Spreadsheets Silently Accept Wrong Values, So AI Agent Edits Need Verification

Writing into an Excel or Sheets cell can appear successful even when the result is wrong, since cell addresses shift when rows are inserted and formulas can be overwritten with plain values. Cells also coerce data silently through formats, locale settings, or dropped leading zeros, while the write call still reports success. The author proposes that any edit be describable as a named target, a diffable change, reversible via a saved copy and hash, and checked by reading back recalculated values. A five-field record of each unattended write is recommended, including the range actually touched and a read-back of the computed result.