Domain exception hierarchy, error codes, GraphQL error formatting, and error logging standards for a NestJS + GraphQL backend.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Error Handling Skill
## Scope
Apply this skill for any task involving error handling, exception design, error responses, or error logging. This project uses **NestJS** with **GraphQL** (code-first) and a global exception filter.
---
## Error Philosophy
Errors are not exceptional — they are expected outcomes that the system must handle gracefully. The error handling strategy has three goals:
1. **Clients receive actionable, consistent error responses** — never raw stack traces or framework errors
2. **Developers can diagnose issues quickly** — structured logs with full context
3. **The system fails safely** — invalid state is never persisted, partial operations are rolled back
---
## Domain Exception Hierarchy
### Base Exception
All domain exceptions extend a base `DomainException` that carries a machine-readable error code:
```typescript
export abstract class DomainException extends Error {
abstract readonly code: string;
constructor(message: string) {
super(message);
this.name = this.constructor.name;
}
}
```
### Naming Convention
Exception class names describe **what went wrong**, not what the system tried to do:
| Pattern | Example |
|---|---|
…
The line at the top of this page pins the label git:20260610.47ec162, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
GET https://markdownregistry.com/api/v1/artifacts/art_jkhlmzm3vjshbzp4
GET https://markdownregistry.com/api/v1/resolve?ref=jvoliveiran/constellation-harness/error-handling
GET https://markdownregistry.com/api/v1/blob/11033bc593bf9c93487573ee468c475c1f05a1e593700413eb1e13771d117487
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