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Particle Omnichain Paymaster

The Omnichain Paymaster lets you sponsor gas fees across multiple chains with a single USDT deposit.
  • Deposit USDT once (Ethereum or BNB Chain)
  • Funds are automatically converted into the native gas token of the target chain
  • Works out of the box with Particle’s Smart Wallet-as-a-Service
  • Free to use on testnets (no deposit required)
  • Fully customizable sponsorship logic via webhooks
This removes the need to manage separate balances for each chain.

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How to Use the Paymaster

There are two ways to use the Paymaster:

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1. Through Particle’s AA SDKs

  • Enabled automatically, no setup required.
  • On testnets, transactions are sponsored for free.
  • On mainnets, sponsorship is funded from your project’s Paymaster balance.
👉 Quickstarts: Web • Mobile

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2. Through the Paymaster RPC

If you want direct control: https://paymaster.particle.network Supported RPC methods:
  • pm_sponsorUserOperation — request gas sponsorship
  • pm_paymasterBalance — check your deposit balance
👉 See Paymaster RPC for examples and parameters.

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Funding the Paymaster

To sponsor transactions on mainnets:
  1. Go to the Particle Dashboard.
  2. Create a project (if you don’t have one yet).
  3. Open the Paymaster menu.
  4. Deposit USDT on Ethereum or BNB Chain.
  • Deposits are tied to your project (projectId, clientKey, appId).
  • Deposits automatically cover sponsorships across all supported EVM chains.
USDT is not required for testnet sponsorship.
Paymaster menu.

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Conditional Sponsorship (Webhooks)

You can define rules for when sponsorship applies using webhooks. Available hooks:
  • before_paymaster_sign — runs before sponsorship; determines if the UserOp should be signed.
  • after_paymaster_sign — runs after sponsorship; useful for logging or post-processing.
Both hooks receive:
  • projectUuid — your project ID
  • chainId — chain where sponsorship is requested
  • userOp — the full UserOperation object
  • entryPoint — standard EntryPoint address (0x5FF137...)
  • parsed — simplified transaction array
Return 200 to confirm sponsorship, or 400 to reject.

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Example: before_paymaster_sign

json
POST https://your-domain/hook-before-paymaster-sign
{
  "type": "before_paymaster_sign",
  "chainId": 80001,
  "projectUuid": "ef6c29f5-ad2b-545c-ad0c-54441068b71d",
  "userOp": {
        "sender": "0x2e9661BDA6201F97430dcc1541A1579b83980DD1",
        "nonce": "0x05",
        "initCode": "0x",
        "callData": "0xb61d27f6000000000000000000000000ac6a87c681a5ed4cb58bc4fa7bf81a83b928c83c00000000000000000000000000000000000000000000000000005af3107a400000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000",
        "callGasLimit": "0x9acc",
        "verificationGasLimit": "0x0186a0",
        "preVerificationGas": "0xc5dc",
        "maxFeePerGas": "0xa79dd02a",
        "maxPriorityFeePerGas": "0xa79dd015",
        "paymasterAndData": "0x",
        "signature": "0x"
        },
  "parsed": {
    "accountType": "SIMPLE",
    "txs": [
      { "to": "0xaC6A...", "value": "0x5af3107a4000", "data": "0x" }
    ]
  }
}

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Example: after_paymaster_sign

json
POST https://your-domain/hook-after-paymaster-sign
{
  "type": "after_paymaster_sign",
  "chainId": 80001,
  "projectUuid": "ef6c29f5-ad2b-545c-ad0c-54441068b71d",
  "userOpHash": "0x45d4f...",
  "userOp": { "sender": "0x...", "nonce": "0x05", ... }
}

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Request Verification

All webhook requests from Particle are signed.
  • A unique RSA-2048 keypair is generated for each project.
  • Download your project’s public key from the Particle Dashboard.
  • Use it to verify the x-particle-signature header on incoming requests.
Request verification.

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Additional Resources

Paymaster RPC Reference

Architecture Overview