Smart-account onboard

Public: https://hash.terp.network/onboard.

POST /onboard/v1/passkey-grant body { "address": "terp1…", "c": "<pedersen hex>" }.

Without c, the server returns 402. It asks DREGG on loopback GET /v1/query/paid?recipient=&c=. Only then it broadcasts the feegrant.

Keplr dests do not need this grant. Passkey dests do, after payment.