Add PowerShell installer path for gh-aw and cover it in Windows CI

.gitattributes

@@ -9,6 +9,7 @@ pkg/workflow/js/*.cjs linguist-generated=true
 pkg/workflow/sh/*.sh linguist-generated=true
 actions/*/index.js linguist-generated=true
 actions/setup-cli/install.sh linguist-generated=true
+actions/setup-cli/install.ps1 linguist-generated=true
 specs/artifacts.md linguist-generated=true merge=ours
 docs/adr/*.md merge=theirs
 # Use bd merge for beads JSONL files

.github/workflows/install.yml

@@ -8,6 +8,7 @@ on:
   pull_request:
     paths:
       - 'install-gh-aw.sh'
+      - 'install-gh-aw.ps1'
       - 'scripts/test-install-script.sh'
       - '.github/workflows/install.yml'
 
@@ -185,10 +186,87 @@ jobs:
           echo ""
           echo "✅ Full installation test passed!"
 
+  test-install-powershell:
+    name: Test PowerShell installer on Windows
+    runs-on: windows-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - name: Capture platform-detection output (expects failure for fake version)
+        # The installer exits 1 when the nonexistent version download fails; that is
+        # expected.  continue-on-error suppresses the step failure so the next step
+        # can assert the platform-detection messages that ran before the download.
+        continue-on-error: true
+        shell: pwsh
+        run: |
+          & ./install-gh-aw.ps1 v999.999.999 6>&1 2>&1 | Tee-Object -FilePath install-ps-output.log
+
+      - name: Assert platform-detection messages from dry run
+        shell: pwsh
+        run: |
+          Set-StrictMode -Version Latest
+          if (-not (Test-Path install-ps-output.log)) {
+            throw "Installer output file (install-ps-output.log) was not created; Tee-Object may have failed"
+          }
+          $outputText = Get-Content install-ps-output.log -Raw
+          if (-not $outputText) { throw "Installer output file (install-ps-output.log) exists but is empty" }
+          if ($outputText -notmatch "Detected OS:")           { throw "OS detection failed" }
+          if ($outputText -notmatch "Detected architecture:") { throw "Architecture detection failed" }
+          if ($outputText -notmatch "Platform:")              { throw "Platform string construction failed" }
+          if ($outputText -notmatch "Failed to download")     { throw "Installer did not report expected download failure for fake version" }
+
+      - name: Test setup-cli composite action (Windows)
+        id: setup-cli-test
+        uses: ./actions/setup-cli
+        with:
+          version: latest
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Verify composite-action binary and installed-version output
+        shell: pwsh
+        run: |
+          Set-StrictMode -Version Latest
+          $ErrorActionPreference = 'Stop'
+
+          $installedVersion = '${{ steps.setup-cli-test.outputs.installed-version }}'
+          if (-not $installedVersion) {
+            throw "installed-version output is empty; action output wiring is broken"
+          }
+          Write-Host "Composite action installed: $installedVersion"
+
+          # Verify via gh aw commands rather than a hardcoded binary path.
+          # `gh extension install` registers the extension under gh's own data dir
+          # (e.g. %APPDATA%\GitHub CLI\extensions on Windows), so using `gh aw`
+          # is the correct cross-platform verification mechanism.
+          gh aw version 2>&1 | Write-Host
+          if ($LASTEXITCODE -ne 0) {
+            throw "'gh aw version' failed with exit code $LASTEXITCODE"
+          }
+
+          gh aw --help 2>&1 | Write-Host
+          if ($LASTEXITCODE -ne 0) {
+            throw "'gh aw --help' failed with exit code $LASTEXITCODE"
+          }
+
+      - name: Upload PowerShell test results
+        if: always()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        with:
+          name: install-test-powershell-windows
+          path: install-ps-output.log
+          retention-days: 7
+          if-no-files-found: ignore
+
   report-failure:
     name: Report Installation Failures
     runs-on: ubuntu-latest
-    needs: test-install
+    needs:
+      - test-install
+      - test-install-powershell
     if: failure()
     permissions:
       issues: write
@@ -211,7 +289,7 @@ jobs:
 
             ## Details
 
-            The install script testing workflow detected failures when testing the \`install-gh-aw.sh\` script across different platforms.
+            The install script testing workflow detected failures when testing the \`install-gh-aw.sh\` and \`install-gh-aw.ps1\` scripts across different platforms.
 
