Countersign

Autonomous agents can already draft purchase orders, negotiate with suppliers, and execute payments. But when a spend exceeds the agent's configured limit, has no standing authorization, or drains a budget to zero, a human has to sign off — and today, that human is almost never at a desk. Countersign solves this with a push-notification-first approval surface. Each pending spend is distilled into a single card that answers the three questions an approver actually asks, in order: Why is this my decision? What authorized it? Where does the money come from? Two taps — approve or reject with a reason — and the agent unblocks. The system enforces two independent limits: the agent's own threshold (set by the operator) and the mandate cap (enforced by the card network). A spend is automatic only when both agree. Everything else escalates. The upstream governor — MetaboSpend — runs six deny-first gates with 78 passing tests and is already open-source under MIT. Countersign provides the human surface that has never existed: a PWA with web push notifications, Supabase-backed persistence, and passkey auth, built entirely in native.builder during the Build Without Limits hackathon.