refactor: deduplicate membership lookup in automated claim target

src/contracts/AutomaticSavingCircles.sol

@@ -49,7 +49,7 @@
    * @param _savingCircles Address of the main SavingCircles contract
    * @param _owner Owner of the automatic deposits extension
    */
   constructor(address _savingCircles, address _owner) Ownable(_owner) {
     SAVING_CIRCLES = ISavingCircles(_savingCircles);
   }
 
@@ -259,10 +259,9 @@
     // Check opt-in before fetching members while retaining the specific error for an invalid circle.
     if (!automaticClaimsEnabled[_circleId][_member]) revert AutomaticClaimsDisabled();
 
-    address[] memory members = SAVING_CIRCLES.getCircleMembers(_circleId);
-    (bool isMember, uint256 memberIndex) = _getMemberIndex(members, _member);
-
-    if (!isMember) revert ISavingCircles.NotMember();
+    // A non-member resolves to index 0 here, but `isMemberWithdrawable` inside the eligibility check
+    // rejects them, so no separate membership lookup is needed.
+    uint256 memberIndex = SAVING_CIRCLES.memberIndex(_circleId, _member);
     if (!_isEligibleForAutomatedClaim(_circleId, _circle, _member, memberIndex)) {
       revert ISavingCircles.NotWithdrawable();
     }
@@ -326,7 +325,7 @@
    * @param _currentBalance Amount already deposited by the member in the active round
    * @return Whether the member can be included in the automation payload
    */
   function _isEligibleForAutomatedDeposit(
     uint256 _circleId,
     ISavingCircles.Circle memory _circle,
     address _member,
@@ -512,21 +511,4 @@
       return (true, _balances[i]);
     }
   }
-
-  /**
-   * @dev Looks up whether a member belongs to the supplied member snapshot and returns their index
-   * @param _members Snapshot of circle members
-   * @param _member Member being searched for
-   * @return isMember Whether the member was found in the snapshot
-   * @return memberIndex The member's zero-based index in the circle
-   */
-  function _getMemberIndex(
-    address[] memory _members,
-    address _member
-  ) internal pure returns (bool isMember, uint256 memberIndex) {
-    for (uint256 i = 0; i < _members.length; i++) {
-      if (_members[i] != _member) continue;
-      return (true, i);
-    }
-  }
 }

src/contracts/SavingCircles.sol

@@ -376,7 +376,8 @@ contract SavingCircles is ISavingCircles, ReentrancyGuardUpgradeable, OwnableUpg
     return _memberStates[_id][_member].lastDepositRound;
   }
 
-  function memberIndex(uint256 _id, address _member) external view returns (uint256 index) {
+  /// @inheritdoc ISavingCircles
+  function memberIndex(uint256 _id, address _member) external view override returns (uint256 index) {
     return _memberStates[_id][_member].memberIndex;
   }
 

src/interfaces/ISavingCircles.sol

@@ -425,6 +425,16 @@ interface ISavingCircles {
    */
   function isMemberWithdrawable(uint256 id, address member) external view returns (bool withdrawable);
 
+  /**
+   * @notice Get a member's zero-based payout round in a circle
+   * @dev Returns 0 for addresses that are not members, indistinguishable from the first member.
+   *      Callers that need to tell them apart must also check membership.
+   * @param id The ID of the circle
+   * @param member The member to look up
+   * @return index The member's zero-based position in the payout order
+   */
+  function memberIndex(uint256 id, address member) external view returns (uint256 index);
+
   /**
    * @notice Get the address of the withdrawable by
    * @param id The ID of the circle

test/unit/AutomaticSavingCircles.t.sol

@@ -623,6 +623,29 @@ contract AutomaticSavingCirclesUnit is SavingCirclesTestBase {
     assertFalse(savingCircles.hasClaimed(baseCircleId, alice));
   }
 
+  function test_BatchExecuteAutomatedClaims_ReportsNotWithdrawableForNonMember() external {
+    address outsider = makeAddr('outsider');
+    _depositRound(baseCircleId);
+    _enableAutomaticClaim(baseCircleId, outsider);
+
+    ISavingCircles.Circle memory circle = savingCircles.getCircle(baseCircleId);
+    vm.warp(circle.effectiveCircleStartTime + DEPOSIT_INTERVAL);
+
+    uint256[] memory circleIds = new uint256[](1);
+    address[] memory targetMembers = new address[](1);
+    circleIds[0] = baseCircleId;
+    targetMembers[0] = outsider;
+
+    vm.prank(automationExecutor);
+    vm.expectEmit(true, true, false, true, address(automaticSavingCircles));
+    emit IAutomaticSavingCircles.AutomatedClaimFailed(
+      baseCircleId, outsider, abi.encodeWithSelector(ISavingCircles.NotWithdrawable.selector)
+    );
+    automaticSavingCircles.batchExecuteAutomatedClaims(circleIds, targetMembers);
+
+    assertEq(token.balanceOf(outsider), 0);
+  }
+
   function test_BatchExecuteAutomatedClaims_ReportsUnknownCircleBeforeDisabledClaim() external {
     uint256 invalidCircleId = savingCircles.nextId();
     uint256[] memory circleIds = new uint256[](1);