sheets-bridgelisted

# Sheets bridge Spreadsheets are where finance actually works, and they are also the most fragile integration surface in the stack: no schema enforcement, no transactions, last-write-wins, and a human editing the same file at the same time as your automation. Every rule here exists to stop the same failure: **an automation silently destroying work a human did.** That failure is usually discovered weeks later, and by then the original values are gone. Load `finance-guardrails` — Rail 2 (single writer per zone) is the governing rule here, and this skill is its most important application. --- ## The zone contract **Before writing anything, declare the zone.** A zone is a specific named range or tab, never a file. Record it where the next person will find it — a `ZONES.md` in the automation repo, and a header comment in the sheet itself: ```markdown # Zone map - FY26 Reporting Workbook | Zone | Owner | Written by | Cadence | Humans may edit? | |---|---|---|---|---| | `Actuals!A1:M500` | finance-automation | close pipeline | monthly, day 4 | NO - overwritten | | `Actuals!N:R` | Controller | humans | ad hoc | YES - never touched by automation | | `Budget!A1:M500` | FP&A | humans | quarterly | YES - read-only to automation | | `Metrics!A1:H80` | finance-automation | metrics refresh | daily 06:00 | NO - overwritten | | `Commentary!A:D` | Controller | humans | monthly | YES - read-only to automation | ``` Rules: - **One automated writer per zone. Never two.** There is no loc