Authentication & Keys

How HyperLink API keys work: agent wallets, EIP-712 signing, permissions, and how to create or revoke keys for programmatic Hyperliquid trading access.

HyperLink authenticates every request with an EIP-712 signature, not bearer tokens or API secrets. An API key is an approved agent wallet: a keypair your master account authorizes to sign trading actions and read queries on its behalf.

HyperLink is a prime broker for Hyperliquid. It mirrors Hyperliquid's agent model and EIP-712 signing, so existing Hyperliquid tooling works against the HyperLink base URL. For a working signed-request example, see API Quickstart.

How it works

The agent private key signs each request; the enclave verifies the agent is approved by your master account, then executes. There are no shared secrets.

Create an API key

In the web app

1. Connect your master wallet to the web app.

2. Go to Settings → API and click Generate.

3. Copy and securely store the private key. It is shown once and cannot be recovered.

With the approveAgent action

Generate the agent keypair locally, then approve its address with an approveAgent action signed by your master account (agents cannot approve other agents). The full schema is in Exchange Methods.

Limits and permissions

Limit	Value
Named agents per account	5
Unnamed agents per account	1
Agent name length	64 characters

Agents can place and cancel orders, update leverage and margin, and run read queries. Agents cannot withdraw funds, approve or revoke other agents, or run master-account transfer actions such as sendAsset and usdClassTransfer. Those require your master account's own user-signed signature. A readOnly agent can query but not trade.

Signing

Each request to /exchange (and each WebSocket subscription) carries an EIP-712 signature plus a millisecond nonce. There are two signing domains; an SDK selects the right one per action.

Scheme	EIP-712 domain	chainId	Used for	Signed by
Agent (L1 action)	Exchange	1337	Orders, cancels, margin, leverage, agent transfers, queries, subscriptions	Agent or master account
User-signed	HyperliquidSignTransaction	42161	withdraw, approveAgent, usdClassTransfer, sendAsset	Master account only

Both domains use version "1" and verifyingContract 0x0000000000000000000000000000000000000000.

These signing chainId values (1337, 42161) are Hyperliquid-compatible EIP-712 domain values, not the HyperEVM network chainId (999). Use the network chainId only for direct on-chain contract calls, such as staking.

Nonces: set nonce to the current Unix time in milliseconds. Each is single-use per signer; a nonce older than 2 days or more than 1 day in the future is rejected.

Sign with an SDK, not by hand. A bad signature recovers a different address and fails with an unhelpful "User or API Wallet … does not exist". The HyperLink Python SDK and Hyperliquid TypeScript SDK implement both schemes correctly, and the Hyperliquid signing reference applies unchanged.

Common causes of signing failures: wrong scheme for the action, field-order or encoding mismatches, trailing zeroes on numeric string fields, or upper-case address characters (lowercase addresses before signing).

Revoke an API key

1. Open Settings → API in the web app.

2. Find the agent by name or address.

3. Click Revoke and sign with your master wallet.

A revoked agent can no longer access your account.

Next steps

• API Quickstart: base URLs, envelope, and a working example.

• Exchange Methods: actions, queries, and schemas.

• WebSocket API: real-time subscriptions.