- Add `isSafeWhoisReferralHost` to reject private/loopback/link-local IPs and malformed hostnames before following WHOIS referrals (SSRF guard)
- Detect WHOIS throttle replies in the referral chain: drop the registrar response, keep the registry record, and surface a warning instead of returning bad data
- Add `looksEmptyWhois` guard in the main lookup path: a "registered" record with no parseable fields now fails with `errorCode: "unparseable"` rather than resolving silently
- Map RDAP 429 responses to a structured `rate_limited` error (including `Retry-After` header) so callers can distinguish throttling from generic HTTP errors and the fallback to WHOIS is recorded in `attempts`
- Add `rate_limited` and `unparseable` to `LookupErrorCode`
- Change `collectWhoisReferralChain` to return `{ results, warnings }` instead of a bare array; warnings are merged onto the final `DomainRecord`
- Remove the `followWhoisReferrals` fallback path from `index.ts` (dead code after the chain API stabilised)
