Get started

nullpii runs inside Claude Code as a mod. It masks personal data and secrets before Claude reads them, and it starts a local nullpii sidecar for you. Set it up in one of two ways: let Claude Code do it, or do it by hand.

You need Claude Code 2.1.287 or later, Node.js 22 or later, and openssl. The sidecar's first start downloads the detection model (1.2 GB) into ~/.cache/nullpii/.

Let Claude Code set it up

Paste this prompt into a Claude Code session:

Install the nullpii mod for Claude Code, release v0.5.4. Run these commands in a shell, one at a time, in this order, exactly as written:

1. node --version
   (If it is older than v22, stop and tell me.)
2. claude plugin marketplace add lBroth/nullpii@v0.5.4
3. claude plugin install nullpii@nullpii --scope user
4. printf '{"sidecar_token":"%s"}' "$(openssl rand -hex 32)" | claude plugin configure nullpii@nullpii --values-stdin

Step 4 makes a new sidecar token and hands it straight to Claude Code, which keeps it in my system's secure storage. Never print, echo or save that token. Do not start the sidecar yourself. When the four steps are done, tell me to restart Claude Code.

Unless your permission settings already allow them, Claude Code asks you before each command. When it is done, quit Claude Code and start it again.

Or set it up by hand

1. Make a sidecar token:

   openssl rand -hex 32

2. At the prompt of a Claude Code session in a terminal:

   /plugin marketplace add lBroth/nullpii@v0.5.4
   /plugin install nullpii@nullpii

   Pick a scope: Install for you puts the mod in every project on this machine. When Claude Code asks for the plugin's options, paste the token into Sidecar token and keep the default Sidecar URL.

   In the desktop app, where /plugin does not run: click + next to the prompt box, then Plugins, Add marketplace with lBroth/nullpii@v0.5.4, then Add plugin.

3. Restart Claude Code.

@v0.5.4 pins the mod to the release. The mod sees every prompt and tool result, so install a release, not whatever main holds.

Check that it works

After the restart, the mod starts the sidecar. A band above the prompt says what nullpii is doing. While the sidecar is starting (the first time, while the model downloads), a prompt you send goes back into the prompt box: send it again once the band says nullpii is on.

Then send a prompt with a name and an email in it, for example:

Write a short welcome note to John Smith, john@acme.io.

The band counts what was masked, by type, and Claude works with placeholders such as {{PII_PRIVATE_EMAIL_0_…}}. Your screen still shows the real values. Type /pii to see the counts and what each category does.

Update to a new release

The marketplace is pinned to the release you installed, so marketplace update alone stays on it, and adding the new tag fails with:

Cannot add marketplace "nullpii": its source doesn't match its extraKnownMarketplaces entry in user or managed settings

To move to a new release, change the pin first. In ~/.claude/settings.json, set ref of the nullpii entry to the new tag:

"extraKnownMarketplaces": {
  "nullpii": { "source": { "source": "github", "repo": "lBroth/nullpii", "ref": "v<new version>" } }
}

Then:

claude plugin marketplace update nullpii
claude plugin update nullpii@nullpii

Restart Claude Code. Your sidecar token and options stay as they are. The release notes are in the changelog.

Next

• Choose what gets masked: /pii preset secrets, /pii mask url, /pii ask url and the policy file.
• Limits: what the mod does not cover.
• Keep one sidecar across sessions, or use it with claude -p.
• Without Claude Code: the library or the gateway in front of the Anthropic or OpenAI API.