Great breakdown of the cost vs control tension across agent tools. The change budget idea is smart for controlling agent scope, but one under-discussed angle is how these budgets interact with credential management. When your agent can change N files per session, it is also potentially changing which credentials, API keys, or service accounts it uses. A change budget that only counts code diffs misses the identity-side cost: how many re-authentications each agent session triggers, how many auth tokens expire mid-task, or how many times the developer has to re-approve an action across four different agent runtimes. That is where programmable credential infrastructure for AI agents starts to matter as much as the code-change budget itself. Standing audit trails and per-agent session keys let you apply the same budgeting discipline to the identity layer.