Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add rules/nedcodes-ok/cursor-doctor/error-handlinggit clone --depth 1 https://github.com/nedcodes-ok/cursor-doctorWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00493 | $0.00493 |
| Opus 5 | $0.00246 | $0.00246 |
| Sonnet 5 | $0.00099 | $0.00099 |
| Haiku 4.5 | $0.00049 | $0.00049 |
Grade A, and why
error-handling scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 50 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Error Handling Cursor Rules
You are an expert at error handling. Follow these rules:
Error Types
- Distinguish operational errors (expected) from programmer errors (bugs)
- Operational: invalid input, network timeout, not found — handle gracefully
- Programmer: null reference, type error, assertion failure — crash and fix
- Use typed/enumerated errors, not string messages, for programmatic handling
- Each error needs: code (machine), message (human), context (debugging)
Boundaries
- Catch errors at module boundaries — dont let implementation details leak
- Translate low-level errors to domain errors: DBError → UserNotFoundError
- Unhandled errors bubble to a global handler that logs and returns 500
- Never catch and ignore. At minimum: log, increment a counter, re-throw
- Use error boundaries in UI: per-feature, not just root level
Error Responses
- Consistent error shape across all API endpoints
- Include error code for client-side handling: "INSUFFICIENT_FUNDS"
- Human-readable message that is safe to show users
- Debug details only in development, never in production responses
- Correlation/request ID in every error for support tracing
Retry & Recovery
- Retry only idempotent operations and transient failures
- Exponential backoff with jitter: base * 2^attempt + random jitter
- Max 3-5 retries. Circuit breaker for persistent failures
- Timeout every external call. No unbounded waits
- Graceful degradation: show cached data, disable feature, not blank page
Logging
- Log errors with full context: user, request, input, stack trace
- Structured logging: { level, error_code, message, context, stack }
- Error level for operational failures, fatal for programmer errors
- Dont log sensitive data in error context (passwords, tokens, PII)
Patterns by Language
- TypeScript: Result<T, E> pattern or neverthrow library
- Python: custom exception hierarchy, not bare except
- Go: errors.Is/As for checking, fmt.Errorf with %w for wrapping
- Rust: ? operator with custom error enums, thiserror for libraries
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 50 lines · 493 tokens per session scan A 049e57711eb4
error-handling is a cursor rule published in the GitHub repository nedcodes-ok/cursor-doctor (9 stars, last pushed 5mo ago), licensed MIT. It adds 493 tokens to every session, about $0.0025 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
Other cursor rules, from other repositories
java
Modern Java: records, sealed classes, streams, virtual threads.
javascript
Modern JavaScript: ES2023+, async patterns, common traps.
accessibility
Accessibility: semantic HTML, ARIA, keyboard navigation, testing.
cross-tool-config
Cross-tool AI config: what transfers between Cursor, Claude Code, Copilot, Windsurf, Gemini, and Codex.
angular
Angular: signals, standalone components, RxJS patterns.
django
Django: models, views, ORM best practices.