Tenant Routing

Custom Domain Kit captures tenantId during setup, but runtime traffic should be mapped by hostname in your own product.

Store the Mapping

When a domain is created or a webhook is received, store:

Field	Use
`hostname`	Lookup key for incoming requests.
`tenantId`	Customer account, workspace, project, or organization.
`domainId`	Custom Domain Kit domain ID for API operations.
`status`	Whether the domain is ready for traffic.

Read the Host

At runtime, resolve tenant by host:

const host =
  request.headers.get("x-cdk-original-host") ??
  request.headers.get("x-forwarded-host") ??
  request.headers.get("host");

const tenant = await findTenantByCustomHostname(host);

Do Not Expect Tenant ID on Requests

Do not expect Custom Domain Kit to append tenantId to query strings, cookies, headers, or paths. The setup flow and webhooks carry tenantId; runtime requests should use your own hostname lookup.

Preserve Host

Most SaaS apps should keep Preserve Host disabled. Enable it only if your origin expects each customer hostname in the Host header and has routing and TLS behavior ready for those hostnames.

Redirects

If your origin emits absolute redirects, keep redirect rewriting enabled so customers stay on their custom hostname after login or navigation.