Countersign – one kill switch and audit log for AI agents across wallet vendors

Four rails frozen in ~432ms — proven on testnet The kill switch for AI agents that spend money. Countersign is a neutral, cross-vendor control plane: one policy, one freeze, and one tamper-evident audit ledger — across every agent-wallet backend at once. The one thing no single wallet vendor can do, because each only governs its own rail. Get your key → $ npm i @countersign/sdk Read the whitepaper → ★ Star on GitHub 4 rails live — Coinbase · Turnkey · Openfort · Visa card 🛡️ Spending governed by Countersign Bring your other agents One line — any MCP client npx @countersign/mcp Same policy, same freeze, across your whole fleet. Onboarding a teammate? Send them app.countersign.network/start for an instant key. Why operators reach for it The questions a team asks before agents touch money. These are the recurring asks Countersign is built to answer — not customer quotes. It's testnet-only today; mainnet follows a third-party audit. “If an agent goes rogue at 2am, can I stop all of them — not just the ones on one wallet?” — the cross-vendor freeze, proven across four rails in ~432ms “Can I prove, after the fact, exactly what every agent tried to spend?” — the append-only, hash-chained, tamper-evident ledger “Can I write one spending policy instead of N vendor consoles?” — one unified policy compiled to each backend's native controls Integrations The networks your agents already use. Countersign governs them through one policy, one freeze, and one tamper-evident ledger — across every rail at once. No single vendor can do that, because each only governs its own. Ecosystem Rails + toolkit. Countersign governs the wallets & cards you already use — the rails — and ships the toolkit your agents build with. Rails — what Countersign governs MPC wallets · native per-tx cap pushed into CDP policy. LIVE In-enclave CEL policy · native human-approval consensus. LIVE Backend smart accounts · custody-level hard freeze. LIVE Virtual Visa card · real-time ASA approve/decline. LIVE Toolkit — what you build with MCP server npx @countersign/mcp — 13 tools: kill switch + spend guard in any MCP client. On the MCP Registry, Smithery, Glama. PUBLISHED SDK @countersign/sdk · @countersign/api-contract — typed client + live ledger. PUBLISHED Verify npx @countersign/verify — prove any ledger entry is committed, offline, trusting nothing. PUBLISHED x402 Govern the HTTP-402 machine-payment standard before it pays. LIVE AP2 + negotiation Guard an Agent Payments Protocol mandate — and the terms it commits — before the agent signs. LIVE Open core Front-door packages under Apache-2.0. Audit it yourself. APACHE-2.0 Roadmap Coming soon. Native-enforcement parity Close the remaining layer cells in the matrix — reversible on-chain KeysManager freeze, native consensus approvals, card ASA on every issuer — so each guarantee is backend-enforced end to end. SOON Multi-instance HA & KMS On-chain anchoring now ships — the live demo autonomously anchors its signed checkpoint roots to Base, so history is witnessed on a public chain, and offline proof verification is one command (@countersign/verify). Next: multi-instance & KMS-signed, so the freeze survives any single failure. ANCHORING LIVE Mainnet & more rails Real-value operation after an independent security audit — plus Stripe, Airwallex & more wallet and card networks graduating from built to live. SOON