# What preconditions does GGPO state for rollback netcode (determinism, fixed quanta, saveable state), and how does it detect violations?

- id: art_01M5MDGZTY5QM07SGSA1TWT5D9
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T08, T18 · tags: none
- updated: 2026-10-23T12:59:41.271Z
- url: https://veyrul.com/articles/art_01M5MDGZTY5QM07SGSA1TWT5D9

GGPO's developer guide (7ddadef8) requires a fully deterministic simulation, fully encapsulated and serializable game state, and the ability to load, save and step one frame without rendering; it recommends (not enforces) a fixed time quantum per frame and separating game state from render state, requires RNG seed and state in the game state, and offers a sync-test session that rolls back one frame every frame and errors on state differences. Its frame-delay thresholds (more than 1 frame noticeable in fighting games; 4-5 tolerable in board/puzzle games) are author judgement without cited measurements.

GGPO's developer guide (7ddadef8) requires a fully deterministic simulation, fully encapsulated and serializable game state, and the ability to load, save and step one frame without rendering; it recommends (not enforces) a fixed time quantum per frame and separating game state from render state, requires RNG seed and state in the game state, and offers a sync-test session that rolls back one frame every frame and errors on state differences. Its frame-delay thresholds (more than 1 frame noticeable in fighting games; 4-5 tolerable in board/puzzle games) are author judgement without cited measurements.

Curator qualifications: Curator note: the rollback-glitch example in the same section says a 2-frame flash and then calls it a '2-second flash' (documentation slip); do not quote that sentence. Sync test covers same-machine re-execution only (producer synthesis); cross-machine divergence detection not established. README statements (S28) not re-read. Documentation reading only; no GGPO build or session run.

Limitations: Library documentation at one commit.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://github.com/pond3r/ggpo/blob/7ddadef8546a7d99ff0b3530c6056bc8ee4b9c0a/doc/DeveloperGuide.md",
      "note": "doc/DeveloperGuide.md lines 19-21, 176-180, 204-212, 226-236, 281-283 at 7ddadef8"
    },
    {
      "url": "https://github.com/pond3r/ggpo/blob/7ddadef8546a7d99ff0b3530c6056bc8ee4b9c0a/doc/README.md",
      "note": "doc/DeveloperGuide.md lines 19-21, 176-180, 204-212, 226-236, 281-283 at 7ddadef8"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] GGPO's developer guide (7ddadef8) requires a fully deterministic simulation, fully encapsulated and serializable game state, and the ability to load, save and step one frame without rendering; it recommends (not enforces) a fixed time quantum per frame and separating game state from render state, requires RNG seed and state in the game state, and offers a sync-test session that rolls back one frame every frame and errors on state differences. Its frame-delay thresholds (more than 1 frame noticeable in fighting games; 4-5 tolerable in board/puzzle games) are author judgement without cited measurements. · locator: doc/DeveloperGuide.md lines 19-21, 176-180, 204-212, 226-236, 281-283 at 7ddadef8 · source: https://github.com/pond3r/ggpo/blob/7ddadef8546a7d99ff0b3530c6056bc8ee4b9c0a/doc/DeveloperGuide.md

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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