Bun Package Manager

Bun's package manager is a dramatically faster replacement for npm, yarn, and pnpm. Up to 25x faster than npm install.

Quick Start

# Install all dependencies
bun install

# Add packages
bun add react react-dom
bun add -D typescript @types/react

# Remove packages
bun remove lodash

# Update packages
bun update

# Run package binaries
bunx create-next-app

Core Commands

| Command | Description | |---------|-------------| | bun install | Install all dependencies | | bun add <pkg> | Add dependency | | bun add -D <pkg> | Add dev dependency | | bun add -O <pkg> | Add optional dependency | | bun add --peer <pkg> | Add peer dependency | | bun remove <pkg> | Remove dependency | | bun update [pkg] | Update dependencies | | bunx <pkg> | Run package binary | | bun pm cache rm | Clear cache |

Installation Flags

# Production mode (no devDependencies)
bun install --production

# Frozen lockfile (CI/CD)
bun install --frozen-lockfile
bun ci  # shorthand

# Dry run
bun install --dry-run

# Verbose/Silent
bun install --verbose
bun install --silent

# Force reinstall
bun install --force

# Global packages
bun install -g cowsay

Lockfile

Bun uses bun.lock (text-based since v1.2):

# Generate text lockfile
bun install --save-text-lockfile

# Upgrade from binary bun.lockb
bun install --save-text-lockfile --frozen-lockfile --lockfile-only
rm bun.lockb

Workspaces (Monorepos)

{
  "name": "my-monorepo",
  "workspaces": ["packages/*", "apps/*"]
}

Run commands across workspaces:

# Run in matching packages
bun run --filter 'pkg-*' build

# Run in all workspaces
bun run --filter '*' test

# Install for specific packages
bun install --filter 'pkg-a'

Lifecycle Scripts

Bun does not run lifecycle scripts from dependencies by default (security). Whitelist trusted packages:

{
  "trustedDependencies": ["my-trusted-package"]
}

# Skip all lifecycle scripts
bun install --ignore-scripts

# Concurrent scripts
bun install --concurrent-scripts 5

Overrides & Resolutions

Force specific versions for nested dependencies:

{
  "overrides": {
    "lodash": "4.17.21"
  }
}

Yarn-style resolutions also supported:

{
  "resolutions": {
    "lodash": "4.17.21"
  }
}

Non-npm Dependencies

{
  "dependencies": {
    "dayjs": "git+https://github.com/iamkun/dayjs.git",
    "lodash": "git+ssh://github.com/lodash/lodash.git#4.17.21",
    "zod": "github:colinhacks/zod",
    "react": "https://registry.npmjs.org/react/-/react-18.2.0.tgz",
    "bun-types": "npm:@types/bun"
  }
}

Installation Strategies

Bun 1.3+ default flip: Starting in Bun 1.3, isolated is the default for workspaces (packages can no longer reach undeclared deps through the hoisted root node_modules). hoisted is now the legacy opt-out — only use it when a workspace package depends on a transitive dep that it doesn't declare.

Hoisted (legacy opt-out; still the default for single non-workspace packages)

Traditional flat node_modules:

bun install --linker hoisted

Isolated (default for workspaces in Bun 1.3+)

pnpm-like strict isolation:

bun install --linker isolated

Isolated prevents "phantom dependencies" - packages can only access declared dependencies. To make this explicit or restore it after an opt-out, set it in bunfig.toml:

[install]
linker = "isolated"   # default for workspaces in Bun 1.3+
# linker = "hoisted"  # legacy opt-out

CI/CD

# GitHub Actions
- uses: oven-sh/setup-bun@v2
- run: bun ci  # frozen lockfile

Platform-Specific

# Install for different platform
bun install --cpu=x64 --os=linux

Secure Installation

When installing packages, follow supply chain security best practices:

• Block post-install scripts — Bun disables them by default; allow specific packages via trustedDependencies in package.json
• Cooldown period — Configure minimumReleaseAge in bunfig.toml to wait 7 days for new versions
• Audit before installing — Run socket package score npm <pkg> or use socket npm install <pkg> to check packages before they reach your project

Load the dependency-upgrade skill for full security configuration including Socket CLI integration, cooldown setup, lockfile validation, and CI enforcement.

Common Errors

| Error | Cause | Fix | |-------|-------|-----| | Cannot find module | Missing dependency | Run bun install | | Lockfile mismatch | package.json changed | Run bun install | | Peer dependency | Missing peer | bun add the peer | | Lifecycle script failed | Untrusted package | Add to trustedDependencies |

Migration from Other Package Managers

From pnpm

Bun automatically migrates pnpm-lock.yaml:

bun install  # Auto-converts to bun.lock

Workspace config moves to package.json:

{
  "workspaces": {
    "packages": ["apps/*", "packages/*"],
    "catalog": {
      "react": "^18.0.0"
    }
  }
}

From npm/Yarn

Simply run bun install - Bun reads package-lock.json and yarn.lock.

When to Load References

Load references/cli-commands.md when:

• Need complete CLI flag reference
• Working with advanced options

Load references/workspaces.md when:

• Setting up monorepos
• Configuring workspace filters

Load references/migration.md when:

• Migrating from npm/yarn/pnpm
• Converting lockfiles