Secure Your Anthropic API Key in Python

The Problem

This is what most Python codebases look like today. The ANTHROPIC_API_KEY key (sk-ant-...) lives directly in the process environment. If your repo, your CI logs, or your deployment config leaks — so does your key.

# api.py — real Anthropic key in ANTHROPIC_API_KEY
import os
import anthropic

client = anthropic.Anthropic(api_key=os.environ["ANTHROPIC_API_KEY"])

def generate(prompt: str) -> str:
    message = client.messages.create(
        model="claude-opus-4-5",
        max_tokens=1024,
        messages=[{"role": "user", "content": prompt}],
    )
    return message.content[0].text

The Fix

Send the request to the KeyVault Edge proxy at https://proxy.keyvaultedge.com with the provider's usual path, your kvt_ token in X-KV-Token and the provider's base URL in X-KV-Target. The proxy refuses requests whose Origin isn't on the token's allowed hosts, then injects your real ANTHROPIC_API_KEY, so it never sits in your app's environment.

# api.py — KVE_TOKEN is host-bound; ANTHROPIC_API_KEY not needed
import os
import httpx

KVE_TOKEN = os.environ["KVE_TOKEN"]

def generate(prompt: str) -> str:
    response = httpx.post(
        "https://proxy.keyvaultedge.com/v1/messages",
        headers={
            "X-KV-Token": os.environ["KVE_TOKEN"],  # kvt_... token
            "X-KV-Target": "https://api.anthropic.com",
            # Must match one of the token's allowed hosts
            "Origin": os.environ["APP_ORIGIN"],
            "Content-Type": "application/json",
        },
        json={
            "model": "claude-opus-4-5",
            "max_tokens": 1024,
            "messages": [{"role": "user", "content": prompt}],
        },
        timeout=60.0,
    )
    response.raise_for_status()
    return response.json()["content"][0]["text"]

Setup in 4 steps

# .env
KVE_TOKEN=kvt_...your_token
APP_ORIGIN=https://yourdomain.com  # one of the token's allowed hosts

pip install httpx  # if not already installed

What this protects, and what it doesn't

• Your real ANTHROPIC_API_KEY stays at the edge, so it can't leak from your repo, logs, bundle or server environment.
• The kvt_ token is still a credential. A copied token can be replayed by anyone who can send the right headers, including a fake Origin from a server. The protection is that each token has its own rate limits, monthly cost cap and endpoint scope, and you can revoke it in one click without rotating the provider key.
• The cost cap is estimated from the usage the provider reports, so a request already in flight can overshoot it slightly.

Plans and limits are on the pricing page.

More Anthropic guides