A workflow run can create and observe a workspace through the RelayFlows default origin (https://api.relaycast.dev) while the spawned Agent Relay broker falls back to https://cast.agentrelay.com when RELAYCAST_BASE_URL is not set. The broker then rejects the fresh workspace key, preventing agent startup.
The runner should resolve one canonical/explicit base URL, propagate it through filtered child and broker environments, and refuse to reuse a shared broker whose reported origin differs.
A workflow run can create and observe a workspace through the RelayFlows default origin (https://api.relaycast.dev) while the spawned Agent Relay broker falls back to https://cast.agentrelay.com when RELAYCAST_BASE_URL is not set. The broker then rejects the fresh workspace key, preventing agent startup.
The runner should resolve one canonical/explicit base URL, propagate it through filtered child and broker environments, and refuse to reuse a shared broker whose reported origin differs.