refactor: streamline test suite - cut 33 files, enable parallel execution (11.9x speedup)

Remove duplicate, low-value, and fragmented test files while preserving
all meaningful coverage. Enable parallel test execution and remove
the entire benchmark infrastructure.

Key changes:
- Consolidate workflow-validator tests (13 files -> 3)
- Consolidate config-validator tests (9 files -> 3)
- Consolidate telemetry tests (11 files -> 6)
- Merge AI validator tests (2 files -> 1)
- Remove example/demo test files, mock-testing files, and already-skipped tests
- Remove benchmark infrastructure (10 files, CI workflow, 4 npm scripts)
- Enable parallel test execution (remove singleThread: true)
- Remove retry:2 that was masking flaky tests
- Slim CI publish-results job

Results: 224 -> 191 test files, 4690 -> 4303 tests, 121K -> 106K lines
Local runtime: 319s -> 27s (11.9x speedup)

Conceived by Romuald Członkowski - www.aiadvisors.pl/en

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/telemetry/telemetry-processing.test.ts

@@ -0,0 +1,938 @@
+import { describe, it, expect, beforeEach, vi, afterEach, beforeAll, afterAll, type MockInstance } from 'vitest';
+import { TelemetryBatchProcessor } from '../../../src/telemetry/batch-processor';
+import { TelemetryEvent, WorkflowTelemetry, WorkflowMutationRecord, TELEMETRY_CONFIG } from '../../../src/telemetry/telemetry-types';
+import { TelemetryError, TelemetryErrorType } from '../../../src/telemetry/telemetry-error';
+import { IntentClassification, MutationToolName } from '../../../src/telemetry/mutation-types';
+import { AddNodeOperation } from '../../../src/types/workflow-diff';
+import type { SupabaseClient } from '@supabase/supabase-js';
+
+// Mock logger to avoid console output in tests
+vi.mock('../../../src/utils/logger', () => ({
+  logger: {
+    debug: vi.fn(),
+    info: vi.fn(),
+    warn: vi.fn(),
+    error: vi.fn(),
+  }
+}));
+
+describe('TelemetryBatchProcessor', () => {
+  let batchProcessor: TelemetryBatchProcessor;
+  let mockSupabase: SupabaseClient;
+  let mockIsEnabled: ReturnType<typeof vi.fn>;
+  let mockProcessExit: MockInstance;
+
+  const createMockSupabaseResponse = (error: any = null) => ({
+    data: null,
+    error,
+    status: error ? 400 : 200,
+    statusText: error ? 'Bad Request' : 'OK',
+    count: null
+  });
+
+  beforeEach(() => {
+    vi.useFakeTimers();
+    mockIsEnabled = vi.fn().mockReturnValue(true);
+
+    mockSupabase = {
+      from: vi.fn().mockReturnValue({
+        insert: vi.fn().mockResolvedValue(createMockSupabaseResponse())
+      })
+    } as any;
+
+    // Mock process events to prevent actual exit
+    mockProcessExit = vi.spyOn(process, 'exit').mockImplementation((() => {
+      // Do nothing - just prevent actual exit
+    }) as any);
+
+    vi.clearAllMocks();
+
+    batchProcessor = new TelemetryBatchProcessor(mockSupabase, mockIsEnabled);
+  });
+
+  afterEach(() => {
+    // Stop the batch processor to clear any intervals
+    batchProcessor.stop();
+    mockProcessExit.mockRestore();
+    vi.clearAllTimers();
+    vi.useRealTimers();
+  });
+
+  describe('start()', () => {
+    it('should start periodic flushing when enabled', () => {
+      const setIntervalSpy = vi.spyOn(global, 'setInterval');
+
+      batchProcessor.start();
+
+      expect(setIntervalSpy).toHaveBeenCalledWith(
+        expect.any(Function),
+        TELEMETRY_CONFIG.BATCH_FLUSH_INTERVAL
+      );
+    });
+
+    it('should not start when disabled', () => {
+      mockIsEnabled.mockReturnValue(false);
+      const setIntervalSpy = vi.spyOn(global, 'setInterval');
+
+      batchProcessor.start();
+
+      expect(setIntervalSpy).not.toHaveBeenCalled();
+    });
+
+    it('should not start without Supabase client', () => {
+      const processor = new TelemetryBatchProcessor(null, mockIsEnabled);
+      const setIntervalSpy = vi.spyOn(global, 'setInterval');
+
+      processor.start();
+
+      expect(setIntervalSpy).not.toHaveBeenCalled();
+      processor.stop();
+    });
+
+    it('should set up process exit handlers', () => {
+      const onSpy = vi.spyOn(process, 'on');
+
+      batchProcessor.start();
+
+      expect(onSpy).toHaveBeenCalledWith('beforeExit', expect.any(Function));
+      expect(onSpy).toHaveBeenCalledWith('SIGINT', expect.any(Function));
+      expect(onSpy).toHaveBeenCalledWith('SIGTERM', expect.any(Function));
+    });
+  });
+
+  describe('stop()', () => {
+    it('should clear flush timer', () => {
+      const clearIntervalSpy = vi.spyOn(global, 'clearInterval');
