fix(core): Resolve legacy $item accessor properties in vm expression engine (no-changelog) (backport to release-candidate/2.26.x) (#32563)

Co-authored-by: Mike Repeć <mike.repec@n8n.io>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Danny Martini <danny@n8n.io>

packages/@n8n/expression-runtime/src/runtime/context.ts

@@ -167,13 +167,11 @@ export function buildContext(
 	// Wire builtins so tournament's VariablePolyfill resolves them from ctx
 	initializeBuiltins(target);
 
-	// $item(itemIndex) returns a sub-proxy for the specified item (legacy syntax)
+	// $item(i) → single lazy proxy at ['$item', i]; the host bridge navigates
+	// data.$item(i).<rest> safely (see isolated-vm-bridge getValueAtPath),
+	// exposing the full accessor surface ($json, $binary, $node, $nodeId, ...).
 	target.$item = function (itemIndex: number) {
-		const indexStr = String(itemIndex);
-		return {
-			$json: createDeepLazyProxy(['$item', indexStr, '$json'], undefined, callbacks),
-			$binary: createDeepLazyProxy(['$item', indexStr, '$binary'], undefined, callbacks),
-		};
+		return createDeepLazyProxy(['$item', String(itemIndex)], undefined, callbacks);
 	};
 
 	// $() function for accessing other nodes.

packages/workflow/test/expression-item-accessor-engine-parity.test.ts

@@ -0,0 +1,110 @@
+// @vitest-environment jsdom
+
+import * as Helpers from './helpers';
+import { createRunExecutionData } from '../src';
+import { Workflow } from '../src/workflow';
+
+// Engine-parity tests for the legacy `$item(index)` accessor surface.
+//
+// `$item(index)` returns a full item-scoped data proxy that exposes the whole
+// accessor surface (`$json`, `$node`, `$nodeId`, `$workflow`, ...), not just
+// `$json`/`$binary`. Under the VM engine the in-isolate `$item` originally
+// returned only `{ $json, $binary }`, so `$item(0).$node[...]` and
+// `$item(0).$nodeId` resolved to undefined at runtime while the legacy engine
+// (and the editor preview) returned the correct value (CAT-3496).
+//
+// These cases run under both the legacy and VM engines (see `vitest.config.ts`)
+// so any divergence fails exactly one project.
+
+describe('Expression — legacy $item(index) accessor surface (engine parity)', () => {
+	const workflow = new Workflow({
+		id: '1',
+		nodes: [
+			{
+				name: 'Init Data',
+				typeVersion: 1,
+				type: 'test.set',
+				id: 'init-data-1',
+				position: [0, 0],
+				parameters: {},
+			},
+			{
+				name: 'Current',
+				typeVersion: 1,
+				type: 'test.set',
+				id: 'current-1',
+				position: [100, 0],
+				parameters: {},
+			},
+		],
+		connections: {
+			'Init Data': {
+				main: [[{ node: 'Current', type: 'main', index: 0 }]],
+			},
+		},
+		active: false,
+		nodeTypes: Helpers.NodeTypes(),
+	});
+	const expression = workflow.expression;
+
+	const runExecutionData = createRunExecutionData({
+		resultData: {
+			runData: {
+				'Init Data': [
+					{
+						startTime: 0,
+						executionTime: 0,
+						executionIndex: 0,
+						source: [],
+						data: { main: [[{ json: { new: '2.27.0' } }]] },
+					},
+				],
+			},
+		},
+	});
+
+	beforeAll(async () => {
+		await expression.acquireIsolate();
+	});
+	afterAll(async () => {
+		await expression.releaseIsolate();
+	});
+
+	const evaluate = (expr: string) =>
+		expression.getParameterValue(
+			expr,
+			runExecutionData,
+			0, // runIndex of the active node
+			0, // itemIndex
+			'Current',
+			[
+				{
+					json: { link: 'right' },
+					binary: { myFile: { data: '', mimeType: 'text/plain', fileName: 'test.txt' } },
+				},
+				{ json: { link: 'left' } },
+			],
+			'manual',
+			{},
+		);
+
+	it('resolves $item(0).$node["Name"].json["key"] (issue repro)', () => {
+		expect(evaluate('={{ $item(0).$node["Init Data"].json["new"] }}')).toBe('2.27.0');
+	});
+
+	it('resolves $item(0).$nodeId to the active node id', () => {
+		expect(evaluate('={{ $item(0).$nodeId }}')).toBe('current-1');
+	});
+
+	it('still resolves $item(0).$json (regression guard)', () => {
+		expect(evaluate('={{ $item(0).$json["link"] }}')).toBe('right');
+	});
+
+	it('still resolves $item(0).$binary (regression guard)', () => {
+		expect(evaluate('={{ $item(0).$binary["myFile"]["fileName"] }}')).toBe('test.txt');
+	});
+
+	it('resolves $item(index) for index > 0 over a multi-item input', () => {
+		expect(evaluate('={{ $item(1).$json["link"] }}')).toBe('left');
+	});
+});

packages/workflow/test/expression-items-engine-parity.test.ts

@@ -1,8 +1,8 @@
 // @vitest-environment jsdom
 
 import * as Helpers from './helpers';
-import { ExpressionError } from '../src/errors/expression.error';
 import { createRunExecutionData } from '../src';
+import { ExpressionError } from '../src/errors/expression.error';
 import { Workflow } from '../src/workflow';
 
 // Engine-parity tests for `$items()` boundary behaviour.