, the rest of each file now stays as it was.

The old script rewrote the whole workbook in place. A formula pointing at another workbook, which is rarely on the machine, came back as a name error, and LibreOffice deleted every link. The script refused to run in that state unless forced.

='[1]Returns Analysis'!$B$2
[1] = a separate file on disk, rarely present
#NAME?   · all external links removed

The script's report gains a list of formulas LibreOffice cannot evaluate, even when the run succeeds. That covers functions it lacks, like XLOOKUP and LET, and links to other workbooks. Those cells keep their old values, where the old script baked a name error into the file.

There is a limit. A sound formula that depends on one of those skipped cells still reports a name error, and a kept value may be out of date. The skill now tells Claude to leave those alone and tell you.

The PowerPoint skill changes how it makes new decks. Unless you ask for a quick throwaway, it builds on a theme, layouts, named placeholders and sections. You can restyle that deck in one place and edit it in PowerPoint without fighting it.

The JavaScript library the skill builds decks with cannot write theme colors, so a deck's scheme colors fell back to Office's stock palette. A new apply theme script writes your colors and theme name into the saved deck.

To read a deck, the skill now uses its own slide text script in place of markitdown. It returns every slide's title, text, tables, chart data, picture alt text and speaker notes, and it reads templates too. Scatter and bubble charts give series names only.

When Claude redlines a contract in Word, a check makes sure every edit is tracked. It now compares headers, footers, footnotes and endnotes against the original as well as the body, so an untracked edit there gets reported.

Word has refused documents whose ZIP archive carries folder entries, when opened through a cloud co-editing service. The Word and PowerPoint skills now pack files without those entries, and new Word files have them stripped before rendering.

zip -Xr ../out.docx .
zip -XrD ../out.docx .

These four skills ship together in the document skills plugin, and this change merged on November 14. If Claude edits your spreadsheets, decks or Word documents, I would pick it up. One limit stays: the PowerPoint validator still misses some faults PowerPoint repairs, so a pass is not proof.