+
+      batchProcessor.start();
+      batchProcessor.stop();
+
+      expect(clearIntervalSpy).toHaveBeenCalled();
+    });
+  });
+
+  describe('flush()', () => {
+    const mockEvents: TelemetryEvent[] = [
+      {
+        user_id: 'user1',
+        event: 'tool_used',
+        properties: { tool: 'httpRequest', success: true }
+      },
+      {
+        user_id: 'user2',
+        event: 'tool_used',
+        properties: { tool: 'webhook', success: false }
+      }
+    ];
+
+    const mockWorkflows: WorkflowTelemetry[] = [
+      {
+        user_id: 'user1',
+        workflow_hash: 'hash1',
+        node_count: 3,
+        node_types: ['webhook', 'httpRequest', 'set'],
+        has_trigger: true,
+        has_webhook: true,
+        complexity: 'medium',
+        sanitized_workflow: { nodes: [], connections: {} }
+      }
+    ];
+
+    it('should flush events successfully', async () => {
+      await batchProcessor.flush(mockEvents);
+
+      expect(mockSupabase.from).toHaveBeenCalledWith('telemetry_events');
+      expect(mockSupabase.from('telemetry_events').insert).toHaveBeenCalledWith(mockEvents);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBe(2);
+      expect(metrics.batchesSent).toBe(1);
+    });
+
+    it('should flush workflows successfully', async () => {
+      await batchProcessor.flush(undefined, mockWorkflows);
+
+      expect(mockSupabase.from).toHaveBeenCalledWith('telemetry_workflows');
+      expect(mockSupabase.from('telemetry_workflows').insert).toHaveBeenCalledWith(mockWorkflows);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBe(1);
+      expect(metrics.batchesSent).toBe(1);
+    });
+
+    it('should flush both events and workflows', async () => {
+      await batchProcessor.flush(mockEvents, mockWorkflows);
+
+      expect(mockSupabase.from).toHaveBeenCalledWith('telemetry_events');
+      expect(mockSupabase.from).toHaveBeenCalledWith('telemetry_workflows');
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBe(3); // 2 events + 1 workflow
+      expect(metrics.batchesSent).toBe(2);
+    });
+
+    it('should not flush when disabled', async () => {
+      mockIsEnabled.mockReturnValue(false);
+
+      await batchProcessor.flush(mockEvents, mockWorkflows);
+
+      expect(mockSupabase.from).not.toHaveBeenCalled();
+    });
+
+    it('should not flush without Supabase client', async () => {
+      const processor = new TelemetryBatchProcessor(null, mockIsEnabled);
+
+      await processor.flush(mockEvents);
+
+      expect(mockSupabase.from).not.toHaveBeenCalled();
+    });
+
+    it('should skip flush when circuit breaker is open', async () => {
+      // Open circuit breaker by failing multiple times
+      const errorResponse = createMockSupabaseResponse(new Error('Network error'));
+      vi.mocked(mockSupabase.from('telemetry_events').insert).mockResolvedValue(errorResponse);
+
+      // Fail enough times to open circuit breaker (5 by default)
+      for (let i = 0; i < 5; i++) {
+        await batchProcessor.flush(mockEvents);
+      }
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.circuitBreakerState.state).toBe('open');
+
+      // Next flush should be skipped
+      vi.clearAllMocks();
+      await batchProcessor.flush(mockEvents);
+
+      expect(mockSupabase.from).not.toHaveBeenCalled();
+      expect(batchProcessor.getMetrics().eventsDropped).toBeGreaterThan(0);
+    });
+
+    it('should record flush time metrics', async () => {
+      const startTime = Date.now();
+      await batchProcessor.flush(mockEvents);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.averageFlushTime).toBeGreaterThanOrEqual(0);
+      expect(metrics.lastFlushTime).toBeGreaterThanOrEqual(0);
+    });
+  });
+
+  describe('batch creation', () => {
+    it('should create single batch for small datasets', async () => {
+      const events: TelemetryEvent[] = Array.from({ length: 10 }, (_, i) => ({
+        user_id: `user${i}`,
+        event: 'test_event',
+        properties: { index: i }
+      }));
+
+      await batchProcessor.flush(events);
+
+      expect(mockSupabase.from('telemetry_events').insert).toHaveBeenCalledTimes(1);
+      expect(mockSupabase.from('telemetry_events').insert).toHaveBeenCalledWith(events);
+    });
+
+    it('should create multiple batches for large datasets', async () => {
+      const events: TelemetryEvent[] = Array.from({ length: 75 }, (_, i) => ({
+        user_id: `user${i}`,
+        event: 'test_event',
+        properties: { index: i }
+      }));
