Table of Contents

Subscriptions

Engine-owned replication. An application declares what each archetype exposes, who sees what, and which commands clients may send; the engine does change detection, quantized encoding, motion segments, per-session visibility, sessions, backpressure, inbound hardening and the wire — in parallel on the worker pool, to native and browser clients.

🔬 Recommended: read in-depth-overview/15-subscriptions.md (Chapter 15) for the mechanism, and Guide ch.7 for an end-to-end walkthrough, before the pages below.

Status: 🚧 Partial — the features below are built; the list of what is not yet is at the end · Category: Subscriptions

🎯 What it solves

A game server's state has to reach thousands of clients, each seeing only the part of the world around it, at tick rate — without the application writing change detection, encoding or networking, and without the cost growing as clients × entities. Subscriptions run replication as an engine track after the tick fence, encode each change once, give each session only what lies around it, and never let a slow client hold up the tick.

Public Features

Feature Summary Status Level
Push replication Replicate after a write; the engine pushes spawns, destroys, moves and migrations itself, compares quantized bytes and encodes each change once ✅ Implemented 🔵 Core
Projections & codecs What of an archetype travels: position as motion segments, fields in change groups, enter-only and owner-only fields, Fraction, Heading, Static ✅ Implemented 🔵 Core
Replication by attributes [Replicated], [Motion], [Replicate], [Owner]… on the data, compiled by a source generator; the builder overrides them ✅ Implemented 🔵 Core
Profiles & observers World, Sphere (leave band, run-time radius, distance bands), ClientRegion with a near budget, an Aggregate tier, cadence ✅ Implemented 🔵 Core
Sessions & admission Declared kinds, an admission hook with roles and limits, session events, staged requests: profile, control, budget, kick ✅ Implemented 🔵 Core
Owner state (SELF) Fields only the controlling session receives, plus the last applied command sequence ✅ Implemented 🔵 Core
Commands & acknowledgements Typed intents, rate/role/pre-check on the transport thread, TryResolve scoped to what the session holds, every refusal answered ✅ Implemented 🔵 Core
Events One-off facts routed near a point, to the sessions that hold an entity, to an owner, to one session, or to all; best effort with a loss count, or reliable (.Reliable(): once, in order, or the session is closed) ✅ Implemented 🟣 Advanced
Backpressure & budgets Skip never queue, catch-up from an 8-tick log, rate classes, per-session byte budgets, the inbound budget and the abuse close ✅ Implemented 🟣 Advanced
Transports & hosting The engine's TCP listener and the ASP.NET Core WebSocket adapter; the catalog endpoint ✅ Implemented 🔵 Core
Client SDKs TypeScript (browser) and .NET (bots, tools) clients: stores, motion extrapolation, commands, reconnection, code generation ✅ Implemented 🔵 Core
Wire protocol & catalog typhon.3: the handshake, the canonical catalog, frames and blocks, close codes ✅ Implemented 🟣 Advanced
Groups Entities sharing a key, held whole — the towns a Sphere meets, the keys a client asked for, a shared board — positioned or not, filled under the enter budget and completed with GROUP_COMPLETE 🚧 Partial 🟣 Advanced
Sessions in realms A session in one realm at a time, each realm served at its own scale, a switch as one RESET + REALM frame; kinds and profile variants; realm-scoped events 🚧 Partial 🟣 Advanced
Diagnostics STATS metrics (built-in and your own), the DEBUG capability, the push validator, runtime counters ✅ Implemented 🟣 Advanced

⚠️ Not built yet

Refused at Start or at the call — never silently ignored:

  • several entity observers in one profile, and per-session observers (SessionRequest.Observe);
  • shared tile and Static snapshot blobs; the WebTransport link.

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