Expiry & Renewal

Every virtual output expires with the batch output that holds it. Before then, renew it in a batch swap, which moves it into a new batch with a new expiry. The SDK does this automatically; see Renewal & Recovery. Expiry lets the operator reclaim the bitcoin it puts into each batch, and keeps Arkade’s onchain footprint small.

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Batch Expiry

Every batch output has a built-in expiry. After it, the operator can sweep the batch output’s bitcoin through its sweep path. If you have not renewed a virtual output when its batch expires, the operator can sweep it. The operator still lets you recover the funds in a new batch (Virtual Output States), but you can no longer claim them onchain alone. To avoid this, join a batch swap before expiry. It creates a fresh, settled virtual output in a new batch.

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Liveness Requirements

Expiry means both the operator and users must be online at times.

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Operator Liveness

If the operator is unavailable, users cannot make new Arkade transactions until it returns. Their funds stay safe: each user can exit unilaterally with the presigned transactions, and should do so before the batch expires.

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User Liveness

Users must renew their virtual outputs in a batch swap before the batch expires, to keep the right to exit onchain alone. Swept virtual outputs can still be recovered in a new batch swap, but only with the operator.

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Delegation

A user who cannot be online at the right time can delegate renewal to a third party, such as a wallet provider or their own server, without giving up custody.

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How Delegation Works

A delegated virtual output has an extra spending path in its script:

• User + operator (collaborative path). Standard spending.
• User + timelock (exit path). Unilateral exit.
• User + delegate + operator (delegation path). All three must sign.

The user presigns a batch registration request that lists exactly which virtual outputs to renew and which outputs to create. The delegate submits it in a batch swap for the user.

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Guarantees

• The user keeps custody. The delegate can only submit what the user signed. Unilateral exit stays available.
• Inputs and outputs are fixed. The delegate cannot change them or move funds.
• Timing is fixed. Each request has a time window, so the delegate cannot submit it early.

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