diff --git a/designer_v2/lib/features/design/interventions/study_schedule_form_controller_mixin.dart b/designer_v2/lib/features/design/interventions/study_schedule_form_controller_mixin.dart
index 8ddde0667..d33d9ea90 100644
--- a/designer_v2/lib/features/design/interventions/study_schedule_form_controller_mixin.dart
+++ b/designer_v2/lib/features/design/interventions/study_schedule_form_controller_mixin.dart
@@ -6,12 +6,14 @@ import 'package:studyu_designer_v2/features/design/study_form_validation.dart';
 import 'package:studyu_designer_v2/features/forms/form_validation.dart';
 import 'package:studyu_designer_v2/features/forms/form_view_model.dart';
 import 'package:studyu_designer_v2/localization/app_translation.dart';
+import 'package:studyu_designer_v2/utils/input_formatter.dart';
 
 mixin StudyScheduleControls {
   static const defaultScheduleType = PhaseSequence.alternating;
   static const defaultScheduleTypeSequence = 'ABAB';
   static const defaultNumCycles = 2;
   static const defaultPeriodLength = 7;
+  static final RegExp customSequencePattern = RegExp(r'^[ABab]+$');
 
   final FormControl<PhaseSequence> sequenceTypeControl = FormControl(
     value: defaultScheduleType,
@@ -110,10 +112,15 @@ mixin StudyScheduleControls {
 
   FormControlValidation get customSequenceRequired => FormControlValidation(
     control: sequenceTypeCustomControl,
-    validators: [Validators.required],
+    validators: [
+      Validators.required,
+      Validators.pattern(customSequencePattern),
+    ],
     validationMessages: {
       ValidationMessage.required: (error) =>
           'Custom sequence needs to be specified.',
+      ValidationMessage.pattern: (error) =>
+          'Custom sequence can only contain A and B.',
     },
   );
 
@@ -128,7 +135,9 @@ mixin StudyScheduleControls {
   StudyScheduleFormData buildStudyScheduleFormData() {
     return StudyScheduleFormData(
       sequenceType: sequenceTypeControl.value!, // required
-      sequenceTypeCustom: sequenceTypeCustomControl.value!, // required
+      sequenceTypeCustom: normalizeStudySequenceInput(
+        sequenceTypeCustomControl.value!,
+      ), // required
       numCycles: numCyclesControl.value!, // required
       phaseDuration: phaseDurationControl.value!, // required
       includeBaseline: includeBaselineControl.value!, // required
diff --git a/designer_v2/lib/features/design/interventions/study_schedule_form_data.dart b/designer_v2/lib/features/design/interventions/study_schedule_form_data.dart
index 1763004ea..cdf014a69 100644
--- a/designer_v2/lib/features/design/interventions/study_schedule_form_data.dart
+++ b/designer_v2/lib/features/design/interventions/study_schedule_form_data.dart
@@ -1,6 +1,7 @@
 import 'package:studyu_core/core.dart';
 import 'package:studyu_designer_v2/features/design/study_form_data.dart';
 import 'package:studyu_designer_v2/features/forms/form_data.dart';
+import 'package:studyu_designer_v2/utils/input_formatter.dart';
 
 class StudyScheduleFormData implements IStudyFormData {
   StudyScheduleFormData({
@@ -30,7 +31,7 @@ class StudyScheduleFormData implements IStudyFormData {
   StudySchedule toStudySchedule() {
     final schedule = StudySchedule();
     schedule.sequence = sequenceType;
-    schedule.sequenceCustom = sequenceTypeCustom;
+    schedule.sequenceCustom = normalizeStudySequenceInput(sequenceTypeCustom);
     schedule.numberOfCycles = numCycles;
     schedule.phaseDuration = phaseDuration;
     schedule.includeBaseline = includeBaseline;
diff --git a/designer_v2/lib/features/design/interventions/study_schedule_form_view.dart b/designer_v2/lib/features/design/interventions/study_schedule_form_view.dart
index 1daf5d281..f07ff1947 100644
--- a/designer_v2/lib/features/design/interventions/study_schedule_form_view.dart
+++ b/designer_v2/lib/features/design/interventions/study_schedule_form_view.dart
@@ -74,9 +74,12 @@ class _StudyScheduleFormViewState extends State<StudyScheduleFormView> {
                 //formControl: widget.formViewModel.sequenceTypeControl,
                 onChanged: widget.formViewModel.sequenceTypeControl.disabled
                     ? null
-                    : (PhaseSequence? value) =>
+                    : (PhaseSequence? value) {
+                        setState(() {
                           widget.formViewModel.sequenceTypeControl.value =
-                              value,
+                              value;
+                        });
+                      },
                 initialValue: widget.formViewModel.sequenceTypeControl.value,
                 decoration: InputDecoration(
                   helperText:
diff --git a/designer_v2/lib/utils/input_formatter.dart b/designer_v2/lib/utils/input_formatter.dart
index b5e924295..123e6713a 100644
--- a/designer_v2/lib/utils/input_formatter.dart
+++ b/designer_v2/lib/utils/input_formatter.dart
@@ -1,5 +1,8 @@
 import 'package:flutter/services.dart';
 
