error-audit - SKILL.md Agent Skill

name: error-audit description: Audit code for silent error swallowing, fallbacks to degraded alternatives, backwards compatibility shims, and UI that fails to show errors to the user. Finds and fixes all occurrences in the specified scope.

Error Audit

The core principle: every error belongs to the user. Not to a catch block, not to a console, not to a null return. Scan the specified code, fix every violation, report what changed.

Step 0: Understand the app's error mechanisms

Before fixing anything, identify how this app surfaces errors to users — toast notifications, error banners, error boundaries, returned error states, alert dialogs, inline messages. Use these patterns exclusively. Don't invent a new one.

Anti-patterns to find and fix

Silent error swallowing — backend/logic layer:

Empty catch blocks: catch(e) {}
Log-and-continue: catch(e) { console.error(e) } with execution proceeding normally
.catch(() => {}) on promises
Functions returning null, undefined, or empty defaults on failure instead of throwing

Silent error swallowing — UI layer:

Data fetching catches an error and returns null/empty → component renders blank with no explanation
Error boundaries that catch but show nothing (or a generic "something went wrong" with no recovery path)
try/catch in a loader or server action that swallows the error and returns partial/empty data
Async operations where the UI has no error state at all — success renders fine, failure renders identical to loading or empty

Fallbacks to degraded alternatives:

Catch → silently switch to a worse model, API, or service
Catch → return cached or stale data without telling the user
Catch → offline/degraded mode with no visible indication

Backwards compatibility shims:

if (legacyFormat) or if (oldVersion) branches
Deprecated fields still being populated alongside new ones
Old code paths running in parallel with new ones

Config defaults that hide misconfiguration:

process.env.X || 'fallback' for required values — missing required config is a startup crash, not a default
Optional environment variables that should be required

Optional chaining hiding missing required data:

user?.profile?.name ?? 'Guest' when profile must always exist — the absence is a bug, not an edge case to handle silently

Fix principles

Throw or re-throw rather than catch-and-continue
In the UI: every error path must render something visible — use the app's established error display mechanism
Required config missing at startup → log a clear message and exit
Delete fallback branches — don't comment them out
When unsure if a fallback was intentional, flag it in your report rather than guessing

Reference files

references/error-patterns.md — Concrete anti-patterns with structural descriptions, bad/good code examples, and false positive notes. Read this before starting the audit.

Report

After fixing, summarize by file: what was found, what the fix was. Be specific — file paths and the pattern removed.