diff --git a/.claude/skills/logging-helper/SKILL.md b/.claude/skills/logging-helper/SKILL.md
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+---
+name: logging-helper
+description: Ensures consistent usage of the @isa/core/logging library across the codebase with best practices for performance and maintainability
+---
+
+# Logging Helper Skill
+
+Ensures consistent and efficient logging using `@isa/core/logging` library.
+
+## When to Use
+
+- Adding logging to new components/services
+- Refactoring existing logging code
+- Reviewing code for proper logging patterns
+- Debugging logging issues
+
+## Core Principles
+
+### 1. Always Use Factory Pattern
+
+```typescript
+import { logger } from '@isa/core/logging';
+
+// ✅ DO
+#logger = logger();
+
+// ❌ DON'T
+constructor(private loggingService: LoggingService) {}
+```
+
+### 2. Choose Appropriate Log Levels
+
+- **Trace**: Fine-grained debugging (method entry/exit)
+- **Debug**: Development debugging (variable states)
+- **Info**: Runtime information (user actions, events)
+- **Warn**: Potentially harmful situations
+- **Error**: Errors affecting functionality
+
+### 3. Context Patterns
+
+**Static Context** (component level):
+```typescript
+#logger = logger({ component: 'UserProfileComponent' });
+```
+
+**Dynamic Context** (instance level):
+```typescript
+#logger = logger(() => ({
+  userId: this.authService.currentUserId,
+  storeId: this.config.storeId
+}));
+```
+
+**Message Context** (use functions for performance):
+```typescript
+// ✅ Recommended - lazy evaluation
+this.#logger.info('Order processed', () => ({
+  orderId: order.id,
+  total: order.total,
+  timestamp: Date.now()
+}));
+
+// ✅ Acceptable - static values
+this.#logger.info('Order processed', {
+  orderId: order.id,
+  status: 'completed'
+});
+```
+
+## Essential Patterns
+
+### Component Logging
+```typescript
+@Component({
+  selector: 'app-product-list',
+  standalone: true,
+})
+export class ProductListComponent {
+  #logger = logger({ component: 'ProductListComponent' });
+
+  ngOnInit(): void {
+    this.#logger.info('Component initialized');
+  }
+
+  onAction(id: string): void {
+    this.#logger.debug('Action triggered', { id });
+  }
+}
+```
+
+### Service Logging
+```typescript
+@Injectable({ providedIn: 'root' })
+export class DataService {
+  #logger = logger({ service: 'DataService' });
+
+  fetchData(endpoint: string): Observable<Data> {
+    this.#logger.debug('Fetching data', { endpoint });
+
+    return this.http.get<Data>(endpoint).pipe(
+      tap((data) => this.#logger.info('Data fetched', () => ({
+        endpoint,
+        size: data.length
+      }))),
+      catchError((error) => {
+        this.#logger.error('Fetch failed', error, () => ({
+          endpoint,
+          status: error.status
+        }));
+        return throwError(() => error);
+      })
+    );
+  }
+}
+```
+
+### Error Handling
+```typescript
+try {
+  await this.processOrder(orderId);
+} catch (error) {
+  this.#logger.error('Order processing failed', error as Error, () => ({
+    orderId,
+    step: this.currentStep,
+    attemptNumber: this.retryCount
+  }));
+  throw error;
+}
+```
+
+### Hierarchical Context
+```typescript
+@Component({
+  providers: [
+    provideLoggerContext({ feature: 'checkout', module: 'sales' })
+  ]
+})
+export class CheckoutComponent {
+  #logger = logger(() => ({ userId: this.userService.currentUserId }));
+
+  // Logs include: feature, module, userId + message context
+}
+```
+
+## Common Mistakes to Avoid
+
+```typescript
+// ❌ Don't use console.log
+console.log('User logged in');
+// ✅ Use logger
+this.#logger.info('User logged in');
+
+// ❌ Don't create expensive context eagerly
