1 invoice paid by 2 wallets and it went through?

[MButcho]

Hi,
I have paid BTC LN invoice from Phoenix, it was pending so I though it would fail (as it did 2 minutes prior) so I moved some fund from Phoenix to WoS and paid for service by WoS. The payment via WoS went through, but I was very suprised when I realized that the payment went through as well via Phoenix ... The problem is that their support wrote they only received 1 payment, because only 1 invoice, 1 pre-image and 1 payment hash exists. How is that possible?

Phoenix:

WoS:

From: Anthony C [email protected]
Sent: Thursday, October 3, 2024 11:57 PM
To: m*****@pm.me
Subject: Re: Payment hash

Hi there MB.

Sorry for the late reply. Here is the proof of payment from our end.
Payment Hash: 3793083ceed78174342e2263ccd87c2656567e6a9763c66dc26137e827d6ef42

Payment Preimage: 03df6bb115a77f97c8019e8d74355537e63095e3964539754ab295dc34754f7b

If you require more assistance just let me know.

Anthony

Wallet of Satoshi
e: [email protected]
www.walletofsatoshi.com

How is that possible? Also, the problem with the service is that they were expecting 0.00655 but received 0.00782909:

I lost 0.00655 * 2 - 0.00782909 = 0.00527091 BTC on this, but no clue who has the extra BTC ...

Any idea what to do?

[MButcho]

From: Phoenix Support [email protected]
Sent: Monday, October 7, 2024 12:55 PM
To: m****@pm.me
Subject: RE: 1 invoice paid by 2 wallets LN wallets? {77722212}

how is it possible, that I have sent the same amount, 655k sats, from both Phoenix and Wos (total 0.0131 BTC, proof is in initial email) and ff.io received totally different amount (782 909 sats)

It is possible because payments on Lightning can be split in multiple parts. Indeed, on closer look what happened here is that the Phoenix payment got split into a 128k sat part and a 529k sat part. The 128k sat part reached the destination (which is why minus fees you got 665k sat + 128k sat), while the 529k sat took a different route (which probably went through a faulty node causing the payment to hang).

The good news is that it turns out that the 529k sat part actually failed, and it was our node that was able to opportunistically use the revealed preimage. So, lucky for you we are able to refund the corresponding 529k sat. Please send us your BOLT12 offer.

Best,

Phoenix Support