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I'm aware that when I first open a channel, all of the channel balance is on my side, so I can only send and not receive.

So, I opened a channel and then sent my counterparty 1500 millisatoshis—but I can still only send and not receive. What's going on?

I'm using Lightning Dev Kit (LDK).

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  • What implementation is at the other end of the channel, also LDK?
    – OptOut
    Jan 13, 2023 at 8:38
  • If using ldk-sample, can you show the output of listchannels commands?
    – OptOut
    Jan 13, 2023 at 8:42
  • To be clear, I've asked and answered this question as it's a commonly asked question on the LDK discord Jan 13, 2023 at 18:56
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    Does the implementation on the other side matter? I would assume that LDK does not permit capacity to be transferred when the remainder falls below the channel reserve. And since it takes two to tango…
    – Murch
    Jan 13, 2023 at 21:48

1 Answer 1

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This is an effect of the channel reserve.

The channel reserve is enforced to ensure each counterparty always has something to lose, if they were to try to cheat. By default, the channel reserve is 1% of the channel capacity, and LDK sets a hard minimum of 1000sats.

Therefore, if you were to send enough such that more than max(1% of channel capacity, 1000sats) were on your counterparty’s side, your available balance for receive would increase.

Since you only sent 1500msats (1.5sats), the amount is still below the channel reserve for the counterparty and none of their funds can move to you.

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  • In the concrete case this is not a plausible explanation (with these values), as the 1500 sats sent is more than 1000.
    – OptOut
    Jan 13, 2023 at 8:43
  • 1500 *msats, not sats :) Is there some way to clarify? Jan 13, 2023 at 18:55
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    I've added another sentence to clarify the two different units in play
    – Murch
    Jan 13, 2023 at 21:46
  • Indeed, I misread it for sats. 1500 msats is way below the 1000 sats minimum capacity.
    – OptOut
    Jan 13, 2023 at 22:25

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