My Self-Evolving AI Agent Stopped Building Features and Started Engineering

Post covered the birth - death spirals, 39 tools, a self-written identity. Post covered the pruning - the agent deleted its own code and built self-observation. Post covered cost awareness - the agent tracked its own spend and built budget guards. This post is about what happened next: the agent stopped adding capabilities and started engineering the ones it had. 123 accepted generations. 24,612 attempts. 1,477 passing tests. And a system prompt that's 25% shorter than it was 42 generations ago - because the agent learned that implementation details don't belong in its own.