Impact Score: 5/10
Bun v0.0.42
Source available — automated, not human-reviewed
Component: bun · Channel: stable. Automated analysis, not a compatibility certification. How this works.
Analysis updated: 2026-11-01.
⚡ Executive Summary (TL;DR)
Bun bun-v0.0.42. Source highlight: tab completions for bun run
Who Does This Impact? (Role-Based Analysis)
💻 Software Engineers & Devs
Check the source notes against the package and APIs you use before upgrading.
📊 Product & Engineering Leads
Use the documented changes to assess relevance to your product; release frequency alone is not a quality measure.
⚙️ DevOps & Security
Verify the target version, runtime requirements and rollback procedure in the official documentation.
🔧 Bug Fixes & Patches (4)
- Fixed an edgecase with the CommonJS transform that affected `export default` (thank you @evanwashere for flagging)
- Several more encoding issues specific to the JavaScriptCore integration were found & fixed, though there are a couple more I still need to fix.
- Fixed a regression with `\0` (and added an integration test)
- Fixed spacing with the CLI help menu (thanks @KishanBagaria for flagging)
📄 View Raw Release Notes (Original Developer Log)
To upgrade:
```bash
bun upgrade
```
## tab completions for bun run
`bun run` now has tab completions for zsh and fish that show `scripts` from package.json and bins from `node_modules/.bin`.
Install:
```bash
bun upgrade
bun completions
```
<img src="https://user-images.githubusercontent.com/709451/139670634-1197777a-d1da-44ab-9cc5-37723beb75e7.gif" height=400 />
Going forward, `bun upgrade` also updates completions, so you shouldn't have to do that again.
### Bun.js
Bun now has a builtin `"supports-color"` polyfill, the package used by `chalk` to detect ANSI color support.
The TypeScript in this screenshot runs 2x faster in Bun.js than in Node.js:
Other stuff:
- `node-fetch` & `isomorphic-fetch` polyfills work now. When an npm package imports `node-fetch`, Bun.js will automatically replace it with Bun's native implementation.
- `Bun.sleep(ms)` lets you synchronously sleep. No promises
- Fixed an edgecase with the CommonJS transform that affected `export default` (thank you @evanwashere for flagging)
- Several more encoding issues specific to the JavaScriptCore integration were found & fixed, though there are a couple more I still need to fix.
### JavaScript Lexer
- Fixed a regression with `\0` (and added an integration test)
### Misc
- `--version` now prints a newline at the end
- `-v` is now shorthand for `--version`
- Fixed spacing with the CLI help menu (thanks @KishanBagaria for flagging)
- `-u` is now shorthand for `--origin`. Might rename that to `--url` in a future release.