Devin vs Fusion | agentconfig.ing

Devin vs FusionComparisonUpdated 2026-03-16

SUMMARY

Devin (Agent) uses markdown configuration while Fusion (IDE) uses mdc. They differ on 5 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.

FEATURE COMPARISON

Feature	Devin	Fusion	Notes
Config format	markdown	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	Agent	✓
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	Devin	Fusion
Project instructions	AGENTS.md	AGENTS.md

SIDE-BY-SIDE CODE SAMPLES

Devin

AGENTS.md

markdown

# Agent Instructions

## Setup
- Python 3.12 with uv package manager
- PostgreSQL 16 and Redis 7
- Run: uv sync && uv run alembic upgrade head

## Commands
- Dev server: uv run uvicorn app.main:app --reload
- Tests: uv run pytest -x --tb=short
- Lint: uv run ruff check . && uv run mypy .
- Format: uv run ruff format .

## Code Style
- FastAPI with async endpoints
- Pydantic v2 for all schemas
- SQLAlchemy 2.0 async sessions
- Repository pattern for data access

## PR Guidelines
- Keep PRs focused on a single issue
- Add tests for new functionality
- Run the full test suite before submitting

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

Devin: markdown. Fusion: mdc.

2. Hierarchy support

Devin: Supported. Fusion: Not supported.

3. Subdirectory scoping

Devin: Supported. Fusion: Not supported.

4. IDE integration

Devin: Agent. Fusion: Supported.

5. Schema / structure

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

WHICH SHOULD I USE?

Recommendation

Choose based on your IDE/CLI preference. If you use Devin, configure AGENTS.md. 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