Describe the bug

On an Alpine Linux / musl container, Copilot CLI auto-update downloaded the linux-x64 package for v1.0.60 instead of the available linuxmusl-x64 package. The next Copilot invocation then failed before ACP initialization with Native addon "runtime" not found for linuxmusl-x64.

This looks like an auto-update platform selection issue rather than a missing release artifact: the v1.0.60 release publishes copilot-linuxmusl-x64.tar.gz and github-copilot-1.0.60-linuxmusl-x64.tgz, but the updater downloaded/selected linux-x64.

Affected version

• Installed CLI: GitHub Copilot CLI 1.0.59
• Auto-updated/downloaded package: 1.0.60
• Runtime mode: copilot --acp

Environment

OS: Alpine Linux v3.23
process.platform: linux
process.arch: x64
Node.js: v20.20.2
detect-libc family: musl
detect-libc isNonGlibcLinuxSync(): true

Observed behavior

First successful run logged:

Successfully downloaded package, restart to update to version 1.0.60
Downloading updated linux-x64 binary...
Failed to update binary: Error: EACCES: permission denied, mkdir .../@github/copilot-linuxmusl-x64/.copilot-update-...

After that, subsequent invocations failed immediately:

Failed to load package index: ~/.cache/copilot/pkg/linuxmusl-x64/1.0.59/index.js Error: Native addon "runtime" not found for linuxmusl-x64. Tried:
  ~/.cache/copilot/pkg/linux-x64/1.0.60/prebuilds/linuxmusl-x64/runtime.node: Cannot find module ...
Require stack:
- ~/.cache/copilot/pkg/linux-x64/1.0.60/app.js
  ~/.cache/copilot/pkg/linux-x64/1.0.60/runtime.linux-x64-musl.node: Cannot find module ...
Require stack:
- ~/.cache/copilot/pkg/linux-x64/1.0.60/app.js

The persisted package cache contained both:

~/.cache/copilot/pkg/linuxmusl-x64/1.0.59
~/.cache/copilot/pkg/linux-x64/1.0.60

The linux-x64/1.0.60 package contains prebuilds/linux-x64/runtime.node, but the runtime correctly tries to load a musl addon (prebuilds/linuxmusl-x64/runtime.node) once running on Alpine/musl, so it cannot start.

Expected behavior

When running on Alpine/musl x64, auto-update should download/select the linuxmusl-x64 package for the target version, not linux-x64.

Workaround

Setting the environment variable below avoids the broken auto-update path and keeps the existing musl-compatible package running:

COPILOT_AUTO_UPDATE=false

With that env var, copilot --version stays on 1.0.59 and copilot --acp starts successfully again.

Additional context

This was observed in a restricted container where the home/cache directory is persistent across restarts, while global npm install paths are read-only to the runtime user. The failure occurs on the next invocation after the bad linux-x64/1.0.60 package has been downloaded into the persistent cache.