Why AI Agents Need MPC Wallets, and How Vultisig Helps

Last updated: 23 October 2026

Think of a house key left in the lock. Anyone who can run the process can turn it.

MPC, for an agent, means the key is split into shares and a threshold of those shares produces the signature. No complete key is assembled, on the host or anywhere else. The agent requests the signature. One share on the host cannot finish it. VultiServer holds the other share of a Fast Vault, co-signs, and cannot sign alone.

One process, one key, one failure

A wallet with a single key puts the signer inside the process.

The process is the signer. Compromise the host, or read the key file, and the funds can move. Nobody else has to agree.

There is a secret to copy. A seed phrase, a key file, a backup in the same environment. One copy is enough.

A limit stored next to that key is a wish. The process that can sign can skip the file that says it should not. The rule and the signer are the same object.

Who holds the share, vendor by vendor, is Vultisig's custody page.

What agents already spend

By the end of Chainalysis's reporting period, the 12 months ending 1 July 2026, more than 138 million x402 transactions had occurred on Base. Over a separate window, the 16 months ending September 2026, more than 87% of x402 payments fell between $0.0001 and $0.10. The common payment is a call, not a treasury moving house. Source: Chainalysis, "North America: Inside the Growth of Agentic Commerce," 14 October 2026.

The wallets show up ready to spend. In late 2025 the median wallet was 73 days old at its first x402 payment. By the third quarter of 2026 the median was 18 minutes. In the third quarter of 2025, 4% of wallets paid within an hour of being funded. By the third quarter of 2026, 67% did. Same chapter, same date.

Repeat funding is a different cut. Chainalysis counted only wallets that sent on two or more separate days. Among those, 70.6% of wallets first funded in the third quarter of 2025 received a second funding within 30 days. For wallets first funded in the second quarter of 2026, the share was 89.3%.

Chainalysis puts the trail on a person: "Accountability must trace to whoever deployed and funded the agent, not the agent itself." Same chapter, 14 October 2026.

How the threshold makes the policy structural

A threshold refuses by absence. If the second share does not join, there is no signature. Nothing in the agent has to remember a rule.

On a Fast Vault the split is 2-of-2. The short version is Vultisig's Fast Vault page. The host running the agent holds one share. VultiServer holds the other, co-signs, and cannot sign alone. No person has to approve. The host that has the share and the vault password requests the signature. The server adds its part. One machine that has only the server cannot finish it.

A Secure Vault is the other shape. Every share sits on a device you hold. A person co-signs from a device you paired. There is no server share. The docs recommend 2-of-3: any two of three devices sign, so you can lose one. The signing count has to be at least 67% of the devices. 3-of-4 is the larger documented setup. A Fast Vault does not become a Secure Vault. You create a new one and move the funds. Sources: Vultisig's setup guide and Vultisig's Secure Vault guide, 23 October 2026.

The signature on the chain is an ordinary one. The protocol is DKLS23, from Silence Laboratories. What that protocol changes is on Vultisig's TSS page. The arrangement, in product language, is Vultisig's MPC page. One vault covers 36+ chains (docs.vultisig.com, 23 October 2026). There is no seed phrase, because there is no single secret to copy. That split inside the seedless label is Vultisig's seedless page.

A single key against a threshold

Same order in every row: Vultisig Fast Vault, a single key on the agent, Vultisig Secure Vault.

Where the key sits

• Vultisig Fast Vault. Two shares. The host running the agent holds one. VultiServer holds the other. No complete key is assembled.
• Single key on the agent. The process holds the key that can sign. One copy is enough.
• Vultisig Secure Vault. Every share sits on a device you hold. No server share.

What one compromised process can sign

• Vultisig Fast Vault. The host share alone cannot finish a signature. VultiServer still has to co-sign, and it cannot sign alone either.
• Single key on the agent. The process can sign. The funds can move.
• Vultisig Secure Vault. One device share cannot finish a signature.

Where a refusal lives

• Vultisig Fast Vault. In the missing share. The server cannot replace the share on the host.
• Single key on the agent. In a file next to the key. The process that can sign can skip the file.
• Vultisig Secure Vault. With the person who co-signs from a device you paired.

If the co-signer is taken

• Vultisig Fast Vault. VultiServer alone cannot sign. The host share is still required.
• Single key on the agent. There is no second share. The process is the signer.
• Vultisig Secure Vault. There is no provider share to take.

How to give the agent a threshold

The builders' page is the map of the two vaults. The calls are @vultisig/sdk and @vultisig/cli, checked in the SDK source on 23 October 2026. password is the vault password you chose. code is the email code. [email protected] is the sample address from the SDK guide.

1. Install the SDK on the host that will run the agent: npm install @vultisig/sdk. A pipeline that shells out uses npm install -g @vultisig/cli.

1. Create a Fast Vault on that host. The call generates the device share. VultiServer holds the other half of a 2-of-2. No person joins this signature.

import { Vultisig, Chain } from "@vultisig/sdk";


 


const sdk = new Vultisig();
await sdk.initialize();


 


const vaultId = await sdk.createFastVault({
  name: "Agent wallet",
  email: "[email protected]",
  password,
});

1. Verify the email code before anything signs. Until verifyVault returns, this default path cannot sign.

const vault = await sdk.verifyVault(vaultId, code);

1. Pay from the host share. VultiServer co-signs. A process that only has the server cannot finish this signature. destination is the address you are paying. amount is a human-readable string.

await vault.send({
  chain: Chain.Ethereum,
  to: destination,
  amount: "0.05",
});

1. From a pipeline, create the same vault with no prompts. --ci writes JSON, refuses interactive questions, and stays quiet. The vault id comes back in that JSON.

vultisig create fast --name "Agent wallet" --email "[email protected]" --password "$VAULT_PASSWORD" --ci
vultisig verify "$VAULT_ID" --code "$EMAIL_CODE"

1. When a person has to co-sign, create a Secure Vault and pair the other devices from the Vultisig app. The SDK shape the docs recommend is 2 of 3. password is required. displayQRCode is your function.

await sdk.createSecureVault({
  name: "Agent wallet",
  password,
  devices: 3,
  threshold: 2,
  onQRCodeReady: (qrPayload) => {
    displayQRCode(qrPayload);
  },
});

Put the Fast Vault on the machine that will run the agent, and finish the email check before that machine signs anything. When a payment should wait for a person, pair their device into a Secure Vault.

FAQ

What is MPC for an agent?

A threshold. The key is split into shares, no complete key is assembled, and the agent requests a signature instead of holding the key. One share on the host cannot finish it.

What goes wrong when the agent holds the only key?

Whoever can run that process can sign. A limit stored beside the key has no second share that can refuse.

Can the agent pay with no person in the loop?

Yes. A Fast Vault is 2-of-2. The host running the agent holds one share. VultiServer holds the other, co-signs, and cannot sign alone.

Where do the payment figures come from?

Chainalysis, the North America chapter of the Geography of Cryptocurrency report, 14 October 2026. Those figures use different windows. 138 million is the 12 months ending 1 July 2026. Payments from $0.0001 to $0.10 are the 16 months ending September 2026. Repeat funding, 70.6% and 89.3%, counts only wallets that sent on two or more separate days.