Mandate lets you give an AI agent a budget instead of your keys. You fund a mandate with a spending cap, an expiry and an optional merchant allowlist. Every payment the agent proposes waits in a veto window on Arbitrum, and until it closes you can reverse it with one transaction.
AI agents are starting to shop, book travel, buy compute and pay for software. The payment options they have today are all bad:
A hot wallet is all or nothing. One prompt injection or leaked key drains everything in it.
Approving every purchase kills autonomy. At that point the human is the agent and the agent is a typist.
On-chain payments are final. Cards have chargebacks. Stablecoins do not. Nobody has built the missing grace period for software that spends on your behalf.
Mandate is a non-custodial payment vault on Arbitrum. An owner funds a mandate for one agent with hard limits: a total budget, a per-purchase cap, an expiry, a veto window and, optionally, an allowlist of merchants. The agent never holds the money. It can only call spend, which the contract validates, reserves funds for and places in a veto window.
Inside the window the owner can veto the payment (funds return to the mandate), approve it early, rotate a leaked agent key, or revoke the mandate and get the free balance refunded. If the owner does nothing, anyone can settle the payment once the window closes, so merchants never depend on the owner being online. The interface also flags payments that deserve a second look: first-time merchants, amounts near the cap, bursts of activity and merchants vetoed before.
The worst case for a compromised agent is bounded by the budget, the cap and a single window.
Every wallet, agent framework and operator putting money in an agent's hands has the same question: how much can I trust this thing? Mandate answers it with a number, a window and an undo button. It is a new financial primitive for agentic commerce: reversible, bounded, auditable spending authority.
The design only works if a payment, a veto and a settlement each cost a fraction of a cent, and if budgets are held in stablecoins an agent can actually spend. Arbitrum's low fees, EVM tooling and stablecoin ecosystem (including USDG) make that practical.
Limits live on-chain, not in a system prompt. A prompt is a suggestion; a contract is a rule.
It is the only model here where a payment can be undone before it settles, without giving anyone custody.
Settlement is permissionless and every payment carries a memo with the agent's stated reason, giving a built-in audit trail.
No admin keys and no upgrade path on the vault.
Built from scratch during the Buildathon and shipped end to end: Smart contracts. MandateVault.sol: mandates, escrow, per-purchase cap, expiry, merchant allowlists, veto windows, early approval, permissionless settlement, key rotation, revoke with refunds, top-ups, on-chain memos and merchant reputation counters. MockUSDG.sol: a testnet stablecoin with a faucet. Test suite. 13 passing tests covering escrow, parameter validation, window enforcement, veto, approval, cap and budget accounting with funds in flight, allowlists, expiry, revoke semantics, key rotation, top-ups and indexing. Deployed to Arbitrum Sepolia. Vault and test token are live and verifiable on Arbiscan (addresses above). Web application. Landing page with a live interactive feed, a full dashboard, and two modes: an in-browser simulation of the vault with agents spending in real time, and a live on-chain mode that connects a wallet to the deployed contract (create mandates, act as the agent, veto, approve, top up, rotate keys, revoke). Production deployment. Hosted at https://mandate-arbitrum.vercel.app with the contract addresses configured. Open source. MIT-licensed repository with documentation, security model and roadmap. Demo and pitch videos produced for the submission. Next up: merchant dashboard (incoming payments), policy modules (velocity limits, co-signers), session-key and smart-account support so agents need no gas, notifications for flagged payments, a third-party audit and an Arbitrum One deployment.
Mandate is pre-funding and bootstrapped. No outside capital has been raised. I am applying for Arbitrum grants and the Founder House program to fund a third-party audit, an Arbitrum One launch and the first design-partner integrations, and I am open to angel and pre-seed conversations after the Founder House pitch.
