staticaddr: fractional swap amount #887

hieblmi · 2025-02-20T14:47:14Z

first relevant commit in this PR is 81c4117

This PR adds an amount flag to static loop-in swaps that allows the caller to only swap a fraction of the value of the selected deposits. If only amount is selected, the client selects deposits automatically to cover for the swaps amount.

To ensure backwards UX compatibility, omitting the new flag (--amount=0) selects the total deposit amount for swapping.

This PR also adds a method SelectDeposits to the loop-in manager that is used to coin-select deposits in case the user
only provides a static swap amount.

TODO

Sign sweepless sweep and htlc tx with change output if needed
integration test

hieblmi · 2025-04-30T10:51:28Z

Rebased

lightninglabs-deploy · 2025-07-23T22:55:36Z

@bhandras: review reminder
@hieblmi, remember to re-request review from reviewers when ready

Copilot

Pull Request Overview

This pull request adds a --amount flag to static loop-in swaps that allows users to swap only a fraction of their deposit value. The remaining value is sent back as change to the static address.

Key changes:

Added amount field to swap server RPC for fractional swap amounts
Extended sweep batcher to handle change outputs in transaction construction
Created deposit selection mechanism for automatic coin selection when only amount is specified

Reviewed Changes

Copilot reviewed 41 out of 42 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
utils/dust_limit.go	New utility function for calculating dust limits
swapserverrpc/staticaddr.proto	Added optional amount field to loop-in request
sweepbatcher/sweep_batcher.go	Extended batcher to support change outputs and presigning
sweepbatcher/sweep_batch.go	Enhanced transaction construction with change output handling
staticaddr/loopin/sql_store.go	Added selected amount storage and migration support

Comments suppressed due to low confidence (1)

staticaddr/loopin/sql_store.go:23

Changing the constant name from outpointSeparator to OutpointSeparator makes it exported, which may not be intended if it's only used internally. Consider if this should remain private.

const OutpointSeparator = ";"

Copilot · 2025-07-28T13:26:41Z

sweepbatcher/sweep_batcher_test.go

@@ -2798,6 +2798,8 @@ func testSweepBatcherComposite(t *testing.T, store testStore,
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()

+	lnd.SetMinRelayFee(200)


The hardcoded minimum relay fee value (200) is used inconsistently throughout the test file. Consider defining this as a constant or using a more descriptive variable to improve maintainability and make the test intentions clearer.

Suggested change

lnd.SetMinRelayFee(200)

lnd.SetMinRelayFee(minRelayFee)

Copilot · 2025-07-28T13:26:42Z

sweepbatcher/sweep_batcher_presigned_test.go

@@ -113,7 +128,7 @@ func (h *mockPresignedHelper) DestPkScript(ctx context.Context,
 }

 // SignTx tries to sign the transaction. If all the inputs are online, it signs
-// the exact transaction passed and adds it to presignedBatches. Otherwise it
+// the exact transaction passed and adds it to presignedBatches. Otherwise, it


[nitpick] The comment should maintain consistent punctuation. The sentence should end without a comma: 'Otherwise it' rather than 'Otherwise, it'.

Suggested change

// the exact transaction passed and adds it to presignedBatches. Otherwise, it

// the exact transaction passed and adds it to presignedBatches. Otherwise it

Copilot · 2025-07-28T13:26:42Z

sweepbatcher/sweep_batch.go

@@ -1382,15 +1484,21 @@ func (b *batch) publishMixedBatch(ctx context.Context) (btcutil.Amount, error,
 	// known in advance to be non-cooperative (nonCoopHint) and not failed
 	// to sign cooperatively in previous rounds (coopFailed). If any of them
 	// fails, the sweep is excluded from all following rounds and another
-	// round is attempted. Otherwise the cycle completes and we sign the
+	// round is attempted. Otherwise, the cycle completes and we sign the


[nitpick] The comment should maintain consistent punctuation. The sentence should end without a comma: 'Otherwise the cycle completes' rather than 'Otherwise, the cycle completes'.

Suggested change

// round is attempted. Otherwise, the cycle completes and we sign the

// round is attempted. Otherwise the cycle completes and we sign the

Copilot · 2025-07-28T13:26:42Z

sweepbatcher/sweep_batch.go

@@ -1450,7 +1559,7 @@ func (b *batch) publishMixedBatch(ctx context.Context) (btcutil.Amount, error,
 		// If there was any failure of cooperative signing, we need to
 		// update weight estimates (since non-cooperative signing has
 		// larger witness) and hence update the whole transaction and
-		// all the signatures. Otherwise we complete cooperative part.
+		// all the signatures. Otherwise, we complete cooperative part.


[nitpick] The comment should maintain consistent punctuation. The sentence should end without a comma: 'Otherwise we complete cooperative part' rather than 'Otherwise, we complete cooperative part'.

Suggested change

// all the signatures. Otherwise, we complete cooperative part.

// all the signatures. Otherwise we complete the cooperative part.

Copilot · 2025-07-28T13:26:42Z

staticaddr/loopin/selected_amount_migration.go

+		}
+	}
+
+	log.Infof("Updating selected swap amounts for %d loop out swaps",


The log message refers to 'loop out swaps' but this is migrating loop-in swaps. The message should be corrected to 'loop in swaps'.

