use-bun

A guide for using Bun, a toolkit that combines a JavaScript and TypeScript runtime, package manager, test runner, and build tool. It helps answer Bun-specific questions and write code with Bun APIs.

In plain words
What is it for?
Use it to check a project's Bun version, work with Bun's server, files, processes, database clients, shell commands, tests, and build tools, and write Bun-based JavaScript or TypeScript.
Why use it?
It reduces guesswork when Bun's version or built-in tools differ between projects. It also helps use Bun features correctly instead of treating Bun like another JavaScript runtime.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/pleaseai/claude-code-plugins/use-bun
Any agent
npx skills add pleaseai/claude-code-plugins --skill use-bun
Clone the repo
git clone --depth 1 https://github.com/pleaseai/claude-code-plugins

Made for: Claude Code, Codex.

Per session 241 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,903 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 3 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00241 $0.02903
Opus 5 $0.00120 $0.01452
Sonnet 5 $0.00048 $0.00581
Haiku 4.5 $0.00024 $0.00290

Measured 2d ago against content hash 622f4ad24e32, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

use-bun scanned grade C with 3 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/resolve-bun-version.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

curl -fsSL https://bun.sh/install | bash

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -fsSL https://bun.sh/install | bash

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

- **Spawning processes**: prefer `Bun.spawn()` / `Bun.$` over `node:child_process` — better defaults, streaming stdio, async iterators.
plugins/bun/skills/use-bun/SKILL.md · 133 lines

How it starts

The opening of the file, as written. The whole thing — 133 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Prerequisites

Verify the ask CLI is available (which ask). It is the primary tool for reading the exact Bun version installed in the project — it fetches the version-tagged source from GitHub once and caches it at ~/.ask/. If ask is not installed, fall back to the local bun binary's built-in help and the official docs at https://bun.com/docs (which always tracks the latest release).

Before writing Bun-specific code, detect the project's Bun version. The skill bundles a helper that resolves it in the correct priority order (.bun-versionpackage.json.packageManagerengines.bun → global bun):

# Resolve project pin; GitHub release tags use the `bun-vX.Y.Z` form
BUN_REF="bun-v$(${CLAUDE_SKILL_DIR}/scripts/resolve-bun-version.sh)" || exit 1
echo "$BUN_REF"   # e.g. bun-v1.3.14

# Lockfile format — Bun migrated from binary bun.lockb to text bun.lock at 1.2.0
ls bun.lock bun.lockb 2>/dev/null

See references/versions.md for the resolution rules and the underlying script (scripts/resolve-bun-version.sh).

If Bun is not installed, install it once:

# Recommended — official installer
curl -fsSL https://bun.sh/install | bash

# Or via npm / brew / proto / asdf — see https://bun.com/docs/installation

Critical: Do Not Trust Internal Knowledge

Bun ships fast — APIs land, change shape, or move modules between minor releases. Common pitfalls from outdated training data:

  • Bun.serve routes (routes: { "/users/:id": handler }) — requires Bun 1.2.3+. Before that you wrote fetch(req) with manual URL parsing. Do not suggest routes on older versions.
  • bun.lock (text JSONC) vs bun.lockb (binary) — Bun 1.2.0+ writes bun.lock by default (the text format was introduced as opt-in earlier and became the default at 1.2). Existing bun.lockb files migrate via bun install --save-text-lockfile --frozen-lockfile --lockfile-only. If you see both, the text one wins.
  • Catalogs (catalog: / catalogs: in package.json / bunfig.toml) — added in Bun 1.2+. Not available earlier.
  • Isolated installs (linker = "isolated") — added in Bun 1.2.x. Earlier versions only support hoisted.
  • bun:sql / Bun.SQL — Postgres client landed in Bun 1.2+; native MySQL/SQLite are different surfaces (bun:sqlite has always existed).
  • Bun.RedisClient / Bun.redis — Valkey/Redis client is recent (Bun 1.2.x). Older code uses third-party libs.
  • bun build --compile — single-file executables stabilised in 1.1+; flags like --bytecode, --target=bun-linux-x64-baseline, and Windows cross-compile are newer.
  • mock.module() — module mocking in bun:test. Stable across all current Bun releases; very old (early 1.0.x) versions only had mock() for function-level mocks. If you need to support a specific pre-1.1 version, verify the API against that release's docs.
  • Bun.$ (shell) — promoted from experimental in Bun 1.0.24+. API stabilised since.
  • trustedDependencies in package.json — Bun does not run installed dependencies' lifecycle scripts by default for security; you must allowlist via this field. Different default than npm/yarn.

Read the full file on GitHub · 133 lines

Files

What ships with it

7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 133 lines · 241 tokens per session scan C 622f4ad24e32

Subscribe to this mod's changes

use-bun is a skill published in the GitHub repository pleaseai/claude-code-plugins (13 stars, last pushed 7d ago), licensed MIT. It adds 241 tokens to every session and 2,903 once invoked, about $0.0012 per session on Opus 5. A static security scan graded it C with 3 findings (downloads and executes remote code, makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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