From 81a67825fea8a3982469e8a15732c102f57428b3 Mon Sep 17 00:00:00 2001
From: Dagur Valberg Johannsson <dagurval@pvv.ntnu.no>
Date: Mon, 16 Mar 2026 16:53:56 +0100
Subject: [PATCH] Don't require input path for all inputs

Not all inputs need a signature; only require it for the input paths
that do.
---
 docs/dapp.md                                         |  2 +-
 docs/protocol.md                                     | 12 ++++++------
 packages/core/src/protocols/hdwalletv1.test.ts       | 11 +++++++----
 packages/core/src/protocols/hdwalletv1.ts            |  9 +++++----
 packages/wallet/src/integration/sign-request.test.ts | 12 ++++++------
 5 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/docs/dapp.md b/docs/dapp.md
index d656a05..acf9046 100644
--- a/docs/dapp.md
+++ b/docs/dapp.md
@@ -133,7 +133,7 @@ const request: SignTransactionRequest = {
     userPrompt: "Confirm swap",
     broadcast: true,
   },
-  inputPaths: [["receive", 0], ["defi", 5]],  // one per sourceOutput
+  inputPaths: [[0, "receive", 0], [1, "defi", 5]],  // [inputIndex, pathName, addressIndex]
 };
 
 try {
diff --git a/docs/protocol.md b/docs/protocol.md
index 3e1818f..0b918c7 100644
--- a/docs/protocol.md
+++ b/docs/protocol.md
@@ -229,7 +229,7 @@ interface SignTransactionRequest {
   action: "sign_transaction_request";
   transaction: WcSignTransactionRequest;  // from @bch-wc2/interfaces
   sequence: number;
-  inputPaths: [PathName, number][];       // [pathName, addressIndex] per sourceOutput
+  inputPaths: [number, PathName, number][];  // [inputIndex, pathName, addressIndex]
   time: number;
 }
 ```
@@ -242,11 +242,11 @@ to match responses to requests.
 (for signing), version, locktime, and an optional `userPrompt` string shown to the user in the
 wallet UI.
 
-`inputPaths` is a parallel array to `transaction.sourceOutputs` (and to `transaction.transaction.inputs`).
-Each entry is a `[PathName, number]` tuple identifying the HD derivation path name and address index
-that the dapp used to derive the locking script for that input. This allows the wallet to sign each
-input without scanning or guessing which key was used. The array must have the same length as
-`sourceOutputs`.
+`inputPaths` is a sparse array of `[inputIndex, PathName, addressIndex]` tuples. Each entry identifies
+the HD derivation path name and address index the dapp used to derive the locking script for the input
+at position `inputIndex`. Only inputs that require wallet signing need an entry — contract inputs with
+pre-set unlocking bytecode can be omitted. This allows the wallet to sign each input without scanning
+or guessing which key was used.
 
 ### sign_transaction_response
 
diff --git a/packages/core/src/protocols/hdwalletv1.test.ts b/packages/core/src/protocols/hdwalletv1.test.ts
index 210f6b0..22ddf5a 100644
--- a/packages/core/src/protocols/hdwalletv1.test.ts
+++ b/packages/core/src/protocols/hdwalletv1.test.ts
@@ -11,8 +11,8 @@ describe("isSignTransactionRequest", () => {
     transaction: { transaction: {}, sourceOutputs: [] },
     sequence: 1,
     inputPaths: [
-      ["receive", 0],
-      ["change", 3],
+      [0, "receive", 0],
+      [2, "change", 3],
     ],
     time: 1000,
   };
@@ -39,13 +39,16 @@ describe("isSignTransactionRequest", () => {
 
   it("rejects tuple with wrong types", () => {
     expect(
-      isSignTransactionRequest({ ...valid, inputPaths: [[0, "receive"]] }),
+      isSignTransactionRequest({
+        ...valid,
+        inputPaths: [["receive", 0, 1]],
+      }),
     ).toBe(false);
   });
 
   it("rejects tuple with wrong length", () => {
     expect(
-      isSignTransactionRequest({ ...valid, inputPaths: [["receive"]] }),
+      isSignTransactionRequest({ ...valid, inputPaths: [[0, "receive"]] }),
     ).toBe(false);
   });
 
diff --git a/packages/core/src/protocols/hdwalletv1.ts b/packages/core/src/protocols/hdwalletv1.ts
index ea3699b..ae967c6 100644
--- a/packages/core/src/protocols/hdwalletv1.ts
+++ b/packages/core/src/protocols/hdwalletv1.ts
@@ -114,7 +114,7 @@ export interface SignTransactionRequest extends ProtocolMessage {
   action: RelayMsgAction.SignTransactionRequest;
   transaction: WcSignTransactionRequest;
   sequence: number;
-  inputPaths: [PathName, number][]; // [pathName, addressIndex] per sourceOutput
+  inputPaths: [number, PathName, number][]; // [inputIndex, pathName, addressIndex]
 }
 
 export interface SignTransactionResponse extends ProtocolMessage {
@@ -161,9 +161,10 @@ export function isSignTransactionRequest(
     msg.inputPaths.every(
       (p: any) =>
         Array.isArray(p) &&
-        p.length === 2 &&
-        typeof p[0] === "string" &&
-        typeof p[1] === "number",
+        p.length === 3 &&
+        typeof p[0] === "number" &&
+        typeof p[1] === "string" &&
+        typeof p[2] === "number",
     )
   );
 }
diff --git a/packages/wallet/src/integration/sign-request.test.ts b/packages/wallet/src/integration/sign-request.test.ts
index 88b3268..c79d400 100644
--- a/packages/wallet/src/integration/sign-request.test.ts
+++ b/packages/wallet/src/integration/sign-request.test.ts
@@ -116,9 +116,9 @@ describe("WalletConnectionManager — sign_transaction_request with inputPaths",
         broadcast: false,
       },
       inputPaths: [
-        ["receive", 0],
-        ["defi", 5],
-        ["change", 2],
+        [0, "receive", 0],
+        [1, "defi", 5],
+        [2, "change", 2],
       ],
       time: Math.floor(Date.now() / 1000),
     };
@@ -131,9 +131,9 @@ describe("WalletConnectionManager — sign_transaction_request with inputPaths",
 
     expect(pendingRequests[0].connectionId).toBe(connectionId);
     expect(pendingRequests[0].request.inputPaths).toEqual([
-      ["receive", 0],
-      ["defi", 5],
-      ["change", 2],
+      [0, "receive", 0],
+      [1, "defi", 5],
+      [2, "change", 2],
     ]);
   }, 15000);