diff --git a/bin/omarchy-iso-make b/bin/omarchy-iso-make
index 500de4b..b38001c 100755
--- a/bin/omarchy-iso-make
+++ b/bin/omarchy-iso-make
@@ -130,6 +130,10 @@ BUILD_SCRIPT="builder/build-iso.sh"
 BUILD_ROOT=$(realpath "${BASH_SOURCE[0]%/*}/..")
 BUILD_RELEASE_PATH="$BUILD_ROOT/release"
 mkdir -p "$BUILD_RELEASE_PATH"
+# Each build writes into its own directory, so concurrent builds (such as a
+# global and a regional one) never pick up and rename each other's ISO.
+BUILD_OUT=$(mktemp -d "$BUILD_RELEASE_PATH/.build-XXXXXX")
+trap 'rm -rf "$BUILD_OUT"' EXIT
 
 OMARCHY_ISO_REF="${OMARCHY_ISO_REF:-quattro}"
 OMARCHY_MIRROR="${OMARCHY_MIRROR:-stable}"
@@ -143,7 +147,7 @@ DOCKER_ARGS=(
   -e "OMARCHY_INSTALL_DEBUG=${OMARCHY_INSTALL_DEBUG:-}"
   -e "HOST_UID=$(id -u)"
   -e "HOST_GID=$(id -g)"
-  -v "$BUILD_RELEASE_PATH/:/out/"
+  -v "$BUILD_OUT/:/out/"
   -v "$BUILD_ROOT/$BUILD_SCRIPT:/$BUILD_SCRIPT:ro"
   -v "$BUILD_ROOT/archiso:/archiso:ro"
   -v "$BUILD_ROOT/builder:/builder:ro"
@@ -187,9 +191,14 @@ fi
 
 "${DOCKER[@]}" run "${DOCKER_ARGS[@]}" archlinux/archlinux:latest /$BUILD_SCRIPT
 
-latest_iso=$(\ls -t "$BUILD_RELEASE_PATH"/*.iso | head -n1)
-iso_ref="${latest_iso%.*}-${OMARCHY_ISO_REF}${region_suffix}.iso"
-mv -f "$latest_iso" "$iso_ref"
+built_isos=("$BUILD_OUT"/*.iso)
+if (( ${#built_isos[@]} != 1 )) || [[ ! -f ${built_isos[0]} ]]; then
+  echo "Error: expected exactly one ISO in $BUILD_OUT" >&2
+  exit 1
+fi
+built_iso_name=$(basename "${built_isos[0]}" .iso)
+iso_ref="$BUILD_RELEASE_PATH/$built_iso_name-${OMARCHY_ISO_REF}${region_suffix}.iso"
+mv -f "${built_isos[0]}" "$iso_ref"
 
 if [[ -z "${NO_BOOT_OFFER:-}" ]]; then
   echo
diff --git a/test/unit/test_region.py b/test/unit/test_region.py
index 3961b56..75d16b4 100644
--- a/test/unit/test_region.py
+++ b/test/unit/test_region.py
@@ -179,7 +179,9 @@ class RegionMakeTest(unittest.TestCase):
             "docker": '''#!/bin/bash
 if [[ $1 == version ]]; then exit 0; fi
 printf '%s\\n' "$@" > "$TEST_LOG"
-touch "$TEST_ROOT/release/omarchy-test-x86_64.iso"
+for arg in "$@"; do
+  if [[ $arg == *:/out/ ]]; then touch "${arg%:/out/}/omarchy-test-x86_64.iso"; fi
+done
 ''',
         }
         for name, content in stubs.items():
@@ -217,6 +219,17 @@ touch "$TEST_ROOT/release/omarchy-test-x86_64.iso"
         self.assertIn("/iso_stable/", self.log.read_text())
         self.assertTrue((self.root / "release/omarchy-test-x86_64-quattro.iso").exists())
 
+    def test_build_renames_only_its_own_iso(self):
+        release = self.root / "release"
+        release.mkdir()
+        other = release / "omarchy-other-x86_64.iso"
+        other.touch()
+        result = self.make("--region", "cn")
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertTrue(other.exists())
+        self.assertTrue((release / "omarchy-test-x86_64-quattro-cn.iso").exists())
+        self.assertEqual(list(release.glob(".build-*")), [])
+
     def test_local_source_keeps_region_and_mounts_both_checkouts(self):
         for name in ("runtime", "packages"):
             (self.root / name).mkdir()