Error Shape Taxonomy

# Error Shape Taxonomy

## Skill Profile
*(Select at least one profile to enable specific modules)*
- [ ] **DevOps**
- [x] **Backend**
- [ ] **Frontend**
- [ ] **AI-RAG**
- [ ] **Security Critical**

## Overview
Organization-wide standard error response format covering error codes, categories, and structure that enables clients and monitoring tools to understand errors immediately.

## Why This Matters
- **Debuggability**: รู้ทันทีว่า error มาจากไหน ทำไม
- **Client handling**: Frontend/mobile handle errors ได้ถูกต้อง
- **Monitoring**: Alert และ dashboard แยก error types ได้
- **Documentation**: Error catalog ที่ reference ได้

---

## Core Concepts
#

## Inputs / Outputs / Contracts
* **Inputs**:
  - <e.g., env vars, request payload, file paths, schema>
* **Entry Conditions**:
  - <Pre-requisites: e.g., Repo initialized, DB running, specific branch checked out>
* **Outputs**:
  - <e.g., artifacts (PR diff, docs, tests, dashboard JSON)>
* **Artifacts Required (Deliverables)**:
  - <e.g., Code Diff, Unit Tests, Migration Script, API Docs>
* **Acceptance Evidence**:
  - <e.g., Test Report (screenshot/log), Benchmark Result, Security Scan Report>
* **Success Criteria**:
  - <e.g., p95 < 300ms, coverage ≥ 80%>

## Skill Composition
* **Depends on**: None
* **Compatible with**: None
* **Conflicts with**: None
* **Related Skills**: None

## Quick Start
```typescript
export type ErrorCategory = "AUTH" | "AUTHZ" | "VAL" | "BIZ" | "RATE" | "SYS";

export interface ErrorResponse {
  error: {
    code: string;
    category: ErrorCategory;
    message: string;
    status: number;
    requestId: string;
    timestamp: string;
    path?: string;
    method?: string;
    retryable?: boolean;
    retryAfterSeconds?: number;
    details?: Record<string, unknown>;
    validationErrors?: Array<{ field: string; reason: string }>;
  };
}
```

## Assumptions / Constraints / Non-goals

* **Assumptions**:
  - Development environment is properly configured
  - Required dependencies are available
  - Team has basic understanding of domain
* **Constraints**:
  - Must follow existing codebase conventions
  - Time and resource limitations
  - Compatibility requirements
* **Non-goals**:
  - This skill does not cover edge cases outside scope
  - Not a replacement for formal training


## Compatibility & Prerequisites

* **Supported Versions**:
  - Python 3.8+
  - Node.js 16+
  - Modern browsers (Chrome, Firefox, Safari, Edge)
* **Required AI Tools**:
  - Code editor (VS Code recommended)
  - Testing framework appropriate for language
  - Version control (Git)
* **Dependencies**:
  - Language-specific package manager
  - Build tools
  - Testing libraries
* **Environment Setup**:
  - `.env.example` keys: `API_KEY`, `DATABASE_URL` (no values)


## Test Scenario Matrix (QA Strategy)

| Type | Focus Area | Required Scenarios / Mocks |
| :--- | :--- | :--- |
| **Unit** | Core Logic | Must cover primary logic and at least 3 edge/error cases. Target minimum 80% coverage |
| **Integration** | DB / API | All external API calls or database connections must be mocked during unit tests |
| **E2E** | User Journey | Critical user flows to test |
| **Performance** | Latency / Load | Benchmark requirements |
| **Security** | Vuln / Auth | SAST/DAST or dependency audit |
| **Frontend** | UX / A11y | Accessibility checklist (WCAG), Performance Budget (Lighthouse score) |


## Technical Guardrails & Security Threat Model

### 1. Security & Privacy (Threat Model)
* **Top Threats**: Injection attacks, authentication bypass, data exposure
- [ ] **Data Handling**: Sanitize all user inputs to prevent Injection attacks. Never log raw PII
- [ ] **Secrets Management**: No hardcoded API keys. Use Env Vars/Secrets Manager
- [ ] **Authorization**: Validate user permissions before state changes

### 2. Performance & Resources
- [ ] **Execution Efficiency**: Consider time complexity for algorithms
- [ ] **Memory Management**: Use streams/pagination for large data
- [ ] **Resource Cleanup**: Close DB connections/file handlers in finally blocks

### 3. Architecture & Scalability
- [ ] **Design Pattern**: Follow SOLID principles, use Dependency Injection
- [ ] **Modularity**: Decouple logic from UI/Frameworks

### 4. Observability & Reliability
- [ ] **Logging Standards**: Structured JSON, include trace IDs `request_id`
- [ ] **Metrics**: Track `error_rate`, `latency`, `queue_depth`
- [ ] **Error Handling**: Standardized error codes, no bare except
- [ ] **Observability Artifacts**:
    - **Log Fields**: timestamp, level, message, request_id
    - **Metrics**: request_count, error_count, response_time
    - **Dashboards/Alerts**: High Error Rate > 5%


## Agent Directives & Error Recovery
*(ข้อกำหนดสำหรับ AI Agent ในการคิดและแก้ปัญหาเมื่อเกิดข้อผิดพลาด)*

- **Thinking Process**: Analyze root cause before fixing. Do not brute-force.
- **Fallback Strategy**: Stop after 3 failed test attempts. Output root cause and ask for human intervention/clarification.
- **Self-Review**: Check against Guardrails & Anti-patterns before finalizing.
- **Output Constraints**: Output ONLY the modified code block. Do not explain unless asked.


## Definition of Done (DoD) Checklist

- [ ] Tests passed + coverage met
- [ ] Lint/Typecheck passed
- [ ] Logging/Metrics/Trace implemented
- [ ] Security checks passed
- [ ] Documentation/Changelog updated
- [ ] Accessibility/Performance requirements met (if frontend)


## Anti-patterns
1. **Generic errors**: "Something went wrong"
2. **Leaking internals**: Stack traces to client
3. **Inconsistent shape**: Different format per service
4. **Missing correlation**: No request ID
5. **Changing meaning**: เปลี่ยน semantics ของ code เดิม ทำให้ client/alert พัง

## Reference Links & Examples

* Internal documentation and examples
* Official documentation and best practices
* Community resources and discussions


## Versioning & Changelog

* **Version**: 1.0.0
* **Changelog**:
  - 2026-02-22: Initial version with complete template structure