First open-source release of Rollback Core — deterministic GGPO-style rollback netcode for Unreal Engine 5, MIT-licensed.

What's in the box

• URollbackManager — fixed-step (60 Hz default, configurable 15–240 Hz) simulation loop with AdvanceFrame() / RollbackToFrame() and a per-frame debug-history API.
• URollbackStateComponent — automatic snapshot/restore of any UPROPERTY(SaveGame) on the owning actor, plus transform + velocity. No per-actor Serialize() boilerplate.
• URollbackMovementComponent — deterministic axis-input integration suitable as a starting point.
• URollbackNetSubsystem — UDP transport with input redundancy, reliable ACK/resend, heartbeats, peer-timeout detection, multi-peer (up to 8), and simulated packet loss + latency for in-editor testing.
• URollbackNetworkBlueprintLibrary — full Blueprint surface.
• URollbackCoreSettings — Project Settings entries for tick rate, max rollback depth, ports, redundancy, peer counts, timeouts.
• Performance instrumentation (FRollbackPerformanceStats) — avg/max sim & rollback times, snapshot sizes, bandwidth, rollbacks-per-second.
• Console commands: Rollback.NetHost, Rollback.NetClient, Rollback.NetConnect, Rollback.NetDisconnect, Rollback.NetPeers, Rollback.Perf.
• Demo map RC_BasicDemo.umap showing two pawns with artificial latency and live rollback corrections.
• Eight automation tests under RollbackCore.* covering state save/restore, late input correction, network buffer apply, debug history scrub, UDP loopback, multi-peer connect, peer-timeout detection, and performance stats.

Verified

Compiles cleanly under UE 5.7 with both VS2022 and VS2026 toolchains across all three configurations (UnrealEditor Development, UnrealGame Development, UnrealGame Shipping). Zero warnings, zero errors.

Install

Submodule:
```sh
git submodule add https://github.com/gregorik/Rollback-Core.git Plugins/RollbackCore
```

Or download the source ZIP from this release and extract into `YourProject/Plugins/RollbackCore/`. See the README for full instructions and a quick start.

Rollback Core vs Rollback Core Pro

A commercial superset — Rollback Core Pro — is available on the Unreal Fab marketplace with OnlineSubsystem (LAN/EOS/Steam) matchmaking, a visual frame-scrubber debugger, desync inspection tooling, multi-engine-version packages (5.4–5.7), and additional demos (network-packet-loss simulator, 2D viking fighter). See the feature comparison in the README for which fits your project.