# HistoryCallback [Integration guide](https://docs.lumencharts.com/charting-library/reference/compatibility) · [Reference index](https://docs.lumencharts.com/charting-library/api/) Public contract reference. This declaration describes types and callback shapes; availability is constrained by the linked integration guide and the runtime capability. Legacy product-specific fields are not a promise of implementation. ```ts export type HistoryCallback = (bars: Bar[], meta?: HistoryMetadata) => void; ``` ## Related types - [Bar](https://docs.lumencharts.com/charting-library/api/Bar) - [HistoryMetadata](https://docs.lumencharts.com/charting-library/api/HistoryMetadata) --- Documentation page: https://docs.lumencharts.com/charting-library/api/HistoryCallback