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@@ -1,302 +1,342 @@
 ---
 name: backend-dev-guidelines
-description: Comprehensive backend development guide for Node.js/Express/TypeScript microservices. Use when creating routes, controllers, services, repositories, middleware, or working with Express APIs, Prisma database access, Sentry error tracking, Zod validation, unifiedConfig, dependency injection, or async patterns. Covers layered architecture (routes → controllers → services → repositories), BaseController pattern, error handling, performance monitoring, testing strategies, and migration from legacy patterns.
+description: Opinionated backend development standards for Node.js + Express + TypeScript microservices. Covers layered architecture, BaseController pattern, dependency injection, Prisma repositories, Zod validation, unifiedConfig, Sentry error tracking, async safety, and testing discipline.
 ---

 # Backend Development Guidelines

-## Purpose
+**(Node.js · Express · TypeScript · Microservices)**

-Establish consistency and best practices across backend microservices (blog-api, auth-service, notifications-service) using modern Node.js/Express/TypeScript patterns.
+You are a **senior backend engineer** operating production-grade services under strict architectural and reliability constraints.

-## When to Use This Skill
+Your goal is to build **predictable, observable, and maintainable backend systems** using:

-Automatically activates when working on:
- Creating or modifying routes, endpoints, APIs
- Building controllers, services, repositories
- Implementing middleware (auth, validation, error handling)
- Database operations with Prisma
- Error tracking with Sentry
- Input validation with Zod
- Configuration management
- Backend testing and refactoring
+* Layered architecture
+* Explicit error boundaries
+* Strong typing and validation
+* Centralized configuration
+* First-class observability
+
+This skill defines **how backend code must be written**, not merely suggestions.

 ---

-## Quick Start
+## 1. Backend Feasibility & Risk Index (BFRI)

-### New Backend Feature Checklist
+Before implementing or modifying a backend feature, assess feasibility.

- [ ] **Route**: Clean definition, delegate to controller
- [ ] **Controller**: Extend BaseController
- [ ] **Service**: Business logic with DI
- [ ] **Repository**: Database access (if complex)
- [ ] **Validation**: Zod schema
- [ ] **Sentry**: Error tracking
- [ ] **Tests**: Unit + integration tests
- [ ] **Config**: Use unifiedConfig
+### BFRI Dimensions (1–5)

-### New Microservice Checklist
+| Dimension                     | Question                                                         |
+| ----------------------------- | ---------------------------------------------------------------- |
+| **Architectural Fit**         | Does this follow routes → controllers → services → repositories? |
+| **Business Logic Complexity** | How complex is the domain logic?                                 |
+| **Data Risk**                 | Does this affect critical data paths or transactions?            |
+| **Operational Risk**          | Does this impact auth, billing, messaging, or infra?             |
+| **Testability**               | Can this be reliably unit + integration tested?                  |

- [ ] Directory structure (see [architecture-overview.md](architecture-overview.md))
- [ ] instrument.ts for Sentry
- [ ] unifiedConfig setup
- [ ] BaseController class
- [ ] Middleware stack
- [ ] Error boundary
- [ ] Testing framework
+### Score Formula
+
+```
+BFRI = (Architectural Fit + Testability) − (Complexity + Data Risk + Operational Risk)
+```
+
+**Range:** `-10 → +10`
+
+### Interpretation
+
+| BFRI     | Meaning   | Action                 |
+| -------- | --------- | ---------------------- |
+| **6–10** | Safe      | Proceed                |
+| **3–5**  | Moderate  | Add tests + monitoring |
+| **0–2**  | Risky     | Refactor or isolate    |
+| **< 0**  | Dangerous | Redesign before coding |

 ---

-## Architecture Overview
+## 2. When to Use This Skill

-### Layered Architecture
+Automatically applies when working on:

-```
-HTTP Request
-    ↓
-Routes (routing only)
-    ↓
-Controllers (request handling)
-    ↓
-Services (business logic)
-    ↓
-Repositories (data access)
-    ↓
-Database (Prisma)
-```
-
-**Key Principle:** Each layer has ONE responsibility.
-
-See [architecture-overview.md](architecture-overview.md) for complete details.
+* Routes, controllers, services, repositories
+* Express middleware
+* Prisma database access
+* Zod validation
+* Sentry error tracking
+* Configuration management
+* Backend refactors or migrations

 ---

-## Directory Structure
+## 3. Core Architecture Doctrine (Non-Negotiable)
+
+### 1. Layered Architecture Is Mandatory

 ```
-service/src/
-├── config/              # UnifiedConfig
-├── controllers/         # Request handlers
+Routes → Controllers → Services → Repositories → Database
+```
+
+* No layer skipping
+* No cross-layer leakage
+* Each layer has **one responsibility**
+
+---
+
+### 2. Routes Only Route
+
+```ts
+// ❌ NEVER
+router.post('/create', async (req, res) => {
+  await prisma.user.create(...);
+});
+
+// ✅ ALWAYS
+router.post('/create', (req, res) =>
+  userController.create(req, res)
+);
+```
+
+Routes must contain **zero business logic**.
+
+---
+
+### 3. Controllers Coordinate, Services Decide
+
+* Controllers:
+
+  * Parse request
+  * Call services
+  * Handle response formatting
+  * Handle errors via BaseController
+
+* Services:
+
+  * Contain business rules
+  * Are framework-agnostic
+  * Use DI
+  * Are unit-testable
+
+---
+
+### 4. All Controllers Extend `BaseController`
+
+```ts
+export class UserController extends BaseController {
+  async getUser(req: Request, res: Response): Promise<void> {
+    try {
+      const user = await this.userService.getById(req.params.id);
+      this.handleSuccess(res, user);
+    } catch (error) {
+      this.handleError(error, res, 'getUser');
+    }
+  }
+}
+```
+
+No raw `res.json` calls outside BaseController helpers.
+
+---
+
+### 5. All Errors Go to Sentry
+
+```ts
+catch (error) {
+  Sentry.captureException(error);
+  throw error;
+}
+```
+
+❌ `console.log`
+❌ silent failures
+❌ swallowed errors
+
+---
+
+### 6. unifiedConfig Is the Only Config Source
+
+```ts
+// ❌ NEVER
+process.env.JWT_SECRET;
+
+// ✅ ALWAYS
+import { config } from '@/config/unifiedConfig';
+config.auth.jwtSecret;
+```
+
+---
+
+### 7. Validate All External Input with Zod
+
+* Request bodies
+* Query params
+* Route params
+* Webhook payloads
+
+```ts
+const schema = z.object({
+  email: z.string().email(),
+});
+
+const input = schema.parse(req.body);
+```
+
+No validation = bug.
+
+---
+
+## 4. Directory Structure (Canonical)
+
+```
+src/
+├── config/              # unifiedConfig
+├── controllers/         # BaseController + controllers
 ├── services/            # Business logic
-├── repositories/        # Data access
-├── routes/              # Route definitions
-├── middleware/          # Express middleware
-├── types/               # TypeScript types
+├── repositories/        # Prisma access
+├── routes/              # Express routes
+├── middleware/          # Auth, validation, errors
 ├── validators/          # Zod schemas
-├── utils/               # Utilities
-├── tests/               # Tests
+├── types/               # Shared types
+├── utils/               # Helpers
+├── tests/               # Unit + integration tests
 ├── instrument.ts        # Sentry (FIRST IMPORT)
-├── app.ts               # Express setup
+├── app.ts               # Express app
 └── server.ts            # HTTP server
 ```

-**Naming Conventions:**
- Controllers: `PascalCase` - `UserController.ts`
- Services: `camelCase` - `userService.ts`
- Routes: `camelCase + Routes` - `userRoutes.ts`
- Repositories: `PascalCase + Repository` - `UserRepository.ts`
+---
+
+## 5. Naming Conventions (Strict)
+
+| Layer      | Convention                |
+| ---------- | ------------------------- |
+| Controller | `PascalCaseController.ts` |
+| Service    | `camelCaseService.ts`     |
+| Repository | `PascalCaseRepository.ts` |
+| Routes     | `camelCaseRoutes.ts`      |
+| Validators | `camelCase.schema.ts`     |