+String normalizeStudySequenceInput(String value) =>
+    value.replaceAll(RegExp(r'\s+'), '').toUpperCase();
+
 class NumericalRangeFormatter extends TextInputFormatter {
   NumericalRangeFormatter({this.min, this.max});
 
@@ -30,14 +33,15 @@ class StudySequenceFormatter extends TextInputFormatter {
     TextEditingValue oldValue,
     TextEditingValue newValue,
   ) {
-    if (newValue.text == '') {
-      return newValue.copyWith(text: newValue.text.toUpperCase());
-    } else if (newValue.text
-        .replaceAll(' ', '')
-        .contains(RegExp(r'^[abAB]+$'))) {
-      return newValue.copyWith(text: newValue.text.toUpperCase());
-    } else {
+    final normalized = normalizeStudySequenceInput(newValue.text);
+
+    if (normalized.isNotEmpty && !RegExp(r'^[AB]+$').hasMatch(normalized)) {
       return oldValue;
     }
+
+    return TextEditingValue(
+      text: normalized,
+      selection: TextSelection.collapsed(offset: normalized.length),
+    );
   }
 }
diff --git a/designer_v2/test/features/design/interventions/study_schedule_form_data_test.dart b/designer_v2/test/features/design/interventions/study_schedule_form_data_test.dart
new file mode 100644
index 000000000..2c8a9f3b7
--- /dev/null
+++ b/designer_v2/test/features/design/interventions/study_schedule_form_data_test.dart
@@ -0,0 +1,22 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:studyu_core/core.dart';
+import 'package:studyu_designer_v2/features/design/interventions/study_schedule_form_data.dart';
+
+void main() {
+  group('StudyScheduleFormData', () {
+    test(
+      'normalizes custom sequence before applying it to the domain model',
+      () {
+        final data = StudyScheduleFormData(
+          sequenceType: PhaseSequence.customized,
+          sequenceTypeCustom: ' a b B a ',
+          numCycles: 2,
+          phaseDuration: 7,
+          includeBaseline: true,
+        );
+
+        expect(data.toStudySchedule().sequenceCustom, 'ABBA');
+      },
+    );
+  });
+}
diff --git a/designer_v2/test/utils/input_formatter_test.dart b/designer_v2/test/utils/input_formatter_test.dart
new file mode 100644
index 000000000..f40f63400
--- /dev/null
+++ b/designer_v2/test/utils/input_formatter_test.dart
@@ -0,0 +1,28 @@
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:studyu_designer_v2/utils/input_formatter.dart';
+
+void main() {
+  group('StudySequenceFormatter', () {
+    final formatter = StudySequenceFormatter();
+
+    TextEditingValue format(String oldText, String newText) {
+      return formatter.formatEditUpdate(
+        TextEditingValue(text: oldText),
+        TextEditingValue(text: newText),
+      );
+    }
+
+    test('uppercases valid sequence input', () {
+      expect(format('', 'abba').text, 'ABBA');
+    });
+
+    test('removes whitespace from pasted sequence input', () {
+      expect(format('', ' A b B A ').text, 'ABBA');
+    });
+
+    test('rejects characters other than A and B', () {
+      expect(format('AB', 'ABC').text, 'AB');
+    });
+  });
+}