Bolt vs Fusion | agentconfig.ing

Bolt vs FusionComparisonUpdated 2026-03-16

SUMMARY

Bolt (Platform) uses text configuration while Fusion (IDE) uses mdc. They differ on 3 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.

FEATURE COMPARISON

Feature	Bolt	Fusion	Notes
Config format	text	mdc
Hierarchy support	✗	✗	Whether config files can be placed at multiple directory levels
Global config	✗	✗	User-wide configuration outside any project
Project config	✓	✓
Subdirectory scoping	✗	✗	Config files in subdirectories that apply only to that subtree
File inclusion / imports	✗	✗	Ability to include or reference other files from config
Ignore file	✗	✗
IDE integration	Platform	✓
Schema / structure	Free-form (Markdown)	Hybrid (MDC frontmatter + Markdown)	Whether config uses structured schema or free-form content
Git committed	✓	✓	Whether primary config files are intended to be version-controlled
Encoding	UTF-8	UTF-8

FILE MAPPING

Purpose	Bolt	Fusion
Project instructions	.bolt/prompt	AGENTS.md

SIDE-BY-SIDE CODE SAMPLES

Bolt

.bolt/prompt

text

You are building a SaaS dashboard application.

Stack: Remix with TypeScript, Prisma ORM, PostgreSQL, TailwindCSS.

Key rules:
- Use server loaders for data fetching, not client-side fetch
- All forms use Remix Form with progressive enhancement
- Use Prisma for all database operations
- Style with TailwindCSS utility classes, no custom CSS
- Components go in app/components/, routes in app/routes/
- Use zod for form validation on both client and server

Fusion

.builder/rules/*.mdc

mdc

---
description: React component conventions
globs: src/components/**/*.tsx
alwaysApply: false
---

# React Component Rules

## Structure
- Use functional components with TypeScript
- Define props interface above the component
- Export components as named exports

## Styling
- Use the project design system tokens for spacing and colors
- Prefer utility classes over custom CSS
- Keep component-specific styles colocated

## Patterns
- Wrap async data in Suspense boundaries
- Use forwardRef for reusable interactive components
- Keep components under 150 lines; extract hooks for logic

## Accessibility
- All interactive elements need aria-labels
- Use semantic HTML elements (nav, main, section)
- Ensure keyboard navigation works for custom widgets

KEY DIFFERENCES

1. Config format

Bolt: text. Fusion: mdc.

2. IDE integration

Bolt: Platform. Fusion: Supported.

3. Schema / structure

Bolt: Free-form (Markdown). Fusion: Hybrid (MDC frontmatter + Markdown).

WHICH SHOULD I USE?

Recommendation

Choose based on your IDE/CLI preference. If you use Bolt, configure .bolt/prompt. If you use Fusion, configure .builder/rules/*.mdc. Many projects include config files for multiple tools so each team member can use their preferred editor.

PORTABILITY TIP

sync-instructions.sh

bash

# Maintain a single source of truth:
cp AI-INSTRUCTIONS.md CLAUDE.md
cp AI-INSTRUCTIONS.md .cursorrules
cp AI-INSTRUCTIONS.md AGENTS.md