diff --git a/packages/frontend/editor-ui/src/components/Node/NodeCreation.vue b/packages/frontend/editor-ui/src/components/Node/NodeCreation.vue
index ccbfe220c6..5eab16a6df 100644
--- a/packages/frontend/editor-ui/src/components/Node/NodeCreation.vue
+++ b/packages/frontend/editor-ui/src/components/Node/NodeCreation.vue
@@ -145,6 +145,7 @@ function onAskAssistantButtonClick() {
 				icon="panel-right"
 				:class="focusPanelActive ? $style.activeButton : ''"
 				:active="focusPanelActive"
+				data-test-id="toggle-focus-panel-button"
 				@click="toggleFocusPanel"
 			/>
 		</KeyboardShortcutTooltip>
diff --git a/packages/frontend/editor-ui/src/components/ParameterInput.vue b/packages/frontend/editor-ui/src/components/ParameterInput.vue
index 3c14a9c1a3..ca02141847 100644
--- a/packages/frontend/editor-ui/src/components/ParameterInput.vue
+++ b/packages/frontend/editor-ui/src/components/ParameterInput.vue
@@ -201,6 +201,7 @@ const dateTimePickerOptions = ref({
 	],
 });
 const isFocused = ref(false);
+const isMapperShown = ref(false);
 
 const contextNode = expressionLocalResolveCtx?.value?.workflow.getNode(
 	expressionLocalResolveCtx.value.nodeName,
@@ -611,11 +612,7 @@ const showDragnDropTip = computed(
 
 const shouldCaptureForPosthog = computed(() => node.value?.type === AI_TRANSFORM_NODE_TYPE);
 
-const shouldShowMapper = computed(
-	() =>
-		isFocused.value &&
-		(isModelValueExpression.value || props.forceShowExpression || props.modelValue === ''),
-);
+const mapperElRef = computed(() => mapperRef.value?.contentRef);
 
 function isRemoteParameterOption(option: INodePropertyOptions) {
 	return remoteParameterOptionsKeys.value.includes(option.name);
@@ -802,6 +799,10 @@ async function setFocus() {
 		}
 
 		isFocused.value = true;
+
+		if (isModelValueExpression.value || props.forceShowExpression || props.modelValue === '') {
+			isMapperShown.value = true;
+		}
 	}
 
 	emit('focus');
@@ -942,17 +943,19 @@ function expressionUpdated(value: string) {
 }
 
 function onBlur(event?: FocusEvent | KeyboardEvent) {
-	if (
-		event?.target instanceof HTMLElement &&
-		mapperRef.value?.contentRef &&
-		(event.target === mapperRef.value.contentRef ||
-			mapperRef.value.contentRef.contains(event.target))
-	) {
-		return;
-	}
-
 	emit('blur');
 	isFocused.value = false;
+
+	if (
+		!(event?.target instanceof Node && mapperElRef.value?.contains(event.target)) &&
+		!(
+			event instanceof FocusEvent &&
+			event.relatedTarget instanceof Node &&
+			mapperElRef.value?.contains(event.relatedTarget)
+		)
+	) {
+		isMapperShown.value = false;
+	}
 }
 
 function onPaste(event: ClipboardEvent) {
@@ -998,6 +1001,12 @@ function onUpdateTextInput(value: string) {
 	onTextInputChange(value);
 }
 
+function onClickOutsideMapper() {
+	if (!isFocused.value) {
+		isMapperShown.value = false;
+	}
+}
+
 async function optionSelected(command: string) {
 	const prevValue = props.modelValue;
 
@@ -1012,6 +1021,7 @@ async function optionSelected(command: string) {
 
 		case 'removeExpression':
 			isFocused.value = false;
+			isMapperShown.value = false;
 			valueChanged(
 				parseFromExpression(
 					props.modelValue,
@@ -1210,7 +1220,7 @@ onUpdated(async () => {
 	}
 });
 
-onClickOutside(wrapper, onBlur);
+onClickOutside(mapperElRef, onClickOutsideMapper);
 </script>
 
 <template>
@@ -1239,7 +1249,7 @@ onClickOutside(wrapper, onBlur);
 			:workflow="expressionLocalResolveCtx?.workflow"
 			:node="node"
 			:input-node-name="expressionLocalResolveCtx?.inputNode?.name"
-			:visible="shouldShowMapper"
+			:visible="isMapperShown"
 			:virtual-ref="wrapper"
 		/>
 
diff --git a/packages/testing/playwright/pages/CanvasPage.ts b/packages/testing/playwright/pages/CanvasPage.ts
index cd73373c75..a8dfe28c3c 100644
--- a/packages/testing/playwright/pages/CanvasPage.ts
+++ b/packages/testing/playwright/pages/CanvasPage.ts
@@ -360,6 +360,10 @@ export class CanvasPage extends BasePage {
 		return this.page.getByTestId('canvas-wrapper');
 	}
 
