Error Code Guide

Language: English | 繁體中文

Version: 1.0.0 Last Updated: 2025-12-30 Applicability: Claude Code Skills

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Purpose

This skill helps design consistent error codes following the standard format, enabling better debugging, monitoring, and user experience.

Quick Reference

Error Code Format

<PREFIX>_<CATEGORY>_<NUMBER>

Component	Description	Example
PREFIX	Application/service identifier	AUTH, PAY, USR
CATEGORY	Error category	VAL, SYS, BIZ
NUMBER	Unique numeric identifier	001, 100, 404

Examples

AUTH_VAL_001    → Authentication validation error
PAY_SYS_503     → Payment system unavailable
USR_BIZ_100     → User business rule violation
API_NET_408     → API network timeout

Error Categories

Category	Full Name	Description	HTTP Status
VAL	Validation	Client input validation failures	400
BIZ	Business	Business rule violations	422
SYS	System	Internal system failures	500
NET	Network	Communication failures	502/503/504
AUTH	Auth	Security-related errors	401/403

Category Code Ranges

Range	Description	Example
*_VAL_001-099	Field validation	Missing required field
*_VAL_100-199	Format validation	Invalid email format
*_VAL_200-299	Constraint validation	Password too short
*_BIZ_001-099	State violations	Order already cancelled
*_BIZ_100-199	Rule violations	Cannot return after 30 days
*_BIZ_200-299	Limit violations	Daily limit exceeded
*_AUTH_001-099	Authentication	Invalid credentials
*_AUTH_100-199	Authorization	Insufficient permissions
*_AUTH_200-299	Token/session	Token expired

HTTP Status Code Mapping

Category	HTTP Status	Description
VAL	400	Bad Request
BIZ	422	Unprocessable Entity
AUTH (001-099)	401	Unauthorized
AUTH (100-199)	403	Forbidden
SYS	500	Internal Server Error
NET	502/503/504	Gateway errors

Detailed Guidelines

For complete standards, see:

• Error Code Standards

AI-Optimized Format (Token-Efficient)

For AI assistants, use the YAML format files for reduced token usage:

• Base standard: ai/standards/error-codes.ai.yaml

Error Response Format

Single Error

{
  "success": false,
  "error": {
    "code": "AUTH_VAL_001",
    "message": "Email is required",
    "field": "email",
    "requestId": "req_abc123"
  }
}

Multiple Errors

{
  "success": false,
  "errors": [
    {
      "code": "AUTH_VAL_001",
      "message": "Email is required",
      "field": "email"
    },
    {
      "code": "AUTH_VAL_201",
      "message": "Password must be at least 8 characters",
      "field": "password"
    }
  ],
  "requestId": "req_abc123"
}

Internal Error Object

interface ApplicationError {
  // Core fields
  code: string;          // "AUTH_VAL_001"
  message: string;       // Technical message for logs

  // User-facing
  userMessage: string;   // Localized user message
  userMessageKey: string; // i18n key: "error.auth.val.001"

  // Context
  field?: string;        // Affected field: "email"
  details?: object;      // Additional context

  // Debugging
  timestamp: string;     // ISO 8601
  requestId: string;     // Correlation ID
}

Internationalization (i18n)

Message Key Format

error.<prefix>.<category>.<number>

Example Translation Files

# en.yaml
error:
  auth:
    val:
      001: "Email is required"
      101: "Invalid email format"
    auth:
      001: "Invalid credentials"

# zh-TW.yaml
error:
  auth:
    val:
      001: "電子郵件為必填欄位"
      101: "電子郵件格式無效"
    auth:
      001: "帳號或密碼錯誤"

Examples

✅ Good Error Codes

AUTH_VAL_001  // Missing required field: email
AUTH_VAL_101  // Invalid email format
ORDER_BIZ_001 // Order already cancelled
ORDER_BIZ_201 // Daily purchase limit exceeded
DB_SYS_001    // Database query failed
SEC_AUTH_001  // Invalid credentials
SEC_AUTH_201  // Token expired

❌ Bad Error Codes

ERR_001       // Too vague, no prefix or category
INVALID       // Not descriptive
error         // Not a code
AUTH_ERROR    // Missing number

Checklist

• Unique code for each error
• Category matches error type
• User message is localized
• HTTP status is correct
• Error is documented
• Code is in registry

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Configuration Detection

This skill supports project-specific configuration.

Detection Order

1. Check for existing error code patterns in codebase
2. Check CONTRIBUTING.md for error code guidelines
3. If not found, default to PREFIX_CATEGORY_NUMBER format

First-Time Setup

If no error code standard found:

1. Suggest: "This project hasn't configured error code standards. Would you like to set up an error code registry?"
2. Suggest creating errors/registry.ts:

export const ErrorCodes = {
  AUTH_VAL_001: {
    code: 'AUTH_VAL_001',
    httpStatus: 400,
    messageKey: 'error.auth.val.001',
    description: 'Email field is required',
  },
  // ... more codes
} as const;

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Related Standards

• Error Code Standards
• Logging Standards

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Version History

Version	Date	Changes
1.0.0	2025-12-30	Initial release

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License

This skill is released under CC BY 4.0.

Source: universal-dev-standards