Getting started

Use the Replication API when your client can open raw UDP sockets (Unreal Engine, native desktop/mobile, dedicated game servers acting as clients). GraphQL handles authentication and Buddy assignment; all replication traffic is UDP to Buddy.

What you need

Item	Description
Management API URL	register / login → identity session token; then mintAppToken → app-scoped token (hex) + gameTokenId
App ID	Numeric app identifier for your world (passed to mintAppToken; also used in spatial message headers)
Game API URL	serverWithLeastClients — returns Buddy address and registers your session (use the app token; mintAppToken returns the app's gameApiUrl)
UDP capability	Outbound UDP to Buddy clientPort (typically 9091)

You do not need any server-side secrets on the client. The platform registers your app-scoped token with the assigned Buddy when you call serverWithLeastClients. Buddy only accepts a token_type='app' token bound to this app — the identity session token is rejected (see Portals & app-scoped tokens).

Integration flow

Management API          Game API                    Buddy (UDP)
──────────────          ────────                    ─────────────
register / login  ──▶   (identity session token)
mintAppToken      ──▶   (app-scoped token + gameApiUrl)
                        serverWithLeastClients ──▶  (session registration)
                        ◀── ip4, ip6, clientPort
(wait ~1.5 s)
ACTOR_UPDATE_REQUEST_2 ──────────────────────────▶
                        ◀── notifications (UDP)
(refreshAppToken before expiresAt to keep playing)

Related guides

• Authenticate and assign — mutations and query shapes
• GraphQL UDP proxy — browser / JS path (no raw UDP)
• Game API intro — world GraphQL (chunks, actors, …)

Do not call assignment on Management API

serverWithLeastClients lives on the Game API only. The Management API handles identity, orgs, marketplace, and billing—not Buddy assignment.