TamgaBrowser extension

Chat sites,checked atsend

Text typed into a chat site goes from the browser to that site and never reaches a proxy. This extension asks your own Tamga what the policy says about the text at paste and at send, and acts before the site receives anything.

No. 001What the person sees

Held until there is a verdict

A send is always held until the text in the box at that moment has a verdict. A paste is not held: the box is checked straight away so a problem shows before the person goes on writing.

A chat site in a browser with the extension, simulated

Not sent

Your organisation's policy blocks this text: credit_card (1).

BLOCK

Please check the invoice for Jane Doe, card 4532 0151 1283 0366.

BLOCK: nothing is sent to the site. The notice names the kind of finding, not the value.

The key stays in the extension's service worker, which makes the only network request there is, to your Tamga. Content scripts get a verdict and never the key. The text is not stored.

No. 002Verdicts

Each action, in the browser

PASS: Nothing is shown. The message is sent.
WARN: The warning, with the kinds of finding. "Send anyway" sends it.
REDACT: The text Tamga returned, with placeholders. "Use this text" puts it in the box; the person sends it, and that send is checked again.
STRIP: Not sent. For one typed message, stripping the whole text leaves nothing to send; the notice says so.
BLOCK, ROUTE: Not sent. The notice names the kinds of finding, never a value. ROUTE is treated as a block.
no verdict: Unreachable, a 2.5 second timeout, a 5xx or a 429. Under failMode: closed, the default, the send is held; under open it goes and a notice says it was not checked.

No. 003Not covered

What it does not cover

It is a control for people who are not trying to get round it. It is not a data-loss-prevention boundary.

01Browsers other than Chromium: Chrome and Edge 111 or later only. Not Firefox, not Safari.
02Sites other than claude.ai, chatgpt.com and gemini.google.com, and the same products under another address.
03The sites' mobile and desktop apps.
04File uploads, pasted images, dragged documents and voice input. Only text in the message box is read.
05The sites' answers. Only what the person sends is checked.
06A person who removes or turns off the extension, unless it is force-installed by policy, or who uses another browser or device.
07Conversation context: each text is judged as one user message, so something split over several messages is judged piece by piece.

No. 004Setup

What your Tamga needs

No change to the proxy was needed. You load the directory unpacked, or pack and sign it yourself and force-install it by policy.

/api/v1/scan: Reachable from the browsers over HTTPS. The scan route stores nothing, so the console shows nothing about browser checks.
proxy key: Treat it as known to everyone who has the extension. Use one key per group: the route allows 60 calls a minute per key.
30 / min / tab: The extension's own limit, so a page that scripts pastes cannot use up the key.
~250 KB: Longer text gets no verdict from the scan route, so under failMode: closed it cannot be sent at all.

managed storage · settings

{
  "tamgaUrl": "https://tamga.internal",
  "tamgaKey": "tk_your_key_here",
  "failMode": "closed",
  "autoRedact": false,
  "sites": ["claude", "chatgpt", "gemini"],
  "timeoutMs": 2500
}