secondsky/claude-skills/bun-runtime

Name: bun-runtime
Author: secondsky

Trust tier 3

community
ext:[{"type":"hook","description":"Pre/post lifecycle hooks"}]

Source check pending

Checking that the SKILL.md file is still in the repository.

Use for Bun runtime, bunfig.toml, watch/hot modes, env vars, CLI flags, and module resolution.

Install

npx vskill@latest install secondsky/claude-skills/bun-runtime

Semi-extensibleMentions customization, but needs skill-specific knowledge. Read the extensible skills standard

SKILL.md

Bun Runtime

Bun is a fast all-in-one JavaScript runtime built on JavaScriptCore (Safari's engine). It provides 4x faster startup than Node.js on Linux.

Quick Start

bash

# Run a file
bun run index.ts
bun index.ts  # shorthand
 
# Run with watch mode
bun --watch run index.ts
 
# Run package.json script
bun run dev
 
# Run with hot reloading
bun --hot run server.ts

Core CLI Flags

Flag	Purpose
`--watch`	Restart on file changes
`--hot`	Hot module replacement (preserves state)
`--smol`	Reduce memory usage (slower GC)
`--inspect`	Enable debugger
`--preload`	Load modules before execution
`--env-file`	Load specific .env file
`-e, --eval`	Evaluate code string

Running Files

Bun transpiles TypeScript and JSX on-the-fly:

bash

bun run index.js
bun run index.ts
bun run index.jsx
bun run index.tsx

Important: Put Bun flags immediately after bun:

bash

bun --watch run dev    # Correct
bun run dev --watch    # Wrong - flag passed to script

Package.json Scripts

bash

# Run script
bun run dev
bun dev  # shorthand (if no Bun command conflicts)
 
# List available scripts
bun run
 
# Run with Bun instead of Node
bun run --bun vite

Bun respects lifecycle hooks (preclean, postclean, etc.).

Watch Mode vs Hot Reloading

Mode	Flag	Behavior
Watch	`--watch`	Full process restart on changes
Hot	`--hot`	Replace modules, preserve state

bash

# Watch mode - full restart
bun --watch run server.ts
 
# Hot reloading - preserves connections/state
bun --hot run server.ts

Environment Variables

Bun automatically loads .env files:

bash

# Loads automatically: .env, .env.local, .env.development
bun run index.ts
 
# Specify env file
bun --env-file .env.production run index.ts
 
# Disable auto-loading
# In bunfig.toml: env = false

Access in code:

typescript

const apiKey = process.env.API_KEY;
const bunEnv = Bun.env.NODE_ENV;

Globals Available

Global	Source	Notes
`Bun`	Bun	Main API object
`Buffer`	Node.js	Binary data
`process`	Node.js	Process info
`fetch`	Web	HTTP requests
`Request/Response`	Web	HTTP types
`WebSocket`	Web	WebSocket client
`crypto`	Web	Cryptography
`console`	Web	Logging
`__dirname`	Node.js	Current directory
`__filename`	Node.js	Current file

Preload Scripts

Load modules before your main script:

bash

bun --preload ./setup.ts run index.ts

Or in bunfig.toml:

toml

preload = ["./setup.ts"]

Use cases: polyfills, global setup, instrumentation.

Stdin Execution

bash

# Pipe code to Bun
echo "console.log('Hello')" | bun run -
 
# Redirect file
bun run - < script.js

Workspaces & Monorepos

bash

# Run script in specific packages
bun run --filter 'pkg-*' build
 
# Run in all workspaces
bun run --filter '*' test

Debugging

bash

# Start debugger
bun --inspect run index.ts
 
# Wait for debugger connection
bun --inspect-wait run index.ts
 
# Break on first line
bun --inspect-brk run index.ts

Connect via Chrome DevTools or VS Code.

Common Errors

Error	Cause	Fix
`Cannot find module`	Missing dependency	Run `bun install`
`Top-level await`	Using await outside async	Wrap in async function or use `.mts`
`--watch not working`	Flag in wrong position	Put flag before `run`

When to Load References

Load references/bunfig.md when:

Configuring bunfig.toml
Setting up test configuration
Configuring package manager behavior
Setting JSX options

Load references/cli-flags.md when:

Need complete CLI flag reference
Configuring advanced runtime options
Setting up debugging

Load references/module-resolution.md when:

Troubleshooting import errors
Configuring path aliases
Understanding Bun's resolution algorithm

Security

Security scanPassed, 90 of 100Pattern checks on the skill's files.
Model reviewPassed

See the full security report

Quality evaluation

Task evaluationNot runNo evaluation yet. Run one in Skill Studio.

See evaluation results

Source

SKILL.md in the repositoryCheckingplugins/bun/skills/bun-runtime/SKILL.md

Popularity

Repository stars: 216
Repository forks: 31
7-day trend score: 27

Stars and forks are for the whole GitHub repository, not this skill alone. Not refreshed yet.

Extension points

hookPre/post lifecycle hooks

Learn the extensible skills standard

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