Aider vs Claude CodeUpdated 2026-03-16

SUMMARY

Aider (CLI) uses markdown configuration while Claude Code (CLI) uses markdown. They differ on 3 of 11 compared features. Both tools provide AI-assisted development but take different approaches to project configuration.

FEATURE COMPARISON

FeatureAiderClaude Code
Config formatmarkdownmarkdown
Hierarchy support
Global config
Project config
Subdirectory scoping
File inclusion / imports
Ignore file.aiderignore.claudeignore
IDE integrationCLICLI
Schema / structureFree-form (Markdown)Free-form (Markdown)
Git committed
EncodingUTF-8UTF-8

FILE MAPPING

PurposeAiderClaude Code
Settings / configuration.aider.conf.yml.claude/settings.json
Settings / configuration.aider.model.settings.yml.claude/settings.local.json
Ignore patterns.aiderignore.claudeignore
Project instructionsCONVENTIONS.mdCLAUDE.md

SIDE-BY-SIDE CODE SAMPLES

Aider
CONVENTIONS.md
markdown
# Project Conventions

## Language
- TypeScript strict mode, no `any` types
- Prefer const over let, never use var
- Use template literals over string concatenation

## Architecture
- Feature-based folder structure under src/features/
- Each feature exports through an index.ts barrel file
- Shared utilities go in src/lib/

## Error Handling
- Use Result<T, E> pattern for expected failures
- Throw only for programmer errors
- Always log errors with structured context

## Testing
- Colocate tests next to source files (*.test.ts)
- Use factories for test data, not fixtures
- Integration tests in __tests__/ directories

Claude Code
CLAUDE.md
markdown
# Project Name

> TypeScript + React monorepo. Deployed on Vercel.

## Code Style

- TypeScript strict mode — no `any`, no `ts-ignore`
- Named exports only (no default exports)
- Prefer functional patterns: map/filter/reduce over for-loops
- Error handling: use Result<T, E> from `src/lib/result.ts`

## Architecture

- `src/routes/`   — Route handlers (thin layer, delegates to services)
- `src/services/`  — Business logic, one file per domain entity
- `src/db/`        — Drizzle ORM schema and query helpers
- `src/lib/`       — Shared utilities (logger, result type, validation)

## Commands

```bash
pnpm install          # Install dependencies
pnpm dev              # Start dev server (port 3000)
pnpm test             # Run Vitest suite
pnpm test:e2e         # Run Playwright tests
pnpm lint             # ESLint + Prettier check
pnpm db:migrate       # Run pending Drizzle migrations
```

## Git Conventions

- Conventional Commits: `feat:`, `fix:`, `chore:`, `docs:`
- Branch naming: `feat/short-description`, `fix/issue-number`
- Squash merge to main; delete branches after merge

## Notes

- The `src/legacy/` directory is being migrated. Do not add new code there.
- All dates are stored as UTC. Never use local time.

@docs/api-patterns.md
@docs/database-conventions.md

KEY DIFFERENCES

1. Hierarchy support

Aider: Not supported. Claude Code: Supported.

2. File inclusion / imports

Aider: Not supported. Claude Code: Supported.

3. Ignore file

Aider: .aiderignore. Claude Code: .claudeignore.

WHICH SHOULD I USE?

Recommendation

Choose based on your IDE/CLI preference. If you use Aider, configure .aider.conf.yml. If you use Claude Code, configure CLAUDE.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

SEE ALSO

agentconfig.ing2026-03-16COMPARE(1)