From e2a6bd39795910d36dfbfafe0c049ac38ca84f0d Mon Sep 17 00:00:00 2001
From: Kyle Cox <kshot9000@gmail.com>
Date: Fri, 9 Oct 2026 00:45:12 +0000
Subject: [PATCH] fix(core): throw InsufficientInputs for token targets no
 input can reach

BoxSelector.select() crashed instead of throwing the documented
InsufficientInputs error in two empty-selection cases:

- When no input holds the target token (and no ERG target pulls any
  input into the selection), _getUnreachedTargets called
  first(inputs).boxId on the empty selection to check the minting
  exemption, and first() asserts with a bare 'Empty array.' error.
- When there are no inputs at all, the minting check at the top of
  select() dereferenced unselected[0].boxId and threw a TypeError.

Both checks now guard on a non-empty list, so an unreached token
target always surfaces as InsufficientInputs carrying the unreached
token and amount. The minting exemption is unchanged when at least
one input is selected.
---
 .changeset/tidy-selection-fails.md            |  5 ++++
 .../src/builder/selector/boxSelector.spec.ts  | 24 +++++++++++++++++++
 .../core/src/builder/selector/boxSelector.ts  |  4 ++--
 3 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/tidy-selection-fails.md

diff --git a/.changeset/tidy-selection-fails.md b/.changeset/tidy-selection-fails.md
new file mode 100644
index 00000000..cfc3ec62
--- /dev/null
+++ b/.changeset/tidy-selection-fails.md
@@ -0,0 +1,5 @@
+---
+"@fleet-sdk/core": patch
+---
+
+fix(core): throw InsufficientInputs when a token target cannot be reached because no selected input holds the token, instead of crashing with "Empty array." or a TypeError on empty selections
diff --git a/packages/core/src/builder/selector/boxSelector.spec.ts b/packages/core/src/builder/selector/boxSelector.spec.ts
index 615a61e5..eb7c5af6 100644
--- a/packages/core/src/builder/selector/boxSelector.spec.ts
+++ b/packages/core/src/builder/selector/boxSelector.spec.ts
@@ -243,6 +243,30 @@ describe("Validations", () => {
     }).toThrow(InsufficientInputs);
   });
 
+  it("Should fail if tokens target is unreached and no input holds the token", () => {
+    const tokenId = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    const selector = new BoxSelector(regularBoxes);
+
+    let error: unknown;
+    try {
+      selector.select({ tokens: [{ tokenId, amount: 100n }] });
+    } catch (e) {
+      error = e;
+    }
+
+    expect(error).toBeInstanceOf(InsufficientInputs);
+    expect((error as InsufficientInputs).unreached.tokens).toEqual([{ tokenId, amount: 100n }]);
+  });
+
+  it("Should fail if tokens target is unreached and there are no inputs at all", () => {
+    const tokenId = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    const selector = new BoxSelector([]);
+
+    expect(() => {
+      selector.select({ tokens: [{ tokenId, amount: 100n }] });
+    }).toThrow(InsufficientInputs);
+  });
+
   it("Should fail if any target is unreached", () => {
     const tokenId = "0cd8c9f416e5b1ca9f986a7f10a84191dfb85941619e49e53c0dc30ebf83324b";
     const selector = new BoxSelector(regularBoxes);
diff --git a/packages/core/src/builder/selector/boxSelector.ts b/packages/core/src/builder/selector/boxSelector.ts
index 86c85b49..13fde675 100644
--- a/packages/core/src/builder/selector/boxSelector.ts
+++ b/packages/core/src/builder/selector/boxSelector.ts
@@ -68,7 +68,7 @@ export class BoxSelector<T extends Box<bigint>> {
     let inclusion = this._ensureInclusionBoxIds;
 
     // if the target has a token that is being minted, then the first input should be included
-    if (target.tokens?.some((x) => x.tokenId === unselected[0].boxId)) {
+    if (some(unselected) && target.tokens?.some((x) => x.tokenId === unselected[0].boxId)) {
       inclusion = new Set(this._ensureInclusionBoxIds).add(unselected[0].boxId);
     }
 
@@ -139,7 +139,7 @@ export class BoxSelector<T extends Box<bigint>> {
     for (const tokenTarget of target.tokens) {
       const totalSelected = utxoSum(inputs, tokenTarget.tokenId);
       if (tokenTarget.amount && tokenTarget.amount > totalSelected) {
-        if (tokenTarget.tokenId === first(inputs).boxId) {
+        if (some(inputs) && tokenTarget.tokenId === first(inputs).boxId) {
           // if the token is the same as the first input, then it is being minted
           continue;
         }