+
+      await batchProcessor.flush(events);
+
+      // Should create 2 batches (50 + 25) based on TELEMETRY_CONFIG.MAX_BATCH_SIZE
+      expect(mockSupabase.from('telemetry_events').insert).toHaveBeenCalledTimes(2);
+
+      const firstCall = vi.mocked(mockSupabase.from('telemetry_events').insert).mock.calls[0][0];
+      const secondCall = vi.mocked(mockSupabase.from('telemetry_events').insert).mock.calls[1][0];
+
+      expect(firstCall).toHaveLength(TELEMETRY_CONFIG.MAX_BATCH_SIZE);
+      expect(secondCall).toHaveLength(25);
+    });
+  });
+
+  describe('workflow deduplication', () => {
+    it('should deduplicate workflows by hash', async () => {
+      const workflows: WorkflowTelemetry[] = [
+        {
+          user_id: 'user1',
+          workflow_hash: 'hash1',
+          node_count: 2,
+          node_types: ['webhook', 'set'],
+          has_trigger: true,
+          has_webhook: true,
+          complexity: 'simple',
+          sanitized_workflow: { nodes: [], connections: {} }
+        },
+        {
+          user_id: 'user2',
+          workflow_hash: 'hash1', // Same hash - should be deduplicated
+          node_count: 2,
+          node_types: ['webhook', 'set'],
+          has_trigger: true,
+          has_webhook: true,
+          complexity: 'simple',
+          sanitized_workflow: { nodes: [], connections: {} }
+        },
+        {
+          user_id: 'user1',
+          workflow_hash: 'hash2', // Different hash - should be kept
+          node_count: 3,
+          node_types: ['webhook', 'httpRequest', 'set'],
+          has_trigger: true,
+          has_webhook: true,
+          complexity: 'medium',
+          sanitized_workflow: { nodes: [], connections: {} }
+        }
+      ];
+
+      await batchProcessor.flush(undefined, workflows);
+
+      const insertCall = vi.mocked(mockSupabase.from('telemetry_workflows').insert).mock.calls[0][0];
+      expect(insertCall).toHaveLength(2); // Should deduplicate to 2 workflows
+
+      const hashes = insertCall.map((w: WorkflowTelemetry) => w.workflow_hash);
+      expect(hashes).toEqual(['hash1', 'hash2']);
+    });
+  });
+
+  describe('error handling and retries', () => {
+    it('should retry on failure with exponential backoff', async () => {
+      const error = new Error('Network timeout');
+      const errorResponse = createMockSupabaseResponse(error);
+
+      // Mock to fail first 2 times, then succeed
+      vi.mocked(mockSupabase.from('telemetry_events').insert)
+        .mockResolvedValueOnce(errorResponse)
+        .mockResolvedValueOnce(errorResponse)
+        .mockResolvedValueOnce(createMockSupabaseResponse());
+
+      const events: TelemetryEvent[] = [{
+        user_id: 'user1',
+        event: 'test_event',
+        properties: {}
+      }];
+
+      await batchProcessor.flush(events);
+
+      // Should have been called 3 times (2 failures + 1 success)
+      expect(mockSupabase.from('telemetry_events').insert).toHaveBeenCalledTimes(3);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBe(1); // Should succeed on third try
+    });
+
+    it('should fail after max retries', async () => {
+      const error = new Error('Persistent network error');
+      const errorResponse = createMockSupabaseResponse(error);
+
+      vi.mocked(mockSupabase.from('telemetry_events').insert).mockResolvedValue(errorResponse);
+
+      const events: TelemetryEvent[] = [{
+        user_id: 'user1',
+        event: 'test_event',
+        properties: {}
+      }];
+
+      await batchProcessor.flush(events);
+
+      // Should have been called MAX_RETRIES times
+      expect(mockSupabase.from('telemetry_events').insert)
+        .toHaveBeenCalledTimes(TELEMETRY_CONFIG.MAX_RETRIES);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsFailed).toBe(1);
+      expect(metrics.batchesFailed).toBe(1);
+      expect(metrics.deadLetterQueueSize).toBe(1);
+    });
+
+    it('should handle operation timeout', async () => {
+      // Mock the operation to always fail with timeout error
+      vi.mocked(mockSupabase.from('telemetry_events').insert).mockRejectedValue(
+        new Error('Operation timed out')
+      );
+
+      const events: TelemetryEvent[] = [{
+        user_id: 'user1',
+        event: 'test_event',
+        properties: {}
+      }];
+
+      // The flush should fail after retries
+      await batchProcessor.flush(events);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsFailed).toBe(1);
+    });
+  });
+
+  describe('dead letter queue', () => {
