One key per system, scoped, with a spend cap
A shared key turns one leak into several rotations and one outage into several. A master key turns a leaked key into a full account. A key with no spend cap turns a leaked key into a bill. Stripe's own guidance: use restricted keys "especially when giving a key to an AI agent."
Where it bit
The Gemini key in 01 was reused by a second internal tool. One leak, two systems to rotate, and the scrub in one system did nothing for the other. In the research: LLMjacking worst cases run over $100,000 a day; OpenAI removed hard spend caps in October 2025 and only restored them in July 2026.
The practice
Stripe restricted keys with an IP policy. One OpenAI project per app with a hard limit. GitHub fine-grained tokens with an expiry. Anthropic spend limits under Billing. Vercel Spend Management set to pause, and set below your real maximum because it checks every few minutes, not continuously.
Check it
Open each provider's key list. Any key used from two places is a shared key. Any key with no "restricted" or "project" scope is a master key.
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What to do with this
If you run a business on something AI built and the checks came back with more than you expected, that is worth a conversation.
We do a free 30-minute Health Check for service businesses that want to know exactly where their biggest leaks are. No slide deck. No pitch. We ask questions, find the gaps, and tell you what we see. If there is no obvious fix, we will tell you that too.
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