Install

A gate, a paywall or both in front of your API, MCP server or WordPress site. No OAuth, no sign-up, no account with us. Agents get in with a key. Install the plugin; connect your payout wallet.

• Gate: admits the keys you list. Each call is signed with the agent's key as a zero-value x402 payment: nothing is paid, the key needs no funds or ETH, nothing goes on chain. A listed key can sign a grant that admits one other key, for one tool or all, until a set time.
• Paywall: agents pay per call in USDC, from a wallet or a pass. You keep 90.01% of every sale. A failed call is not charged; on a line, a call uses the time it runs.
• Both: listed keys, paid per call.

The engine runs in your process with your keys. ZEAM holds none of your money or keys and makes no admission decisions.

• Gas. An agent needs no ETH to pay on the USDC row without Permit2, and you, the seller, need none to be paid. ZEAM's relay sends what your Bridge signed, to where it signed it (claims, payouts and refunds for your channels), and agents' deposits and MPP charges, which the agent signed. It pays the gas of every deposit it sends; of a claim or payout when ZEAM's 9.99% fee on it covers that gas; and of an MPP charge on the same rule (a charge whose fee does not cover it is not sent: the call is not delivered and nothing is charged). A refund has its own rule, under Refunds.
• Deposits. An agent's first call on a channel deposits at least the deposit floor: your price per call, or the gas floor where that is higher (about $0.036 at a gas price of 0.0084 gwei and ETH at $2,370; it tracks gas, and your 402 states the live figure); later calls spend it, and a later top-up meets the same floor.
• Refunds. The unspent balance goes back to the agent through the relay. ZEAM pays the gas when the channel's fees cover the gas of its deposit, its refund and any calls not yet settled, and of every further deposit and every earlier refund ZEAM paid for on that channel, plus 15%; otherwise the agent pays the quoted gas in USDC (15% margin, priced by the relay, public at https://api.zeampass.com/relay/quote). Nothing is claimed for you from it. selfSend: the agent gets a signed refund of the full balance and sends it from any wallet with ETH on Base for gas. Without you: the agent sends initiateWithdraw, then finalizeWithdraw after the withdrawal delay, each from the channel's payer wallet with ETH on Base for gas, for at most the channel's balance minus totalClaimed in the escrow. Detail: Agents guide, section 5. When a buyer paid with a pass and you refuse its refund, the pass service hands that buyer's funding wallet the same escrow withdrawal to broadcast itself; the pass service does not send it or pay its gas.
• MPP clients. For a tool priced per call, your 402 also carries an MPP Payment challenge (the WWW-Authenticate: Payment header) when ZEAM's fee on that one call (9.99% of it; all of it when your payout is the fee address) covers the gas of one USDC transfer plus 15%; an MPP client pays that call with one USDC transfer to your split. Nothing to set up. Below that price your 402 offers x402 only (and, on Node, a session where you have turned sessions on: MPP sessions, below), and so does every tool priced by use and every purchase of line time. A time tool called without a line is a tool priced per call here, at its callUSD.
• Stock x402 clients. Stock x402 clients deposit 5x your price. They work when your price is at least 1/5 of the deposit floor in your 402 deposit line. Example: floor $0.036, price $0.0072 and up. Line time follows the same rule: on a new channel a stock client's first purchase must cost at least 1/5 of the floor, so it buys that many milliseconds or more; a pass and ZEAM :: Pass deposit enough for a small purchase. Use ZEAM :: Pass 4.0.0 or later: earlier versions, formerly @zeam-labs/x402-mcp-bridge, read X402_… settings.

Node only, for now: the Python and WordPress plugins offer no session. Off until you turn it on: sessions: { escrow: '0x5e09aD70b644414cD1cD7Df1d9a10fF7899D92B8', factory: '0xE18fCE1266056becA4a3B0edfc15F8634EA6901B' } in your Bridge's options, in mode paywall or both. Those are the EvmPaymentChannel escrow on Base and its payee factory, both deployed on 2026-10-13 and immutable.

The session contracts are not audited. Nobody outside their authors has reviewed them. A buyer's deposit sits in the escrow, and what a session earns you passes through your payee contract, below.

