Canonical source: libs/oshun/analytics/src/v3-music-sync-drift-budget.ts
Evidence artifact: V3/validation/music-sync-drift-validation.json
Manifest version: v3-music-sync-drift-budget.v1
The Saraswati Stadium-tier music gate validates cross-attendee drift for the Sequencer + MetaSound concert path. The deterministic load simulation exercises 4,096 attendees across the native UE, Pixel Streaming, and Tier-2 fallback cohorts, with 24 sync checkpoints per song across the two-song launch-night fixture.
| Cohort | Attendees | Samples | p50 drift | p95 drift | p99 drift | Max drift |
|---|---|---|---|---|---|---|
native_ue |
256 | 12,288 | 10 ms | 14 ms | 15 ms | 15 ms |
pixel_streaming |
768 | 36,864 | 13 ms | 17 ms | 18 ms | 18 ms |
tier2_fallback |
3,072 | 147,456 | 15 ms | 19 ms | 20 ms | 20 ms |
| All attendees | 4,096 | 196,608 | 14 ms | 19 ms | 20 ms | 20 ms |
The gate is anchored to apps/v3/saraswati-service/src/per_song_execution.rs,
where simulate_stadium_music_sync_drift validates the 4,096-attendee Stadium
mix, active metasound.play with ntp-style-concert-clock, monotonic drift
percentiles, and p95 drift at or below 25 ms. It also stays connected to the
Sequencer compiler and Tier-2 cue-forwarding path so the same MusicSync cue
track drives native, Pixel Streaming, and fallback clients.
pnpm verify:v3 music-sync-drift fails closed when the Stadium attendee mix is
missing, the p95 budget is weakened, the sample count no longer equals attendees
x songs x checkpoints, the MetaSound NTP clock is inactive, any Sequencer cue is
missed, cross-attendee p95 exceeds 25 ms, any cohort p95 exceeds 25 ms,
percentiles are inconsistent, or the verifier/source wiring is missing.