Office Transform

Turn a structural selection of an Office/PDF document into a new derived file.

Two invariants hold for every operation:

1. The source file is read-only. Every result is a new file; both scripts refuse to write to the source path or overwrite an existing file. Never work around this with ad-hoc shell edits to the original.
2. Anchors are structural. Selections address the document's own coordinates — worksheet + A1 range, body-level paragraph ordinal, one-based page number — never screen or DOM positions.

When to use which tool

• Only need to read a document to summarize or answer questions → use mcp__cherry-tools__to_markdown instead (see the cherry-tool-guide skill); it is lossy but built for reading.
• The user wants a file out — an extracted range, a converted fragment, an edited copy → this skill.

Input: selection references

Chat surfaces may hand you a fenced selection-ref block:

{"path": "/abs/report.xlsx", "anchor": {"format": "xlsx", "sheet": "Sheet1", "range": "A1:C10"}, "excerpt": "…", "fileStamp": {"size": 1024, "mtimeMs": 1700000000000}}

The anchor object is exactly what the scripts take via --anchor.

Freshness check. fileStamp.mtimeMs is milliseconds since the Unix epoch, floored to whole milliseconds. Do not compare it to stat's default output: stat -f %m (macOS) and stat -c %Y (GNU) give whole seconds, so multiplying by 1000 loses the sub-second part and never matches. Read whole milliseconds the way the app wrote them:

uv run python -c "import os,sys;st=os.stat(sys.argv[1]);print(st.st_size, st.st_mtime_ns//1_000_000)" '/abs/report.xlsx'

Treat the file as changed when the size differs, or when the mtimes differ by more than 2 ms. The tolerance is small on purpose: both sides floor the same nanosecond timestamp to milliseconds, so they agree exactly, and the couple of milliseconds only covers the rounding of a double that can no longer represent current epoch milliseconds exactly. A wider window would hide real edits — a same-size change made within it would read as unchanged, which is why the anchor check below is not optional. On a change, tell the user the file changed since they selected and ask them to re-select — never silently re-anchor.

Anchor check. Before a patch-copy edit, also verify the anchor still points where the user thinks: extract the anchored region and compare its text with the reference's excerpt, normalizing both sides the same way (NFC, collapse each whitespace run to one space, trim). The two are not equal and are not meant to be — the excerpt is what the user selected, while the extract is the whole region an edit would replace. A selection sitting inside one region makes the excerpt the shorter side; a selection running past that region anchors to where it starts, which makes it the longer one. So the test is containment, whichever way round fits: the excerpt appears inside the extract, or the extract's tail is where the excerpt begins. Only when neither holds has the anchor stopped pointing at the selection — then stop and tell the user, never edit at a mismatched anchor and never go searching for a "close enough" location. Two cases need care because the two sides are not directly comparable as-is:

• xlsx: the excerpt is tab-separated cells and newline-separated rows, while extraction writes csv or md. Compare cell values, not the raw file — read the csv with a csv reader and join the fields with single spaces before normalizing, so , and | never count as a difference. That join drops the cell boundaries on both sides, so a match proves the text is unchanged, not the grid — the same words re-split across cells still reads as a match. The freshness check above is what catches that; never skip it on a passing anchor check. Number formats are the second asymmetry: the excerpt holds what Excel displays, because that is what the user pointed at (1,234.50, 45.67%), while extraction writes the stored value (1234.5, 0.4567). Neither side is wrong, so a formatted cell never matches literally. Compare those cells by value, and leave them out of the joined strings so the containment test runs on the text cells alone. Dates, times and durations are the same asymmetry seen from the other side: extraction writes one fixed shape (2024-01-03,

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