diff --git a/.flake8 b/.flake8
new file mode 100644
index 00000000..a8948ef1
--- /dev/null
+++ b/.flake8
@@ -0,0 +1,7 @@
+[flake8]
+filename =
+    *.py
+max-line-length = 120
+extend-exclude =
+    .venv/
+    venv/
diff --git a/.github/workflows/ci-macos-broker.yml b/.github/workflows/ci-macos-broker.yml
index 15fcb65b..344b9ccc 100644
--- a/.github/workflows/ci-macos-broker.yml
+++ b/.github/workflows/ci-macos-broker.yml
@@ -45,6 +45,9 @@ jobs:
       - name: Install dependencies
         run: brew install cmake
 
+      - name: Test macOS installer quarantine handling
+        run: python3 tests/scripts/test-macos-install.py scripts/macos/install.command
+
       - name: Configure universal build
         env:
           BUILD_VERSION: ${{ inputs.release_version }}
diff --git a/scripts/macos/install.command b/scripts/macos/install.command
index 81054dee..5bd109eb 100755
--- a/scripts/macos/install.command
+++ b/scripts/macos/install.command
@@ -35,6 +35,7 @@ fi
 /usr/bin/sudo /bin/rm -rf "${legacy_broker_app}" "${installed_broker_app}" "${installed_control_app}"
 /usr/bin/sudo /usr/bin/ditto "${broker_app}" "${installed_broker_app}"
 /usr/bin/sudo /usr/bin/ditto "${control_app}" "${installed_control_app}"
+/usr/bin/sudo /usr/bin/xattr -dr com.apple.quarantine "${installed_broker_app}" "${installed_control_app}"
 /usr/bin/sudo /usr/sbin/chown -R root:wheel "${installed_broker_app}" "${installed_control_app}"
 /usr/bin/sudo /bin/chmod -R a+rX "${installed_broker_app}" "${installed_control_app}"
 /usr/bin/sudo /bin/chmod -R go-w "${installed_broker_app}" "${installed_control_app}"
@@ -43,6 +44,7 @@ fi
 /usr/bin/sudo /usr/bin/install -m 0644 \
   "${image_root}/${launchd_plist}" "${service_plist}"
 /usr/bin/sudo /usr/sbin/chown root:wheel "${service_plist}"
+/usr/bin/sudo /usr/bin/xattr -dr com.apple.quarantine "${service_plist}"
 
 if [[ -d "${image_root}/usr/local/include/libvirtualhid" ]]; then
   /usr/bin/sudo /usr/bin/ditto "${image_root}/usr/local/include/libvirtualhid" /usr/local/include/libvirtualhid
@@ -62,6 +64,14 @@ if [[ -d "${image_root}/usr/local/share/licenses/libvirtualhid" ]]; then
   /usr/bin/sudo /usr/bin/ditto "${image_root}/usr/local/share/licenses/libvirtualhid" /usr/local/share/licenses/libvirtualhid
 fi
 
+for installed_path in /usr/local/include/libvirtualhid /usr/local/lib/libvirtualhid.a \
+  /usr/local/bin/libvirtualhid-license /usr/local/lib/cmake/libvirtualhid \
+  /usr/local/share/licenses/libvirtualhid; do
+  if [[ -e "${installed_path}" ]]; then
+    /usr/bin/sudo /usr/bin/xattr -dr com.apple.quarantine "${installed_path}"
+  fi
+done
+
 /usr/bin/sudo /bin/launchctl bootstrap system "${service_plist}"
 /usr/bin/sudo /bin/launchctl kickstart -k "system/${bundle_id}"
 echo 'Virtual HID Broker and Virtual HID Control installed in /Applications.'
diff --git a/tests/scripts/test-macos-install.py b/tests/scripts/test-macos-install.py
new file mode 100644
index 00000000..dc5e6216
--- /dev/null
+++ b/tests/scripts/test-macos-install.py
@@ -0,0 +1,78 @@
+import os
+from pathlib import Path
+import re
+import subprocess
+import sys
+import tempfile
+
+
+def run(*args):
+    return subprocess.run(args, check=True, capture_output=True, text=True).stdout
+
+
+installer = Path(sys.argv[1]).read_text()
+for quarantined in (False, True):
+    for optional in (False, True):
+        with tempfile.TemporaryDirectory(prefix="libvirtualhid-install-", dir="/private/tmp") as temp:
+            root = Path(temp)
+            image = root / "image with spaces"
+            destination = root / "installed"
+            for name in ("VirtualHIDBroker.app", "VirtualHIDControl.app"):
+                executable = image / name / "Contents/MacOS/example"
+                executable.parent.mkdir(parents=True)
+                executable.write_text("fixture")
+            (image / "dev.lizardbyte.app.libvirtualhid.plist").write_text("fixture")
+            if optional:
+                for name in (
+                    "include/libvirtualhid/gamepad.hpp",
+                    "lib/libvirtualhid.a",
+                    "bin/libvirtualhid-license",
+                    "lib/cmake/libvirtualhid/libvirtualhid-config.cmake",
+                    "share/licenses/libvirtualhid/LICENSE.md",
+                ):
+                    path = image / "usr/local" / name
+                    path.parent.mkdir(parents=True, exist_ok=True)
+                    path.write_text("fixture")
+            run("/usr/bin/xattr", "-wr", "user.review_marker", "preserve", str(image))
+            if quarantined:
+                run("/usr/bin/xattr", "-wr", "com.apple.quarantine", "0083;12345678;Safari;test", str(image))
+            (destination / "Applications").mkdir(parents=True)
+            (destination / "Library/LaunchDaemons").mkdir(parents=True)
+            # Redirect fixed installation paths, leaving image-relative payload paths intact.
+            source = re.sub(
+                r"(?<!\})/(Applications|Library|usr/local)(?=[/ \"\n])",
+                lambda match: str(destination) + match.group(),
+                installer,
+            )
+            # Stub only authorization, ownership, signature validation, and launchd.
+            # File copying, permissions, and extended attributes use the real macOS tools.
+            stubs = r'''
+function /usr/bin/codesign() { return 0; }
+function /usr/bin/sudo() {
+  [[ "$1" != -v ]] || return 0
+  case "$1" in
+    /usr/sbin/chown|/usr/bin/codesign) return 0 ;;
+    /bin/launchctl)
+      if [[ "$2" == bootstrap ]]; then
+        if /usr/bin/xattr -lr "$TEST_DESTINATION" | /usr/bin/grep -q com.apple.quarantine; then
+          echo 'quarantine remains at bootstrap' >&2
+          return 1
+        fi
+        /usr/bin/touch "$TEST_BOOTSTRAPPED"
+      fi
+      return 0 ;;
+  esac
+  "$@"
+}
+'''
+            script = image / "Install libvirtualhid.command"
+            script.write_text(stubs + source)
+            marker = root / "bootstrapped"
+            env = dict(os.environ, TEST_DESTINATION=str(destination), TEST_BOOTSTRAPPED=str(marker))
+            result = subprocess.run(["/bin/bash", str(script)], env=env, capture_output=True, text=True)
+            assert result.returncode == 0, (quarantined, optional, result.stderr)
+            assert marker.exists(), "bootstrap was skipped"
+            assert "user.review_marker: preserve" in run("/usr/bin/xattr", "-lr", str(destination))
+            if quarantined:
+                assert "com.apple.quarantine" in run("/usr/bin/xattr", "-lr", str(image))
+            print(f"PASS: quarantined={quarantined}, optional_payload={optional}")