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Draft: synchronized X launch thread

Do not post. This is final local copy for owner publication. Publish only after the article and evidence links pass logged-out preflight.

Launch window

Publish Post 1 within the same ten-minute window as the Hacker News submission. Use the package-drift bar chart as the only attachment to Post 1. Post the rest as a native thread, then add the Hacker News link as a reply after the submission is live.

Thread

Post 1

An AI agent edits one cell. What else changes inside the workbook?

I re-saved five valid XLSX files through LibreOffice bundled with ChatGPT Desktop's Codex runtime. It changed 8 to 151 unrelated OOXML parts. WolfXL changed 0.

We published the receipts.

Post 2

The test was intentionally boring: open, request no content change, save to a new file, then compare every OOXML package part.

Fixtures covered external links, validation and protection, custom XML, a pivot chart with slicers, and a PowerPivot model.

Post 3

Changed does not mean corrupted. Office export filters can legitimately normalize XML and relationships.

The finding is mutation blast radius: a no-op save touched 8, 19, 14, 31, and 151 unrelated parts. That is state an agent should inspect before replacing the source.

Post 4

Same-source macOS benchmark, 3 samples per row: WolfXL was 2.2x to 3.9x faster on the paired tasks, and its measured install was 37.5 MB vs 423.0 MB.

The red row stays in: isolated footprint RSS favored LibreOffice, 34.5 MiB vs 53.1 MiB.

Post 5

WolfXL's agent path is a guarded transaction:

  1. declare operations and ranges
  2. patch an isolated copy
  3. verify the requested change and unrelated drift
  4. publish atomically

Unsupported work fails visibly or uses an explicitly named fallback.

Post 6

Full method, exact-source receipts, counter-results, and reproduction links:

https://wolfgangschoenberger.com/blog/when-an-ai-agent-edits-a-spreadsheet

If you test your own workbook, use a public or synthetic file. Please do not upload confidential workbooks.

Reply after Hacker News is live

The Hacker News discussion is here: [HN URL]

I would especially value adversarial fixtures and feedback on which workbook features should be hard refusal boundaries for an agent.

Asset

Use the final package-drift chart exported for this launch. Do not use the older speed or footprint cards because they contain source-mismatched values.

Recommended alt text:

Package drift after a no-op XLSX open and save. Across five fixtures, WolfXL changed zero unrelated OOXML parts. Bundled LibreOffice changed 8, 19, 14, 31, and 151 unrelated parts.

Pre-post checks

  • The portfolio article is live and loads while logged out.
  • The three github.com/SynthGL/wolfxl/blob/main/docs/trust/ receipt links load.
  • Pull request 626, or its exact replacement commit, is on the public default branch.
  • Every selected number matches the 2026-09-03 source-matched receipts.
  • The package-drift image uses the same five values and makes no corruption claim.
  • No private path, hostname, session identifier, workbook, screenshot, token, or mutable temporary result appears.
  • The owner posts from the intended account.