Glossary #

App ID : A 16-character base58 identifier assigned by Hypersnap when you register a mini app. Appears in URLs for the client token webhook and the send endpoint.

Cast : The core Farcaster message type — a short post, optionally with parent context (a cast being replied to, or a channel parent URL).

Channel : A parent-URL-scoped subcommunity. Casts can be posted into a channel by setting their parent_url. Channels have their own feeds, members, and lead moderators.

Custody address : The Ethereum address currently in charge of an FID, per the on-chain IdRegistry. Signing a Hypersnap management request means producing an EIP-712 signature with this key.

Dedupe window : The 24-hour time window over which (fid, notificationId) pairs are deduplicated on mini-app sends. Re-sending the same uuid to the same FID inside the window is a no-op.

EIP-712 : The Ethereum typed-data signing standard Hypersnap uses for management-request auth. Produces a structured signature distinct from arbitrary message signing.

FID : Farcaster ID. A u64 assigned by the on-chain IdRegistry. Permanent and non-transferable; the custody address that controls it can change.

Grace period : The window during which a previously-active signing or send secret keeps working after a rotation. Default 24 hours. Exists so receivers and senders can switch over without downtime.

HMAC-SHA512 : The signing scheme used on outbound webhook deliveries. The per-webhook signing secret is the HMAC key; the raw HTTP body is the message.

JFS : JSON Farcaster Signature. An Ed25519 signing envelope Farcaster clients use when POSTing mini-app token events. Defined in the Farcaster Mini App spec.

Mini app : A hosted web app that Farcaster clients can launch inline and push notifications to. Registered with Hypersnap via the signed /v2/farcaster/frame/app/ endpoints.

Nonce : A 32-byte random value in every signed management request. Deduped in-memory for the duration of the signed_at window to prevent replay attacks.

Notification token : The opaque per-(fid, app, client) identifier that a Farcaster client hands to a mini app when the user opts in. Used by the client to route push notifications.

Op string : The string naming the operation a signed request is performing, e.g. webhook.create, app.rotate_secret. Both the X-Hypersnap-Op header and the op field inside the EIP-712 typed data carry this.

Retry queue : A RocksDB-backed persistent queue holding webhook deliveries that hit transient failures. Re-injected onto the delivery pool with exponential backoff.

Send secret : The per-mini-app bearer token used as the x-api-key header when calling the notification send endpoint. Rotated via POST /v2/farcaster/frame/app/secret/rotate.

Signed operation : Any HTTP request that Hypersnap requires an EIP-712 signature for. The webhook management and mini-app registration endpoints are the signed surfaces today.

Signer : An Ed25519 key registered to an FID via the on-chain KeyRegistry. Signs Farcaster messages (casts, reactions, follows) and JFS envelopes. Distinct from the custody address.

Subscription : A filter spec attached to a webhook that picks which events get delivered. See Subscription filters.

Webhook : A registered HTTP endpoint that receives filtered Farcaster events as HMAC-signed POSTs. Created and managed via /v2/farcaster/webhook/.