Validate SObject types in getFirstRecord input list

force-app/main/default/classes/CollectionGetFirstRecord_Records.cls

@@ -12,6 +12,22 @@ public with sharing class CollectionGetFirstRecord_Records {
                 continue;
             }
 
+            Schema.SObjectType expectedType = req.records[0] != null ? req.records[0].getSObjectType() : null;
+            Boolean mixedTypes = false;
+            for (SObject record : req.records) {
+                if (record == null || record.getSObjectType() != expectedType) {
+                    mixedTypes = true;
+                    break;
+                }
+            }
+
+            if (mixedTypes) {
+                resp.record = null;
+                resp.errorMessage = 'Mixed SObject types detected in the input list. All records must be of the same SObject type.';
+                results.add(resp);
+                continue;
+            }
+
             resp.record = req.records[0];
             results.add(resp);
         }
@@ -27,5 +43,8 @@ public with sharing class CollectionGetFirstRecord_Records {
     public class Response {
         @InvocableVariable(label='Record' description='The first record from the provided collection')
         public SObject record;
+
+        @InvocableVariable(label='Error Message' description='Error message when records contain mixed SObject types')
+        public String errorMessage;
     }
 }

force-app/main/default/classes/CollectionGetFirstRecord_RecordsTest.cls

@@ -25,6 +25,28 @@ private class CollectionGetFirstRecord_RecordsTest {
         System.assertEquals(a1.Name, returned.Name, 'Name should match the first account');
     }
 
+    @isTest
+    static void testGetFirstRecord_MixedSObjectTypesReturnsNullWithError() {
+        // Create test records of different SObject types
+        Account acc = new Account(Name='Test Account');
+        insert acc;
+        Contact con = new Contact(LastName='Test Contact', AccountId=acc.Id);
+        insert con;
+
+        CollectionGetFirstRecord_Records.Request req = new CollectionGetFirstRecord_Records.Request();
+        req.records = new List<SObject>{ acc, con };
+
+        List<CollectionGetFirstRecord_Records.Request> requests = new List<CollectionGetFirstRecord_Records.Request>{ req };
+
+        Test.startTest();
+        List<CollectionGetFirstRecord_Records.Response> responses = CollectionGetFirstRecord_Records.getFirstRecord(requests);
+        Test.stopTest();
+
+        System.assertEquals(1, responses.size(), 'Should return one response');
+        System.assertEquals(null, responses[0].record, 'Mixed types should yield null record');
+        System.assertNotEquals(null, responses[0].errorMessage, 'Mixed types should set an error message');
+    }
+
     @isTest
     static void testGetFirstRecord_EmptyAndNullListsReturnNull() {
         // Empty list