fix(cue): enable multi-agent pipeline output passing and polish editor UX

src/__tests__/main/cue/cue-completion-chains.test.ts

@@ -156,7 +156,7 @@ describe('CueEngine completion chains', () => {
 			engine.stop();
 		});
 
-		it('truncates sourceOutput to 5000 chars', () => {
+		it('truncates sourceOutput to 5000 chars and sets outputTruncated to true', () => {
 			const config = createMockConfig({
 				subscriptions: [
 					{
@@ -180,6 +180,34 @@ describe('CueEngine completion chains', () => {
 			const request = (deps.onCueRun as ReturnType<typeof vi.fn>).mock.calls[0][0];
 			const event = request.event as CueEvent;
 			expect((event.payload.sourceOutput as string).length).toBe(5000);
+			expect(event.payload.outputTruncated).toBe(true);
+
+			engine.stop();
+		});
+
+		it('sets outputTruncated to false when output is under limit', () => {
+			const config = createMockConfig({
+				subscriptions: [
+					{
+						name: 'on-done',
+						event: 'agent.completed',
+						enabled: true,
+						prompt: 'follow up',
+						source_session: 'agent-a',
+					},
+				],
+			});
+			mockLoadCueConfig.mockReturnValue(config);
+			const deps = createMockDeps();
+			const engine = new CueEngine(deps);
+			engine.start();
+
+			vi.clearAllMocks();
+			engine.notifyAgentCompleted('agent-a', { stdout: 'short output' });
+
+			const request = (deps.onCueRun as ReturnType<typeof vi.fn>).mock.calls[0][0];
+			const event = request.event as CueEvent;
+			expect(event.payload.outputTruncated).toBe(false);
 
 			engine.stop();
 		});
@@ -451,6 +479,42 @@ describe('CueEngine completion chains', () => {
 			engine.stop();
 		});
 
+		it('sets outputTruncated in fan-in aggregate event when any source is truncated', () => {
+			const config = createMockConfig({
+				subscriptions: [
+					{
+						name: 'all-done',
+						event: 'agent.completed',
+						enabled: true,
+						prompt: 'aggregate',
+						source_session: ['agent-a', 'agent-b'],
+					},
+				],
+			});
+			mockLoadCueConfig.mockReturnValue(config);
+			const deps = createMockDeps();
+			const engine = new CueEngine(deps);
+			engine.start();
+
+			vi.clearAllMocks();
+
+			const longOutput = 'x'.repeat(10000);
+			engine.notifyAgentCompleted('agent-a', { sessionName: 'Agent A', stdout: longOutput });
+			engine.notifyAgentCompleted('agent-b', { sessionName: 'Agent B', stdout: 'short' });
+
+			expect(deps.onCueRun).toHaveBeenCalledWith(
+				expect.objectContaining({
+					event: expect.objectContaining({
+						payload: expect.objectContaining({
+							outputTruncated: true,
+						}),
+					}),
+				})
+			);
+
+			engine.stop();
+		});
+
 		it('logs waiting message during fan-in', () => {
 			const config = createMockConfig({
 				subscriptions: [
@@ -565,6 +629,49 @@ describe('CueEngine completion chains', () => {
 
 			engine.stop();
 		});
+
+		it('includes outputTruncated in continue-mode timeout payload', () => {
+			const config = createMockConfig({
+				subscriptions: [
+					{
+						name: 'all-done',
+						event: 'agent.completed',
+						enabled: true,
+						prompt: 'aggregate',
+						source_session: ['agent-a', 'agent-b'],
+					},
+				],
+				settings: {
+					timeout_minutes: 1,
+					timeout_on_fail: 'continue',
+					max_concurrent: 1,
+					queue_size: 10,
+				},
+			});
+			mockLoadCueConfig.mockReturnValue(config);
+			const deps = createMockDeps();
+			const engine = new CueEngine(deps);
+			engine.start();
+
+			vi.clearAllMocks();
+			const longOutput = 'x'.repeat(10000);
+			engine.notifyAgentCompleted('agent-a', { stdout: longOutput });
+
+			vi.advanceTimersByTime(1 * 60 * 1000 + 100);
+
+			expect(deps.onCueRun).toHaveBeenCalledWith(
+				expect.objectContaining({
+					event: expect.objectContaining({
+						payload: expect.objectContaining({
+							outputTruncated: true,
+							partial: true,
+						}),
+					}),
+				})
+			);
+
+			engine.stop();
+		});
 	});
 
 	describe('hasCompletionSubscribers', () => {

src/__tests__/renderer/components/CuePipelineEditor/utils/pipelineChainIntegration.test.ts

