Replies come from the OpenClaw session chat pipeline (sessions_send + sessions_history). If you get chat_no_reply, verify CHAT_SESSION_KEY (or CHAT_SESSION_LABEL on deployments that route by label). If your gateway deployment does not expose the sessions tools, set CHAT_TOOL_NAMESPACE / CHAT_TOOL_ACTION. Use /api/chat/diag for a safe, read-only probe of which path is available.