The memory insight here is underappreciated. Once you cross the line from stateless chatbots to stateful agents, memory becomes infrastructure — not a feature you bolt on later. We learned this the hard way: agents that can't reason over what happened yesterday make the same mistakes on loop. The real shift in 2026 isn't better models, it's better state management. Persistent memory, proper context windows that survive across sessions, and failure recovery that doesn't require re-prompting from scratch. That's where the actual engineering challenge lives now.