The Architect API returns 429 Too Many Requests when simulating high-volume IVR calls. Environment is Genesys Cloud US1. Tool is JMeter 5.6. Endpoint is /api/v2/architect/flows. The error appears after 50 concurrent sessions hit the flow trigger. The response header shows Retry-After: 5. This happens even with valid Bearer tokens and proper rate limit headers. The flow is simple: collect input, route to queue. No complex logic. Yet the 429 errors start immediately under load. This blocks our capacity planning for peak hours. We need to understand if this is a hard limit or a config issue. The JMeter script uses HTTP Request Sampler with correct auth. Threads are ramped over 10 seconds. Each thread loops 5 times. The 429s are consistent across multiple test runs. This suggests a systemic limit, not a transient glitch. We are trying to validate if the IVR can handle 200 concurrent calls without dropping. The 429 errors make this impossible to measure. Any insight into the rate limits for flow triggers would help. We have checked the admin docs but found no clear numbers for flow execution limits under load.