A leaked key should hit a fence, not your whole account.
No major AI provider caps spend per API key — caps live at the project, workspace or billing-account level, if they exist at all. So SPEND/FENCE designs the structure that actually holds: one container per tool, one enforced cap per container, alerts before the wall — and a budget-gate proxy that hard-stops a fence at its cap.
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OpenAI, Anthropic and Google offer no per-API-key spend cap. A copied key spends against the whole container it lives in.
THE CONTAINER IS THE FENCE
Isolate each tool into its own project / workspace / billing scope, cap the container, and one leak = one capped fence.
HARD STOP > ALERT
Billing alerts email you after the money is gone. The SPEND/FENCE proxy returns 429 at the cap — before the charge.
1 · Design your fences
Free: 1 provider, up to 2 fences. Pro: every provider, unlimited fences, exports and the proxy Worker.
3 · Budget-gate proxy (Pro)
Native caps are soft or missing on some providers — the proxy is the hard stop. It meters each fence from provider usage fields and returns 429 at the cap. Your real provider keys live as Worker secrets, never in the generated code. Streaming calls pass through unmetered in v1 — disable streaming in fenced tools or treat those fences as alert-only.
Pro feature. Get Pro below to generate your proxy.
Pro — $19 one-time
Every provider, unlimited fences, Markdown/JSON plan exports, and the budget-gate proxy Worker generated from your plan. One payment, yours forever.
No keys, no setup: when checkout completes, Stripe brings you straight back here with Pro unlocked on this device. Bookmark the page you land on to unlock another device.