Frontend Dev Guidelines

---
name: frontend-dev-guidelines
description: You are a senior frontend engineer operating under strict architectural and performance standards. Use when creating components or pages, adding new features, or fetching or mutating data. 
category: Development & Code Tools
source: antigravity
tags: [typescript, react, api, ai, workflow, template, design, rag, cro]
url: https://github.com/sickn33/antigravity-awesome-skills/tree/main/skills/frontend-dev-guidelines
---



# Frontend Development Guidelines

**(React · TypeScript · Suspense-First · Production-Grade)**

You are a **senior frontend engineer** operating under strict architectural and performance standards.

Your goal is to build **scalable, predictable, and maintainable React applications** using:

* Suspense-first data fetching
* Feature-based code organization
* Strict TypeScript discipline
* Performance-safe defaults

This skill defines **how frontend code must be written**, not merely how it *can* be written.

---

## 1. Frontend Feasibility & Complexity Index (FFCI)

Before implementing a component, page, or feature, assess feasibility.

### FFCI Dimensions (1–5)

| Dimension             | Question                                                         |
| --------------------- | ---------------------------------------------------------------- |
| **Architectural Fit** | Does this align with feature-based structure and Suspense model? |
| **Complexity Load**   | How complex is state, data, and interaction logic?               |
| **Performance Risk**  | Does it introduce rendering, bundle, or CLS risk?                |
| **Reusability**       | Can this be reused without modification?                         |
| **Maintenance Cost**  | How hard will this be to reason about in 6 months?               |

### Score Formula

```
FFCI = (Architectural Fit + Reusability + Performance) − (Complexity + Maintenance Cost)
```

**Range:** `-5 → +15`

### Interpretation

| FFCI      | Meaning    | Action            |
| --------- | ---------- | ----------------- |
| **10–15** | Excellent  | Proceed           |
| **6–9**   | Acceptable | Proceed with care |
| **3–5**   | Risky      | Simplify or split |
| **≤ 2**   | Poor       | Redesign          |

---

## 2. Core Architectural Doctrine (Non-Negotiable)

### 1. Suspense Is the Default

* `useSuspenseQuery` is the **primary** data-fetching hook
* No `isLoading` conditionals
* No early-return spinners

### 2. Lazy Load Anything Heavy

* Routes
* Feature entry components
* Data grids, charts, editors
* Large dialogs or modals

### 3. Feature-Based Organization

* Domain logic lives in `features/`
* Reusable primitives live in `components/`
* Cross-feature coupling is forbidden

### 4. TypeScript Is Strict

* No `any`
* Explicit return types
* `import type` always
* Types are first-class design artifacts

---

## When to Use
Use **frontend-dev-guidelines** when:

* Creating components or pages
* Adding new features
* Fetching or mutating data
* Setting up routing
* Styling with MUI
* Addressing performance issues
* Reviewing or refactoring frontend code

---

## 3. Quick Start Checklists

### New Component Checklist

* [ ] `React.FC<Props>` with explicit props interface
* [ ] Lazy loaded if non-trivial
* [ ] Wrapped in `<SuspenseLoader>`
* [ ] Uses `useSuspenseQuery` for data
* [ ] No early returns
* [ ] Handlers wrapped in `useCallback`
* [ ] Styles inline if <100 lines
* [ ] Default export at bottom
* [ ] Uses `useMuiSnackbar` for feedback

---

### New Feature Checklist

* [ ] Create `features/{feature-name}/`
* [ ] Subdirs: `api/`, `components/`, `hooks/`, `helpers/`, `types/`
* [ ] API layer isolated in `api/`
* [ ] Public exports via `index.ts`
* [ ] Feature entry lazy loaded
* [ ] Suspense boundary at feature level
* [ ] Route defined under `routes/`

---

## 4. Import Aliases (Required)

| Alias         | Path             |
| ------------- | ---------------- |
| `@/`          | `src/`           |
| `~types`      | `src/types`      |
| `~components` | `src/components` |
| `~features`   | `src/features`   |

Aliases must be used consistently. Relative imports beyond one level are discouraged.

---

## 5. Component Standards

### Required Structure Order

1. Types / Props
2. Hooks
3. Derived values (`useMemo`)
4. Handlers (`useCallback`)
5. Render
6. Default export

### Lazy Loading Pattern

```ts
const HeavyComponent = React.lazy(() => import('./HeavyComponent'));
```

Always wrapped in `<SuspenseLoader>`.

---

## 6. Data Fetching Doctrine

### Primary Pattern

* `useSuspenseQuery`
* Cache-first
* Typed responses

### Forbidden Patterns

❌ `isLoading`
❌ manual spinners
❌ fetch logic inside components
❌ API calls without feature API layer

### API Layer Rules

* One API file per feature
* No inline axios calls
* No `/api/` prefix in routes

---

## 7. Routing Standards (TanStack Router)

* Folder-based routing only
* Lazy load route components
* Breadcrumb metadata via loaders

```ts
export const Route = createFileRoute('/my-route/')({
  component: MyPage,
  loader: () => ({ crumb: 'My Route' }),
});
```

---

## 8. Styling Standards (MUI v7)

### Inline vs Separate

* `<100 lines`: inline `sx`
* `>100 lines`: `{Component}.styles.ts`

### Grid Syntax (v7 Only)

```tsx
<Grid size={{ xs: 12, md: 6 }} /> // ✅
<Grid xs={12} md={6} />          // ❌
```

Theme access must always be type-safe.

---

## 9. Loading & Error Handling

### Absolute Rule

❌ Never return early l