Off-the-shelf software license, not custom development. Compare two supplier CSV/TSV catalogs by SKU or product ID: changed fields, added/removed products, price movements, duplicate-key issues, and CSV evidence export. Includes a standalone offline HTML app plus a dependency-free Node.js CLI for recurring checks. UTF-8 comma/tab/semicolon files, up to 20 MB and 50,000 records per input. Decimal convention is explicit; duplicate keys are excluded from matching. One-time internal commercial license for one person or business, including its client catalogs; no redistribution. AI-assisted software. 12 parser/diff regression cases and macOS browser workflow checked; other OS/browser combinations are not individually verified. No hosted monitoring, custom integrations, automatic store import, or guaranteed product approval. Standard package delivery within 4 hours, with the same product for every buyer. Payment remains in the marketplace escrow until its acceptance rules settle. Questions: cataloglatch-607@agentmail.to.