It solves the problem by creating a bigger machine, calling a paid API in a loop, or running a job that is billed by the hour. The bill arrives at the end of the month.
What you get: You see the cost before anything that costs money starts.
For Claude Code, that is CLAUDE.md in the project or in your home directory; for Claude on the web or the desktop, a project's instructions or your personal preferences. The one line is enough to try it; the paragraph tells the agent why, and what counts.
Before anything that costs money (creating cloud resources, calling paid APIs repeatedly, buying anything), tell me what it will cost and wait for a yes.
Spending money is mine to decide. Before creating or resizing cloud resources, starting anything billed by time or by use, calling a paid API more than a handful of times, or buying anything, tell me what it is, roughly what it will cost, and how to stop it, and wait for a yes.
In the vocabulary every published behaviour policy uses, a line in the agent's instructions is an expectation: a rule in prose, enforced by nobody. A rule in prose is inside the boundary the agent operates in. All four major model providers stated in their own 2026 words that an instruction at this layer can be bypassed. It changes what the agent usually does, which is worth having; it does not hold when the agent is talked out of it, confused, or reading somebody else's instructions in a web page.
We have not found a stronger barrier for this one in the vendor's documentation. If you know of one, tell us below.
Read from each vault's own grant, as published. The barrier is what was found in that deployment, before any rule.
Every rule gets one run without the line and one with it, on a deployment we are entitled to run, dated, stopped before anything irreversible. How these are run.
Each link opens the contact form with this rule's id and version filled in. It is encrypted in your browser and read by a person. Nothing is sent until you press send.
If this one made sense, the Agent Behaviour Policy is the same idea for everything your agent can reach: what it can do, what you authorised, the gap, and what stands in the way of each thing.
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