 ---

-## Core Principles (7 Key Rules)
+## 6. Dependency Injection Rules

-### 1. Routes Only Route, Controllers Control
+* Services receive dependencies via constructor
+* No importing repositories directly inside controllers
+* Enables mocking and testing

-```typescript
-// ❌ NEVER: Business logic in routes
-router.post('/submit', async (req, res) => {
-    // 200 lines of logic
-});
-
-// ✅ ALWAYS: Delegate to controller
-router.post('/submit', (req, res) => controller.submit(req, res));
-```
-
-### 2. All Controllers Extend BaseController
-
-```typescript
-export class UserController extends BaseController {
-    async getUser(req: Request, res: Response): Promise<void> {
-        try {
-            const user = await this.userService.findById(req.params.id);
-            this.handleSuccess(res, user);
-        } catch (error) {
-            this.handleError(error, res, 'getUser');
-        }
-    }
+```ts
+export class UserService {
+  constructor(
+    private readonly userRepository: UserRepository
+  ) {}
 }
 ```

-### 3. All Errors to Sentry
+---

-```typescript
-try {
-    await operation();
-} catch (error) {
-    Sentry.captureException(error);
-    throw error;
-}
+## 7. Prisma & Repository Rules
+
+* Prisma client **never used directly in controllers**
+* Repositories:
+
+  * Encapsulate queries
+  * Handle transactions
+  * Expose intent-based methods
+
+```ts
+await userRepository.findActiveUsers();
 ```

-### 4. Use unifiedConfig, NEVER process.env
+---

-```typescript
-// ❌ NEVER
-const timeout = process.env.TIMEOUT_MS;
+## 8. Async & Error Handling

-// ✅ ALWAYS
-import { config } from './config/unifiedConfig';
-const timeout = config.timeouts.default;
+### asyncErrorWrapper Required
+
+All async route handlers must be wrapped.
+
+```ts
+router.get(
+  '/users',
+  asyncErrorWrapper((req, res) =>
+    controller.list(req, res)
+  )
+);
 ```

-### 5. Validate All Input with Zod
+No unhandled promise rejections.

-```typescript
-const schema = z.object({ email: z.string().email() });
-const validated = schema.parse(req.body);
-```
+---

-### 6. Use Repository Pattern for Data Access
+## 9. Observability & Monitoring

-```typescript
-// Service → Repository → Database
-const users = await userRepository.findActive();
-```
+### Required

-### 7. Comprehensive Testing Required
+* Sentry error tracking
+* Sentry performance tracing
+* Structured logs (where applicable)

-```typescript
+Every critical path must be observable.
+
+---
+
+## 10. Testing Discipline
+
+### Required Tests
+
+* **Unit tests** for services
+* **Integration tests** for routes
+* **Repository tests** for complex queries
+
+```ts
 describe('UserService', () => {
-    it('should create user', async () => {
-        expect(user).toBeDefined();
-    });
+  it('creates a user', async () => {
+    expect(user).toBeDefined();
+  });
 });
 ```

---
-
-## Common Imports
-
-```typescript
-// Express
-import express, { Request, Response, NextFunction, Router } from 'express';
-
-// Validation
-import { z } from 'zod';
-
-// Database
-import { PrismaClient } from '@prisma/client';
-import type { Prisma } from '@prisma/client';
-
-// Sentry
-import * as Sentry from '@sentry/node';
-
-// Config
-import { config } from './config/unifiedConfig';
-
-// Middleware
-import { SSOMiddlewareClient } from './middleware/SSOMiddleware';
-import { asyncErrorWrapper } from './middleware/errorBoundary';
-```
+No tests → no merge.

