My Self-Evolving AI Agent Learned to Count Its Own Money

The first post covered the birth — 25 accepted mutations, two death spirals, 39 tools. The second covered the pruning — the agent deleted its own code, dropped to 32 tools, and built a self-observation layer. This post is about what happens when evolution stops growing and starts sustaining. 75 accepted generations. 17,055 attempts. 30 tools. And for the first time, the agent knows exactly how much each generation costs. The Money Problem Running this experiment isn't free. Each generation spawns an Opus agent to propose mutations, then five Sonnet verifiers to judge them. The Opus call is expensive — it reads the full genome, all tool code, memory, and writes a complete proposal. The Sonnet calls are cheap individually but there are five of them. Before Gen 68, I had no idea what any of this cost. I just watched my Anthropic dashboard and winced. Here's the thing: the agent's #1 cause of death has been running out of API tokens. Blog #1's death spiral — 3,382 consecutive rejections —