+    it('should add failed events to dead letter queue', async () => {
+      const error = new Error('Persistent error');
+      const errorResponse = createMockSupabaseResponse(error);
+      vi.mocked(mockSupabase.from('telemetry_events').insert).mockResolvedValue(errorResponse);
+
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'event1', properties: {} },
+        { user_id: 'user2', event: 'event2', properties: {} }
+      ];
+
+      await batchProcessor.flush(events);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.deadLetterQueueSize).toBe(2);
+    });
+
+    it('should process dead letter queue when circuit is healthy', async () => {
+      const error = new Error('Temporary error');
+      const errorResponse = createMockSupabaseResponse(error);
+
+      // First 3 calls fail (for all retries), then succeed
+      vi.mocked(mockSupabase.from('telemetry_events').insert)
+        .mockResolvedValueOnce(errorResponse)  // Retry 1
+        .mockResolvedValueOnce(errorResponse)  // Retry 2
+        .mockResolvedValueOnce(errorResponse)  // Retry 3
+        .mockResolvedValueOnce(createMockSupabaseResponse());  // Success on next flush
+
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'event1', properties: {} }
+      ];
+
+      // First flush - should fail after all retries and add to dead letter queue
+      await batchProcessor.flush(events);
+      expect(batchProcessor.getMetrics().deadLetterQueueSize).toBe(1);
+
+      // Second flush - should process dead letter queue
+      await batchProcessor.flush([]);
+      expect(batchProcessor.getMetrics().deadLetterQueueSize).toBe(0);
+    });
+
+    it('should maintain dead letter queue size limit', async () => {
+      const error = new Error('Persistent error');
+      const errorResponse = createMockSupabaseResponse(error);
+      // Always fail - each flush will retry 3 times then add to dead letter queue
+      vi.mocked(mockSupabase.from('telemetry_events').insert).mockResolvedValue(errorResponse);
+
+      // Circuit breaker opens after 5 failures, so only first 5 flushes will be processed
+      // 5 batches of 5 items = 25 total items in dead letter queue
+      for (let i = 0; i < 10; i++) {
+        const events: TelemetryEvent[] = Array.from({ length: 5 }, (_, j) => ({
+          user_id: `user${i}_${j}`,
+          event: 'test_event',
+          properties: { batch: i, index: j }
+        }));
+
+        await batchProcessor.flush(events);
+      }
+
+      const metrics = batchProcessor.getMetrics();
+      // Circuit breaker opens after 5 failures, so only 25 items are added
+      expect(metrics.deadLetterQueueSize).toBe(25); // 5 flushes * 5 items each
+      expect(metrics.eventsDropped).toBe(25); // 5 additional flushes dropped due to circuit breaker
+    });
+
+    it('should handle mixed events and workflows in dead letter queue', async () => {
+      const error = new Error('Mixed error');
+      const errorResponse = createMockSupabaseResponse(error);
+      vi.mocked(mockSupabase.from).mockImplementation((table) => ({
+        insert: vi.fn().mockResolvedValue(errorResponse),
+        url: { href: '' },
+        headers: {},
+        select: vi.fn(),
+        upsert: vi.fn(),
+        update: vi.fn(),
+        delete: vi.fn()
+      } as any));
+
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'event1', properties: {} }
+      ];
+
+      const workflows: WorkflowTelemetry[] = [
+        {
+          user_id: 'user1',
+          workflow_hash: 'hash1',
+          node_count: 1,
+          node_types: ['webhook'],
+          has_trigger: true,
+          has_webhook: true,
+          complexity: 'simple',
+          sanitized_workflow: { nodes: [], connections: {} }
+        }
+      ];
+
+      await batchProcessor.flush(events, workflows);
+
+      expect(batchProcessor.getMetrics().deadLetterQueueSize).toBe(2);
+
+      // Mock successful operations for dead letter queue processing
+      vi.mocked(mockSupabase.from).mockImplementation((table) => ({
+        insert: vi.fn().mockResolvedValue(createMockSupabaseResponse()),
+        url: { href: '' },
+        headers: {},
+        select: vi.fn(),
+        upsert: vi.fn(),
+        update: vi.fn(),
+        delete: vi.fn()
+      } as any));
+
+      await batchProcessor.flush([]);
+      expect(batchProcessor.getMetrics().deadLetterQueueSize).toBe(0);
+    });
+  });
+
+  describe('circuit breaker integration', () => {
+    it('should update circuit breaker on success', async () => {