+this.#logger.debug('Processing', {
+  data: this.computeExpensive() // Always executes
+});
+// ✅ Use function for lazy evaluation
+this.#logger.debug('Processing', () => ({
+  data: this.computeExpensive() // Only if debug enabled
+}));
+
+// ❌ Don't log in tight loops
+for (const item of items) {
+  this.#logger.debug('Item', { item });
+}
+// ✅ Log aggregates
+this.#logger.debug('Batch processed', () => ({
+  count: items.length
+}));
+
+// ❌ Don't log sensitive data
+this.#logger.info('User auth', { password: user.password });
+// ✅ Log safe identifiers only
+this.#logger.info('User auth', { userId: user.id });
+
+// ❌ Don't miss error object
+this.#logger.error('Failed');
+// ✅ Include error object
+this.#logger.error('Failed', error as Error);
+```
+
+## Configuration
+
+### App Configuration
+```typescript
+// app.config.ts
+import { ApplicationConfig, isDevMode } from '@angular/core';
+import {
+  provideLogging, withLogLevel, withSink,
+  LogLevel, ConsoleLogSink
+} from '@isa/core/logging';
+
+export const appConfig: ApplicationConfig = {
+  providers: [
+    provideLogging(
+      withLogLevel(isDevMode() ? LogLevel.Debug : LogLevel.Warn),
+      withSink(ConsoleLogSink),
+      withContext({ app: 'ISA', version: '1.0.0' })
+    )
+  ]
+};
+```
+
+## Testing
+
+```typescript
+import { createComponentFactory, Spectator } from '@ngneat/spectator/jest';
+import { LoggingService } from '@isa/core/logging';
+
+describe('MyComponent', () => {
+  const createComponent = createComponentFactory({
+    component: MyComponent,
+    mocks: [LoggingService]
+  });
+
+  it('should log error', () => {
+    const spectator = createComponent();
+    const loggingService = spectator.inject(LoggingService);
+
+    spectator.component.riskyOperation();
+
+    expect(loggingService.error).toHaveBeenCalledWith(
+      expect.any(String),
+      expect.any(Error),
+      expect.any(Function)
+    );
+  });
+});
+```
+
+## Code Review Checklist
+
+- [ ] Uses `logger()` factory, not `LoggingService` injection
+- [ ] Appropriate log level for each message
+- [ ] Context functions for expensive operations
+- [ ] No sensitive information (passwords, tokens, PII)
+- [ ] No `console.log` statements
+- [ ] Error logs include error object
+- [ ] No logging in tight loops
+- [ ] Component/service identified in context
+- [ ] E2E attributes on interactive elements
+
+## Quick Reference
+
+```typescript
+// Import
+import { logger, provideLoggerContext } from '@isa/core/logging';
+
+// Create logger
+#logger = logger();                              // Basic
+#logger = logger({ component: 'Name' });         // Static context
+#logger = logger(() => ({ id: this.id }));       // Dynamic context
+
+// Log messages
+this.#logger.trace('Detailed trace');
+this.#logger.debug('Debug info');
+this.#logger.info('General info', () => ({ key: value }));
+this.#logger.warn('Warning');
+this.#logger.error('Error', error, () => ({ context }));
+
+// Component context
+@Component({
+  providers: [provideLoggerContext({ feature: 'users' })]
+})
+```
+
+## Additional Resources
+
+- Full documentation: `libs/core/logging/README.md`
+- Examples: `.claude/skills/logging-helper/examples.md`
+- Quick reference: `.claude/skills/logging-helper/reference.md`
+- Troubleshooting: `.claude/skills/logging-helper/troubleshooting.md`
diff --git a/.claude/skills/logging-helper/examples.md b/.claude/skills/logging-helper/examples.md
new file mode 100644
index 000000000..90e6d114c
--- /dev/null
+++ b/.claude/skills/logging-helper/examples.md
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+# Logging Examples
+
+Concise real-world examples of logging patterns.
