Fusion vs Gemini Code Assist

Fusion vs Gemini Code AssistComparisonUpdated 2026-03-18

SUMMARY

Fusion (IDE) uses mdc configuration while Gemini Code Assist (IDE) uses markdown. They differ on 4 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.

FEATURE COMPARISON

Feature	Fusion	Gemini Code Assist	Notes
Config format	mdc	markdown
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	✓	✓
Schema / structure	Hybrid (MDC frontmatter + Markdown)	Free-form (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	Fusion	Gemini Code Assist
Project instructions	AGENTS.md	GEMINI.md

SIDE-BY-SIDE CODE SAMPLES

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

Gemini Code Assist

GEMINI.md

markdown

# Project Rules

## Overview
E-commerce platform built with Go microservices and React frontend.
All services communicate via gRPC with Protocol Buffers.

## Go Services
- Follow standard Go project layout (cmd/, internal/, pkg/)
- Use structured logging with slog (not log or fmt.Println)
- Error handling: always wrap errors with fmt.Errorf("%w", err)
- Database access through repository pattern in internal/repo/
- All public functions must have godoc comments

## API Design
- Proto files live in proto/ directory with buf for linting
- Use field masks for partial updates
- Pagination via cursor-based tokens, not offset

## Testing
- Table-driven tests for all business logic
- Use testcontainers-go for integration tests
- Minimum 80% coverage on internal/ packages
- Mock external services with gomock interfaces

## Do Not
- Use global variables or init() functions
- Import internal packages across service boundaries
- Commit generated .pb.go files (CI generates them)

KEY DIFFERENCES

1. Config format

Fusion: mdc. Gemini Code Assist: markdown.

2. Hierarchy support

Fusion: Not supported. Gemini Code Assist: Supported.

3. Subdirectory scoping

Fusion: Not supported. Gemini Code Assist: Supported.

4. Schema / structure

Fusion: Hybrid (MDC frontmatter + Markdown). Gemini Code Assist: Free-form (Markdown).

WHICH SHOULD I USE?

Recommendation

Choose based on your IDE/CLI preference. If you use Fusion, configure .builder/rules/*.mdc. If you use Gemini Code Assist, configure GEMINI.md. 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