Custom Domains

Each coding agent runs in its own sandboxed VM. By default, services inside the VM are not reachable from the internet. Exposed Ports opens a port, proxies it through the live worker connection, and gives you a public HTTPS URL — or lets you connect your own domain.

Exposing a port#

1. Go to your agent's Settings tab.
2. Under Exposed Ports, enter the port your service listens on (e.g. 3000).
3. Click Expose Port.
4. You get a public URL immediately. On production this is a subdomain like https://myagent-abc12345-3000.ports.chat.dev; some environments (e.g. staging) use a path-based URL like https://<server>/p/<agentId>/<port> instead — always use the exact URL shown in Settings.

TLS certificates are provisioned automatically.

The port proxy uses the live worker websocket, so exposing a port does not by itself require restarting a running machine. The service inside the VM still has to be listening on that port.

What the proxy supports#

• Plain HTTP and HTTPS — all methods, request bodies, and response streaming (SSE and chunked responses are forwarded live).
• Redirects — passed through to the browser, so OAuth callbacks and login flows work.
• Not supported: WebSockets. Upgrade requests get a 501 — the public URL terminates at an HTTP proxy that can't carry a WebSocket connection. If your app needs realtime updates behind an exposed port, use SSE or polling instead.

Connecting a custom domain#

Point your own domain at any exposed port. This works with any registrar (Porkbun, Namecheap, Cloudflare, GoDaddy, etc.).

1. Expose the port#

Make sure the port is exposed first (see above). You need the auto-generated URL as your CNAME target.

2. Add the domain in chat.dev#

1. In Settings, scroll to Custom Domains.
2. Enter your domain (e.g. app.example.com) and select which exposed port it should route to.
3. Click Add Domain.
4. You'll see a CNAME target to configure in your DNS.

3. Add a CNAME record at your registrar#

In your registrar's DNS settings, add a CNAME record:

• For app.example.com, the Name is app.
• For root domains (example.com), you need a registrar that supports CNAME flattening (e.g. Cloudflare).
• TTL: automatic or 300 seconds.

4. Verify and get TLS#

1. Back in chat.dev, click Verify next to your domain.
2. chat.dev checks that your CNAME resolves correctly.
3. A TLS certificate is automatically provisioned once verified.
4. Your domain is live with HTTPS within a few minutes.

Troubleshooting#

• "No CNAME record found" — DNS propagation can take a few minutes. Wait and try again.
• CNAME target mismatch — Make sure the value exactly matches the target shown in chat.dev.
• Port URL opens but the app does not load — confirm the process is listening on 0.0.0.0:<port> or 127.0.0.1:<port> inside the agent VM and that the exposed port number matches.
• Root domain — CNAME records can't be set on bare root domains. Use a subdomain or a registrar with CNAME flattening.

Multiple ports#

You can expose multiple ports on the same agent. Each gets its own URL and can have its own custom domain — useful for running a frontend on port 3000 and an API on port 8080, for example.

Removing ports and domains#

• To remove a custom domain, click the delete button next to it in Settings. The TLS certificate is cleaned up automatically.
• To remove an exposed port, click the delete button. This also removes any custom domains attached to that port.