+
+## 1. Component with Observable
+
+```typescript
+import { Component, OnInit } from '@angular/core';
+import { logger } from '@isa/core/logging';
+
+@Component({
+  selector: 'app-product-list',
+  standalone: true,
+})
+export class ProductListComponent implements OnInit {
+  #logger = logger({ component: 'ProductListComponent' });
+
+  constructor(private productService: ProductService) {}
+
+  ngOnInit(): void {
+    this.#logger.info('Component initialized');
+    this.loadProducts();
+  }
+
+  private loadProducts(): void {
+    this.productService.getProducts().subscribe({
+      next: (products) => {
+        this.#logger.info('Products loaded', () => ({ count: products.length }));
+      },
+      error: (error) => {
+        this.#logger.error('Failed to load products', error);
+      }
+    });
+  }
+}
+```
+
+## 2. Service with HTTP
+
+```typescript
+import { Injectable, inject } from '@angular/core';
+import { HttpClient } from '@angular/common/http';
+import { logger } from '@isa/core/logging';
+import { catchError, tap } from 'rxjs/operators';
+
+@Injectable({ providedIn: 'root' })
+export class OrderService {
+  private http = inject(HttpClient);
+  #logger = logger({ service: 'OrderService' });
+
+  getOrder(id: string): Observable<Order> {
+    this.#logger.debug('Fetching order', { id });
+
+    return this.http.get<Order>(`/api/orders/${id}`).pipe(
+      tap((order) => this.#logger.info('Order fetched', () => ({
+        id,
+        status: order.status
+      }))),
+      catchError((error) => {
+        this.#logger.error('Fetch failed', error, () => ({ id, status: error.status }));
+        throw error;
+      })
+    );
+  }
+}
+```
+
+## 3. Hierarchical Context
+
+```typescript
+import { Component } from '@angular/core';
+import { logger, provideLoggerContext } from '@isa/core/logging';
+
+@Component({
+  selector: 'oms-return-process',
+  standalone: true,
+  providers: [
+    provideLoggerContext({ feature: 'returns', module: 'oms' })
+  ],
+})
+export class ReturnProcessComponent {
+  #logger = logger(() => ({
+    processId: this.currentProcessId,
+    step: this.currentStep
+  }));
+
+  private currentProcessId = crypto.randomUUID();
+  private currentStep = 1;
+
+  startProcess(orderId: string): void {
+    // Logs include: feature, module, processId, step, orderId
+    this.#logger.info('Process started', { orderId });
+  }
+}
+```
+
+## 4. NgRx Effect
+
+```typescript
+import { Injectable } from '@angular/core';
+import { Actions, createEffect, ofType } from '@ngrx/effects';
+import { logger } from '@isa/core/logging';
+import { map, catchError, tap } from 'rxjs/operators';
+import { of } from 'rxjs';
+
+@Injectable()
+export class OrdersEffects {
+  #logger = logger({ effect: 'OrdersEffects' });
+
+  loadOrders$ = createEffect(() =>
+    this.actions$.pipe(
+      ofType(OrdersActions.loadOrders),
+      tap((action) => this.#logger.debug('Loading orders', () => ({
+        page: action.page
+      }))),
+      mergeMap((action) =>
+        this.orderService.getOrders(action.filters).pipe(
+          map((orders) => {
+            this.#logger.info('Orders loaded', () => ({ count: orders.length }));
+            return OrdersActions.loadOrdersSuccess({ orders });
+          }),
+          catchError((error) => {
+            this.#logger.error('Load failed', error);
+            return of(OrdersActions.loadOrdersFailure({ error }));
+          })
+        )
+      )
+    )
+  );
+
+  constructor(
+    private actions$: Actions,
+    private orderService: OrderService
+  ) {}
+}
+```
+
+## 5. Guard with Authorization
+
+```typescript
+import { inject } from '@angular/core';
+import { CanActivateFn, Router } from '@angular/router';
+import { logger } from '@isa/core/logging';
+
+export const authGuard: CanActivateFn = (route, state) => {
+  const authService = inject(AuthService);
+  const router = inject(Router);
+  const log = logger({ guard: 'AuthGuard' });
+
