standard-frontend-error-management

A set of rules for handling crashes and expected errors in a React web interface. It explains when to use the app-wide error screen, a route-specific screen, or inline messages.

In plain words
What is it for?
Use it when building forms, data mutations, routes, or isolated interface widgets that may fail independently.
Why use it?
It prevents duplicated error handling and keeps normal problems, such as invalid form input or failed requests, from being treated like full page crashes.

Cursor rule for Cursor

Install

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.

agentmods
npx agentmods add rules/packmindhub/packmind/standard-frontend-error-management
Clone the repo
git clone --depth 1 https://github.com/PackmindHub/packmind

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 306 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What 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.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00306
Opus 5 $0.00000 $0.00153
Sonnet 5 $0.00000 $0.00061
Haiku 4.5 $0.00000 $0.00031

Measured 2d ago against content hash e7bcd187e5bb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

standard-frontend-error-management 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.

apps/frontend/.cursor/rules/packmind/standard-frontend-error-management.mdc · 18 lines

What it actually says

Standard: Frontend Error Management

A global error boundary is already configured at the root level (in root.tsx) that automatically catches all page crashes, 404s, and loader failures. This standard defines when and how to use explicit... :

  • Avoid overusing error boundaries as they increase code complexity and make error flows harder to trace
  • Display validation errors inline near the relevant form fields for better user experience
  • Do NOT use error boundaries for errors that should be handled explicitly such as form validation, expected API errors, and user input errors
  • Handle TanStack Query mutation errors using onError callbacks to display contextual error messages
  • Only add a page-level error boundary when you need custom error UI for a specific route that differs from the default error page
  • Only add component-level error boundaries for isolated critical features where partial failure is acceptable, such as independent dashboard widgets that can fail without affecting the rest of the page. Use this mainly when using components we do not manage internally (eg: CodeMirror).
  • Prevent double submissions by checking mutation pending state before triggering operations
  • Use typed error guards such as isPackmindError to safely extract error details from API responses before displaying to users
  • Wrap async operations in try-catch blocks since error boundaries do NOT catch errors in event handlers or async code

Full standard is available here for further request: Frontend Error Management

Changes

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.

  1. 2d ago First seen · 18 lines · 0 tokens per session scan A e7bcd187e5bb

Subscribe to this mod's changes

standard-frontend-error-management is a cursor rule published in the GitHub repository PackmindHub/packmind (306 stars, last pushed 5d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 306 tokens. 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 2026-08-30.