In Retell, there isn’t a separate “allowed languages” setting outside the prompt. The only native place to define that behavior is the agent prompt (system/global prompt). So if you want stricter control beyond just mentioning it once, you reinforce it inside the same prompt but more explicitly and repeatedly in the instruction structure (behavior rules, refusal rules, and response format). That’s what actually makes the model stick to it in Retell. If you need it to be truly enforced (not just guided), then you’d have to handle it outside Retell using an external layer (like Make/n8n) that detects the user’s language before sending it to the agent and blocks or redirects unsupported ones. @jsdev