frontend

A set of rules for building and changing user-facing web interfaces.

In plain words
What is it for?
Choosing existing components and styles, handling UI states, supporting keyboard and assistive technology users, and keeping components manageable.
Why use it?
It helps keep the interface consistent, accessible, and complete across loading, empty, error, and success states.

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/kingemma7/cursor-os/frontend
Clone the repo
git clone --depth 1 https://github.com/KingEmma7/cursor-os

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 228 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 $0.00228
Opus 5 $0.00000 $0.00114
Sonnet 5 $0.00000 $0.00046
Haiku 4.5 $0.00000 $0.00023

Measured 2d ago against content hash 868a15cad9ae, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend 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.

template/.cursor/rules/frontend.mdc · 16 lines

What it actually says

Opt-in frontend discipline. Localization should delete this file if the project has no UI, or replace the generic guidance with the project's real component, state, and styling conventions.

  • Reuse the existing component library, design tokens, and styling system. Don't introduce a second way to do the same thing.
  • Do not introduce a new styling system unless the project already uses it or the user explicitly approves it.
  • Handle every state: loading, empty, error, and success. Don't ship the happy path alone.
  • Make interactive elements accessible: real semantics, keyboard support, focus states, and labels for assistive tech.
  • Keep components focused. Extract a subcomponent or hook when one grows too large or mixes concerns.
  • Derive UI from state; avoid duplicating server data into local state that can drift.
  • Match existing data-fetching, error-handling, and form-validation patterns rather than inventing new ones.
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 · 16 lines · 228 tokens per session scan A 868a15cad9ae

Subscribe to this mod's changes

frontend is a cursor rule published in the GitHub repository KingEmma7/cursor-os (2 stars, last pushed 20d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 228 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 2026-08-31.