Suggested change

log.Infof("Updating selected swap amounts for %d loop out swaps",

log.Infof("Updating selected swap amounts for %d loop in swaps",

since deposits have been normalized in the db in the context of a static address swap this commit now retrieves the deposit information as part of GetLoopInByHash and GetStaticAddressLoopInSwapsByStates.

The QuoteRequest adds a field select_deposits to signal that the specified quote amount should be coin-selected from the client's deposits in order to determine the number of deposits to quote for. The StaticAddressLoopInRequest gets a new amount field that either indicates that the swap amount should be allocated from the passed deposits or coin-selected from all available deposits.

In this commit we add a new function SelectDeposits to the loop-in manager. It coin-selects deposits that meet an arbitrary swap amount provided by the client. We have to ensure that the server creates the correct change outputs for the htlc- and sweepless sweep transactions.

If a quote request contains an amount and flag SelectDeposits set to true the quoting coin- selects the required deposits to meet the swap amount in order to quote for the number of deposits.

The selected_amount column of all previous swaps is filled with the total value of deposits that partook in these swaps.

hieblmi added the static-loop-in label Feb 20, 2025

hieblmi self-assigned this Feb 20, 2025

hieblmi marked this pull request as draft February 20, 2025 14:47

hieblmi force-pushed the static-arb-amount-swap branch 3 times, most recently from fd6cc75 to f54115f Compare February 21, 2025 15:23

hieblmi force-pushed the static-arb-amount-swap branch 6 times, most recently from 67612da to b3522b1 Compare March 19, 2025 11:27

hieblmi force-pushed the static-arb-amount-swap branch 6 times, most recently from 8b33f65 to 21fb9ac Compare April 2, 2025 13:48

hieblmi requested a review from Copilot April 2, 2025 13:52

hieblmi marked this pull request as ready for review April 2, 2025 13:52

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hieblmi force-pushed the static-arb-amount-swap branch 3 times, most recently from 4b1058d to 5625af3 Compare April 3, 2025 15:02

hieblmi requested review from starius, bhandras and sputn1ck April 4, 2025 12:09

hieblmi force-pushed the static-arb-amount-swap branch from 5625af3 to 569359f Compare April 4, 2025 12:09

hieblmi force-pushed the static-arb-amount-swap branch from 569359f to 8be2c65 Compare April 30, 2025 10:51

hieblmi force-pushed the static-arb-amount-swap branch 3 times, most recently from 0127354 to 8adb766 Compare July 16, 2025 10:18

hieblmi force-pushed the static-arb-amount-swap branch 5 times, most recently from d58da27 to 90d2ee6 Compare July 23, 2025 10:16

hieblmi force-pushed the static-arb-amount-swap branch from 90d2ee6 to 24c68d2 Compare July 28, 2025 11:57

hieblmi requested review from Copilot and sputn1ck July 28, 2025 13:25

Copilot AI reviewed Jul 28, 2025

View reviewed changes

hieblmi force-pushed the static-arb-amount-swap branch from 24c68d2 to dd855df Compare July 30, 2025 07:43

hieblmi and others added 15 commits August 1, 2025 10:34

staticaddr: don't append to public variable PendingStates

35901d1

staticaddr: migrate swap hashes to deposits

6e7441b

staticaddr: remove unused fsm transition

a1af860

staticaddr: relax scope of ToDeposit

d7ac314

loopdb: add query DepositsForSwapHash

d5e3075

staticaddr: fetch deposits as part of swap retrieval

fe7622d

since deposits have been normalized in the db in the context of a static address swap this commit now retrieves the deposit information as part of GetLoopInByHash and GetStaticAddressLoopInSwapsByStates.

build: bump tapd

53b7265

swapserverrpc: arbitrary static swap amount

9532bac

sqlc: add amount column to static swaps

01424ca

loopd: deposit selection for GetLoopInQuote

c0ac0cd

If a quote request contains an amount and flag SelectDeposits set to true the quoting coin- selects the required deposits to meet the swap amount in order to quote for the number of deposits.

staticaddr: fix swap amount in listswaps command

db5a19b

staticaddr: selected swap amount migration

5da8070

The selected_amount column of all previous swaps is filled with the total value of deposits that partook in these swaps.

loopd: fractional static address swap amount

6af4a98

hieblmi force-pushed the static-arb-amount-swap branch from dd855df to 6af4a98 Compare August 1, 2025 13:14

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hieblmi commented Feb 20, 2025 •

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	// the exact transaction passed and adds it to presignedBatches. Otherwise, it
	// the exact transaction passed and adds it to presignedBatches. Otherwise it

	// round is attempted. Otherwise, the cycle completes and we sign the
	// round is attempted. Otherwise the cycle completes and we sign the

	// all the signatures. Otherwise, we complete cooperative part.
	// all the signatures. Otherwise we complete the cooperative part.

	log.Infof("Updating selected swap amounts for %d loop out swaps",
	log.Infof("Updating selected swap amounts for %d loop in swaps",

staticaddr: fractional swap amount #887

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Pull Request Overview

Reviewed Changes

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hieblmi commented Feb 20, 2025 •

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