useleak (typescript)

Drop-in cost tracking for the Anthropic TypeScript SDK. See exactly where your LLM spend goes — broken down by feature, user, and model.

Install

pnpm add useleak
# or
npm install useleak
# or
yarn add useleak

Usage

Get a workspace SDK key from Settings → Workspace SDK key in your Leak dashboard. Set it as LEAK_KEY in your env (alongside ANTHROPIC_API_KEY).

import Anthropic from "useleak";

const client = new Anthropic();  // picks up ANTHROPIC_API_KEY + LEAK_KEY

const response = await client.messages.create({
  model: "claude-opus-4-7",
  feature: "icp-scoring",     // ← the one extra param Leak needs
  user: "user_123",            // optional but lets you group by customer
  max_tokens: 1024,
  messages: [{ role: "user", content: "..." }],
});

console.log(response.content);

That's it. Every call gets tracked to your Leak dashboard within a few seconds: model, tokens in/out, cost, feature, user, request ID.

API

new Anthropic(opts) accepts every option the official @anthropic-ai/sdk accepts, plus two of its own:

| Option | Default | Description | |---|---|---| | leakKey | LEAK_KEY env | Your workspace SDK key (lk_live_...) | | leakUrl | https://useleak.cloud/api/ingest | Ingest endpoint, override only if self-hosting |

client.messages.create({...}) accepts every parameter the Anthropic SDK accepts, plus three of its own:

| Field | Required | Description | |---|---|---| | feature | recommended | The feature in your app that triggered this call ("icp-scoring", "playground", etc.) | | user | optional | An end-user identifier — lets you see who is burning tokens | | api_key_label | optional | Free-form label like "Production" / "Staging" |

Tracking is async and non-blocking (using fetch with keepalive: true). If useleak.cloud is down, your Anthropic call still succeeds — Leak failures never propagate.

What it tracks

• model
• input tokens / output tokens
• USD cost (computed locally from the Anthropic price table)
• feature, user, api_key_label (your tags)
• Anthropic request ID

It does not send prompts, responses, or any message content.

Runtimes

Works on Node 18+, Bun, Deno, Cloudflare Workers, Vercel Edge — anywhere fetch exists.

License

MIT