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      await batchProcessor.flush(events);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.circuitBreakerState.state).toBe('closed');
+      expect(metrics.circuitBreakerState.failureCount).toBe(0);
+    });
+
+    it('should update circuit breaker on failure', async () => {
+      const error = new Error('Network error');
+      const errorResponse = createMockSupabaseResponse(error);
+      vi.mocked(mockSupabase.from('telemetry_events').insert).mockResolvedValue(errorResponse);
+
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      await batchProcessor.flush(events);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.circuitBreakerState.failureCount).toBeGreaterThan(0);
+    });
+  });
+
+  describe('metrics collection', () => {
+    it('should collect comprehensive metrics', async () => {
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'event1', properties: {} },
+        { user_id: 'user2', event: 'event2', properties: {} }
+      ];
+
+      await batchProcessor.flush(events);
+
+      const metrics = batchProcessor.getMetrics();
+
+      expect(metrics).toHaveProperty('eventsTracked');
+      expect(metrics).toHaveProperty('eventsDropped');
+      expect(metrics).toHaveProperty('eventsFailed');
+      expect(metrics).toHaveProperty('batchesSent');
+      expect(metrics).toHaveProperty('batchesFailed');
+      expect(metrics).toHaveProperty('averageFlushTime');
+      expect(metrics).toHaveProperty('lastFlushTime');
+      expect(metrics).toHaveProperty('rateLimitHits');
+      expect(metrics).toHaveProperty('circuitBreakerState');
+      expect(metrics).toHaveProperty('deadLetterQueueSize');
+
+      expect(metrics.eventsTracked).toBe(2);
+      expect(metrics.batchesSent).toBe(1);
+    });
+
+    it('should track flush time statistics', async () => {
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      // Perform multiple flushes to test average calculation
+      await batchProcessor.flush(events);
+      await batchProcessor.flush(events);
+      await batchProcessor.flush(events);
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.averageFlushTime).toBeGreaterThanOrEqual(0);
+      expect(metrics.lastFlushTime).toBeGreaterThanOrEqual(0);
+    });
+
+    it('should maintain limited flush time history', async () => {
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      // Perform more than 100 flushes to test history limit
+      for (let i = 0; i < 105; i++) {
+        await batchProcessor.flush(events);
+      }
+
+      // Should still calculate average correctly (history is limited internally)
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.averageFlushTime).toBeGreaterThanOrEqual(0);
+    });
+  });
+
+  describe('resetMetrics()', () => {
+    it('should reset all metrics to initial state', async () => {
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      // Generate some metrics
+      await batchProcessor.flush(events);
+
+      // Verify metrics exist
+      let metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBeGreaterThan(0);
+      expect(metrics.batchesSent).toBeGreaterThan(0);
+
+      // Reset metrics
+      batchProcessor.resetMetrics();
+
+      // Verify reset
+      metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBe(0);
+      expect(metrics.eventsDropped).toBe(0);
+      expect(metrics.eventsFailed).toBe(0);
+      expect(metrics.batchesSent).toBe(0);
+      expect(metrics.batchesFailed).toBe(0);
+      expect(metrics.averageFlushTime).toBe(0);
+      expect(metrics.rateLimitHits).toBe(0);
+      expect(metrics.circuitBreakerState.state).toBe('closed');
+      expect(metrics.circuitBreakerState.failureCount).toBe(0);
+    });
+  });
+
+  describe('edge cases', () => {
+    it('should handle empty arrays gracefully', async () => {
+      await batchProcessor.flush([], []);
+
+      expect(mockSupabase.from).not.toHaveBeenCalled();
+
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBe(0);
+      expect(metrics.batchesSent).toBe(0);
+    });
+
+    it('should handle undefined inputs gracefully', async () => {
+      await batchProcessor.flush();
+
+      expect(mockSupabase.from).not.toHaveBeenCalled();
+    });
+
+    it('should handle null Supabase client gracefully', async () => {
+      const processor = new TelemetryBatchProcessor(null, mockIsEnabled);
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      await expect(processor.flush(events)).resolves.not.toThrow();
+    });
+
+    it('should handle concurrent flush operations', async () => {