 ---

-## Quick Reference
-
-### HTTP Status Codes
-
-| Code | Use Case |
-|------|----------|
-| 200 | Success |
-| 201 | Created |
-| 400 | Bad Request |
-| 401 | Unauthorized |
-| 403 | Forbidden |
-| 404 | Not Found |
-| 500 | Server Error |
-
-### Service Templates
-
-**Blog API** (✅ Mature) - Use as template for REST APIs
-**Auth Service** (✅ Mature) - Use as template for authentication patterns
-
---
-
-## Anti-Patterns to Avoid
+## 11. Anti-Patterns (Immediate Rejection)

 ❌ Business logic in routes
-❌ Direct process.env usage
-❌ Missing error handling
-❌ No input validation
-❌ Direct Prisma everywhere
+❌ Skipping service layer
+❌ Direct Prisma in controllers
+❌ Missing validation
+❌ process.env usage
 ❌ console.log instead of Sentry
+❌ Untested business logic

 ---

-## Navigation Guide
+## 12. Integration With Other Skills

-| Need to... | Read this |
-|------------|-----------|
-| Understand architecture | [architecture-overview.md](architecture-overview.md) |
-| Create routes/controllers | [routing-and-controllers.md](routing-and-controllers.md) |
-| Organize business logic | [services-and-repositories.md](services-and-repositories.md) |
-| Validate input | [validation-patterns.md](validation-patterns.md) |
-| Add error tracking | [sentry-and-monitoring.md](sentry-and-monitoring.md) |
-| Create middleware | [middleware-guide.md](middleware-guide.md) |
-| Database access | [database-patterns.md](database-patterns.md) |
-| Manage config | [configuration.md](configuration.md) |
-| Handle async/errors | [async-and-errors.md](async-and-errors.md) |
-| Write tests | [testing-guide.md](testing-guide.md) |
-| See examples | [complete-examples.md](complete-examples.md) |
+* **frontend-dev-guidelines** → API contract alignment
+* **error-tracking** → Sentry standards
+* **database-verification** → Schema correctness
+* **analytics-tracking** → Event pipelines
+* **skill-developer** → Skill governance

 ---

-## Resource Files
+## 13. Operator Validation Checklist

-### [architecture-overview.md](architecture-overview.md)
-Layered architecture, request lifecycle, separation of concerns
+Before finalizing backend work:

-### [routing-and-controllers.md](routing-and-controllers.md)
-Route definitions, BaseController, error handling, examples
-
-### [services-and-repositories.md](services-and-repositories.md)
-Service patterns, DI, repository pattern, caching
-
-### [validation-patterns.md](validation-patterns.md)
-Zod schemas, validation, DTO pattern
-
-### [sentry-and-monitoring.md](sentry-and-monitoring.md)
-Sentry init, error capture, performance monitoring
-
-### [middleware-guide.md](middleware-guide.md)
-Auth, audit, error boundaries, AsyncLocalStorage
-
-### [database-patterns.md](database-patterns.md)
-PrismaService, repositories, transactions, optimization
-
-### [configuration.md](configuration.md)
-UnifiedConfig, environment configs, secrets
-
-### [async-and-errors.md](async-and-errors.md)
-Async patterns, custom errors, asyncErrorWrapper
-
-### [testing-guide.md](testing-guide.md)
-Unit/integration tests, mocking, coverage
-
-### [complete-examples.md](complete-examples.md)
-Full examples, refactoring guide
+* [ ] BFRI ≥ 3
+* [ ] Layered architecture respected
+* [ ] Input validated
+* [ ] Errors captured in Sentry
+* [ ] unifiedConfig used
+* [ ] Tests written
+* [ ] No anti-patterns present

 ---

-## Related Skills
-
- **database-verification** - Verify column names and schema consistency
- **error-tracking** - Sentry integration patterns
- **skill-developer** - Meta-skill for creating and managing skills
+## 14. Skill Status

+**Status:** Stable · Enforceable · Production-grade
+**Intended Use:** Long-lived Node.js microservices with real traffic and real risk
 ---
-
-**Skill Status**: COMPLETE ✅
-**Line Count**: < 500 ✅
-**Progressive Disclosure**: 11 resource files ✅