diff --git a/packages/components/package-lock.json b/packages/components/package-lock.json
index 5fc69e55f4..1f1f183540 100644
--- a/packages/components/package-lock.json
+++ b/packages/components/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@labkey/components",
-  "version": "7.29.3",
+  "version": "7.29.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@labkey/components",
-      "version": "7.29.3",
+      "version": "7.29.4",
       "license": "SEE LICENSE IN LICENSE.txt",
       "dependencies": {
         "@hello-pangea/dnd": "18.0.1",
diff --git a/packages/components/package.json b/packages/components/package.json
index 83c26fdd23..40d54e6d32 100644
--- a/packages/components/package.json
+++ b/packages/components/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@labkey/components",
-  "version": "7.29.3",
+  "version": "7.29.4",
   "description": "Components, models, actions, and utility functions for LabKey applications and pages",
   "sideEffects": false,
   "files": [
diff --git a/packages/components/releaseNotes/components.md b/packages/components/releaseNotes/components.md
index 9a94d645ea..5e7639e679 100644
--- a/packages/components/releaseNotes/components.md
+++ b/packages/components/releaseNotes/components.md
@@ -1,6 +1,10 @@
 # @labkey/components
 Components, models, actions, and utility functions for LabKey applications and pages
 
+### version 7.29.4
+*Released*: 9 April 2026
+- GitHub Issue 954: Add error for duplicate values for parent inputs
+
 ### version 7.29.3
 *Released*: 8 April 2026
 - GitHub Issue 928: Spaces not shown between text choices in identifying fields in editable grid
diff --git a/packages/components/src/internal/components/editable/actions.test.ts b/packages/components/src/internal/components/editable/actions.test.ts
index ff3771c6f6..a9198a0bbc 100644
--- a/packages/components/src/internal/components/editable/actions.test.ts
+++ b/packages/components/src/internal/components/editable/actions.test.ts
@@ -836,6 +836,48 @@ describe('parsePastedLookup', () => {
             ]),
         });
     });
+
+    test('duplicate values', () => {
+        // single duplicate
+        expect(parsePastedLookup(multiValueLookup, stringLookupValues, 'A,A')).toStrictEqual({
+            message: { message: 'Duplicate values not allowed: "A".' },
+            valueDescriptors: List([
+                { display: 'A', raw: 'a' },
+                { display: 'A', raw: 'a' },
+            ]),
+        });
+
+        // multiple duplicates
+        expect(parsePastedLookup(multiValueLookup, stringLookupValues, 'A,b,A,b')).toStrictEqual({
+            message: { message: 'Duplicate values not allowed: "A", "b".' },
+            valueDescriptors: List([
+                { display: 'A', raw: 'a' },
+                { display: 'b', raw: 'B' },
+                { display: 'A', raw: 'a' },
+                { display: 'b', raw: 'B' },
+            ]),
+        });
+
+        // duplicate with other valid values
+        expect(parsePastedLookup(multiValueLookup, stringLookupValues, 'A,C,A')).toStrictEqual({
+            message: { message: 'Duplicate values not allowed: "A".' },
+            valueDescriptors: List([
+                { display: 'A', raw: 'a' },
+                { display: 'C', raw: 'C' },
+                { display: 'A', raw: 'a' },
+            ]),
+        });
+
+        // unmatched takes precedence over duplicates
+        expect(parsePastedLookup(multiValueLookup, stringLookupValues, 'A,A,notfound')).toStrictEqual({
+            message: { message: 'Could not find "notfound"' },
+            valueDescriptors: List([
+                { display: 'A', raw: 'a' },
+                { display: 'A', raw: 'a' },
+                { display: 'notfound', raw: 'notfound' },
+            ]),
+        });
+    });
 });
 
 describe('insertPastedData', () => {
diff --git a/packages/components/src/internal/components/editable/actions.ts b/packages/components/src/internal/components/editable/actions.ts
index 45402a45a6..910046041c 100644
--- a/packages/components/src/internal/components/editable/actions.ts
+++ b/packages/components/src/internal/components/editable/actions.ts
@@ -1123,6 +1123,7 @@ export function parsePastedLookup(
     let message: CellMessage;
     let values: ValueDescriptor[];
     const unmatched: string[] = [];
+    const dupValues = new Set<string>();
 
     // Parse pasted strings to split properly around quoted values.
     // Remove the quotes for storing the actual values in the grid.
@@ -1134,10 +1135,15 @@ export function parsePastedLookup(
         unmatched.push(vt);
         values = [{ display: vt, raw: vt }];
     } else {
+        const foundValues = new Set<string>();
         values = parsedValues.flatMap(v => {
             const vt = v.trim();
             if (!vt) return [];
 
+            if (foundValues.has(vt)) {
+                dupValues.add(vt);
+            }
+            foundValues.add(vt);
             const vl = vt.toLowerCase();
             const vd = descriptors.find(d => d.display && d.display.toString().toLowerCase() === vl);
             if (vd) return [vd];
@@ -1153,6 +1159,12 @@ export function parsePastedLookup(
             .map(u => '"' + u + '"')
             .join(', ');
         message = { message: lookupValidationErrorMessage(valueStr, true) };
+    } else if (dupValues.size > 0) {
+        const valueStr = Array.from(dupValues)
+            .slice(0, 4)
+            .map(u => '"' + u + '"')
+            .join(', ');
+        message = { message: `Duplicate values not allowed: ${valueStr}.` };
     }
 
     return { message, valueDescriptors: List(values) };