{
  "schema_version": "1.0.0",
  "format": "newline-delimited JSON compressed with GZIP",
  "timestamp_contract": {
    "timestamp_monotonic_ns": "Primary ordering clock from Android sensor hardware or elapsedRealtimeNanos",
    "timestamp_epoch_ms": "Wall clock for cross-device alignment; clock changes must be considered"
  },
  "fields": {
    "sequence": "int64, repository order",
    "source_sequence": "int64, service acquisition order; -1 for UI annotations",
    "record_type": "sensor | location | battery | annotation_auto | annotation_manual",
    "timestamp_epoch_ms": "int64 milliseconds since Unix epoch",
    "timestamp_monotonic_ns": "int64 nanoseconds since boot",
    "sensor": "stable sensor key",
    "accuracy": "Android sensor accuracy or estimated location accuracy",
    "unit": "unit contract for values",
    "values": "array<number|null>; source sensor values retain Float32 precision, location retains Float64",
    "known_activity": "protocol label supplied by contributor",
    "auto_motion": "coarse automatic estimate, not ground truth",
    "phase": "baseline | pre_failure | failure | recovery",
    "event_type": "nullable event label",
    "confidence": "nullable heuristic confidence 0..1",
    "details": "nullable explanation"
  },
  "integrity": {
    "blocks.jsonl": "SHA-256 chain over canonical JSONL bytes in blocks",
    "integrity.json": "SHA-256 and byte size for every exported artifact"
  }
}