• What a buyer sees. Your 402 for every tool priced per call carries a second MPP Payment challenge, intent="session" (draft-evm-session-00), at the same price as every other way to pay, whether or not it carries a charge. A tool priced by use and a purchase of line time get none.
• How a buyer pays. One deposit into the escrow, which the relay sends from the buyer's signed authorization (for a pass, the pass service sends it), then one signed voucher per call. A call that fails is not charged.
• Your payee. A session pays your SessionPayee contract, at the factory's addressOf(your settle key's address, your split). It signs for your split, which cannot sign, and forwards all it receives to it; your split and its 90.01% and 9.99% are as they were. Your 402 publishes the split, its salt and the settle key's address beside the challenge so a buyer can check the payee. The relay creates the payee with your first session payout.
• Settlement. Each background run claims session channels that have been idle 20 seconds, once ZEAM's fee on what it claims covers the gas. The payout that follows sweeps the payee to your split, distributes the split and withdraws to your wallet, by the rule under Payouts below break-even. You need no ETH.
• A buyer leaves. On a buyer's close you are paid what it spent and the rest of its deposit returns to it in the same transaction; the relay sends that free when the channel's fees cover the gas of its open, of every top-up and close request the relay sent for it, and of its close, and otherwise takes the gas in USDC from what returns to the buyer, who needs no ETH. A buyer can also leave without you: it asks the escrow to close and withdraws after 15 minutes, and a background run in that time claims what it spent without waiting for the channel to be idle. A buyer you have taken off your access list can still close.

What a buyer signs and checks: Agents guide, section 7.

• What an agent sends. A zero-value x402 exact payment signed with its key, on every call (any x402 client makes one). It moves nothing and is never sent to the chain. Your Bridge verifies the signature in your process, refuses a replay, and admits the key if its address is on your list. Agent side: Agents guide, section 3.

• Grants. A listed key can admit one other key: it signs a grant naming that key, one tool (or *) and an end time; the agent sends the grant as the x-grant header. A call signed by any other key is refused bad_grant. Remove the signing key from your list and every grant it signed ends. On a line the list is checked when the channel pays, at its deposit and at each purchase of time, not on each call that rides the line: a key you remove can use up time it already bought and can buy no more.

  Node:

  import { signGrant } from '@zeambridge/bridge'
  
  const grant = await signGrant({ key: process.env.ADMITTED_KEY, delegate: '0xTheirKeyAddress', scope: 'search', until: '2026-12-31T00:00:00Z' })

  Python:

  import os
  from zeam_bridge import sign_grant
  
  grant = sign_grant(os.environ["ADMITTED_KEY"], "0xTheirKeyAddress", "2026-12-31T00:00:00Z", scope="search")

  key: the private key of a listed address. scope: a tool's name, or * (the default) for every tool. until: an ISO time, a Date or a timezone-aware datetime. Both return the x-grant value for the agent. WordPress: the Grants box on the settings page signs with your browser wallet when it holds a listed key.

  The grant is base64url JSON {delegate, scope, until, signature}; signature is the admitted key's EIP-191 signature of:

  ZEAM Pass grant
  delegate: <the key's address, lowercase>
  scope: <tool, lowercase, or *>
  until: <ISO time>

  A grant made by hand with no scope is signed with the line scope: self; it covers every tool, as * does.

• Price.

  • 10,000 checks a month are free.
  • Your Bridge makes a credit wallet the first time it runs in gate or both mode; status() (WordPress: the settings page, in gate mode) shows its address. It holds the gate's USDC on Base and needs no ETH. Node: keys: { credit } sets your own.
  • Credit is 2,000 checks at a time for $1 USDC ($0.50 per 1,000), bought after the month's 10,000 free checks are used and again below 200 remaining. Keep $1 USDC on Base in the credit wallet.
  • Credit at 0: refuse (default), or with "onEmpty": "allow", admit and warn.

• Both mode: paid calls are not gate checks. both mode needs no USDC in the credit wallet.

status() (WordPress: the settings page) answers:

• unclaimed: microUSD paid to you and not yet claimed from the escrow, over channels channels.
• claimedNotPaid: microUSD claimed and not yet paid to your wallet. splitDeployed is false until your first payout creates your split.
• lastPayout: when, how much, which transactions. lastTick: the last background run.
• gate: this month's used checks, the free allowance, credit left, onEmpty, and unpaidAt when calls were admitted with no credit.
• creditWallet: its address and usdcMicro balance.
• chainError: the chain read for the figures above failed.

Payouts below break-even. The relay pays out when ZEAM's 9.99% of the payout covers its gas; you keep 90.01%. The gas is priced live: your Bridge asks the relay, which estimates the payout transaction itself at the current gas price, adds Base's L1 fee and 15%. Only when the relay cannot be asked does your Bridge fall back to its own fixed estimate. A payout (claim, settle, distribute, withdraw) goes out as one Multicall3 transaction in that order, all or nothing. Below break-even, unclaimed or claimedNotPaid stays above 0, lastTick.claims.USDC.waiting reads "below break-even: waits until the fee share covers the gas", and payout() (Python: payout_now()) answers paidBy: "you" with valueUSD, gasUSD and a transaction to send from your own wallet, the seller's, which then needs ETH on Base for gas. Nothing else a seller does needs ETH.

• The ZEAM :: Bridge relay: sends to Base the transactions your Bridge signed (claims, payouts and refunds for your channels) and agents' deposits and MPP charges. It pays the gas of every deposit it sends, and of a claim, payout, refund or MPP charge by the rules under Money.
• The ZEAM :: Bridge credit service: sells gate checks.

Neither holds anything of yours.