+      const events: TelemetryEvent[] = [
+        { user_id: 'user1', event: 'test_event', properties: {} }
+      ];
+
+      // Start multiple flush operations concurrently
+      const flushPromises = [
+        batchProcessor.flush(events),
+        batchProcessor.flush(events),
+        batchProcessor.flush(events)
+      ];
+
+      await Promise.all(flushPromises);
+
+      // Should handle concurrent operations gracefully
+      const metrics = batchProcessor.getMetrics();
+      expect(metrics.eventsTracked).toBeGreaterThan(0);
+    });
+  });
+
+  describe('process lifecycle integration', () => {
+    it('should flush on process beforeExit', async () => {
+      const flushSpy = vi.spyOn(batchProcessor, 'flush');
+
+      batchProcessor.start();
+
+      // Trigger beforeExit event
+      process.emit('beforeExit', 0);
+
+      expect(flushSpy).toHaveBeenCalled();
+    });
+
+    it('should flush and exit on SIGINT', async () => {
+      const flushSpy = vi.spyOn(batchProcessor, 'flush');
+
+      batchProcessor.start();
+
+      // Trigger SIGINT event
+      process.emit('SIGINT', 'SIGINT');
+
+      expect(flushSpy).toHaveBeenCalled();
+      expect(mockProcessExit).toHaveBeenCalledWith(0);
+    });
+
+    it('should flush and exit on SIGTERM', async () => {
+      const flushSpy = vi.spyOn(batchProcessor, 'flush');
+
+      batchProcessor.start();
+
+      // Trigger SIGTERM event
+      process.emit('SIGTERM', 'SIGTERM');
+
+      expect(flushSpy).toHaveBeenCalled();
+      expect(mockProcessExit).toHaveBeenCalledWith(0);
+    });
+  });
+
+  describe('Issue #517: workflow data preservation', () => {
+    // This test verifies that workflow mutation data is NOT recursively converted to snake_case
+    // Previously, the toSnakeCase function was applied recursively which caused:
+    // - Connection keys like "Webhook" to become "_webhook"
+    // - Node fields like "typeVersion" to become "type_version"
+
+    it('should preserve connection keys exactly as-is (node names)', async () => {
+      const mutation: WorkflowMutationRecord = {
+        userId: 'user1',
+        sessionId: 'session1',
+        workflowBefore: {
+          nodes: [],
+          connections: {}
+        },
+        workflowAfter: {
+          nodes: [
+            { id: '1', name: 'Webhook', type: 'n8n-nodes-base.webhook', typeVersion: 1, position: [0, 0], parameters: {} }
+          ],
+          // Connection keys are NODE NAMES - must be preserved exactly
+          connections: {
+            'Webhook': { main: [[{ node: 'AI Agent', type: 'main', index: 0 }]] },
+            'AI Agent': { main: [[{ node: 'HTTP Request', type: 'main', index: 0 }]] },
+            'HTTP Request': { main: [[{ node: 'Send Email', type: 'main', index: 0 }]] }
+          }
+        },
+        workflowHashBefore: 'hash1',
+        workflowHashAfter: 'hash2',
+        userIntent: 'Test',
+        intentClassification: IntentClassification.ADD_FUNCTIONALITY,
+        toolName: MutationToolName.UPDATE_PARTIAL,
+        operations: [],
+        operationCount: 0,
+        operationTypes: [],
+        validationImproved: null,
+        errorsResolved: 0,
+        errorsIntroduced: 0,
+        nodesAdded: 1,
+        nodesRemoved: 0,
+        nodesModified: 0,
+        connectionsAdded: 3,
+        connectionsRemoved: 0,
+        propertiesChanged: 0,
+        mutationSuccess: true,
+        durationMs: 100
+      };
+
+      let capturedData: any = null;
+      vi.mocked(mockSupabase.from).mockImplementation((table) => ({
+        insert: vi.fn().mockImplementation((data) => {
+          if (table === 'workflow_mutations') {
+            capturedData = data;
+          }
+          return Promise.resolve(createMockSupabaseResponse());
+        }),
+        url: { href: '' },
+        headers: {},
+        select: vi.fn(),
+        upsert: vi.fn(),
+        update: vi.fn(),
+        delete: vi.fn()
+      } as any));
+
+      await batchProcessor.flush(undefined, undefined, [mutation]);
+
+      expect(capturedData).toBeDefined();
+      expect(capturedData).toHaveLength(1);
+
+      const savedMutation = capturedData[0];
+
+      // Top-level keys should be snake_case for Supabase
+      expect(savedMutation).toHaveProperty('user_id');
+      expect(savedMutation).toHaveProperty('session_id');
+      expect(savedMutation).toHaveProperty('workflow_after');
+
+      // Connection keys should be preserved EXACTLY (not "_webhook", "_a_i _agent", etc.)
