The 429 pattern
if (queueFillPercent > 90) {
throw new A2AException(A2AKind.RATE_LIMITED, "Backpressure");
}Advertisement
Retry-After hint
Server includes Retry-After: 5 in the response. Compliant clients wait, then retry.
Advertisement
Client honors it
ADK Java client parses Retry-After and delays automatically. Custom clients should too.