numbers.extension_taken

numbers.extension_taken means another active SIP credential in this workspace already uses that extension.

Cause

An extension is unique across the workspace, not across one number, so 1001 reaches one device whichever of your numbers that device was issued on. If two requests ask for the same extension at the same moment, one of them gets this error.

Resolution

Pick a free extension, or free the one you want.

To see what is in use, list the credentials on each of your numbers with GET /v1/numbers/{id}/sip-credentials. Every credential in the response carries its extension.

To move an extension between devices, clear it from the old one first by sending an empty string:

await fetch(
  `https://api.sautikit.com/v1/numbers/${numberId}/sip-credentials/${credentialId}`,
  {
    method: "PATCH",
    headers: {
      Authorization: `Bearer ${process.env.SAUTIKIT_API_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({ extension: "" }),
  }
);

Revoking a credential also frees its extension.

Related

• numbers.extension_invalid: the extension is not exactly four digits.