@@ -0,0 +1,198 @@
+/**
+ * Integration tests for pipeline chain output variable substitution.
+ *
+ * Verifies that the full flow works end-to-end:
+ * pipelineToYamlSubscriptions → {{CUE_SOURCE_OUTPUT}} injection → substituteTemplateVariables resolution
+ */
+
+import { describe, it, expect } from 'vitest';
+import { pipelineToYamlSubscriptions } from '../../../../../renderer/components/CuePipelineEditor/utils/pipelineToYaml';
+import { substituteTemplateVariables } from '../../../../../shared/templateVariables';
+import type { CuePipeline } from '../../../../../shared/cue-pipeline-types';
+import type { TemplateContext, TemplateSessionInfo } from '../../../../../shared/templateVariables';
+
+function makePipeline(overrides: Partial<CuePipeline> = {}): CuePipeline {
+	return {
+		id: 'p1',
+		name: 'test-pipeline',
+		color: '#06b6d4',
+		nodes: [],
+		edges: [],
+		...overrides,
+	};
+}
+
+const stubSession: TemplateSessionInfo = {
+	id: 'test-session',
+	name: 'test-agent',
+	toolType: 'claude-code',
+	cwd: '/tmp/test',
+};
+
+describe('pipeline chain output integration', () => {
+	it('generated chain prompt resolves {{CUE_SOURCE_OUTPUT}} to actual output', () => {
+		const pipeline = makePipeline({
+			nodes: [
+				{
+					id: 't1',
+					type: 'trigger',
+					position: { x: 0, y: 0 },
+					data: { eventType: 'file.changed', label: 'Files', config: { watch: '**/*' } },
+				},
+				{
+					id: 'a1',
+					type: 'agent',
+					position: { x: 300, y: 0 },
+					data: {
+						sessionId: 's1',
+						sessionName: 'builder',
+						toolType: 'claude-code',
+						inputPrompt: 'Build the project',
+					},
+				},
+				{
+					id: 'a2',
+					type: 'agent',
+					position: { x: 600, y: 0 },
+					data: {
+						sessionId: 's2',
+						sessionName: 'tester',
+						toolType: 'claude-code',
+						inputPrompt: 'Review the changes',
+					},
+				},
+			],
+			edges: [
+				{ id: 'e1', source: 't1', target: 'a1', mode: 'pass' },
+				{ id: 'e2', source: 'a1', target: 'a2', mode: 'pass' },
+			],
+		});
+
+		const subs = pipelineToYamlSubscriptions(pipeline);
+		const chainSub = subs.find((s) => s.event === 'agent.completed');
+		expect(chainSub).toBeDefined();
+		expect(chainSub!.prompt).toContain('{{CUE_SOURCE_OUTPUT}}');
+
+		// Simulate the engine substituting the template variable
+		const context: TemplateContext = {
+			session: stubSession,
+			cue: {
+				sourceOutput: 'Build completed successfully. 42 files compiled.',
+				sourceSession: 'builder',
+			},
+		};
+		const resolved = substituteTemplateVariables(chainSub!.prompt!, context);
+		expect(resolved).toContain('Build completed successfully. 42 files compiled.');
+		expect(resolved).toContain('Review the changes');
+		expect(resolved).not.toContain('{{CUE_SOURCE_OUTPUT}}');
+	});
+
+	it('preserves user prompt content alongside injected source output', () => {
+		const pipeline = makePipeline({
+			nodes: [
+				{
+					id: 't1',
+					type: 'trigger',
+					position: { x: 0, y: 0 },
+					data: { eventType: 'file.changed', label: 'Files', config: { watch: '**/*' } },
+				},
+				{
+					id: 'a1',
+					type: 'agent',
+					position: { x: 300, y: 0 },
+					data: {
+						sessionId: 's1',
+						sessionName: 'builder',
+						toolType: 'claude-code',
+						inputPrompt: 'Build',
+					},
+				},
+				{
+					id: 'a2',
+					type: 'agent',
+					position: { x: 600, y: 0 },
+					data: {
+						sessionId: 's2',
+						sessionName: 'reviewer',
+						toolType: 'claude-code',
+						inputPrompt: 'Review the code changes and suggest improvements',
+					},
+				},
+			],
+			edges: [
+				{ id: 'e1', source: 't1', target: 'a1', mode: 'pass' },
+				{ id: 'e2', source: 'a1', target: 'a2', mode: 'pass' },
+			],
+		});
+
+		const subs = pipelineToYamlSubscriptions(pipeline);
+		const chainSub = subs.find((s) => s.event === 'agent.completed')!;
+
+		const context: TemplateContext = {
+			session: stubSession,
+			cue: {
+				sourceOutput: 'Diff: +5 -3 lines',
+				sourceSession: 'builder',
+			},
+		};
+		const resolved = substituteTemplateVariables(chainSub.prompt!, context);
+
+		// Both the source output AND user instructions should be present
+		expect(resolved).toContain('Diff: +5 -3 lines');
+		expect(resolved).toContain('Review the code changes and suggest improvements');
+	});
+
+	it('handles empty source output gracefully', () => {
+		const pipeline = makePipeline({
+			nodes: [
+				{
+					id: 't1',
+					type: 'trigger',
+					position: { x: 0, y: 0 },
+					data: { eventType: 'file.changed', label: 'Files', config: { watch: '**/*' } },
+				},
+				{
+					id: 'a1',
+					type: 'agent',
+					position: { x: 300, y: 0 },
+					data: {
+						sessionId: 's1',
+						sessionName: 'builder',
+						toolType: 'claude-code',
+						inputPrompt: 'Build',
+					},
+				},
+				{
+					id: 'a2',
+					type: 'agent',
+					position: { x: 600, y: 0 },
+					data: {
+						sessionId: 's2',
+						sessionName: 'tester',
+						toolType: 'claude-code',
+						inputPrompt: 'Run tests',
+					},
+				},
+			],
+			edges: [
+				{ id: 'e1', source: 't1', target: 'a1', mode: 'pass' },
+				{ id: 'e2', source: 'a1', target: 'a2', mode: 'pass' },
+			],
+		});
+
+		const subs = pipelineToYamlSubscriptions(pipeline);
+		const chainSub = subs.find((s) => s.event === 'agent.completed')!;
+
+		// Simulate empty source output
+		const context: TemplateContext = {
+			session: stubSession,
+			cue: {
+				sourceOutput: '',
+				sourceSession: 'builder',
+			},
+		};
+		const resolved = substituteTemplateVariables(chainSub.prompt!, context);
+		expect(resolved).not.toContain('{{CUE_SOURCE_OUTPUT}}');
+		expect(resolved).toContain('Run tests');
+	});
+});