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)

Score Formula

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

Range: -5 → +15

Interpretation

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)

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

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

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)

<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

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

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.