Bun v1.2.12

This release includes a new --console flag for bun ./index.html to stream browser console logs to the terminal. Bun's frontend dev server now uses less memory, and Node.js compatibility improvements for timers, vm, net, http, and bugfixes for TextDecoder, hot reloading reliability bugfixes.

To install Bun

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

npm install -g bun

powershell -c "irm bun.sh/install.ps1|iex"

scoop install bun

brew tap oven-sh/bun

brew install bun

docker pull oven/bun

docker run --rm --init --ulimit memlock=-1:-1 oven/bun

To upgrade Bun

bun upgrade

Stream browser console logs to your terminal

The --console flag for bun ./index.html streams console logs from the browser to the terminal.

This lets AI tools see console logs & errors from browsers without worrying about MCP or browser extensions.

Here are two ways to enable console log streaming:

For full-stack development, use the console: true option in Bun.serve()

import homepage from "./index.html";
import { serve } from "bun";

serve({
  development: {
    // New: enable console log streaming
    console: true,

    // Enable hot module reloading
    hmr: true,
  },
  routes: {
    "/": homepage,
  },
});

For frontend development, use the --console flag

When enabled, all browser console.log and console.error calls will be broadcast to the terminal that started the server, reusing the existing WebSocket connection from hot module reloading. This is useful for debugging frontend code by seeing the browser console output in the same place you run your server.

console logs from the browser are prefixed with [browser] to make them easy to spot. In future versions of Bun, we might enable this by default.

Thanks to @zackradisic for the contribution!

Dev Server uses less memory

Bun's full-stack & frontend dev servers now use significantly less memory.

The below screenshot comparison is a simple React app that imports the entire lucide-react library and hot reloads 307 times.

This involved several optimizations & architecture changes related to sourcemaps.

Fixed: Global package postinstall scripts

Bun previously blocked global postinstall scripts from running, even when those explicitly opted into running with trusted dependencies. This was vestigal behavior from before Bun supported trustedDependencies to control which packages are allowed to run postinstall scripts.

This impacted popular packages like Claude Code where it could cause an error with better-sqlite3 to appear.

Thanks to @dylan-conway for the contribution!

Micro-optimization: 30μs faster startup

Bun now starts 30μs faster.

❯ poop "bun-1.2.11 --version" "bun --version"

Benchmark 1 (7065 runs): bun-1.2.11 --version
  measurement          mean ± σ            min … max
  wall_time           697us ± 43.8us     546us … 1.14ms

Benchmark 2 (7898 runs): bun --version
  measurement          mean ± σ            min … max
  wall_time           626us ± 35.9us     494us …  914us

Node.js compatibility improvements

98.4% of Node's timers tests pass in Bun

node:vm cachedData Support

Bun now supports the cachedData and produceCachedData options in the Node.js vm.Script API, along with the createCachedData method. This allows for improved performance by caching and reusing compiled JavaScript code.

// Create a script with cached bytecode
const script = new vm.Script('console.log("Hello world!")', {
  produceCachedData: true,
});

// Later use the cached data
const cachedData = script.createCachedData();

// Create a new script with the cached bytecode
const newScript = new vm.Script('console.log("Hello world!")', {
  cachedData: cachedData,
});

Thanks to @heimskr for the contribution!

node:net BlockList support

Bun now implements the BlockList class from the Node.js net module, allowing you to create rules to block specific IP addresses, ranges, or subnets.

// Create a new BlockList
const blockList = new net.BlockList();

// Add rules
blockList.addAddress("123.123.123.123");
blockList.addRange("10.0.0.1", "10.0.0.10");
blockList.addSubnet("8.8.8.8", 24);

// Check if an address is blocked
blockList.check("123.123.123.123"); // true
blockList.check("8.8.8.9"); // true
blockList.check("192.168.1.1"); // false

Thanks to @nektro for the contribution!

node:http compatibility improvements

This release fixes several edge cases in the node:http module, including:

• Agent abort handling
• Extra arguments passed to urls in http.request

More bugfixes

Fixed: rare crash when importing invalid file URLs

Fixed an issue where importing invalid file URLs could sometimes cause Bun to crash.

Fixed: Erroring in TextDecoder encoding label handling

Fixed issues with TextDecoder encoding label handling, bringing implementation in line with the WHATWG spec. Invalid labels containing null bytes now properly throw errors, and TextDecoder.encoding correctly returns the normalized encoding name for all supported encodings.

// Previously allowed, now correctly throws:
try {
  new TextDecoder("utf-8\0");
} catch (e) {
  console.error("Error:", e); // RangeError: ERR_ENCODING_NOT_SUPPORTED
}

// Now correctly returns the normalized encoding name
const decoder = new TextDecoder("utf-16be");
console.log(decoder.encoding); // "utf-16be" (previously returned empty string)

Thanks to @pfgithub for the contribution!

Fixed: TextDecoder 'fatal' option coercion

The TextDecoder's fatal option now properly coerces values to boolean instead of requiring strict boolean types. This matches browser behavior where values like 0, 1, null, or strings are automatically converted to appropriate boolean values.

// Now works without errors
const decoder1 = new TextDecoder("utf-8", { fatal: 1 });
console.log(decoder1.fatal); // true

const decoder2 = new TextDecoder("utf-8", { fatal: 0 });
console.log(decoder2.fatal); // false

const decoder3 = new TextDecoder("utf-8", { fatal: "any string" });
console.log(decoder3.fatal); // true

const decoder4 = new TextDecoder("utf-8", { fatal: null });
console.log(decoder4.fatal); // false

Thanks to @albus-droid for the contribution!

Hot reloading reliability bugfixes

A couple bugs have been fixed that could cause bun --hot to spuriously crash after a long time.

Thanks to 10 contributors!

• @190n
• @albus-droid
• @alii
• @dylan-conway
• @electroid
• @heimskr
• @jarred-sumner
• @nektro
• @paperclover
• @pfgithub