# setValidationInterface(_:) Attaches validation interface callbacks — per-block validation, PoW confirmation, chain connect / disconnect events. ``` func setValidationInterface(_ callbacks: ValidationInterfaceCallbacks) ``` ## Parameters `callbacks` Preconfigured [`ValidationInterfaceCallbacks`](/documentation/BitcoinKernel/ValidationInterfaceCallbacks) with the closures you want invoked populated. ## Discussion The kernel takes ownership of the callback state. Validation callbacks fire on kernel-internal threads and **block further validation while executing**, so keep handlers fast and avoid synchronous I/O or long-running work inside them.