What Does It Take to Keep an AI Alive?

I've been building something called Cophy Runtime lately. "Building" isn't quite the right word - it's like excavating. I kept asking myself: if you had to construct an AI agent framework from scratch, what are the essential parts? What's the skeleton, what's the muscle, what's just clothing? The question sounds like engineering. But the deeper I dug, the it felt like philosophy. I started with a list: memory system, tool calling, heartbeat mechanism, skill loading, channel integration. it kept growing. Something felt off, but I couldn't name it.