loopin: Route invoices over asset channels by sputn1ck · Pull Request #1212 · lightninglabs/loop

sputn1ck · 2026-08-26T12:54:39Z

Summary

expose an asset ID and optional asset edge node on Loop In RPC and CLI
requests
create the swap and probe invoices through tapd, pin both to the
negotiated asset edge, and pass that peer to the server as the final hop
validate incompatible invoice-routing options and cover invoice creation,
peer selection, and request validation

Testing

GOWORK=off go test ./...
GOWORK=off make lint workers=4
GOWORK=off make rpc
GOWORK=off make docs-check
GOWORK=off make commitmsg-lint range="origin/master..HEAD"

Pull Request Checklist

Added an entry to docs/release-notes/release-notes-next.md

Wrap tapd's asset-aware invoice RPC so Loop In can create regular and hold invoices payable through a selected asset channel.

Create Loop In swap and probe invoices through tapd, pin both invoices to the negotiated asset edge, and pass that edge to the server as the final hop.

Let RPC and CLI callers select an asset and optional channel peer for Loop In while preserving the existing BTC invoice behavior by default.

Record the new Taproot Asset invoice path in the next Loop release notes.

Copilot

Pull request overview

This PR extends Loop In to support routing swap/probe invoices over Taproot Asset channels by exposing asset routing parameters on the Loop In RPC/CLI and creating the invoices via tapd, pinned to the negotiated asset edge peer.

Changes:

Add asset_info (asset ID + optional asset edge node) to Loop In RPC/Swagger/CLI, and validate incompatible routing options.
Update Loop In swap initiation to create both swap and probe invoices through tapd when asset_info is set, pinning server payment/probe to the negotiated edge peer.
Add test coverage for asset invoice creation, peer pinning, and request validation; update session fixtures and release notes.

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
`server_mock_test.go`	Extend mock server to capture Loop In last-hop and initiator passed during swap creation.
`looprpc/client.swagger.json`	Document new Loop In `asset_info` fields in the REST/Swagger surface.
`looprpc/client.proto`	Add `AssetLoopInRequest` and `LoopInRequest.asset_info` to the public RPC API.
`looprpc/client.pb.go`	Regenerated protobuf bindings to include the new Loop In `asset_info` message/field.
`loopin.go`	Implement asset-aware Loop In flow: validate options and create swap/probe invoices via `tapd`.
`loopin_test.go`	Add tests verifying tapd invoice creation, peer pinning, and request validation for asset Loop Ins.
`loopd/swapclient_server.go`	Parse/validate `asset_info` on the daemon RPC boundary and map into internal `LoopInRequest`.
`interface.go`	Extend internal `LoopInRequest` with `AssetId` and `AssetEdgeNode`.
`docs/release-notes/release-notes-next.md`	Add release note entry for Taproot Asset channel invoice routing in Loop In.
`cmd/loop/testdata/sessions/loopin/06_loop-in-external-force.json`	Update CLI golden session output to include `asset_info`.
`cmd/loop/testdata/sessions/basic-swaps/02_loop-in.json`	Update CLI golden session output to include `asset_info`.
`cmd/loop/loopin.go`	Add CLI flags for asset loop-ins and plumb `asset_info` into the Loop In RPC request.
`client.go`	Improve logging/validation around asset loop-in usage in the client entrypoint.
`assets/client.go`	Add `TapdClient.AddAssetInvoice` helper to create (hold) invoices via tapd asset channels.
`assets/client_test.go`	Add tests for `AddAssetInvoice` covering hold vs regular invoice and incomplete responses.

Files not reviewed (1)

looprpc/client.pb.go: Generated file

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

+		assetID, err := hex.DecodeString(cmd.String("asset_id"))
+		if err != nil {
+			return fmt.Errorf("invalid asset id: %w", err)
+		}
+
+		var assetEdgeNode []byte
+		if cmd.IsSet("asset_edge_node") {
+			assetEdgeNode, err = hex.DecodeString(
+				cmd.String("asset_edge_node"),
+			)
+			if err != nil {
+				return fmt.Errorf("invalid asset edge node: %w", err)
+			}
+		}


Include the new asset Loop In flags in the generated man page and Markdown command reference.

sputn1ck · 2026-08-26T13:14:42Z

/gateway review

lightninglabs-gateway · 2026-08-26T13:15:04Z

👀 gateway review starting…

sputn1ck · 2026-08-26T18:44:57Z

/gateway review

hieblmi · 2026-09-01T14:45:46Z

+    The optional node identity public key of the asset channel peer to use for
+    RFQ negotiation. If omitted, tapd selects from the eligible asset channels.
+    */
+    bytes asset_edge_node = 2;


[P1] Require a minimum asset output: The request specifies only an asset ID and optional peer. It provides no minimum asset amount or rate floor, even though the edge quote determines how many asset units the client receives for its on-chain BTC. The quote is negotiated only after CLI confirmation and is never returned, displayed, or persisted. The daemon-wide tapd price-deviation check is not per-swap user consent. Add a quote phase or fields such as minimum_asset_amount or rate_limit, show the resulting asset amount, and enforce the limit in AddInvoiceRequest before committing the swap.