+  if (authService.isAuthenticated()) {
+    log.debug('Access granted', () => ({ route: state.url }));
+    return true;
+  }
+
+  log.warn('Access denied', () => ({
+    attemptedRoute: state.url,
+    redirectTo: '/login'
+  }));
+  return router.createUrlTree(['/login']);
+};
+```
+
+## 6. HTTP Interceptor
+
+```typescript
+import { HttpInterceptorFn } from '@angular/common/http';
+import { inject } from '@angular/core';
+import { tap, catchError } from 'rxjs/operators';
+import { LoggingService } from '@isa/core/logging';
+
+export const loggingInterceptor: HttpInterceptorFn = (req, next) => {
+  const loggingService = inject(LoggingService);
+  const startTime = performance.now();
+
+  loggingService.debug('HTTP Request', () => ({
+    method: req.method,
+    url: req.url
+  }));
+
+  return next(req).pipe(
+    tap((event) => {
+      if (event.type === HttpEventType.Response) {
+        loggingService.info('HTTP Response', () => ({
+          method: req.method,
+          url: req.url,
+          status: event.status,
+          duration: `${(performance.now() - startTime).toFixed(2)}ms`
+        }));
+      }
+    }),
+    catchError((error) => {
+      loggingService.error('HTTP Error', error, () => ({
+        method: req.method,
+        url: req.url,
+        status: error.status
+      }));
+      return throwError(() => error);
+    })
+  );
+};
+```
+
+## 7. Form Validation
+
+```typescript
+import { Component, OnInit } from '@angular/core';
+import { FormBuilder, FormGroup, Validators } from '@angular/forms';
+import { logger } from '@isa/core/logging';
+
+@Component({
+  selector: 'shared-user-form',
+  standalone: true,
+})
+export class UserFormComponent implements OnInit {
+  #logger = logger({ component: 'UserFormComponent' });
+  form!: FormGroup;
+
+  constructor(private fb: FormBuilder) {}
+
+  ngOnInit(): void {
+    this.form = this.fb.group({
+      name: ['', Validators.required],
+      email: ['', [Validators.required, Validators.email]]
+    });
+  }
+
+  onSubmit(): void {
+    if (this.form.invalid) {
+      this.#logger.warn('Invalid form submission', () => ({
+        errors: this.getFormErrors()
+      }));
+      return;
+    }
+
+    this.#logger.info('Form submitted');
+  }
+
+  private getFormErrors(): Record<string, unknown> {
+    const errors: Record<string, unknown> = {};
+    Object.keys(this.form.controls).forEach((key) => {
+      const control = this.form.get(key);
+      if (control?.errors) errors[key] = control.errors;
+    });
+    return errors;
+  }
+}
+```
+
+## 8. Async Progress Tracking
+
+```typescript
+import { Injectable } from '@angular/core';
+import { logger } from '@isa/core/logging';
+import { Observable } from 'rxjs';
+import { tap } from 'rxjs/operators';
+
+@Injectable({ providedIn: 'root' })
+export class ImportService {
+  #logger = logger({ service: 'ImportService' });
+
+  importData(file: File): Observable<number> {
+    const importId = crypto.randomUUID();
+
+    this.#logger.info('Import started', () => ({
+      importId,
+      fileName: file.name,
+      fileSize: file.size
+    }));
+
+    return this.processImport(file).pipe(
+      tap((progress) => {
+        if (progress % 25 === 0) {
+          this.#logger.debug('Import progress', () => ({
+            importId,
+            progress: `${progress}%`
+          }));
+        }
+      }),
+      tap({
+        complete: () => this.#logger.info('Import completed', { importId }),
+        error: (error) => this.#logger.error('Import failed', error, { importId })
+      })
+    );
+  }
+
+  private processImport(file: File): Observable<number> {
+    // Implementation
+  }
+}
+```
+
+## 9. Global Error Handler
+
+```typescript
+import { Injectable, ErrorHandler } from '@angular/core';
+import { logger } from '@isa/core/logging';
+
+@Injectable()
+export class GlobalErrorHandler implements ErrorHandler {
+  #logger = logger({ handler: 'GlobalErrorHandler' });
+
