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I have unconfirmed transactions in my bitcoind wallet. Some of the are mine and some are incoming third party transactions.

I want to speed up their confirmation by creating CHPFP transaction - spending unconfirmed inputs in one transaction with substantial fee. This would make mining unconfirmed inputs profitable. This is possible in electrum wallet.

How should i do it in bitcoind ? I suppose i should use sendtoaddress, but this will not use third party unconfirmed inputs and even change returns reported by spendable are ignored and bitcoind respond with "insufficient balance"

is there any setting or config, which would enable this ?

Pavel Niedoba
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1 Answers1

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CPFP - Child Pays For Parent

Child transaction that spends unconfirmed output of parent transaction. Child transaction uses a higher fee rate, prioritized by miners, however it is dependent on other transaction (parent) so both are included in the same block.

Example:

Parent tx: https://blockstream.info/testnet/tx/1fe69c98608653dd129c0abc42324aca8d9fe463235c79c4a293e88eb29273cb

Child tx: https://blockstream.info/testnet/tx/fc07a13c4b919496efbdd5e62b57b9fe6e4080ed43c52a678bab30fe9e195d8e

I used the below commands in bitcoin core to do this:

  1. getnewaddress to get new address. Sent 0.011 BTC to the address in Parent tx mentioned above.

  2. getnewaddress get one more address for Child tx: tb1qazka5ds83ad4nz5qxxgz0dar59hpuradd4xwzj

  3. listunspent 0 0 "[\"tb1qrldlrqajfwujwqfxcgeyrq90q5gw6uw9ge5xm6\"]"

output

  1. Create a raw transaction to send 0.01 BTC to the address I got from Step 2 and 0.001 fee for the transaction (915.3 sat/vB)
createrawtransaction "[{\"txid\":\"1fe69c98608653dd129c0abc42324aca8d9fe463235c79c4a293e88eb29273cb\",\"vout\":1}]" "[{\"tb1qazka5ds83ad4nz5qxxgz0dar59hpuradd4xwzj\":0.01}]"
  1. Sign transaction
signrawtransactionwithwallet 0200000001cb7392b28ee893a2c4795c2363e49f8dca4a3242bc0a9c12dd538660989ce61f0100000000ffffffff0140420f0000000000160014e8adda36078f5b598a80319027b7a3a16e1e0fad00000000
  1. Broadcast transaction
sendrawtransaction 02000000000101cb7392b28ee893a2c4795c2363e49f8dca4a3242bc0a9c12dd538660989ce61f0100000000ffffffff0140420f0000000000160014e8adda36078f5b598a80319027b7a3a16e1e0fad0247304402203039e3673a8681a3625e38a7980cd9c17f4ee15acac07f60b8d055f9d495eb4a02204da56bec7b8c668bf57ebd082668e9af7fdb92d8cae7c5e9797919b177808c65012102ef547994e2371acbcf6300c343085ad9eee13edfdd00b52bc051006aa8b89d0400000000

Both transactions got confirmed in block 1865124