hieblmi · 2026-09-01T14:45:52Z

-		return nil, err
+	var probeInvoice string
+	if assetLoopIn {
+		assetProbe, err := cfg.assets.AddAssetInvoice(


[P1] Probe the exact RFQ used by the swap: This second AddAssetInvoice call negotiates a new RFQ. Checking only that its peer matches is insufficient: the probe and swap invoices have different RFQ IDs, virtual SCIDs, rates, limits, and policies. A probe can therefore succeed with a smaller asset requirement or different final-hop fee while the actual swap quote fails after the BTC HTLC is funded. Create the probe and swap invoices from the same accepted RFQ-backed route hint, or otherwise verify and reserve the exact rate, SCID, and capacity used by the swap invoice.

hieblmi · 2026-09-01T14:45:58Z

+
+		// Pin the probe and the server payment to the same edge node as
+		// the swap invoice.
+		request.LastHop = &quotePeer


[P1] Do not treat the tapd reference quote as edge selection: When no edge is supplied, tapd negotiates with multiple peers and returns its most-expensive quote as the reference quote while putting multiple RFQ hints in the invoice. That response is not a selected route, but this code treats its peer as one and pins the server to it, forcing the worst-priced edge and disabling the other hints. The server fee quote was also calculated earlier with LastHop unset, so its invoice amount may not match this route fee. Require an explicit edge for now, or add a pre-swap selection phase that chooses an approved quote before calculating server fees.

hieblmi · 2026-09-01T14:46:04Z

+// assetLoopInInvoiceExpiry is the invoice lifetime an asset edge must cover
+// with its RFQ quote. If an on-chain funding transaction does not confirm in
+// this window, the swap fails safely and the client can reclaim the HTLC.
+const assetLoopInInvoiceExpiry = int64(60 * 60)


[P1] Invoice lifetime is shorter than the payment lifecycle: The asset invoice and RFQ expire after one hour, but the server normally waits 3-6 confirmations and retries failed payments only after one hour. Normal block variance alone makes expiration likely, particularly for six-confirmation swaps. Once funded, failure can send the client to the default 1000-block refund path. The RFQ must cover confirmation and retry time, or RFQ and invoice creation must be deferred until the HTLC is sufficiently confirmed.

hieblmi · 2026-09-01T14:46:26Z

+
+		assetInfo = &looprpc.AssetLoopInRequest{
+			AssetId:       assetID,
+			AssetEdgeNode: assetEdgeNode,


[P2] Quote the explicit asset edge in the CLI: asset_edge_node is placed in AssetInfo here, but the preflight quote below uses only the separate last_hop flag. The CLI therefore displays and uses a fee cap for a different route, while Loop internally re-quotes with the asset edge and may fail with ErrSwapFeeTooHigh. Make asset_edge_node the effective LoopInLastHop and reject conflicting values.

sputn1ck added 4 commits August 26, 2026 14:49

assets: Add asset invoice creation

4e90125

Wrap tapd's asset-aware invoice RPC so Loop In can create regular and hold invoices payable through a selected asset channel.

loopin: Route invoices over asset channels

f8713f0

Create Loop In swap and probe invoices through tapd, pin both invoices to the negotiated asset edge, and pass that edge to the server as the final hop.

looprpc: Expose asset Loop In options

9dd827e

Let RPC and CLI callers select an asset and optional channel peer for Loop In while preserving the existing BTC invoice behavior by default.

docs: Note asset Loop In support

e451209

Record the new Taproot Asset invoice path in the next Loop release notes.

Copilot AI lite review requested due to automatic review settings August 26, 2026 12:54

Copilot started reviewing on behalf of sputn1ck August 26, 2026 12:55 View session

Copilot AI reviewed Aug 26, 2026

View reviewed changes

docs: Regenerate CLI reference

aad0785

Include the new asset Loop In flags in the generated man page and Markdown command reference.

hieblmi self-requested a review September 1, 2026 13:29

hieblmi reviewed Sep 1, 2026

View reviewed changes

Navigation Menu

Uh oh!

loopin: Route invoices over asset channels - #1212

loopin: Route invoices over asset channels#1212
sputn1ck wants to merge 5 commits into
masterfrom
kon/asset-loop-in-invoices

sputn1ck commented Aug 26, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

sputn1ck commented Aug 26, 2026

Uh oh!

lightninglabs-gateway Bot commented Aug 26, 2026

Uh oh!

sputn1ck commented Aug 26, 2026

Uh oh!

hieblmi Sep 1, 2026

Uh oh!

hieblmi Sep 1, 2026

Uh oh!

hieblmi Sep 1, 2026

Uh oh!

hieblmi Sep 1, 2026

Uh oh!

hieblmi Sep 1, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Uh oh!

Conversation

sputn1ck commented Aug 26, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Testing

Pull Request Checklist

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

sputn1ck commented Aug 26, 2026

Uh oh!

lightninglabs-gateway Bot commented Aug 26, 2026

Uh oh!

sputn1ck commented Aug 26, 2026

Uh oh!

hieblmi Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

hieblmi Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

hieblmi Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

hieblmi Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

hieblmi Sep 1, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

sputn1ck commented Aug 26, 2026 •

edited

Loading