+	toggleFocusPanelButton(): Locator {
+		return this.page.getByTestId('toggle-focus-panel-button');
+	}
+
 	// Actions
 
 	async addInitialNodeToCanvas(nodeName: string): Promise<void> {
diff --git a/packages/testing/playwright/pages/NodeDetailsViewPage.ts b/packages/testing/playwright/pages/NodeDetailsViewPage.ts
index 1a133f4256..9223356c5a 100644
--- a/packages/testing/playwright/pages/NodeDetailsViewPage.ts
+++ b/packages/testing/playwright/pages/NodeDetailsViewPage.ts
@@ -20,7 +20,7 @@ export class NodeDetailsViewPage extends BasePage {
 	}
 
 	getParameterByLabel(labelName: string) {
-		return this.page.locator('.parameter-item').filter({ hasText: labelName });
+		return this.getContainer().locator('.parameter-item').filter({ hasText: labelName });
 	}
 
 	/**
diff --git a/packages/testing/playwright/tests/ui/9999-SUG-121-fields-reset-after-closing-ndv.spec.ts b/packages/testing/playwright/tests/ui/9999-SUG-121-fields-reset-after-closing-ndv.spec.ts
new file mode 100644
index 0000000000..6a75613cb4
--- /dev/null
+++ b/packages/testing/playwright/tests/ui/9999-SUG-121-fields-reset-after-closing-ndv.spec.ts
@@ -0,0 +1,30 @@
+import { test, expect } from '../../fixtures/base';
+import type { TestRequirements } from '../../Types';
+
+const requirements: TestRequirements = {
+	workflow: {
+		'Test_workflow_1.json': 'Test',
+	},
+	storage: {
+		N8N_EXPERIMENT_OVERRIDES: JSON.stringify({ ndv_in_focus_panel: 'variant' }),
+	},
+};
+
+test.describe('SUG-121 Fields reset after closing NDV', () => {
+	test('should preserve changes to parameters after closing NDV when focus panel is open', async ({
+		n8n,
+		setupRequirements,
+	}) => {
+		await setupRequirements(requirements);
+		await n8n.canvas.clickZoomToFitButton();
+		await n8n.canvas.toggleFocusPanelButton().click();
+		await n8n.canvas.canvasPane().click();
+		await n8n.canvas.nodeByName('Code').dblclick();
+		await n8n.ndv.getParameterByLabel('JavaScript').getByRole('textbox').fill('alert(1)');
+		await n8n.ndv.close();
+		await n8n.canvas.nodeByName('Code').dblclick();
+		await expect(n8n.ndv.getParameterByLabel('JavaScript').getByRole('textbox')).toHaveText(
+			'alert(1)',
+		);
+	});
+});
diff --git a/packages/testing/playwright/utils/requirements.ts b/packages/testing/playwright/utils/requirements.ts
index ce16210d0a..b859ad205f 100644
--- a/packages/testing/playwright/utils/requirements.ts
+++ b/packages/testing/playwright/utils/requirements.ts
@@ -10,8 +10,18 @@ export async function setupTestRequirements(
 	context: BrowserContext,
 	requirements: TestRequirements,
 ): Promise<void> {
-	const n8n = new n8nPage(page);
+	// 0. Setup browser storage before creating a new page
+	if (requirements.storage) {
+		await context.addInitScript((storage) => {
+			// Set localStorage items
+			for (const [key, value] of Object.entries(storage)) {
+				window.localStorage.setItem(key, value);
+			}
+		}, requirements.storage);
+	}
+
 	const api = new ApiHelpers(context.request);
+	const n8n = new n8nPage(page, api);
 
 	// 1. Setup frontend settings override
 	if (requirements.config?.settings) {
@@ -57,14 +67,4 @@ export async function setupTestRequirements(
 			}
 		}
 	}
-
-	// 5. Setup browser storage
-	if (requirements.storage) {
-		await context.addInitScript((storage) => {
-			// Set localStorage items
-			for (const [key, value] of Object.entries(storage)) {
-				window.localStorage.setItem(key, value);
-			}
-		}, requirements.storage);
-	}
 }