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Bitrune supports atomic swaps between BTC and Runes through constant-product (x × y = k) liquidity pools. Two swap directions exist, each with slightly different signing requirements.

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BTC to Rune (AToB)

1

Request a quote

Provide the target liquidity pool, swap direction (BTC to Rune), BTC amount in satoshis, and maximum acceptable slippage in basis points (default 100).
2

Review the quote

The quote includes estimated Rune units received, price impact, minimum output after slippage tolerance, and swap fee deducted.
3

Sign the transaction

The platform locks the relevant BTC UTXOs and presents BIP-340 sighashes for the user to partially sign using MuSig2. The user computes Schnorr partial signatures over each sighash using their private key and matching nonces.
4

Submit the signature

The user submits their public nonces and partial signatures. The platform aggregates the MuSig2 partial signatures into a single valid Schnorr signature per input, constructs the final transaction, and broadcasts it to the Bitcoin network.
5

Confirmation

Once the transaction confirms on-chain, the Rune balance is credited to the user’s account.

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Rune to BTC (BToA)

The signing flow depends on whether the pool holds an etched Rune (a Rune created through Bitrune’s etching feature).

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Pools without an etched Rune

The platform holds the Rune UTXOs under its own key, so no user signature is required.
  1. Request a swap with the same parameters as the quote step above (specifying the Rune-to-BTC direction).
  2. The platform signs the pool spend directly, broadcasts the transaction, and returns the txid.
  3. BTC is credited to the user once the transaction confirms.

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Pools with an etched Rune

The Rune UTXO is held under a 2-of-2 MuSig2 key, so the same sign-and-submit flow as BTC-to-Rune applies:
  1. Request the swap (specifying the Rune-to-BTC direction).
  2. Sign the returned sighashes.
  3. Submit public nonces and partial signatures.
  4. The platform aggregates, broadcasts, and BTC is credited on confirmation.

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Notes

Swap fee. The default fee is 0.3% (30 bps) of the input amount. Pool creators may configure a different fee rate at pool creation time.
  • Deflationary Runes. Runes with a tax configuration may impose additional buy and/or sell taxes. These are deducted on top of the swap fee. The effective output is reduced accordingly.
  • Slippage protection. The minimum output value included in every quote acts as an on-chain minimum. If the trade would produce fewer tokens than this minimum, the transaction is not constructed.
  • Quote expiry. Quotes are not permanently valid. The user should proceed to the signing step promptly after receiving a quote.