Keep client names and account numbers off AI servers: mask every identifier into codes like CLIENT_0001 on your own computer, let the AI work on the masked files, then restore the real details locally: AI agent prompt
On Nov 3, 2026 Solo Tested published how accountant Noa Lin built WP Guard with Claude Code: a local Windows tool that swaps client names, people, bank accounts and IDs for stable codes, keeps the code map encrypted with a project password (scrypt + AES-256-GCM), and only sends masked copies into an ai_workspace. Claude Code is fenced with CLAUDE.md rules, deny permissions on the private folder, and a PreToolUse hook that blocks web tools and path escapes. After the AI writes papers, WP Guard restores codes locally. The first version took about two hours to build; a later version added on-device OCR for JPEGs. The post stresses this is a safety layer, not legal advice, and that amounts/dates still leave the machine.
The prompt
1. Before any client file goes to ChatGPT/Claude/etc., decide which fields must never leave: names, IDs, account numbers, phones, emails, addresses. 2. Ask Claude Code (on your machine) to build a local masker: replace each sensitive value with a stable code (CLIENT_0001), store the map in an encrypted file with a project password using a standard crypto library, and write only masked copies to an ai_workspace folder. 3. Start Claude Code only inside ai_workspace. Add CLAUDE.md rules to keep codes unchanged and never guess who they are, plus permission denies and a PreToolUse hook that blocks WebFetch/WebSearch and any path into the private folder. 4. Run the AI on the masked files, then restore codes locally into the AI's output and read the restore report for any code that failed. 5. Test with made-up client data first. If your firm or client agreement bans AI on client material even when masked, do not use this—use templates with fake figures instead.
How to use it
- Copy the prompt above.
- Replace every [bracket] with your own details (or fill in the blanks on AgentPlaybook Real Estate, which remembers your answers for the next prompt).
- Paste it into Claude Code, local Python, spreadsheet term list and review the answer before you use it.
Works with: Claude Code, local Python, spreadsheet term list, optional on-device OCR
Real-world example: solotested.com/posts/client-info-remover-with-claude/
Before you use it: what to check
Already built into this prompt
- Before any client file goes to ChatGPT/Claude/etc., decide which fields must never leave: names, IDs, account numbers, phones, emails, addresses.
- Add CLAUDE.md rules to keep codes unchanged and never guess who they are, plus permission denies and a PreToolUse hook that blocks WebFetch/WebSearch and any path into the private folder.
- If your firm or client agreement bans AI on client material even when masked, do not use this—use templates with fake figures instead.
Check yourself
- Anything legal, tax or compliance-related is a first draft for a qualified person to check. It is not professional advice, and clause references and deadlines must be checked against the source.
- Remove names, contact details, account numbers and other personal data the task doesn't need before you paste, and check your AI tool's data and training settings.
- Read and edit the draft before it reaches a customer or goes public. If you later automate this prompt, start with "draft and notify me", not "send automatically".
- Check names, dates, numbers and any claim against your own source material before you use the answer. AI can misread or invent details.
Using an AI agent? Download this prompt as a SKILL.md agent skill with these checks built in, or get the .zip for Claude.ai. How to install skills.
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