fix(install): support windows-arm64

[harshil-mistry]

Issue for this PR

Closes #44664

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

install works out the platform correctly on Windows ARM64 — uname -s gives MINGW*, which maps to windows, and uname -m gives aarch64, which maps to arm64. So combo ends up as windows-arm64. The problem is the next case statement, which lists the supported combos and never included windows-arm64, so the script fell through to the *) branch and exited with Unsupported OS/Arch: windows/arm64.

That binary does exist. packages/opencode/script/build.ts declares { os: "win32", arch: "arm64" }, and publish.yml signs it, verifies the signature, repacks it and uploads opencode-windows-arm64.zip on every release. Nothing else in the script needed changing: archive_ext is already .zip for windows, and needs_baseline only applies to x64, so the filename it builds is opencode-windows-arm64.zip, which is exactly the published asset name.

Adding the combo to the allowlist is the whole fix. This also unblocks opencode upgrade for curl installs, since that path re-runs this same script (packages/opencode/src/installation/index.ts fetches https://opencode.ai/install).

How did you verify your code works?

I don't have a Windows ARM64 machine, so I want to be upfront that I did not run the installer end to end on one.

What I did check:

• Ran the old and new case statements directly against sample combos. Before: windows-arm64 hits the reject branch. After: it is accepted, and unsupported combos like freebsd-x64 still get rejected, so the allowlist hasn't been loosened beyond the one target.
• Confirmed the asset the script would request actually exists — https://github.com/anomalyco/opencode/releases/latest/download/opencode-windows-arm64.zip returns HTTP 200.
• Confirmed the filename the script builds for this target matches that asset name.

A reviewer can confirm the same by running the installer on Windows ARM64, or by checking the release assets against the allowlist.

Screenshots / recordings

Not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Related PR Found:

• PR feat(desktop): add native Windows ARM64 desktop agent (Electron 38) #44214: feat(desktop): add native Windows ARM64 desktop agent (Electron 38)
  • feat(desktop): add native Windows ARM64 desktop agent (Electron 38) #44214
  • This PR adds Windows ARM64 support to the desktop agent, which is related to the installation fix for Windows ARM64. However, it appears to address a different component (desktop/Electron) rather than the install script allowlist itself.

Note: PR #44665 (current PR) appears to be addressing a specific installation script issue where Windows ARM64 was missing from the supported OS/Arch allowlist, blocking installations and upgrades despite the binaries being built and available. The related PR #44214 adds the actual desktop agent support for Windows ARM64 but doesn't fix the installation script validation.

These are complementary changes rather than duplicates, but worth cross-referencing to ensure coordinated Windows ARM64 support rollout.

[github-actions]

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[github-actions]

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