SUMMARY
JetBrains AI / Junie (IDE) uses markdown configuration while OpenCode (CLI) uses markdown. They differ on 5 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.
FEATURE COMPARISON
| Feature | JetBrains AI / Junie | OpenCode |
|---|---|---|
| Config format | markdown | markdown |
| Hierarchy support | ✗ | ✓ |
| Global config | ✗ | ✓ |
| Project config | ✓ | ✓ |
| Subdirectory scoping | ✗ | ✓ |
| File inclusion / imports | ✗ | ✗ |
| Ignore file | .aiignore | ✗ |
| IDE integration | ✓ | CLI |
| Schema / structure | Free-form (Markdown) | Free-form (Markdown) |
| Git committed | ✓ | ✓ |
| Encoding | UTF-8 | UTF-8 |
FILE MAPPING
| Purpose | JetBrains AI / Junie | OpenCode |
|---|---|---|
| Settings / configuration | .noai | opencode.json |
SIDE-BY-SIDE CODE SAMPLES
# Kotlin Conventions
## Language Features
- Use Kotlin 2.x with coroutines for async work
- Prefer data classes for DTOs and value objects
- Use sealed classes/interfaces for domain errors
- Extension functions over utility classes
## Spring Boot
- Constructor injection (no field injection)
- Use @ConfigurationProperties over @Value
- Prefer WebFlux for reactive endpoints
- Use Spring Security with method-level security
## Testing
- JUnit 5 with Kotest assertions
- MockK for mocking (not Mockito)
- Testcontainers for integration tests
- Use @Nested for test organization
# Project Instructions
## Overview
This is a TypeScript monorepo using pnpm workspaces.
## Code Style
- Use strict TypeScript with no implicit any
- Prefer functional components with hooks
- All exports should be named (no default exports)
## Architecture
- /packages/core — shared business logic
- /packages/ui — React component library
- /apps/web — Next.js frontend
## Build & Test
Run tests with: pnpm test
Build all packages: pnpm build
All PRs must have >80% coverage on changed files.
## Conventions
- Use conventional commits (feat:, fix:, chore:)
- Prefer composition over inheritance
- See @docs/api-guidelines.md for API design patterns
KEY DIFFERENCES
JetBrains AI / Junie: Not supported. OpenCode: Supported.
JetBrains AI / Junie: Not supported. OpenCode: Supported.
JetBrains AI / Junie: Not supported. OpenCode: Supported.
JetBrains AI / Junie: .aiignore. OpenCode: Not supported.
JetBrains AI / Junie: Supported. OpenCode: CLI.
WHICH SHOULD I USE?
Choose based on your IDE/CLI preference. If you use JetBrains AI / Junie, configure .aiassistant/rules/*.md. If you use OpenCode, configure AGENTS.md. Many projects include config files for multiple tools so each team member can use their preferred editor.
PORTABILITY TIP
# Maintain a single source of truth:
cp AI-INSTRUCTIONS.md CLAUDE.md
cp AI-INSTRUCTIONS.md .cursorrules
cp AI-INSTRUCTIONS.md AGENTS.md