ERC-4337 smart accounts, bundler, and paymaster infrastructure. Nexus is Biconomy's ERC-7579 modular smart account, giving you gas sponsorship, batched transactions, and pluggable validators on EVM chains.
- 01ERC-4337 smart accounts
- 02gasless transactions
- 03ERC-20 gas payments
- 04batched user operations
- 05modular ERC-7579 accounts
- pnpm add @biconomy/sdk viem
| Variable | Scope | Description |
|---|---|---|
| NEXT_PUBLIC_BICONOMY_BUNDLER_URL | Client | Biconomy bundler URL for the target chain (from the Biconomy dashboard). |
| BICONOMY_PAYMASTER_API_KEY | Server | Biconomy paymaster API key used to sponsor user operations. |
Use Biconomy for ERC-4337 smart accounts and gas sponsorship. Install `@biconomy/sdk` and create a Nexus smart account client with `createSmartAccountClient({ signer, chain, bundlerUrl, paymaster })`. Sponsor gas via the Biconomy paymaster client (`createBicoPaymasterClient({ paymasterUrl })`) and submit batched calls with `smartAccount.sendTransaction({ calls: [...] })`. Wait for inclusion via `waitForUserOperationReceipt` before treating the operation as final. Keep paymaster API keys server-side and proxy sponsorship requests through your backend.
- ⚑Nexus uses EntryPoint v0.7 — make sure your bundler, paymaster, and account factory all target the same EntryPoint version, otherwise userOps will revert.
- ⚑EVM-only: no Solana / non-EVM support. For multi-chain auth pair Biconomy with Privy, Dynamic, or Web3Auth.
- ⚑Paymaster sponsorship policies (allowlists, spending caps, contract method filters) are enforced server-side — a transaction that simulates fine in dev can fail in production if the policy rejects it.
- ⚑Smart account addresses are counterfactual until the first userOp deploys them; don't assume contract code exists when sending tokens to a fresh smart account.
- ⚑Legacy `@biconomy/account` v2 SDK still works but is in maintenance — new projects should use `@biconomy/sdk` (Nexus) for ERC-7579 module support.