bun
Use when using bun.lockb, bunfig.toml, bun install, Bun workspaces, Bun test, Bun runtime APIs, JS or TS scripts run with Bun, bundling, or Node compatibility checks for Bun.
Best use case
bun is best used when you need a repeatable AI agent workflow instead of a one-off prompt.
Use when using bun.lockb, bunfig.toml, bun install, Bun workspaces, Bun test, Bun runtime APIs, JS or TS scripts run with Bun, bundling, or Node compatibility checks for Bun.
Teams using bun should expect a more consistent output, faster repeated execution, less prompt rewriting.
When to use this skill
- You want a reusable workflow that can be run more than once with consistent structure.
When not to use this skill
- You only need a quick one-off answer and do not need a reusable workflow.
- You cannot install or maintain the underlying files, dependencies, or repository context.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/bun/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How bun Compares
| Feature / Agent | bun | Standard Approach |
|---|---|---|
| Platform Support | Not specified | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | Unknown | N/A |
Frequently Asked Questions
What does this skill do?
Use when using bun.lockb, bunfig.toml, bun install, Bun workspaces, Bun test, Bun runtime APIs, JS or TS scripts run with Bun, bundling, or Node compatibility checks for Bun.
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
SKILL.md Source
# Bun Skill
<workflow>
## Core Capabilities
### 1. Runtime
Bun is a drop-in replacement for Node.js, focused on speed.
- **HTTP Server**: `Bun.serve()` is faster than Node's `http` module.
- **File I/O**: `Bun.file()` and `Bun.write()` are optimized.
- **TypeScript**: Native support (no transpilation step needed for dev).
### 2. Task & Test Runner
- **Run Scripts**: `bun run script.ts` replaces `ts-node`.
- **Test**: `bun test` is a Jest-compatible, ultra-fast test runner.
<example>
```bash
bun test --watch
```
</example>
- **Package Manager**: `bun install` is significantly faster than npm/yarn.
## High Performance & Integration Patterns (Vertebra)
This section details how to integrate Bun into high-performance, polyglot systems.
### 1. Inter-Process Communication (IPC)
When integrating with Rust/Python backends:
- **Shared Memory (ShmRing)**: For latency < 10us, avoid piping JSON over stdout/stdin. Use shared memory ring buffers.
- *Pattern*: Pointers/offsets only passed over socket; data stays in shared memory.
- **Unix Domain Sockets (UDS)**: Use `Bun.connect()` and `Bun.listen()` with abstract namespaces (Linux) or file paths (macOS) if Shm not available.
- **Serialization**:
- Avoid `JSON.stringify` on hot paths.
- Use **Msgspec** (via bindings) or **Apache Arrow** (via `apache-arrow` js package) for zero-copy structure sharing.
### 2. Native Bindings (FFI vs N-API)
- **N-API (`napi-rs`)**: Preferred for stability and complex logic. It maps Rust Structs to JS Classes easily.
- **Bun FFI (`bun:ffi`)**: faster for simple C function calls but harder to maintain for complex objects.
- *Recommendation*: Use `napi-rs` for business logic, `bun:ffi` only for ultra-thin C wrappers.
### 3. Performance Gotchas
- **Buffer Copying**: Be careful with `Buffer` vs `Uint8Array`. Node compatibility layers might copy. Use `Uint8Array` natively where possible.
- **Streams**: `Bun.serve()` relies on `ReadableStream`. Buffering the entire request body (`await req.text()`) defeats the purpose of streaming; process chunks if possible.
- **Garbage Collection**: In tight loops, avoid allocating objects. Re-use objects or use typed arrays to keep pressure off the GC.
## Best Practices
- **Linting**: Use **Biome** (`bunx @biomejs/biome`) for instant linting/formatting.
- **Globals**: Use `Bun.env`, `Bun.sleep`, but generally avoid Node.js globals unless necessary for library compatibility.
- **Lockfile**: Commit `bun.lockb` for deterministic builds.
</workflow>
## Official References
- <https://bun.sh/docs>
- <https://bun.sh/docs/test>
- <https://bun.sh/docs/install/lockfile>
- <https://bun.sh/docs/runtime/ffi>
- <https://bun.sh/docs/runtime/node-api>
- <https://github.com/oven-sh/bun/releases>
## Shared Styleguide Baseline
- Use shared styleguides for generic language/framework rules to reduce duplication in this skill.
- [General Principles](https://github.com/cofin/flow/blob/main/templates/styleguides/general.md)
- [TypeScript](https://github.com/cofin/flow/blob/main/templates/styleguides/languages/typescript.md)
- Keep this skill focused on tool-specific workflows, edge cases, and integration details.
<guardrails>
## Guardrails
Add guardrails instructions here.
</guardrails>
<validation>
## Validation
Add validation instructions here.
</validation>Related Skills
flow-memory-keeper
Use at task, phase, flow, sync, archive, finish, revise, or failure checkpoints to keep Flow specs clean, capture learnings and failures, elevate durable patterns, and refine this skill with project-specific nuances
vue
Use when editing Vue projects, .vue files, vue.config.js, Vue 3 components, Composition API, <script setup>, SFC state, deployment workflows, or Vue CI configuration.
vite
Use when editing Vite projects, vite.config.ts, vite.config.js, Vite plugins, HMR, asset bundling, frontend build settings, deployment config, or Litestar/Vite integration.
uvicorn
Use when deploying ASGI apps with uvicorn, editing uvicorn CLI commands, Config or Server usage, workers, reload, event loop selection, SSL, lifespan, logging, or development server behavior.
tracer
Use when tracing execution paths, mapping dependencies, understanding unfamiliar code, following data flow, investigating end-to-end behavior, debugging call chains, or deciding which files to read next.
testing
Use when writing or refactoring tests, editing test_*.py, *.test.ts, *.spec.ts, conftest.py, vitest.config.ts, pytest fixtures, mocks, coverage, async tests, anyio, or test failure debugging.
terraform
Use when creating, adopting, refactoring, or operating Terraform, *.tf files, .terraform.lock.hcl, terragrunt.hcl, root modules, backends, state, workspaces, imports, CI plan/apply, tests, or policy checks.
tanstack
Use when editing TanStack code, @tanstack imports, useQuery, createRouter, React Query, TanStack Router, Table, Form, Store, file-based routing, data fetching, or SPA state management.
tailwind
Use when styling with Tailwind CSS, editing tailwind.config.ts, tailwind.config.js, @tailwind directives, utility classes, responsive layouts, @apply, cn(), @theme config, dark mode, or forms.
svelte
Use when editing Svelte components, .svelte files, svelte.config.js, Svelte 5 runes, $state, $derived, SvelteKit, component state, or migrating away from Svelte 4 patterns.
sqlserver
Use when writing T-SQL, editing SQL Server .sql files, using sqlcmd, SQL Server connection strings, stored procedures, execution plans, indexes, Always On, JSON, security, or connector code.
sqlalchemy
Use when editing SQLAlchemy code, sqlalchemy imports, mapped_column, DeclarativeBase, ORM models, relationships, select() queries, async sessions, engines, events, or migrations.