How agents actually read code, why re-derivation cost has a unit, and why this doesn't go away when context windows grow. series: Grounded Code Second of five articles in the **Grounded Code * series. The first one showed the cost. This one shows the mechanism underneath.* I. The receipt, and what's underneath it In the manifesto I showed a number: 7.5x more tokens for the same feature, with the same final verification on both sides. That's the receipt. This article is about what produced it. The short version is that code has a new primary reader, and the new reader works with a completely different set of tools, a completely different memory model, and a completely different way of recognizing patterns. The patterns we adopted over twenty years answered the old reader's needs. The cost in the new reader's mode of reading wasn't on anyone's chart, because there was no reader to charge it to. There is now. II. How a human reads code For a moment, ignore the agent.…