Error Patterns

Table of Contents

• Overview
• When to Use
• Error Classification
• By Severity
• By Recoverability
• Quick Start
• Standard Error Handler
• Error Result
• Common Patterns
• Authentication Errors (401/403))
• Rate Limit Errors (429))
• Timeout Errors
• Context Too Large (400))
• Integration Pattern
• Detailed Resources
• Exit Criteria

Error Patterns

Overview

Standardized error handling patterns for consistent, production-grade behavior across plugins. Provides error classification, recovery strategies, and debugging workflows.

When To Use

• Building resilient integrations
• Need consistent error handling
• Want graceful degradation
• Debugging production issues

When NOT To Use

• Project doesn't use the leyline infrastructure patterns
• Simple scripts without service architecture needs

Error Classification

By Severity

| Level | Action | Example |

|-------|--------|---------|

| Critical | Halt, alert | Auth failure, service down |

| Error | Retry or secondary strategy | Rate limit, timeout |

| Warning | Log, continue | Partial results, deprecation |

| Info | Log only | Non-blocking issues |

By Recoverability

class ErrorCategory(Enum):
    TRANSIENT = "transient"      # Retry likely to succeed
    PERMANENT = "permanent"       # Retry won't help
    CONFIGURATION = "config"      # User action needed
    RESOURCE = "resource"         # Quota/limit issue

Verification: Run the command with --help flag to verify availability.

Quick Start

Standard Error Handler

from leyline.error_patterns import handle_error, ErrorCategory

try:
    result = service.execute(prompt)
except RateLimitError as e:
    return handle_error(e, ErrorCategory.RESOURCE, {
        "retry_after": e.retry_after,
        "service": "gemini"
    })
except AuthError as e:
    return handle_error(e, ErrorCategory.CONFIGURATION, {
        "action": "Run 'gemini auth login'"
    })

Verification: Run the command with --help flag to verify availability.

Error Result

@dataclass
class ErrorResult:
    category: ErrorCategory
    message: str
    recoverable: bool
    suggested_action: str
    metadata: dict

Verification: Run the command with --help flag to verify availability.

Common Patterns

Authentication Errors (401/403)

• Verify credentials exist
• Check token expiration
• Validate permissions/scopes
• Suggest re-authentication

Rate Limit Errors (429)

• Extract retry-after header
• Log for quota tracking
• Implement backoff
• Consider alternative service

Timeout Errors

• Increase timeout for retries
• Break into smaller requests
• Use async patterns
• Consider different model

Context Too Large (400)

• Estimate tokens before request
• Split into multiple requests
• Reduce input content
• Use larger context model

Integration Pattern

# In your skill's frontmatter
dependencies: [leyline:error-patterns]

Verification: Run the command with --help flag to verify availability.

Detailed Resources

• Classification: See modules/classification.md for error taxonomy
• Recovery: See modules/recovery-strategies.md for handling patterns
• Agent Damage Control: See modules/agent-damage-control.md for multi-agent error recovery and escalation

Exit Criteria

• Error classified correctly
• Appropriate recovery attempted
• User-actionable message provided
• Error logged for debugging