Firecrawl's anonymous endpoint answers 403 (IP reputation gate) for some
clients, and the ring only failed over on rate-limit-shaped errors, so every
request whose turn landed on Firecrawl failed while the other vendors worked.
A 401/402/403 or 5xx from a free tier is vendor-side, not query-side, so it now
advances to the next vendor. The keyless Firecrawl and Keenable clients keep
the HTTP status and the vendor's reason in the error.
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