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: design-ui-ux
risk: unknown
source: community
date_added: "2026-02-27"
---


# 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 loaders
✅ Always rely on Suspense boundaries

### User Feedback

* `useMuiSnackbar` only
* No third-party toast libraries

---

## 10. Performance Defaults

* `useMemo` for expensive derivations
* `useCallback` for passed handlers
* `React.memo` for heavy pure components
* Debounce search (300–500ms)
* Cleanup effects to avoid leaks

Performance regressions are bugs.

---

## 11. TypeScript Standards

* Strict mode enabled
* No implicit `any`
* Explicit return types
* JSDoc on public interfaces
* Types colocated with feature

---

## 12. Canonical File Structure

```
src/
  features/
    my-feature/
      api/
      components/
      hooks/
      helpers/
      types/
      index.ts

  components/
    SuspenseLoader/
    CustomAppBar/

  routes/
    my-route/
      index.tsx
```

---

## 13. Canonical Component Template

```ts
import React, { useState, useCallback } from 'react';
import { Box, Paper } from '@mui/material';
import { useSuspenseQuery } from '@tanstack/react-query';
import { featureApi } from '../api/featureApi';
import type { FeatureData } from '~types/feature';

interface MyComponentProps {
  id: number;
  onAction?: () => void;
}

export const MyComponent: React.FC<MyComponentProps> = ({ id, onAction }) => {
  const [state, setState] = useState('');

  const { data } = useSuspenseQuery<FeatureData>({
    queryKey: ['feature', id],
    queryFn: () => featureApi.getFeature(id),
  });

  const handleAction = useCallback(() => {
    setState('updated');
    onAction?.();
  }, [onAction]);

  return (
    <Box sx={{ p: 2 }}>
      <Paper sx={{ p: 3 }}>
        {/* Content */}
      </Paper>
    </Box>
  );
};

export default MyComponent;
```

---

## 14. Anti-Patterns (Immediate Rejection)

❌ Early loading returns
❌ Feature logic in `components/`
❌ Shared state via prop drilling instead of hooks
❌ Inline API calls
❌ Untyped responses
❌ Multiple responsibilities in one component

---

## 15. Integration With Other Skills

* **godmode-ui-ux** → Visual systems & aesthetics
* **godmode-engineering** → API contract alignment

---

## 16. Operator Validation Checklist

Before finalizing code:

* [ ] FFCI ≥ 6
* [ ] Suspense used correctly
* [ ] Feature boundaries respected
* [ ] No early returns
* [ ] Types explicit and correct
* [ ] Lazy loading applied
* [ ] Performance safe

---

## 17. Skill Status

**Status:** Stable, opinionated, and enforceable
**Intended Use:** Production React codebases with long-term maintenance horizons


### When to Use
This skill is applicable to execute the workflow or actions described in the overview.

## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.


## Overview
Strict architectural and performance standards for senior frontend engineers building robust applications.

## Core Process
1. Review the data fetching strategy and ensure decoupling from presentation.
2. Implement robust error boundaries and fallback UI.
3. Validate state management against global vs local standards.
4. Run performance checks before finalizing the component.

## Common Rationalizations
| Rationalization | Reality |
|---|---|
| I can just fetch this data inside the component directly. | Data fetching should be decoupled from presentation following the established architecture. |
| I'll use a local state instead of the global store because it's quicker. | Bypassing the global store leads to state fragmentation and synchronization bugs. |
| I'm skipping the error boundary here, it won't fail. | All components must fail gracefully without crashing the entire application. |

## Red Flags
- Tightly coupled data fetching and UI components.
- Unhandled promise rejections or missing error boundaries.
- Using deprecated frontend patterns instead of the approved architecture.

## Verification
- [ ] Component separates data fetching from presentation logic.
- [ ] Error states and boundaries are implemented.
- [ ] Performance metrics (e.g. bundle size, render time) are unaffected.