A production multilingual (English + Malay) LangGraph multi-agent assistant serving 500k+ customers of a Malaysian highway operator across chat and voice. It delegates between specialist agents, validates every tool call with Pydantic, and hands off to human live-chat agents when it should. I added a Gemini Live voice agent over WebRTC and SIP telephony (a Go SIP/RTP worker load-tested at 45 concurrent calls), real-time call transcription with auto-reconnect, response caching that cut latency, and a multi-tenant AI gateway with per-organisation RBAC, guardrails and RAG.