             Please review the workflow logs to identify which platform(s) failed and investigate the issue.
 
@@ -225,7 +303,7 @@ jobs:
             ## Next Steps
 
             1. Check the [workflow run logs](${workflowUrl}) for detailed error messages
-            2. Review changes to \`install-gh-aw.sh\` that may have caused the failure
+            2. Review changes to \`install-gh-aw.sh\` and \`install-gh-aw.ps1\` that may have caused the failure
             3. Test the install script locally on the affected platform(s)
             4. Fix the issue and verify with \`scripts/test-install-script.sh\`
 

Makefile

@@ -1032,6 +1032,8 @@ sync-action-scripts:
 	@echo "Syncing install-gh-aw.sh to actions/setup-cli/install.sh..."
 	@cp install-gh-aw.sh actions/setup-cli/install.sh
 	@chmod +x actions/setup-cli/install.sh
+	@echo "Syncing install-gh-aw.ps1 to actions/setup-cli/install.ps1..."
+	@cp install-gh-aw.ps1 actions/setup-cli/install.ps1
 	@echo "✓ Action scripts synced successfully"
 
 # Sync install-gh-aw.sh SHA/hash constants in pkg/cli/copilot_setup.go
@@ -1219,7 +1221,7 @@ help:
 	@echo "  check-stale-lock-files - Fast guard: detect modified .md files without regenerated .lock.yml (no binary needed)"
 	@echo "  install          - Install binary locally"
 	@echo "  sync-action-pins - Sync actions-lock.json from .github/aw to pkg/actionpins/data and pkg/workflow/data (runs automatically during build)"
-	@echo "  sync-action-scripts - Sync install-gh-aw.sh to actions/setup-cli/install.sh (runs automatically during build)"
+	@echo "  sync-action-scripts - Sync install-gh-aw.sh and install-gh-aw.ps1 to actions/setup-cli/ (runs automatically during build)"
 	@echo "  sync-install-script-hashes - Update install-gh-aw.sh SHA and SHA256 constants in pkg/cli/copilot_setup.go (runs automatically during update)"
 	@echo "  update           - Update GitHub Actions and workflows, sync action pins, and rebuild binary"
 	@echo "  fix              - Apply automatic codemod-style fixes to workflow files (depends on build)"

actions/setup-cli/README.md

@@ -169,17 +169,18 @@ The action automatically falls back to direct download when `gh extension instal
 
 ## Development
 
-This action is part of the gh-aw repository. The `install.sh` script is generated during the build process by copying from the root `install-gh-aw.sh` file.
+This action is part of the gh-aw repository. The `install.sh` and `install.ps1` scripts are generated during the build process by copying from the root `install-gh-aw.sh` and `install-gh-aw.ps1` files.
 
 ### Building
 
-The installation script is copied during the build process:
+The installation scripts are copied during the build process:
 
 ```bash
 make build  # Copies install-gh-aw.sh to actions/setup-cli/install.sh
+            # and install-gh-aw.ps1 to actions/setup-cli/install.ps1
 ```
 
-The generated `install.sh` file is marked as `linguist-generated=true` in `.gitattributes`.
+The generated `install.sh` and `install.ps1` files are marked as `linguist-generated=true` in `.gitattributes`.
 
 ## License
 

actions/setup-cli/action.yml

@@ -14,11 +14,24 @@ inputs:
 outputs:
   installed-version:
     description: 'The version that was installed'
+    value: ${{ steps.install-windows.outputs.installed_version || steps.install-unix.outputs.installed_version }}
 
 runs:
   using: 'composite'
   steps:
-    - name: Install gh-aw CLI
+    - name: Install gh-aw CLI (PowerShell)
+      id: install-windows
+      if: runner.os == 'Windows'
+      shell: pwsh
+      env:
+        INPUT_VERSION: ${{ inputs.version }}
+        GH_TOKEN: ${{ inputs.github-token }}
+        ACTION_PATH: ${{ github.action_path }}
+      run: '& "$env:ACTION_PATH/install.ps1"'
+
+    - name: Install gh-aw CLI (Bash)
+      id: install-unix
+      if: runner.os != 'Windows'
       shell: bash
       env:
         INPUT_VERSION: ${{ inputs.version }}