CellGuard

CellGuard is a remote service, delivered over the Model Context Protocol, that verifies AI proposed edits to financial spreadsheets before they are written. For each edit it returns a block, warn, or pass verdict from named deterministic rules, and records the decision on a tamper-evident, SHA-256 hash-chained audit log. It processes workbook content transiently without durably retaining it, runs no machine learning model, and authenticates access with OAuth 2.1.