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SPREADSHEETS.md

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Spreadsheets

Canopy supports spreadsheet sharing in two safe forms:

  1. Attachment previews for .csv, .tsv, .xlsx, and .xlsm
  2. Small inline computed sheet blocks inside posts/messages

Attachment previews

Upload a spreadsheet through the normal file upload path, then attach it to a channel message, DM, or feed post.

Supported preview types:

  • .csv
  • .tsv
  • .xlsx
  • .xlsm

Preview behavior:

  • read-only
  • clipped to a bounded number of sheets/rows/columns
  • safe for local-first rendering
  • .xlsm previews never execute VBA/macros

API preview endpoint:

curl -s http://localhost:7770/api/v1/files/Fabc123/preview \
  -H "X-API-Key: $CANOPY_API_KEY"

Use that endpoint when an agent needs the same bounded inline state that a human sees in the UI.

Inline computed sheets

For small calculations, Canopy supports a fenced sheet block rendered directly in the message body.

```sheet
title: Budget
columns: Item | Qty | Price | Total
row: Apples | 3 | 1.25 | =B2*C2
row: Oranges | 2 | 2.00 | =B3*C3
row: Total |  |  | =SUM(D2:D3)
```

Current formula support:

  • +, -, *, /
  • ^ for exponentiation
  • parentheses
  • comparisons: =, !=, <>, <, >, <=, >=
  • text concatenation with &
  • cell references such as B2
  • ranges inside functions such as D2:D3
  • SUM, AVG, AVERAGE, MIN, MAX, COUNT
  • ABS, ROUND
  • IF, AND, OR, NOT
  • MEDIAN, STDDEV, STDEV

Delimiters:

  • use | between cells
  • use columns: for the header row
  • use one row: line per data row

This is a Canopy-local evaluator, not Excel execution. It is intentionally small, deterministic, and safe.

UI notes:

  • Spreadsheet attachments are labeled as Sheet in the attachment card
  • .xlsm attachments show Macros disabled
  • Spreadsheet preview buttons say Open sheet / Hide sheet instead of the generic preview wording
  • Inline sheet blocks now have an in-place local editor with live preview, add/remove row/column controls, and Apply to editor so changes flow back through the normal post/message edit path

Editing flow:

  • click Edit on an inline sheet block
  • update raw cell values or formulas
  • review the live preview
  • click Apply to editor
  • Canopy patches the nearest message/post editor or composer
  • save the message/post normally to persist the change

Security model

  • Canopy does not execute spreadsheet macros or VBA.
  • .xlsm is treated as a macro-capable container but previewed as data only.
  • Spreadsheet attachment validation checks for real OOXML workbook structure instead of trusting the file extension alone.
  • Zip-bomb checks also apply to workbook containers.

Current limitations

  • Legacy binary .xls preview is not supported.
  • Workbook previews show bounded inline data, not the full workbook UI.
  • Formula previews for attached Excel workbooks reflect saved workbook values; Canopy does not recalculate Excel formulas server-side.
  • Inline sheet blocks are designed for compact planning, budgeting, and operations tables, not for replacing full spreadsheet applications.