NAME

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

RETURN VALUE

On success, an object is returned, containing:

•

dryrun (array of strings, optional): The transcript of what the script would have done:

• 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:

AUTHOR

Dusty <<@dusty_daemon>> is mainly responsible.

SEE ALSO

lightning-splice_signed(7), lightning-splice_update(7)

RESOURCES

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

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: shell 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: shell 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: shell wallet -> 10000sat

We can put funds back into the wallet like so: shell 10000sat -> wallet

Now that we know how to take funds out of a wallet, let's combine them into an individual script: shell 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: shell 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: shell 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: shell 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: shell 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: shell 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: shell 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: shell 8338aef0 -> 10000sat

We can can also move sats to a specific bitcoin address like so: shell 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: shell 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: shell 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: shell 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: shell 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: shell 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: shell 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: shell * -> 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: shell 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: shell 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: shell |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 shell $ lightning-cli splice "8338aef0 -> 10M"

Splice in 10 thousand satoshis from the onchain wallet shell $ lightning-cli splice "wallet -> 10K; 100% -> 8338aef0"

Send 900 thousand satoshis from a channel to an onchain address shell $ lightning-cli splice "8338aef0 -> 0.9M+fee; 0.9M -> 1JfbZRwdDHKZmuiZgYArJZhcuuzuw2HuMu"

Move 1 bitcoin between two channels shell $ lightning-cli splice "8338aef0 -> 1btc; 100% -> 07bfddea"

Splice in 100 thousand sats to the first channel with peer id 034645dc shell $ lightning-cli splice "wallet -> 0.1M; 100% -> 034645dc:?"

Splice in 100 thousand sats split across all channels with peer id 034645dc shell $ 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 shell $ lightning-cli splice "8338aef0 -> 100%; * -> 034645dc:*; * -> 07bfddea"