Cloudflare Workers

Run the same SDK on Workers using Node compatibility. The built-in Cloudflare adapter can call the Workers AI binding without placing a provider API key in the browser.

Create the endpoint#

In an ESM project using Node 24+ tooling:

npm install jev-hooks
npm install --save-dev wrangler typescript
mkdir -p src

Save this as src/index.ts:

import { CloudflareJevAdapter, type CloudflareAiBinding } from "jev-hooks";
import { createJevHandler } from "jev-hooks/server";

interface Env {
  AI: CloudflareAiBinding;
  JEV_ENDPOINT_TOKEN: string;
}
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    if (new URL(request.url).pathname !== "/api/jev")
      return new Response("Not found", { status: 404 });
    return createJevHandler({
      adapter: new CloudflareJevAdapter({ ai: env.AI }),
      authorize: (request) =>
        Boolean(
          env.JEV_ENDPOINT_TOKEN &&
            request.headers.get("authorization") ===
              `Bearer ${env.JEV_ENDPOINT_TOKEN}`,
        ),
    })(request);
  },
};

Download this example

Save this as wrangler.jsonc:

{
  "$schema": "./node_modules/wrangler/config-schema.json",
  "name": "my-jev-api",
  "main": "src/index.ts",
  "compatibility_date": "2026-09-01",
  "compatibility_flags": ["nodejs_compat"],
  "ai": { "binding": "AI", "remote": true },
}

Download this example

This uses the official Jev model binding and Workers Node compatibility. remote: true means local development calls the remote, paid model.

Local and deployed configuration#

Put a private endpoint token in .dev.vars for local development, and exclude that file from Git:

JEV_ENDPOINT_TOKEN="your-private-endpoint-token"

npx wrangler dev
# In another terminal, set the deployed secret when ready:
npx wrangler secret put JEV_ENDPOINT_TOKEN
npx wrangler deploy

Test locally from a trusted terminal with the token exported:

curl http://localhost:8787/api/jev \
  -H "Authorization: Bearer $JEV_ENDPOINT_TOKEN" \
  -H 'Content-Type: application/json' \
  --data '{"state":{"changePct":-4},"questions":{"pressure":{"type":"score","instructions":"How much economic pressure exists?","criteria":["Normal","Elevated","Severe"]}}}'

The provider model identifier is typesafe/jev. The exact response model can differ as the provider updates its deployment; inspect returned metadata or configure an expected response model when you need strict pinning.

Offline development#

Replace the Cloudflare adapter with new MockJudgmentAdapter() imported from jev-hooks, and remove the AI binding from the local mock configuration. The mock path makes no provider requests. Its default answers are constant fixtures, not interpretations of your input.

Connect a frontend#

Serve your React assets and API on the same origin, then use createJevClient({ endpoint: "/api/jev" }). Replace the private bearer-token example with your application's session authorization before connecting a public browser. Never bundle the shared endpoint token in frontend code.

If using a separate origin, your Worker must implement an explicit CORS policy and authenticate those requests. createJevHandler does not implement CORS for you.

State and usage#

An isolate's memory is neither shared nor durable. Use Durable Objects, KV or another application store when shared cache/accounting semantics require it. Worldline uses a Durable Object to retain public usage counts and budgets; the SDK does not provision that infrastructure automatically.

The AI binding does not guarantee that a disconnected HTTP client cancels remote inference. Do not infer a zero bill from a cancelled browser request. See production behavior.