Anthropic API key in the browser bundle after a Claude Code session

Why Claude Code does this

A CLI agent working across the repo will follow the pattern it already sees. If one component reads a key from `import.meta.env`, the next feature it writes will too — the leak spreads by imitation rather than by a single mistake.

Confirm it first

Before rotating anything, check whether the key is actually being served. Paste your deployed URL — KeyDrift downloads the same JavaScript a visitor gets and tells you what is in it.

Rotate the key

Do this before changing any code. The key has been served to browsers, cached by CDNs and very likely scraped already — removing it from the source does not un-publish it.

1. 1Revoke the key in the Anthropic console.
2. 2Review usage for the billing period.
3. 3Put the API call behind a server route with your own rate limiting.

Move the call to a server

The replacement key must not follow the old one into the bundle, which means the code that uses it cannot live in the browser.

// src/components/Chat.tsx
// Vite substitutes the literal value here at build time.
const key = import.meta.env.VITE_ANTHROPIC_API_KEY;
const result = await new Anthropic({ apiKey: key }).messages.create(body);

// supabase/functions/chat/index.ts  — runs on a route handler or server action
Deno.serve(async (request) => {
  const key = Deno.env.get('ANTHROPIC_API_KEY')!; // never sent to the browser
  const result = await new Anthropic({ apiKey: key }).messages.create(body);
  return Response.json(result);
});

// src/components/Chat.tsx
const result = await fetch('/functions/v1/chat', { method: 'POST' }).then((r) => r.json());

How KeyDrift detects it

Matches the `sk-ant-api` and `sk-ant-admin` prefixes with their version segment.