Dealing with Monorepo's Hell with Bun

So you’re rocking a monorepo with Turborepo and Bun 🫂.

If you’ve tried installing dependencies in a specific workspace and ended in your root package.json, you’re not alone my friend. Bun’s workspace handling is a bit… different HELL. Here’s how to make it behave.

The Gotcha

You might think you can do something like:

bun add express --filter server

But surprise! That lands express in the root package.json, not in apps/server like you wanted. Bun doesn’t play the same way as other package managers when it comes to workspace filters.

The Fix

Use the --cwd flag to tell Bun exactly where to drop the goods:

bun add <package-name> --cwd <workspace-path>

🗣️ BECAUSE THE SUPPORT IS IN BETAAAAAA!!!!

At the moment 2025 august, maybe tomorrow works 🙂

Sample Monorepo Layout

Just to set the scene:

my-monorepo/
├── apps/
│   ├── native/          # React Native app
│   └── server/          # Node.js server
├── packages/
│   └── shared/          # Shared utilities
├── package.json         # Root config
├── turbo.json
└── bun.lockb

Real-World Installs

Server Workspace

bun add express --cwd apps/server
bun add -d @types/node --cwd apps/server
bun add express cors helmet --cwd apps/server

Native Workspace

bun add react-native-vector-icons --cwd apps/native
bun add -d @types/react --cwd apps/native

Shared Package

bun add lodash --cwd packages/...😐 Got it dude?

Why `--cwd` Is Your Friend

It basically tells Bun: “Hey, pretend you’re inside this folder when you run the command.” That way:

Dependencies go to the right package.json
Bun respects your workspace setup
The lockfile stays clean and centralized

The Old-School Way (meh)

You could cd into the workspace and run bun add there:

cd apps/server
bun add express
cd ../..

But that creates a local node_modules folder, which kinda messes with the monorepo vibe. Using --cwd keeps things tidy and lets you stay at the root like a boss.

Turborepo Plays Nice

This method works perfectly with Turborepo’s caching and task runner:

turbo build --filter=server
turbo build

No hiccups. Just smooth builds.

Pro Tips from the Trenches

✅ Double-check your package.json—make sure the dependency landed where you wanted.

🛠️ Add some helper scripts to your root package.json:

{
  "scripts": {
    "add:server": "bun add --cwd apps/server",
    "add:native": "bun add --cwd apps/native"
  }
}

🔒 Bun updates the bun.lockb file automatically, so your lockfile stays in sync.

Wrap-Up

If you’re working with Bun in a Monorepo setup, --cwd is your golden ticket to clean, workspace-specific installs. No more rogue dependencies in the root. Just run:

bun add <package> --cwd <workspace-path>

🧘‍♂️ Don’t thanks me, give me a coffee !