+  handleError(error: Error): void {
+    this.#logger.error('Uncaught error', error, () => ({
+      url: window.location.href,
+      userAgent: navigator.userAgent,
+      timestamp: new Date().toISOString()
+    }));
+  }
+}
+```
+
+## 10. WebSocket Component
+
+```typescript
+import { Component, OnInit, OnDestroy } from '@angular/core';
+import { logger } from '@isa/core/logging';
+import { Subject, takeUntil } from 'rxjs';
+
+@Component({
+  selector: 'oms-live-orders',
+  standalone: true,
+})
+export class LiveOrdersComponent implements OnInit, OnDestroy {
+  #logger = logger({ component: 'LiveOrdersComponent' });
+  private destroy$ = new Subject<void>();
+
+  constructor(private wsService: WebSocketService) {}
+
+  ngOnInit(): void {
+    this.#logger.info('Connecting to WebSocket');
+
+    this.wsService.connect('orders').pipe(
+      takeUntil(this.destroy$)
+    ).subscribe({
+      next: (msg) => this.#logger.debug('Message received', () => ({
+        type: msg.type,
+        orderId: msg.orderId
+      })),
+      error: (error) => this.#logger.error('WebSocket error', error),
+      complete: () => this.#logger.info('WebSocket closed')
+    });
+  }
+
+  ngOnDestroy(): void {
+    this.#logger.debug('Component destroyed');
+    this.destroy$.next();
+    this.destroy$.complete();
+  }
+}
+```
diff --git a/.claude/skills/logging-helper/reference.md b/.claude/skills/logging-helper/reference.md
new file mode 100644
index 000000000..54b138865
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+++ b/.claude/skills/logging-helper/reference.md
@@ -0,0 +1,192 @@
+# Logging Quick Reference
+
+## API Signatures
+
+```typescript
+// Factory
+function logger(ctx?: MaybeLoggerContextFn): LoggerApi
+
+// Logger API
+interface LoggerApi {
+  trace(message: string, context?: MaybeLoggerContextFn): void;
+  debug(message: string, context?: MaybeLoggerContextFn): void;
+  info(message: string, context?: MaybeLoggerContextFn): void;
+  warn(message: string, context?: MaybeLoggerContextFn): void;
+  error(message: string, error?: Error, context?: MaybeLoggerContextFn): void;
+}
+
+// Types
+type MaybeLoggerContextFn = LoggerContext | (() => LoggerContext);
+interface LoggerContext { [key: string]: unknown; }
+```
+
+## Common Patterns
+
+| Pattern | Code |
+|---------|------|
+| Basic logger | `#logger = logger()` |
+| Static context | `#logger = logger({ component: 'Name' })` |
+| Dynamic context | `#logger = logger(() => ({ id: this.id }))` |
+| Log info | `this.#logger.info('Message')` |
+| Log with context | `this.#logger.info('Message', () => ({ key: value }))` |
+| Log error | `this.#logger.error('Error', error)` |
+| Error with context | `this.#logger.error('Error', error, () => ({ id }))` |
+| Component context | `providers: [provideLoggerContext({ feature: 'x' })]` |
+
+## Configuration
+
+```typescript
+// app.config.ts
+import { provideLogging, withLogLevel, withSink, withContext,
+         LogLevel, ConsoleLogSink } from '@isa/core/logging';
+
+export const appConfig: ApplicationConfig = {
+  providers: [
+    provideLogging(
+      withLogLevel(isDevMode() ? LogLevel.Debug : LogLevel.Warn),
+      withSink(ConsoleLogSink),
+      withContext({ app: 'ISA', version: '1.0.0' })
+    )
+  ]
+};
+```
+
+## Log Levels
+
+| Level | Use Case | Example |
+|-------|----------|---------|
+| `Trace` | Method entry/exit | `this.#logger.trace('Entering processData')` |
+| `Debug` | Development info | `this.#logger.debug('Variable state', () => ({ x }))` |
+| `Info` | Runtime events | `this.#logger.info('User logged in', { userId })` |
+| `Warn` | Warnings | `this.#logger.warn('Deprecated API used')` |
+| `Error` | Errors | `this.#logger.error('Operation failed', error)` |
+| `Off` | Disable logging | `withLogLevel(LogLevel.Off)` |
+
+## Decision Trees
+
+### Context Type Decision
+```
+Value changes at runtime?
+├─ Yes → () => ({ value: this.getValue() })
+└─ No  → { value: 'static' }
+
+Computing value is expensive?
