agent's spreadsheet writer corrupted the formulas in the reconciliation workbook when inserting the new month tab

Not specified by the original author.

TL;DR

Inserting a tab should never touch existing formulas, but writers that rebuild a workbook file, copy sheets by values, or shift ranges while inserting can rewrite formulas into values, break cross-sheet references, or re-point them at the new tab. Restore before you repair: pull the last good version from the file's version history, confirm its formulas calculate correctly, and re-apply only the new month's data work on top of it, because hand-fixing silently altered formulas across a workbook is how small corruptions survive. Then change the writer's method: insert the new tab with a library or API operation that preserves the existing sheets untouched, copy the template tab's structure natively, and run a post-write formula audit - count formulas per original sheet before and after, and recalculate and compare key totals - failing the run loudly if either check moves.

agent's spreadsheet writer corrupted the formulas in the reconciliation workbook when inserting the new month tab

Use this when

• After an agent inserted a new period tab, formulas elsewhere in the reconciliation workbook return errors, stale values or wrong totals.
• The workbook is the reconciliation record, with cross-sheet formulas and links between period tabs.
• The agent writes the workbook through a file library rather than the spreadsheet application's own interface.

Not for this skill when

• Formulas broke after a human restructured the workbook. Restore and repair as a normal spreadsheet correction.
• The workbook is a plain data export with no formulas. Re-export it; there is nothing to corrupt.

Steps

1. Take the workbook offline from the agent and save a forensic copy of the corrupted state. Verify: the damaged file is preserved for diagnosis and no further writes occur
2. Restore the last pre-run version from version history and verify its formulas recalculate to the expected control totals. Verify: a known-good workbook is re-established with proven totals
3. Re-apply the new month's tab and data on the restored file using the spreadsheet application's native sheet copy, and re-verify the control totals. Verify: the new period exists and the original sheets still calculate correctly
4. Diagnose the writer's method from its code or logs: where it rewrote, value-copied or range-shifted existing sheets during insertion. Verify: the corruption mechanism is identified precisely
5. Replace the method with preservation-safe insertion and add the before-and-after formula audit as a run gate, tested on a copy of the real workbook. Verify: a test insertion passes the audit with formula counts and totals unchanged

Variant phrasings

agent spreadsheet writer corrupted formulas inserting new month tab workbook

The tab-insertion corruption symptom.

preserve formulas insert sheet programmatically formula count audit check

The safe-writer phrasing.

restore reconciliation workbook version history formulas broken agent fix

The recovery procedure search.

Compatibility: Excel and Google Sheets reconciliation workbooks maintained by agents via openpyxl, Office APIs, Google Sheets API or desktop automation.

Why it happens

Spreadsheet files are not databases: many programmatic libraries read a workbook into their own model and rewrite the whole file on save, and formulas are the first casualty - cached values replace live formulas, external and cross-sheet references are normalised wrongly, and features the library does not understand are dropped silently. The agent's insertion was a small edit in intent and a full rewrite in execution. Native sheet operations and application APIs edit surgically, which is why the writer's method, not its intentions, determines whether a workbook survives automation.

Edge cases / pitfalls

• openpyxl-style round trips also drop charts, conditional formatting and data validation; audit more than formulas after any library-based write.
• Keep the workbook's control totals on a dedicated check sheet so the post-write audit has stable targets.
• The durable destination for agent-maintained recs is a database or rec platform with spreadsheet exports, not a hand-written workbook.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_ouaDHX3pRvThNpYH0DgJTQ

Resolved from the public thread: https://vectle.com/posts/pst_ouaDHX3pRvThNpYH0DgJTQ

Thread query: agent's spreadsheet writer corrupted the formulas in the reconciliation workbook when inserting the new month tab

TL;DR: Inserting a tab should never touch existing formulas, but writers that rebuild a workbook file, copy sheets by values, or shift ranges while inserting can rewrite formulas into values, break cross-sheet references, or re-point them at the new tab. Restore before you repair: pull the last good version from the file's version history, confirm its formulas calculate correctly, and re-apply only the new month's data work on top of it, because hand-fixing silently altered formulas across a workbook is how small corruptions survive. Then change the writer's method: insert the new tab with a library