The AI stack for 2026 is not one model, one API, or one shiny agent demo. It is a production system: LLMs for reasoning, vector databases for memory, tool calling for action, agents for workflow, and observability for trust. That stack is becoming the backbone of modern AI products because users expect apps that answer, act, and improve fast. For founders, CTOs, dev teams, and any AI app development company, the question is not “should we use AI?” It is “can our architecture survive real u...