Bevy

Who this is for

Any Rust game using a lockstep or rollback netcode library — GGRS specifically has a first-class integration, since Foldback can ride the checksum a GGRS game already computes instead of adding a second simulation hook.

Overview

The core foldback-core API (Level 1 hashing, the Session type) works from any Rust project with no GGRS dependency — see the Quickstart. foldback-rs’s ggrs feature adds two helpers, checksum and record_desync — see below. examples/ggrs-demo proves a real GGRS SyncTestSession end to end, recording a real two-peer .foldback file the UI can open.

Install

[dependencies]
foldback-core = { git = "https://github.com/FelixMiddelhoff/foldback", package = "foldback-core" }
foldback-rs = { git = "https://github.com/FelixMiddelhoff/foldback", package = "foldback-rs", features = ["ggrs"] }

Minimal example

See Cookbook recipe 1 — works today with any Rust simulation, GGRS or not.

GGRS-specific integration

See Cookbook recipe 3 — GGRS has no hookable “checksum callback” to wrap (a game computes its own checksum and hands it to GameStateCell::save), so the real integration is two small helpers rather than a session-wrapping extension trait: checksum(state_bytes) so a game’s own GGRS checksum is Foldback’s hash, and record_desync(..) to feed GGRS’s own DesyncDetected event (from a real networked P2pSession) into a Foldback Session for recording/bisection. SyncTestSession (single-process — see examples/ggrs-demo) doesn’t need the bridge; it catches mismatches internally.

Reflective hashing

Landed: foldback-rs’s bevy feature walks bevy_reflect component fields marked #[foldback(hash)]/#[foldback(reflect)] and hashes them without hand-written hash_entity/hash_field calls, plus a bevy-debug-panel feature for an in-egui live view of what got captured. See Auto/Reflective Hashing for the full picture, including what’s a deliberate non-goal rather than unfinished.

CI integration

foldback ci-check <file> works today for a file-based check. See CI Integration.

Troubleshooting

Nothing specific yet — file an issue if you hit something integrating against the current API; this section grows from real reports rather than speculation.

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