Updates

Introduction

We’ve implemented a batteries included update mechanism. All you need is to bring your own static file host like AWS S3, Cloudflare R2, or GitHub Releases.

• Update API to check for, download, and update your apps.
• CLI to build your app bundle, codesign, and generate artifacts.
• A custom BSDIFF implementation in zig that takes advantage of SIMD operations for performance and lets you distribute updates as small as 14KB

Hosting on GitHub Releases

GitHub Releases is a convenient option for hosting your update artifacts, especially for open source projects. Electrobun uses a flat, prefix-based naming scheme (e.g., stable-macos-arm64-update.json) that works with hosts that don’t support folder structures.

Configuration

Set your baseUrl in electrobun.config to point to your GitHub Releases:

electrobun.config.ts

export default {
  // ...
  release: {
    baseUrl: "https://github.com/YOUR_ORG/YOUR_REPO/releases/latest/download",
  },
};

Example GitHub Action

Here’s an example workflow that builds and publishes releases when you push a tag:

name: Build and Release

on:
  push:
    tags:
      - 'v*'

jobs:
  build-macos-arm64:
    runs-on: macos-14  # Apple Silicon runner

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Setup Bun
        uses: oven-sh/setup-bun@v2
        with:
          bun-version: latest

      - name: Install dependencies
        run: bun install

      - name: Determine build environment
        id: build-env
        run: |
          if [[ "${{ github.ref_name }}" == *"-canary"* ]]; then
            echo "env=canary" >> $GITHUB_OUTPUT
          else
            echo "env=stable" >> $GITHUB_OUTPUT
          fi

      - name: Build app
        env:
          ELECTROBUN_DEVELOPER_ID: ${{ secrets.ELECTROBUN_DEVELOPER_ID }}
          APPLE_ID: ${{ secrets.APPLE_ID }}
          APPLE_APP_SPECIFIC_PASSWORD: ${{ secrets.APPLE_APP_SPECIFIC_PASSWORD }}
          APPLE_TEAM_ID: ${{ secrets.APPLE_TEAM_ID }}
        run: |
          if [ "${{ steps.build-env.outputs.env }}" = "canary" ]; then
            bun run build:canary
          else
            bun run build:stable
          fi

      - name: Create Release
        uses: softprops/action-gh-release@v1
        with:
          files: artifacts/*
          draft: false
          prerelease: ${{ steps.build-env.outputs.env == 'canary' }}
          generate_release_notes: true
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

The generate_release_notes: true option uses GitHub’s automatic release notes feature, which lists merged PRs and contributors since the last release.

Limitations

Single Patch File

Electrobun only generates a single patch file per build - from the immediately previous version to the current version. This means:

• Users updating from the previous version get a small delta patch (often just a few KB)
• Users more than one version behind will automatically fall back to downloading the full .tar.zst bundle

This is a practical tradeoff that keeps the build process simple while still providing delta updates for users who update regularly.

Canary Builds on GitHub Releases

GitHub’s /releases/latest/download URL only resolves to non-prerelease builds. This means:

• Stable builds: Auto-updates work correctly via /releases/latest/download
• Canary builds: Will not auto-update when hosted on GitHub Releases because the latest URL won’t point to prerelease versions

If you need auto-updating canary builds, consider using a static file host like Cloudflare R2 or AWS S3 where you control the URL structure directly.