# Error Handling

> Use when: design error handling so failures are explicit, recoverable, and never silently swallowed.

- Skill: `kimtth/error-handling` (Agent Skill)
- Install (CLI): `npx skillmds@latest add kimtth/error-handling`
- Raw SKILL.md: https://api.skillmd.com/api/skills/kimtth/error-handling/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: kimtth (https://skillmd.com/u/kimtth)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/kimtth/error-handling

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Goal: failures that are visible, contextual, and handled deliberately.

Use for:
- deciding how functions signal and propagate failure
- reviewing try/catch, error types, and recovery
- fixing swallowed errors and vague messages

Workflow:
1. Distinguish expected failures from programmer bugs.
2. Model expected errors explicitly (results or typed exceptions).
3. Handle errors where you can act; otherwise propagate with context.
4. Add context as errors cross boundaries, without losing the cause.
5. Fail fast on invariant violations; do not limp on.
6. Surface actionable messages; log details once, near the source.

Patterns:
- typed errors or result types over generic throws
- wrap-and-rethrow to add context, preserving the cause
- retry with backoff for transient failures only
- a single place that maps errors to user-facing responses

Rules:
- never swallow an error silently
- do not catch broadly just to continue; handle or rethrow
- include context, never the bare message
- distinguish retryable failures from permanent ones