+      const connections = savedMutation.workflow_after.connections;
+      expect(connections).toHaveProperty('Webhook');  // NOT "_webhook"
+      expect(connections).toHaveProperty('AI Agent'); // NOT "_a_i _agent"
+      expect(connections).toHaveProperty('HTTP Request'); // NOT "_h_t_t_p _request"
+    });
+
+    it('should preserve node field names in camelCase', async () => {
+      const mutation: WorkflowMutationRecord = {
+        userId: 'user1',
+        sessionId: 'session1',
+        workflowBefore: { nodes: [], connections: {} },
+        workflowAfter: {
+          nodes: [
+            {
+              id: '1',
+              name: 'Webhook',
+              type: 'n8n-nodes-base.webhook',
+              // These fields MUST remain in camelCase for n8n API compatibility
+              typeVersion: 2,
+              webhookId: 'abc123',
+              onError: 'continueOnFail',
+              alwaysOutputData: true,
+              continueOnFail: false,
+              retryOnFail: true,
+              maxTries: 3,
+              notesInFlow: true,
+              waitBetweenTries: 1000,
+              executeOnce: false,
+              position: [100, 200],
+              parameters: {}
+            }
+          ],
+          connections: {}
+        },
+        workflowHashBefore: 'hash1',
+        workflowHashAfter: 'hash2',
+        userIntent: 'Test',
+        intentClassification: IntentClassification.ADD_FUNCTIONALITY,
+        toolName: MutationToolName.UPDATE_PARTIAL,
+        operations: [],
+        operationCount: 0,
+        operationTypes: [],
+        validationImproved: null,
+        errorsResolved: 0,
+        errorsIntroduced: 0,
+        nodesAdded: 1,
+        nodesRemoved: 0,
+        nodesModified: 0,
+        connectionsAdded: 0,
+        connectionsRemoved: 0,
+        propertiesChanged: 0,
+        mutationSuccess: true,
+        durationMs: 100
+      };
+
+      let capturedData: any = null;
+      vi.mocked(mockSupabase.from).mockImplementation((table) => ({
+        insert: vi.fn().mockImplementation((data) => {
+          if (table === 'workflow_mutations') {
+            capturedData = data;
+          }
+          return Promise.resolve(createMockSupabaseResponse());
+        }),
+        url: { href: '' },
+        headers: {},
+        select: vi.fn(),
+        upsert: vi.fn(),
+        update: vi.fn(),
+        delete: vi.fn()
+      } as any));
+
+      await batchProcessor.flush(undefined, undefined, [mutation]);
+
+      expect(capturedData).toBeDefined();
+      const savedNode = capturedData[0].workflow_after.nodes[0];
+
+      // Node fields should be preserved in camelCase (NOT snake_case)
+      expect(savedNode).toHaveProperty('typeVersion');        // NOT type_version
+      expect(savedNode).toHaveProperty('webhookId');          // NOT webhook_id
+      expect(savedNode).toHaveProperty('onError');            // NOT on_error
+      expect(savedNode).toHaveProperty('alwaysOutputData');   // NOT always_output_data
+      expect(savedNode).toHaveProperty('continueOnFail');     // NOT continue_on_fail
+      expect(savedNode).toHaveProperty('retryOnFail');        // NOT retry_on_fail
+      expect(savedNode).toHaveProperty('maxTries');           // NOT max_tries
+      expect(savedNode).toHaveProperty('notesInFlow');        // NOT notes_in_flow
+      expect(savedNode).toHaveProperty('waitBetweenTries');   // NOT wait_between_tries
+      expect(savedNode).toHaveProperty('executeOnce');        // NOT execute_once
+
+      // Verify values are preserved
+      expect(savedNode.typeVersion).toBe(2);
+      expect(savedNode.webhookId).toBe('abc123');
+      expect(savedNode.maxTries).toBe(3);
+    });
+
