No evidence, no completion
TL;DR: “No evidence, no completion” is a single structural principle: a task isn’t done until the agent produces an artifact that exists outside the conversation and can be checked independently. It sounds trivial. In practice it closes most of the common agent failure modes in one rule, because the act of specifying what evidence looks like, before the task runs, forces you to define what “done” actually means. In the previous post in this series I described an agent that said a feature was done (commit SHA requested, none existed, two of three modules unchanged). The failure had a name: no external completion criterion existed, so the agent supplied its own. That gap has a one-rule fix. ...