diff --git a/packages/forms/src/blueprint.ts b/packages/forms/src/blueprint.ts
index 4bcfae75..442e8334 100644
--- a/packages/forms/src/blueprint.ts
+++ b/packages/forms/src/blueprint.ts
@@ -11,6 +11,7 @@ import {
   type FieldsetPattern,
   type PagePattern,
   type PageSetPattern,
+  type RepeaterPattern,
   type SequencePattern,
 } from './patterns';
 import { type Blueprint, type FormOutput, type FormSummary } from './types';
@@ -396,45 +397,75 @@ export const copyPattern = (
   return { bp: updatedBp, pattern: newPattern };
 };
 
-export const addPatternToFieldset = (
+export const addPatternToCompoundField = (
   bp: Blueprint,
-  fieldsetPatternId: PatternId,
+  patternId: PatternId,
   pattern: Pattern,
+  type: 'fieldset' | 'repeater',
   index?: number
 ): Blueprint => {
-  const fieldsetPattern = bp.patterns[fieldsetPatternId] as FieldsetPattern;
-  if (fieldsetPattern.type !== 'fieldset') {
-    throw new Error('Pattern is not a page.');
+  const targetPattern = bp.patterns[patternId] as
+    | FieldsetPattern
+    | RepeaterPattern;
+  if (targetPattern.type !== type) {
+    throw new Error(`Pattern is not a ${type}.`);
   }
 
-  let updatedPagePattern: PatternId[];
-
-  if (index !== undefined) {
-    updatedPagePattern = [
-      ...fieldsetPattern.data.patterns.slice(0, index + 1),
-      pattern.id,
-      ...fieldsetPattern.data.patterns.slice(index + 1),
-    ];
-  } else {
-    updatedPagePattern = [...fieldsetPattern.data.patterns, pattern.id];
-  }
+  const updatedPatterns =
+    index !== undefined
+      ? [
+          ...targetPattern.data.patterns.slice(0, index + 1),
+          pattern.id,
+          ...targetPattern.data.patterns.slice(index + 1),
+        ]
+      : [...targetPattern.data.patterns, pattern.id];
 
   return {
     ...bp,
     patterns: {
       ...bp.patterns,
-      [fieldsetPattern.id]: {
-        ...fieldsetPattern,
+      [targetPattern.id]: {
+        ...targetPattern,
         data: {
-          ...fieldsetPattern.data,
-          patterns: updatedPagePattern,
+          ...targetPattern.data,
+          patterns: updatedPatterns,
         },
-      } satisfies FieldsetPattern,
+      } satisfies FieldsetPattern | RepeaterPattern,
       [pattern.id]: pattern,
     },
   };
 };
 
+export const addPatternToFieldset = (
+  bp: Blueprint,
+  fieldsetPatternId: PatternId,
+  pattern: Pattern,
+  index?: number
+): Blueprint => {
+  return addPatternToCompoundField(
+    bp,
+    fieldsetPatternId,
+    pattern,
+    'fieldset',
+    index
+  );
+};
+
+export const addPatternToRepeater = (
+  bp: Blueprint,
+  repeaterPatternId: PatternId,
+  pattern: Pattern,
+  index?: number
+): Blueprint => {
+  return addPatternToCompoundField(
+    bp,
+    repeaterPatternId,
+    pattern,
+    'repeater',
+    index
+  );
+};
+
 export const addPageToPageSet = (
   bp: Blueprint,
   pattern: Pattern
diff --git a/packages/forms/src/builder/index.ts b/packages/forms/src/builder/index.ts
index e4db9c4c..f31057f1 100644
--- a/packages/forms/src/builder/index.ts
+++ b/packages/forms/src/builder/index.ts
@@ -2,8 +2,8 @@ import { type VoidResult } from '@atj/common';
 import {
   addPageToPageSet,
   addPatternToFieldset,
-  addPatternToRepeater,
   addPatternToPage,
+  addPatternToRepeater,
   copyPattern,
   createOnePageBlueprint,
   movePatternBetweenPages,
diff --git a/packages/forms/src/index.ts b/packages/forms/src/index.ts
index 526a63bb..9adfe2cd 100644
--- a/packages/forms/src/index.ts
+++ b/packages/forms/src/index.ts
@@ -29,4 +29,4 @@ export {
   type FormRoute,
   type RouteData,
   getRouteDataFromQueryString,
-} from './route-data.js';
\ No newline at end of file
+} from './route-data.js';
diff --git a/packages/forms/src/services/submit-form.test.ts b/packages/forms/src/services/submit-form.test.ts
index 5dba1149..6e6726d3 100644
--- a/packages/forms/src/services/submit-form.test.ts
+++ b/packages/forms/src/services/submit-form.test.ts
@@ -97,11 +97,11 @@ describe('submitForm', () => {
           data: {
             errors: {
               'element-1': {
-                message: 'Required',
+                message: 'Invalid input',
                 type: 'custom',
               },
               'element-2': {
-                message: 'Required',
+                message: 'Invalid input',
                 type: 'custom',
               },
             },
@@ -297,7 +297,7 @@ describe('multi-page form', () => {
           data: {
             errors: {
               'element-1': {
-                message: 'Required',
+                message: 'Invalid input',
                 type: 'custom',
               },
             },