Prompt structure and guardrails, A/B comparisons between models on real traffic, tradeoffs across latency, cost, and quality, and the practical limits (context budgets, rate limits, tool-calling reliability) that decide whether a design survives production. You sit close to our most strategic clients, watch their real call traffic, and debug their failures yourself, working through agent traces, LLM tool-call payloads, service logs, and the client's own API until you can name the actual defect.