# Building a German Speaking Partner with ElevenLabs Agents and Cloudflare Workers

> Source: <https://dev.to/asazhin/building-a-german-speaking-partner-with-elevenlabs-agents-and-cloudflare-workers-4fgj>
> Published: 2026-10-04 00:52:27+00:00

Anyone who has learned a foreign language knows the gap between a passed exam and real fluency with native speakers. Closing it takes practice with someone at native level, and not everyone has a native-speaking partner or the budget and time for endless lessons.

So I asked myself: what if an AI voice agent could be that partner? Someone to have casual conversations with, like a buddy who speaks at native level, never loses patience, and points out your mistakes when they matter.

I built it with ElevenLabs agents and Cloudflare Workers.

An ElevenLabs agent handles the voice, and a Cloudflare Worker (Hono) does everything else: it serves a small Vite + TypeScript page, stores data in D1, and exposes the endpoints the agent calls.

`recall`, which returns what happened in recent sessions, and `store`, which saves items from the conversation.
**Memory.** When I built this, ElevenLabs agents had no built-in memory across sessions, so I added it myself: the webhook stores each session, and the agent calls `recall` when a call starts. I load only the last two or three sessions. Pulling in more makes the agent sound robotic. Nobody remembers a hundred earlier conversations with a friend.

**No secrets in the browser.** The Worker puts the user's identity into the page before it reaches the browser, as an HMAC-signed ID. The signing key only exists in the Worker.

``` js
const rewritten = new HTMLRewriter()
  .on('elevenlabs-convai', {
    element(el) {
      el.setAttribute(
        'dynamic-variables',
        JSON.stringify({ user_id: token, name: displayName }),
      );
    },
  })
  .transform(response);

rewritten.headers.set('Cache-Control', 'no-store');
```

The `no-store` header matters, because this page is personalized and must never be served from a shared cache.

**The agent's endpoints are not public.** The agent never decides whose data it touches. The widget passes the signed user ID to the agent as a dynamic variable, and every tool call sends it back. The tool routes verify the signature before reading or writing anything, so an invented or altered ID is rejected. The post-call webhook has its own check. Route wiring, simplified:

```
app.get('/tools/recall', recallHandler);   // verifies the signed user_id first
app.post('/tools/store', storeHandler);    // same check before any write
app.post('/api/webhook', saveSession);     // webhook signature check
```

The browser sees the signed ID but can't create a new one.

**Routing.** Static files come straight from the asset bundle. Only `/`, `/api/*` and `/tools/*` invoke the Worker.

If you're building voice agents and want to know more about my agent - drop a comment, I'm happy to share details.