Wallet Fence: hard spend limits for agents that hold crypto keys

Almost every piece of the core co-signer is already shipping. That includes allowlisted payees, per-call and daily caps, and blocking before signing. The big wallet platforms build it in for free: Coinbase CDP, Privy and Turnkey (including its consensus co-approval). PolicyLayer already sells it as a standalone layer that doesn't hold your keys and wraps any wallet, with x402 support. There are also several open-source versions. So a startup choosing a wallet provider today gets most of this at no extra cost. A new entrant probably can't win on policy enforcement alone. There are narrower openings, though. The first is a provider-neutral co-signer for teams that run agents across several key stacks: their own MPC, Safe multisigs, Coinbase, Privy, and different chains. Those teams would want one policy and one audit log instead of one setup per provider. The second is the audit side: logging the agent's stated reason and comparing it with its assigned task, which can flag a prompt-injected transfer even when it fits within the caps. Turning those logs into compliance-ready records for finance and risk teams is part of the same opening. The third is trading-specific rules that the generic engines don't handle well, such as slippage, position size and limits on which contracts the agent can call. Each of these is a feature the incumbents could add quickly. A newcomer would need to win on being neutral across providers and on depth of auditing, not on the basic fence.

• Coinbase CDP Agentic Wallets / AgentKit

  Launched February 2026. The CDP docs say wallet owners set per-call and per-session spend caps that agents can't change, and agents can only pay x402 services. Third-party summaries say the policy engine enforces the limits before the enclave signs. A competing vendor says it lacks recipient allowlisting and per-endpoint limits.

• Privy agent wallets (Stripe)

  Key-level policy engine with per-transaction and time-window transfer caps, recipient and contract allowlists, network limits, calldata rules, and scoped signers that can be revoked. This covers nearly all of the proposed policy set.

• Turnkey agentic wallets

  Policies run inside the enclave and can restrict by recipient, contract, function selector, chain and value. It also documents consensus policies where the agent and a risk service must both approve larger trades, which is effectively a policy co-signer.

• PolicyLayer

  Closest direct match. It's a non-custodial policy layer that wraps an existing wallet and checks each transaction before signing, with daily and per-transaction caps, recipient allowlists, x402 per-endpoint limits, duplicate-payment detection, and an MCP proxy with a kill switch.

• MetaMask Agent Wallet

  2026 consumer launch with spending caps, allowlists, transaction simulation, threat scanning and 2FA approvals for agent trading.

• imprest

  Open-source Ethereum agent wallet policy engine: per-transaction caps, hourly and daily budgets, allow and deny lists, rate limits and approval thresholds, on a separately funded wallet.

• Agentic Wallet (open source, Solana)

  Open-source policy engine that checks agent intents against spend limits, address allowlists and protocol restrictions. A separate signer holds the keys, so the agent never touches them.

• XRPL wallet MCP server

  MCP wallet with tiered policy. Large payments or new destinations need a co-signature, some get a delay with veto, and blocklisted destinations are rejected.

• Fystack

  Wallet infrastructure vendor marketing spend limits, velocity caps, allowlists, approval workflows and policy-engine enforcement for agents on payment rails.

• Rain Agent Control Layer

  Reported June 2026 launch. It blocks non-compliant agent card and money-movement attempts when they're issued or started, rather than after settlement. It sits on adjacent card and fiat rails.

Checked 2026-10-16