lightning-dev-splice -- Command to initiate a channel to a peer

SYNOPSIS

(WARNING: experimental-splicing only)

dev-splice script_or_json [dryrun] [force_feerate] [debug_log] [dev-wetrun]

DESCRIPTION

Command added in v24.11.

splice is the command to move funds into or out of a channel. Multiple actions can be combined together resulting in a single onchain transaction. Funds may be moved out of a channel and into another in a single batch enabling cross-channel movement.

script_or_json (string): The splice script to execute or json equivilent
dryrun (boolean, optional): Don't execute any actions and output a transcript of what would have been done
force_feerate (boolean, optional): By default splices will fail if the fee provided looks too high. This is to protect against accidentally setting your fee higher than intended. Set force_feerate to true to skip this saftey check
debug_log (boolean, optional): Adds a verbose log of each splice calculation step to the result
dev-wetrun (boolean, optional): Executes the splice up until the point signatures would be sent and then aborts

USAGE

The primary method is to make a script containing one or more splice actions
that will be merged into a single transaction. If possible the entire operation
will be completed and broadcast to the mempool.

However if you specified your own inputs using psbt, then the command will
return a psbt that you must sign and then pass to splice_signed.

It is required to pass script_or_json.

It is recommended you first do a dryrun to confirm your script does what you
expect it to do.

script The splice script to execute

dryrun Don't execute any actions and output a transcript of what would have
been done

psbt An initial psbt to begin the splice with

user_provided_sats The amount of sats being contributed by the initial psbt

force_feerate By default splices will fail if the fee provided looks too high.
This is to protect against accidentally setting your fee higher than intended.
Set to true to skip this saftey check

json A json payload of instructions can be passed instead of script

debug_log Adds a verbose log of each splice calculation step to the result

dev-wetrun Executes the splice up until the point signatures would be sent and then aborts

The primary purpose of splice script is to execute all types of splices using
a single command. You can perform all these actions manually using the lower
level api (see splice_init) however this splice command interface is much simpler to use
and it provides some security against signing maliciously inserted inputs.

SCRIPT

A splice script is a series of 'segments' that are separated by newlines or
semicolons. Each segment represents one splice action which is typically adding
to or removing from a channel. The funds are designated as going into the
channel or coming out of the channel by which side of an arrow "->" the channel
identifier is placed on. The amount of funds is placed on the other side of the
arrow.

Take this example:

8338aef0 -> 10000sat

This is how we take 10,000 sats out of channel 8338aef0.

To put 10,000 sats into the channel, we make the arrow point into the channel
like so:

10000sat -> 8338aef0

In the last two examples we specified the first 8 digits of the channel
identifier. You can specify as few as 4 digits of the beginning of the channel
identifier and it will be autocompleted to the matching channel. If the code
matches more than one channel or node id, the script will fail with an error.

In order to put funds into a channel however, we need get the funds from
somewhere. The simplest place to get them is the built in onchain wallet. The
"wallet" operator can be placed just like channel identifiers. We can take funds
out of the wallet like so:

wallet -> 10000sat

We can put funds back into the wallet like so:

10000sat -> wallet

Now that we know how to take funds out of a wallet, let's combine them into an
individual script:

wallet -> 10000sat
10000sat -> 8338aef0

The first line withdraws 10,000 sats from the wallet and puts them in the
script's "general script funds." The second line takes 10,000 sats from the
"general script funds" and places them into channel 8338aef0. This example is
called a "splice in."

In order for this script to work, we need one more thing. Onchain fees must be
funded from somewhere. The simplest way to pay the fee from the "general script
funds." If we change the amount going into the channel to a percentage, the fee
will automatically be taken from the "general script funds" like so:

wallet -> 10000sat
100% -> 8338aef0

When specifying a percentage instead of an amount, it means take that percentage
out of the "general script fund."

This will take 10,000 sats from the onchain wallet and put that amount less any
onchain fees into channel 8338aef0. The feerate used will be the node's
standard opening feerate. In order to use your own feerate you must us the fee
operator.

The fee operator is attached to an amount. If you want to take out extra to
cover the fee, use "+fee" and if you want to reduce the amount being sent
somewhere use the "-fee" suffix. Take this example:

wallet -> 10000sat+fee
10000sat -> 8338aef0

In this example we add precisely 10,000 sats to channel 8338aef0 and withdraw
enough from the wallet to cover the 10,000 sats and the onchain fee.

To control the amount of fee, you can specify a fee-rate with the use of the at
"@" symbol after fee. After the at symbol, specify a number of sats to pay per
kiloweight (aka. perkw) like so:

wallet -> 10000sat+fee@300
10000sat -> 8338aef0

This example pays a fee rate of 300 sats per thousand weight units. To view this
amount in other units (ie. sats/vbyte) execute a dryrun of the script.

Instead of withdrawing extra from the wallet, we can reduce the amount going to
channel 8338aef0 using the "-fee" operator like so:

wallet -> 10000sat
10000sat-fee -> 8338aef0

This example withdraws 10,000 sats from the onchain wallet, pays the onchain
fee from that amount, and puts the rest into channel 8338aef0.

You can also specify the feerate here like so:

wallet -> 10000sat
10000sat-fee@300 -> 8338aef0

Now let's build a script that takes funds out of a channel and puts them into
the onchain wallet:

8338aef0 -> 10000sat
100% -> wallet

By default however, scripts that leave sats in the "general script fund," will
be automatically sent to the wallet. So the second line is not needed, we can
simplify the script to:

8338aef0 -> 10000sat

We can can also move sats to a specific bitcoin address like so:

8338aef0 -> 10000sat+fee
100% -> 1JfbZRwdDHKZmuiZgYArJZhcuuzuw2HuMu

This example pays 10,000 sats to the address 1JfbZRwdDHKZmuiZgYArJZhcuuzuw2HuMu
out of your channel balance in 8338aef0.