+├─ Yes → () => ({ data: this.compute() })
+└─ No  → Either works
+```
+
+### Log Level Decision
+```
+Method flow details? → Trace
+Development debug?  → Debug
+Runtime information? → Info
+Potential problem?  → Warn
+Error occurred?     → Error
+```
+
+## Performance Tips
+
+```typescript
+// ✅ DO: Lazy evaluation
+this.#logger.debug('Data', () => ({
+  result: this.expensive() // Only runs if debug enabled
+}));
+
+// ❌ DON'T: Eager evaluation
+this.#logger.debug('Data', {
+  result: this.expensive() // Always runs
+});
+
+// ✅ DO: Log aggregates
+this.#logger.info('Batch done', () => ({ count: items.length }));
+
+// ❌ DON'T: Log in loops
+for (const item of items) {
+  this.#logger.debug('Item', { item }); // Performance hit
+}
+```
+
+## Testing
+
+```typescript
+import { createComponentFactory, Spectator } from '@ngneat/spectator/jest';
+import { LoggingService } from '@isa/core/logging';
+
+describe('MyComponent', () => {
+  const createComponent = createComponentFactory({
+    component: MyComponent,
+    mocks: [LoggingService]
+  });
+
+  it('logs error', () => {
+    const spectator = createComponent();
+    const logger = spectator.inject(LoggingService);
+
+    spectator.component.operation();
+
+    expect(logger.error).toHaveBeenCalled();
+  });
+});
+```
+
+## Custom Sink
+
+```typescript
+import { Injectable } from '@angular/core';
+import { Sink, LogLevel, LoggerContext } from '@isa/core/logging';
+
+@Injectable()
+export class CustomSink implements Sink {
+  log(level: LogLevel, message: string, context?: LoggerContext, error?: Error): void {
+    // Implementation
+  }
+}
+
+// Register
+provideLogging(withSink(CustomSink))
+```
+
+## Sink Function (with DI)
+
+```typescript
+import { inject } from '@angular/core';
+import { SinkFn, LogLevel } from '@isa/core/logging';
+
+export const remoteSink: SinkFn = () => {
+  const http = inject(HttpClient);
+
+  return (level, message, context, error) => {
+    if (level === LogLevel.Error) {
+      http.post('/api/logs', { level, message, context, error }).subscribe();
+    }
+  };
+};
+
+// Register
+provideLogging(withSinkFn(remoteSink))
+```
+
+## Common Imports
+
+```typescript
+// Main imports
+import { logger, provideLoggerContext } from '@isa/core/logging';
+
+// Configuration imports
+import {
+  provideLogging,
+  withLogLevel,
+  withSink,
+  withContext,
+  LogLevel,
+  ConsoleLogSink
+} from '@isa/core/logging';
+
+// Type imports
+import {
+  LoggerApi,
+  Sink,
+  SinkFn,
+  LoggerContext
+} from '@isa/core/logging';
+```
diff --git a/.claude/skills/logging-helper/troubleshooting.md b/.claude/skills/logging-helper/troubleshooting.md
new file mode 100644
index 000000000..1df623b13
--- /dev/null
+++ b/.claude/skills/logging-helper/troubleshooting.md
@@ -0,0 +1,235 @@
+# Logging Troubleshooting
+
+## 1. Logs Not Appearing
+
+**Problem:** Logger called but nothing in console.
+
+**Solutions:**
+```typescript
+// Check log level
+provideLogging(
+  withLogLevel(isDevMode() ? LogLevel.Debug : LogLevel.Warn)
+)
+
+// Add sink
+provideLogging(
+  withLogLevel(LogLevel.Debug),
+  withSink(ConsoleLogSink) // Required!
+)
+
+// Verify configuration in app.config.ts
+export const appConfig: ApplicationConfig = {
+  providers: [
+    provideLogging(...) // Must be present
+  ]
+};
+```
+
+## 2. NullInjectorError
+
+**Error:** `NullInjectorError: No provider for LoggingService!`
+
+**Solution:**
+```typescript
+// app.config.ts
+import { provideLogging, withLogLevel, withSink,
+         LogLevel, ConsoleLogSink } from '@isa/core/logging';
+
+export const appConfig: ApplicationConfig = {
+  providers: [
+    provideLogging(
+      withLogLevel(LogLevel.Debug),
+      withSink(ConsoleLogSink)
+    )
+  ]
+};
+```
+
+## 3. Context Not Showing
+
+**Problem:** Context passed but doesn't appear.
+
+**Check:**
+```typescript
+// ✅ Both work:
+this.#logger.info('Message', () => ({ id: '123' })); // Function
+this.#logger.info('Message', { id: '123' });          // Object
+
+// ❌ Common mistake:
+const ctx = { id: '123' };
+this.#logger.info('Message', ctx); // Actually works!
+
+// Verify hierarchical merge:
+// Global → Component → Instance → Message
+```
+
+## 4. Performance Issues
+
+**Problem:** Slow when debug logging enabled.
