POCs are easy. Production AI is hard. The question isn't build vs. buy on the whole solution — it's build vs. buy on each layer.
Core principle
Own what differentiates you. Buy what is commodity.
Orchestration + evals = your moat
Infra + model access = commodity
Speed vs. control — decide per layer.
Layer 0
Use case plugins
Every new intent is a plugin. Platform stays unchanged.