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This quickstart takes you from installation to a working request through SELAT Router. The SDK supports private keys, Circle Agent Wallets, Circle Developer-Controlled Wallets, and remote signers. This quickstart uses the recommended Circle Agent Wallet, so private keys stay entirely outside the SDK environment. For the other signers, see Signers.

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Prerequisites

Before you begin, you must have:
  • Node.js 18 or newer
  • The Circle CLI installed and authenticated, with a Circle Agent Wallet. Set both up with Circle’s Agent Wallet quickstart
  • A Circle Gateway balance for that wallet. The SDK pays from Gateway, not from USDC sitting in the wallet. See the funding step below
  • A target endpoint that is reachable through SELAT

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Get started

1

Install

Install the SDK and the Circle CLI in the same app. The Agent Wallet signer then resolves the CLI without relying on a global circle binary.
2

Fund your Gateway balance

Move USDC from your Agent Wallet into Circle Gateway with the Circle CLI:
A direct deposit lands on the same chain it comes from. Check where your balance sits:
The Circle CLI spells chains in uppercase (ARC, BASE). The SDK uses lowercase (arc, base).
3

Set your wallet address and chain

Export your Agent Wallet address and the chain that holds its Gateway balance:
4

Send a paid request

Create the signer and client, then call fetch against your target endpoint. Pass the same chain to both.
The Agent Wallet signer runs the local Circle CLI, which doesn’t exist in serverless functions such as Vercel or AWS Lambda. For serverless deployments, use the HTTP remote signer.