> For the complete documentation index, see [llms.txt](https://docs.twilight.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.twilight.org/boomerang/bitcoin-fragment-sweep.md).

# Bitcoin Fragment Sweep

<figure><img src="/files/2f7sAgpBcH8WJlGEKHr0" alt=""><figcaption><p>Sequence Diagram for SweepTx and RefundTx</p></figcaption></figure>

Intuitively, this sweep process works like commitmentTx in lightning, where the client always have an exit transaction available in case the counterparty refuses to respond.&#x20;

In Boomerang, before a Fragment signs on the SweepTx, the new Fragment Judge proposes a Refund Transaction on the previous state of the reserve. Once all the new Fragment signatories sign on the refund transaction, the Sweep signing begins on the unlocked Fragment address.