Get a challenge

POST /v1/session/challenge

Private reads (your account, your orders, your withdrawals, your WebSocket account channel) need a session. You get one by signing a challenge with your account's key, or with a signing key you registered on chain.

Sessions are for reading. Orders, cancels and withdrawals carry their own signatures and need none.

body addressstringrequired

The account's address, 0x-prefixed.

Response

12345{
  "challenge": "q3V0...",
  "message": "app.hypervolic.com wants you to sign in with your Ethereum account:\n0xAb58…aeC9B\n\nSign in to Hypervolic. This signature only opens a session to view your account: it moves no funds and places no orders.\n\nURI: https://app.hypervolic.com\nVersion: 1\nChain ID: 8453\nNonce: …\nIssued At: …\nExpiration Time: …",
  "expires": 1793500000
}

message is a Sign-In with Ethereum (EIP-4361) message, so a wallet shows it as a sign-in rather than an opaque string. The challenge is good for 5 minutes (expires is unix seconds).