+
+**Solutions:**
+```typescript
+// ✅ Use lazy evaluation
+this.#logger.debug('Data', () => ({
+  expensive: this.compute() // Only if debug enabled
+}));
+
+// ✅ Reduce log frequency
+this.#logger.debug('Batch', () => ({
+  count: items.length // Not each item
+}));
+
+// ✅ Increase production level
+provideLogging(
+  withLogLevel(isDevMode() ? LogLevel.Debug : LogLevel.Warn)
+)
+```
+
+## 5. Error Object Not Logged
+
+**Problem:** Error shows as `[object Object]`.
+
+**Solution:**
+```typescript
+// ❌ Wrong
+this.#logger.error('Failed', { error }); // Don't wrap in object
+
+// ✅ Correct
+this.#logger.error('Failed', error as Error, () => ({
+  additionalContext: 'value'
+}));
+```
+
+## 6. TypeScript Errors
+
+**Error:** `Type 'X' is not assignable to 'MaybeLoggerContextFn'`
+
+**Solution:**
+```typescript
+// ❌ Wrong type
+this.#logger.info('Message', 'string'); // Invalid
+
+// ✅ Correct types
+this.#logger.info('Message', { key: 'value' });
+this.#logger.info('Message', () => ({ key: 'value' }));
+```
+
+## 7. Logs in Tests
+
+**Problem:** Test output cluttered with logs.
+
+**Solutions:**
+```typescript
+// Mock logging service
+import { createComponentFactory, Spectator } from '@ngneat/spectator/jest';
+import { LoggingService } from '@isa/core/logging';
+
+const createComponent = createComponentFactory({
+  component: MyComponent,
+  mocks: [LoggingService] // Mocks all log methods
+});
+
+// Or disable in tests
+TestBed.configureTestingModule({
+  providers: [
+    provideLogging(withLogLevel(LogLevel.Off))
+  ]
+});
+```
+
+## 8. Undefined Property Error
+
+**Error:** `Cannot read property 'X' of undefined`
+
+**Problem:** Accessing uninitialized property in logger context.
+
+**Solutions:**
+```typescript
+// ❌ Problem
+#logger = logger(() => ({
+  userId: this.userService.currentUserId // May be undefined
+}));
+
+// ✅ Solution 1: Optional chaining
+#logger = logger(() => ({
+  userId: this.userService?.currentUserId ?? 'unknown'
+}));
+
+// ✅ Solution 2: Delay access
+ngOnInit() {
+  this.#logger.info('Init', () => ({
+    userId: this.userService.currentUserId // Safe here
+  }));
+}
+```
+
+## 9. Circular Dependency
+
+**Error:** `NG0200: Circular dependency in DI detected`
+
+**Cause:** Service A ← → Service B both inject LoggingService.
+
+**Solution:**
+```typescript
+// ❌ Creates circular dependency
+constructor(private loggingService: LoggingService) {}
+
+// ✅ Use factory (no circular dependency)
+#logger = logger({ service: 'MyService' });
+```
+
+## 10. Custom Sink Not Working
+
+**Problem:** Sink registered but never called.
+
+**Solutions:**
+```typescript
+// ✅ Correct registration
+provideLogging(
+  withSink(MySink) // Add to config
+)
+
+// ✅ Correct signature
+export class MySink implements Sink {
+  log(
+    level: LogLevel,
+    message: string,
+    context?: LoggerContext,
+    error?: Error
+  ): void {
+    // Implementation
+  }
+}
+
+// ✅ Sink function must return function
+export const mySinkFn: SinkFn = () => {
+  const http = inject(HttpClient);
+  return (level, message, context, error) => {
+    // Implementation
+  };
+};
+```
+
+## Quick Diagnostics
+
+```typescript
+// Enable all logs temporarily
+provideLogging(withLogLevel(LogLevel.Trace))
+
+// Check imports
+import { logger } from '@isa/core/logging'; // ✅ Correct
+import { logger } from '@isa/core/logging/src/lib/logger.factory'; // ❌ Wrong
+
+// Verify console filters in browser DevTools
+// Ensure Info, Debug, Warnings are enabled
+```
+
+## Common Error Messages
+
+| Error | Cause | Fix |
+|-------|-------|-----|
+| `NullInjectorError: LoggingService` | Missing config | Add `provideLogging()` |
+| `Type 'X' not assignable` | Wrong context type | Use object or function |
+| `Cannot read property 'X'` | Undefined property | Use optional chaining |
+| `Circular dependency` | Service injection | Use `logger()` factory |
+| Stack overflow | Infinite loop in context | Don't call logger in context |