+    it('should convert only top-level mutation record fields to snake_case', async () => {
+      const mutation: WorkflowMutationRecord = {
+        userId: 'user1',
+        sessionId: 'session1',
+        workflowBefore: { nodes: [], connections: {} },
+        workflowAfter: { nodes: [], connections: {} },
+        workflowHashBefore: 'hash1',
+        workflowHashAfter: 'hash2',
+        workflowStructureHashBefore: 'struct1',
+        workflowStructureHashAfter: 'struct2',
+        isTrulySuccessful: true,
+        userIntent: 'Test intent',
+        intentClassification: IntentClassification.ADD_FUNCTIONALITY,
+        toolName: MutationToolName.UPDATE_PARTIAL,
+        operations: [{ type: 'addNode', node: { name: 'Test', type: 'n8n-nodes-base.set', position: [0, 0] } } as AddNodeOperation],
+        operationCount: 1,
+        operationTypes: ['addNode'],
+        validationBefore: { valid: false, errors: [] },
+        validationAfter: { valid: true, errors: [] },
+        validationImproved: true,
+        errorsResolved: 1,
+        errorsIntroduced: 0,
+        nodesAdded: 1,
+        nodesRemoved: 0,
+        nodesModified: 0,
+        connectionsAdded: 0,
+        connectionsRemoved: 0,
+        propertiesChanged: 0,
+        mutationSuccess: true,
+        mutationError: undefined,
+        durationMs: 150
+      };
+
+      let capturedData: any = null;
+      vi.mocked(mockSupabase.from).mockImplementation((table) => ({
+        insert: vi.fn().mockImplementation((data) => {
+          if (table === 'workflow_mutations') {
+            capturedData = data;
+          }
+          return Promise.resolve(createMockSupabaseResponse());
+        }),
+        url: { href: '' },
+        headers: {},
+        select: vi.fn(),
+        upsert: vi.fn(),
+        update: vi.fn(),
+        delete: vi.fn()
+      } as any));
+
+      await batchProcessor.flush(undefined, undefined, [mutation]);
+
+      expect(capturedData).toBeDefined();
+      const saved = capturedData[0];
+
+      // Top-level fields should be converted to snake_case
+      expect(saved).toHaveProperty('user_id', 'user1');
+      expect(saved).toHaveProperty('session_id', 'session1');
+      expect(saved).toHaveProperty('workflow_before');
+      expect(saved).toHaveProperty('workflow_after');
+      expect(saved).toHaveProperty('workflow_hash_before', 'hash1');
+      expect(saved).toHaveProperty('workflow_hash_after', 'hash2');
+      expect(saved).toHaveProperty('workflow_structure_hash_before', 'struct1');
+      expect(saved).toHaveProperty('workflow_structure_hash_after', 'struct2');
+      expect(saved).toHaveProperty('is_truly_successful', true);
+      expect(saved).toHaveProperty('user_intent', 'Test intent');
+      expect(saved).toHaveProperty('intent_classification');
+      expect(saved).toHaveProperty('tool_name');
+      expect(saved).toHaveProperty('operation_count', 1);
+      expect(saved).toHaveProperty('operation_types');
+      expect(saved).toHaveProperty('validation_before');
+      expect(saved).toHaveProperty('validation_after');
+      expect(saved).toHaveProperty('validation_improved', true);
+      expect(saved).toHaveProperty('errors_resolved', 1);
+      expect(saved).toHaveProperty('errors_introduced', 0);
+      expect(saved).toHaveProperty('nodes_added', 1);
+      expect(saved).toHaveProperty('nodes_removed', 0);
+      expect(saved).toHaveProperty('nodes_modified', 0);
+      expect(saved).toHaveProperty('connections_added', 0);
+      expect(saved).toHaveProperty('connections_removed', 0);
+      expect(saved).toHaveProperty('properties_changed', 0);
+      expect(saved).toHaveProperty('mutation_success', true);
+      expect(saved).toHaveProperty('duration_ms', 150);
+    });
+  });
+});