Telegram error 400: Bad Request: bad webhook: failed to resolve host

setWebhook accepted the URL syntactically but Telegram's servers could not resolve the hostname to an address. The description begins bad webhook: failed to resolve host: and continues with the resolver's detail, commonly no address associated with hostname or Name or service not known. An older variant you may still find in library code reads bad webhook: getaddrinfo: Temporary failure in name resolution. All mean DNS lookup failed from Telegram's side.

Telegram verifies the host at registration, which is why this error appears on setWebhook rather than later. A typo, a brand-new DNS record that has not propagated, a private hostname, or an internal-only domain all produce it.

Once DNS is fixed the same setWebhook call succeeds; there is no state to clean up.

{"ok":false,"error_code":400,"description":"Bad Request: bad webhook: failed to resolve host: no address associated with hostname"}

Make webhook registration a step that runs after DNS and TLS are confirmed reachable from the public internet, not during the first boot of a fresh host. Keep tunnel-based URLs out of persistent configuration.

Registration-time failures like this one are the easy half of webhook debugging, because setWebhook tells you immediately; delivery-time failures show up only in getWebhookInfo.last_error_message and are walked through in the webhook debugging guide. The other registration rules (HTTPS scheme, the four ports, certificate matching) are under webhook limits, and their errors are HTTPS url must be provided and the port-list rejection.