frontend-engineering

A set of rules for building user interfaces, including their structure, data handling, forms, accessibility, and responsive behavior.

In plain words
What is it for?
It helps organize frontend code, manage local and server data, design accessible forms, and cover loading, error, empty, and success states.
Why use it?
It reduces tangled components, misplaced state, incomplete form behavior, and interfaces that are difficult to use or maintain.

Cursor rule

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/jterratsdev/ableton-live-mcp/frontend-engineering
Clone the repo
git clone --depth 1 https://github.com/jterratsdev/ableton-live-mcp
Per session 304 This file is loaded in full into every session.
When invoked 304 The same file — it is already loaded in full.
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 $0.00304 $0.00304
Opus 5 $0.00152 $0.00152
Sonnet 5 $0.00061 $0.00061
Haiku 4.5 $0.00030 $0.00030

Measured yesterday against content hash 5720bee649d7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-engineering 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 yesterday.

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.

rules/frontend-engineering.mdc · 33 lines

What it actually says

Frontend Engineering

Frontend code must keep user experience, state, accessibility, and maintainability aligned.

Architecture

  • Separate presentation, state orchestration, data access, and domain logic.
  • Keep components small and purpose-specific. Extract hooks, services, or view models when logic grows.
  • Prefer existing design system components, tokens, and layout primitives over custom styling.
  • Do not duplicate API types, validation schemas, or constants when they can be imported or generated.

State

  • Separate local UI state from server/cache state.
  • Keep state ownership close to the component or workflow that owns it.
  • Avoid global state for data that is route-local, form-local, or derivable.
  • Model loading, empty, error, success, stale, and optimistic states explicitly.

Forms

  • Forms need labels, validation, helper text, disabled states, submission states, and recovery paths.
  • Validate on the client for feedback and on the server for authority.
  • Preserve user input when validation fails.
  • Avoid destructive default actions and require confirmation for irreversible operations.

Accessibility & Responsive

  • Preserve semantic HTML, keyboard navigation, focus states, readable contrast, and screen reader labels.
  • Test common mobile, tablet, and desktop widths for user-facing flows.
  • Do not hide required information behind hover-only interactions.
  • Use tooltips for clarification, not as the only way to complete a task.
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. yesterday First seen · 33 lines · 304 tokens per session scan A 5720bee649d7

Subscribe to this mod's changes

frontend-engineering is a cursor rule published in the GitHub repository jterratsdev/ableton-live-mcp (0 stars, last pushed 8d ago), licensed MIT. It adds 304 tokens to every session, about $0.0015 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.