Percentages on the right side take out that amount of available funds from a
channel. For example:

8338aef0 -> 100%

This takes all available funds out of channel 8338aef0 and puts them into the
onchain wallet. Note that available funds is restricted by pending HTLCs and
the 1% reserve requirement. To get all the funds you need to close the channel.
More useful would be something like this:

8338aef0 -> 50%
100% -> 07bfddea

This example takes half the available funds from channel 8338aef0 and puts them
into channel 07bfddea.

We can also split this amount like so:

8338aef0 -> 50%
50% -> 07bfddea
50% -> 09ad6278

This example takes half the funds in 8338aef0 and splits them between channels
07bfddea and 09ad6278.

If we want to send funds to more channels calculating percentages can get
unwieldy so we can use the asterisk operator "*" which divides the "general
script funds" amongst all destinations using it, like so:

8338aef0 -> 50%
* -> 07bfddea
* -> 09ad6278
* -> efc2a7ff

This example takes half the available funds in 8338aef0 and splits them evenly
among three achannels.

Sats can be specified with multiple suffixes including sat, msat, btc, M, or K.
The M suffix is shorthand for a million satoshis and the K suffix is shorthand
for a thousand satoshis. These can be combined with a decimal point like so:

07bfddea -> 1.23M
09ad6278 -> 900K
efc2a7ff -> 0.01btc

This example takes 1,230,000 sats from 07bfddea, 900,000 sats from 09ad6278, and
1,000,000 sats from efc2a7ff and puts them in the onchain wallet.

Another way to specify channel ids is a channel query. These take the form of a
node id, a colon, and a number or symbol (ie. "034645dc:0") which results in
your first channel with the peer whose node id starts with 034645dc. Change the
number after the colon to get a different index like so:

034645dc:0 -> 10K
034645dc:1 -> 10K
034645dc:2 -> 10K

This example takes 10,000 sats out of the first three channels with peer
034645dc and puts the total minus fees into the onchain wallet.

In addition to index numbers, the symbol after the colon can be a question mark
"?" or an asterisk "*" which mean match the first unused channel or all the
remaining channels respectively like so:

* -> 034645dc:?
* -> 03e3d03e:0
03e3d03e:* -> 100%

This example takes 100% of available funds from all of 03e3d03e's channels
except the first one and splits them between 03e3d03e's first channel and
034645dc's first channel.

The node id prefix can also be replaced with the asterisk "*" which means match
all nodes. This can be combined with the asterisk "*" that matches all unused
channels like so:

wallet -> 10000sat
100% -> *:*

This example takes 10,000 sats from the onchain wallet and divides them between
all channels.

It is possible to request a peer to add funds to a channel with a lease request.
This is done using the pipe "|" symbol and optionally specifying the maximum fee
you authorize using the at "@" symbol. After the pipe you specify the amount of
sats you would like to lease, followed by the at symbol and a percentage value
like so:

wallet -> 10M+fee
100%|10M@1% -> 8338aef0

This example splices 10,000,000 sats into channel and requests your peer also
add 10,000,000 sats to the channel. If they fee they demand is over 1% or the lease
amount is too small the operation will be aborted. Whatever lease fee they do
charge will come out of the 10,000,000 sats going into the channel balance. The
onchain fee will be paid by taking extra funds out of the onchain wallet.

Lease requests do not need to combined with splicing in funds but you must pay
the onchain fee from somewhere. One simple location to take the fees from is
your existing channel balance. Doing so requires using two arrows since funds
are going into and out of the channel at the same time, like so:

|10M@1% -> 8338aef0 -> 0+fee

This example makes a lease request from your peer on 8338aef0 for 10,000,000
sats and pays the onchain fee using the channel balance. This is a particularly
elegant way to pay the onchain fee without adding any inputs or outputs beyond
the channel funding itself.

When passing via the command line using semicolons can be simpler instead of
newlines. Here are some command line examples:

Splice out 10 million satoshis to the onchain wallet

lightning-cli splice "8338aef0 -> 10M"

Splice in 10 thousand satoshis from the onchain wallet

lightning-cli splice "wallet -> 10K; 100% -> 8338aef0"

Send 900 thousand satoshis from a channel to an onchain address

lightning-cli splice "8338aef0 -> 0.9M+fee; 0.9M -> 1JfbZRwdDHKZmuiZgYArJZhcuuzuw2HuMu"

Move 1 bitcoin between two channels

lightning-cli splice "8338aef0 -> 1btc; 100% -> 07bfddea"

Splice in 100 thousand sats to the first channel with peer id 034645dc

lightning-cli splice "wallet -> 0.1M; 100% -> 034645dc:?"

Splice in 100 thousand sats split across all channels with peer id 034645dc

lightning-cli splice "wallet -> 100000; 100% -> 034645dc:*"

Take the maximum out of one chanel and split the value across peer 034645dc's
channel plus one more channel

lightning-cli splice "8338aef0 -> 100%; * -> 034645dc:*; * -> 07bfddea"

RETURN VALUE

On success, an object is returned, containing:

dryrun (array of strings, optional): The transcript of what the script would have done:
- (string, optional): One action line of the splice script result
psbt (string, optional): The final psbt
tx (string, optional): The final transaction in hex
txid (string, optional): The txid of the final transaction
log (array of strings, optional): A verbose log of each step of splice calcuations:
- (string, optional): A line of detail about splice calcuations

AUTHOR

Dusty <@dusty\_daemon> is mainly responsible.

RESOURCES

Main web site: https://github.com/ElementsProject/lightning