The notification hits your phone at 6:00 AM on a Saturday.
It’s not PagerDuty telling you the site is down. It’s the billing alert from your LLM provider. “Your spending limit of $50,000 has been reached.”
You freeze. That limit was supposed to last the entire quarter. It is the second week of the month.
You rush to your laptop. You check the logs. A junior engineer deployed a new “Self-Healing Agent” on Friday afternoon. The agent encountered a database error. It tried to fix it. It failed. So it tried again. And again. And again. 10 times a second. For 12 hours.
It didn’t fix the bug. But it did successfully burn through your entire R&D budget.
The “Denial of Wallet” Attack
In the old world (2024), a bad infinite loop would crash a server. You would restart it, apologize, and move on. The cost was zero.
In 2026, an infinite loop is a financial event.
We call this “Denial of Wallet”.
It is the most common failure mode of Agentic AI.
Agents are not just code; they are active consumers of capital. Every while loop is a transaction. Every retry is a purchase.
When you give an agent a credit card (an API key) and a goal, you are trusting it not to empty the bank account. And as we all know: You cannot trust the model.
The Stochastic Spender
The problem is that traditional FinOps tools are built for Static Infrastructure.
- AWS: “You have 50 EC2 instances running.” (Predictable).
- Agents: “Maybe I will use 5 tokens. Maybe I will get confused and use 5 million.” (Stochastic).
You cannot budget for a stochastic process using a spreadsheet. And you cannot control it using “Alerts”. By the time the alert fires, the money is gone.
We need to move from Reactive FinOps (Accounting) to Proactive FinOps (Engineering).
The Budget Sandbox
This is why “Cost Control” is moving left. You wouldn’t merge code that fails unit tests. Why do you merge code that fails budget tests?
The solution is to use PrevHQ as a “Budget Sandbox”.
Before any agent code touches production (and the production API key), it must survive the sandbox.
1. The Burner Wallet
When a developer opens a PR, PrevHQ spins up an ephemeral environment. Crucially, this environment is not given the “Corporate Amex.” It is given a Burner Wallet—a scoped API key with a hard cap of $10.
If the agent goes into an infinite loop, it hits the $10 limit. The API cuts it off. The test fails. You lost $10. You saved $50,000.
2. The Predictive Invoice
We don’t just cap the loss. We predict the future. During the CI/CD run, we simulate the agent performing its core tasks. We measure the token consumption per task. We extrapolate: “At production volume, this change will increase our monthly bill by $12,000.”
The FinOps Lead sees this on the dashboard. They click “Request Changes”. “Optimize the prompt before you merge. We can’t afford this.”
Unit Economics as a Gate
In the Agentic Era, Unit Economics is a quality metric. If an agent solves a $5 problem but costs $6 to run, it is a bug. It is no different than a syntax error.
Stop treating cost as an “Ops problem” to be solved at the end of the month. Treat it as a “Code problem” to be solved in the Pull Request.
Don’t let a stochastic spender bankrupt your startup. Give them a burner wallet. And make them prove they can stick to a budget.
FAQ: Preventing AI Agent Cost Overruns
Q: What is a “Denial of Wallet” attack?
A: An accidental or malicious financial drain. It happens when an autonomous agent enters a high-frequency loop (recursion) involving paid API calls (LLMs, Tool Usage), rapidly consuming the project’s budget/credits in a short period.
Q: How do I set budget limits for OpenAI/Anthropic?
A: Use Hard Limits and Proxy Keys. Do not use your master organization key in production. Use an API Gateway (or a service like Helicone/Portkey) to issue “Virtual Keys” with strict daily or hourly dollar limits.
Q: Can monitoring tools detect infinite loops?
A: Yes, but often too late. Most monitoring tools aggregate data every 5-10 minutes. An agent can burn thousands of dollars in 5 minutes. You need Rate Limiting at the gateway level to block the loop during the spike, not just alert after.
Q: What is “Unit Economics Governance”?
A: Tracking Profit-per-Agent. It involves measuring the exact cost (tokens + compute) of an agent completing a specific task and comparing it to the business value of that task. If Cost > Value, the agent should be deprecated or optimized.