diff --git a/packages/xforms-engine/src/lib/reactivity/validation/createAggregatedViolations.ts b/packages/xforms-engine/src/lib/reactivity/validation/createAggregatedViolations.ts
index b444defbf..ac10b017a 100644
--- a/packages/xforms-engine/src/lib/reactivity/validation/createAggregatedViolations.ts
+++ b/packages/xforms-engine/src/lib/reactivity/validation/createAggregatedViolations.ts
@@ -42,7 +42,7 @@ const collectViolationReferences = (
 			}
 
 			default:
-				return child.validationState.violations;
+				return collectViolationReferences(child);
 		}
 	});
 };
diff --git a/packages/xforms-engine/test/lib/reactivity/createAggregatedViolations.test.ts b/packages/xforms-engine/test/lib/reactivity/createAggregatedViolations.test.ts
new file mode 100644
index 000000000..7689089c5
--- /dev/null
+++ b/packages/xforms-engine/test/lib/reactivity/createAggregatedViolations.test.ts
@@ -0,0 +1,309 @@
+import type { HtmlXFormsElement } from '@getodk/common/test/fixtures/xform-dsl/HtmlXFormsElement.ts';
+import {
+	bind,
+	body,
+	group,
+	head,
+	html,
+	input,
+	label,
+	mainInstance,
+	model,
+	t,
+	title,
+} from '@getodk/common/test/fixtures/xform-dsl/index.ts';
+import { beforeEach, describe, expect, it } from 'vitest';
+import { VALIDATION_TEXT } from '../../../src/client/constants.ts';
+import { initializeForm, type ValidationCondition } from '../../../src/index.ts';
+import { reactiveTestScope } from '../../helpers/reactive/internal.ts';
+
+describe('createAggregatedViolations - reactive aggregated `constraint` and `required` validation violations on ancestor nodes', () => {
+	let definition: HtmlXFormsElement;
+
+	beforeEach(() => {
+		// Reduced from https://github.com/sadiqkhoja/web-forms/blob/5e678e133584555990c6a19aeecc59561610f6c9/packages/ui-solid/fixtures/xforms/validation/1-validation.xml
+		// prettier-ignore
+		definition = html(
+			head(
+				title('Validation Form'),
+				model(
+					mainInstance(
+						t('data id="validation"',
+							t('contactdetails',
+								t('residentialAddress'),
+								t('phone',
+										t('home'))),
+							t('meta',
+								t('instanceID')))),
+					bind('/data/contactdetails/residentialAddress').required(),
+					bind('/data/contactdetails/phone/home').required())
+			),
+			body(
+				group(
+					'/data/contactdetails',
+					label('Household'),
+
+					input("/data/contactdetails/residentialAddress",
+						label('Residential address')),
+
+					group("/data/contactdetails/phone",
+						label('Phone numbers'),
+
+						input('/data/contactdetails/phone/home',
+							label('Home phone no.'))))));
+	});
+
+	interface SimplifiedViolation {
+		readonly condition: ValidationCondition;
+		readonly valid: false;
+		readonly message: string;
+	}
+
+	interface SimplifiedViolationReference {
+		readonly reference: string;
+		readonly violation: SimplifiedViolation;
+	}
+
+	// prettier-ignore
+	type ObservedViolationReferences = Array<
+		readonly SimplifiedViolationReference[]
+	>;
+
+	describe('check assumptions: ensure observing violation state is effective', () => {
+		it('observes violations of direct children', async () => {
+			const observed = await reactiveTestScope(async ({ effect, mutable }) => {
+				const root = await initializeForm(definition.asXml(), {
+					config: {
+						stateFactory: mutable,
+					},
+				});
+
+				const contactDetails = root.currentState.children[0];
+
+				if (
+					contactDetails?.nodeType !== 'group' ||
+					contactDetails.currentState.reference !== '/data/contactdetails'
+				) {
+					throw new Error('Expected group /data/contactdetails');
+				}
+
+				const phone = contactDetails.currentState.children[1];
+
+				if (
+					phone?.nodeType !== 'group' ||
+					phone.currentState.reference !== '/data/contactdetails/phone'
+				) {
+					throw new Error('Expected group /data/contactdetails/phone');
+				}
+
+				const observedViolations: ObservedViolationReferences = [];
+
+				effect(() => {
+					observedViolations.push(
+						phone.validationState.violations.map((violationReference) => {
+							const violation: SimplifiedViolation = {
+								condition: violationReference.violation.condition,
+								valid: violationReference.violation.valid,
+								message: violationReference.violation.message.asString,
+							};
+
+							return {
+								reference: violationReference.reference,
+								violation,
+							};
+						})
+					);
+				});
+
+				return observedViolations;
+			});
+
+			expect(observed).toEqual([
+				// Initially invalid
+				[
+					{
+						reference: '/data/contactdetails/phone/home',
+						violation: {
+							condition: 'required',
