diff --git a/.vscode/install_extensions.ps1 b/.vscode/install_extensions.ps1
new file mode 100644
index 0000000..7404aa9
--- /dev/null
+++ b/.vscode/install_extensions.ps1
@@ -0,0 +1,43 @@
+# Package and install the local VS Code Insiders extensions under .vscode/.
+# Usage:
+#   .\install_extensions.ps1
+#   .\install_extensions.ps1 -SkipPackage
+
+param([switch] $SkipPackage)
+
+$path_vscode   = $PSScriptRoot
+$code_insiders = "C:\apps\Microsoft VS Code Insiders\bin\code-insiders.cmd"
+if (-not (test-path -literalpath $code_insiders)) {
+	$found = get-command code-insiders -erroraction silentlycontinue
+	if ($found) { $code_insiders = $found.source }
+}
+
+if (-not (test-path -literalpath $code_insiders)) { throw "code-insiders not found. Install VS Code Insiders or add it to PATH." }
+
+$extensions = @(
+	(join-path $path_vscode "tape-atom-syntax"),
+	(join-path $path_vscode "cozy-and-windy")
+)
+
+foreach ($extension in $extensions) {
+	$package_json = join-path $extension "package.json"
+	if (-not (test-path -literalpath $package_json)) { throw "missing $package_json" }
+
+	$manifest = get-content -literalpath $package_json -raw | convertfrom-json
+	$vsix     = join-path $extension ("{0}-{1}.vsix" -f $manifest.name, $manifest.version)
+
+	if (-not $SkipPackage) {
+		if (-not $manifest.scripts.package) { throw "$package_json has no scripts.package" }
+		write-host "packaging $($manifest.displayName) ($($manifest.name)@$($manifest.version))"
+		& npm --prefix $extension run package
+		if ($LASTEXITCODE -ne 0) { throw "npm run package failed for $extension" }
+	}
+
+	if (-not (test-path -literalpath $vsix)) { throw "missing $vsix" }
+
+	write-host "installing $vsix"
+	& $code_insiders --install-extension $vsix --force
+	if ($LASTEXITCODE -ne 0) { throw "install failed for $vsix" }
+}
+
+write-host "done. reload the Insiders window (Developer: Reload Window)."