When circuit breaker is open, you need a fallback response.
Options:
Cached data: Return last known good response. Stale but useful.
Default value: Return sensible default. "Recommendations unavailable."
Queue for later: Accept request, process when service recovers.
Alternative service: Route to backup provider.
Graceful error: Informative message vs generic failure.
Choose based on business impact. Critical path needs better fallback than optional features.