+							valid: false,
+							message: VALIDATION_TEXT.requiredMsg,
+						},
+					},
+				],
+			]);
+		});
+	});
+
+	it('reactively updates when a direct child becomes valid', async () => {
+		const observed = await reactiveTestScope(async ({ effect, mutable }) => {
+			const root = await initializeForm(definition.asXml(), {
+				config: {
+					stateFactory: mutable,
+				},
+			});
+
+			const contactDetails = root.currentState.children[0];
+
+			if (
+				contactDetails?.nodeType !== 'group' ||
+				contactDetails.currentState.reference !== '/data/contactdetails'
+			) {
+				throw new Error('Expected group /data/contactdetails');
+			}
+
+			const phone = contactDetails.currentState.children[1];
+
+			if (
+				phone?.nodeType !== 'group' ||
+				phone.currentState.reference !== '/data/contactdetails/phone'
+			) {
+				throw new Error('Expected group /data/contactdetails/phone');
+			}
+
+			const observedViolations: ObservedViolationReferences = [];
+
+			effect(() => {
+				observedViolations.push(
+					phone.validationState.violations.map((violationReference) => {
+						const violation: SimplifiedViolation = {
+							condition: violationReference.violation.condition,
+							valid: violationReference.violation.valid,
+							message: violationReference.violation.message.asString,
+						};
+
+						return {
+							reference: violationReference.reference,
+							violation,
+						};
+					})
+				);
+			});
+
+			const home = phone.currentState.children[0];
+
+			if (
+				home?.currentState.reference !== '/data/contactdetails/phone/home' ||
+				home.nodeType !== 'string'
+			) {
+				throw new Error('Expected string node /data/contactdetails/phone/home');
+			}
+
+			// Satisfy `required` condition
+			home.setValue('555-867-5309');
+
+			return observedViolations;
+		});
+
+		expect(observed).toEqual([
+			// Initially invalid
+			[
+				{
+					reference: '/data/contactdetails/phone/home',
+					violation: {
+						condition: 'required',
+						valid: false,
+						message: VALIDATION_TEXT.requiredMsg,
+					},
+				},
+			],
+
+			// Valid after change
+			[],
+		]);
+	});
+
+	it('reactively updates when a deeper descendant becomes valid', async () => {
+		const observed = await reactiveTestScope(async ({ effect, mutable }) => {
+			const root = await initializeForm(definition.asXml(), {
+				config: {
+					stateFactory: mutable,
+				},
+			});
+
+			const contactDetails = root.currentState.children[0];
+
+			if (
+				contactDetails?.nodeType !== 'group' ||
+				contactDetails.currentState.reference !== '/data/contactdetails'
+			) {
+				throw new Error('Expected group /data/contactdetails');
+			}
+
+			const observedViolations: ObservedViolationReferences = [];
+
+			effect(() => {
+				observedViolations.push(
+					contactDetails.validationState.violations.map((violationReference) => {
+						const violation: SimplifiedViolation = {
+							condition: violationReference.violation.condition,
+							valid: violationReference.violation.valid,
+							message: violationReference.violation.message.asString,
+						};
+
+						return {
+							reference: violationReference.reference,
+							violation,
+						};
+					})
+				);
+			});
+
+			const phone = contactDetails.currentState.children[1];
+
+			if (
+				phone?.nodeType !== 'group' ||
+				phone.currentState.reference !== '/data/contactdetails/phone'
+			) {
+				throw new Error('Expected group /data/contactdetails/phone');
+			}
+
+			const home = phone.currentState.children[0];
+
+			if (
+				home?.currentState.reference !== '/data/contactdetails/phone/home' ||
+				home.nodeType !== 'string'
+			) {
+				throw new Error('Expected string node /data/contactdetails/phone/home');
+			}
+
+			// Satisfy `required` condition
+			home.setValue('555-867-5309');
+
+			return observedViolations;
+		});
+
+		expect(observed).toEqual([
+			// Both descendants initially invalid
+			[
+				{
+					reference: '/data/contactdetails/residentialAddress',
+					violation: {
+						condition: 'required',
+						valid: false,
+						message: VALIDATION_TEXT.requiredMsg,
+					},
+				},
+				{
+					reference: '/data/contactdetails/phone/home',
+					violation: {
+						condition: 'required',
+						valid: false,
+						message: VALIDATION_TEXT.requiredMsg,
+					},
+				},
+			],
+
+			// Direct child still invalid; deeper descendant valid after change
+			[
+				{
+					reference: '/data/contactdetails/residentialAddress',
+					violation: {
+						condition: 'required',
+						valid: false,
+						message: VALIDATION_TEXT.requiredMsg,
+					},
+				},
+			],
+		]);
+	});
+});