diff --git a/scripts/storage/format-disk.sh b/scripts/storage/format-disk.sh
index 1f54beee..aa0ebacd 100644
--- a/scripts/storage/format-disk.sh
+++ b/scripts/storage/format-disk.sh
@@ -719,9 +719,17 @@ main() {
         # even when nothing was actually wiped. Capture the failure and
         # continue but report it. Audit Tier 6 — `format-disk.sh` wipefs
         # `|| true` silencia fallos.
+        # blkid -k lists filesystem/RAID signatures, not partition tables.
+        # Use a positive filter so GPT/MBR (including nested tables) survive.
+        local _wipefs_types
+        if ! _wipefs_types=$(blkid -k) || [[ -z "$_wipefs_types" ]]; then
+            msg_error "$(translate "Could not determine filesystem signature types. Aborting.")"
+            return 1
+        fi
+        _wipefs_types=$(paste -sd, <<< "$_wipefs_types")
         local _wipefs_errs=0
         local _wipefs_err_out
-        if ! _wipefs_err_out=$(wipefs -af "$SELECTED_DISK" 2>&1); then
+        if ! _wipefs_err_out=$(wipefs -af --types "$_wipefs_types" "$SELECTED_DISK" 2>&1); then
             _wipefs_errs=$((_wipefs_errs + 1))
             msg_warn "$(translate "wipefs failed on") $SELECTED_DISK: $_wipefs_err_out"
         fi
@@ -730,7 +738,7 @@ main() {
             [[ -z "$pname" ]] && continue
             [[ "/dev/$pname" == "$SELECTED_DISK" ]] && continue
             if [[ -b "/dev/$pname" ]]; then
-                if ! _wipefs_err_out=$(wipefs -af "/dev/$pname" 2>&1); then
+                if ! _wipefs_err_out=$(wipefs -af --types "$_wipefs_types" "/dev/$pname" 2>&1); then
                     _wipefs_errs=$((_wipefs_errs + 1))
                     msg_warn "$(translate "wipefs failed on") /dev/$pname: $_wipefs_err_out"
                 fi
diff --git a/tests/storage/test_preserve_partition_tables.py b/tests/storage/test_preserve_partition_tables.py
new file mode 100644
index 00000000..2b268946
--- /dev/null
+++ b/tests/storage/test_preserve_partition_tables.py
@@ -0,0 +1,122 @@
+"""Regression tests for clean_sigs; only disposable regular files are written.
+
+Run: python3 -m unittest discover -s tests/storage -v
+Requires util-linux (blkid, sfdisk, wipefs) and e2fsprogs (mkfs.ext4).
+The original clean_sigs branch is extracted without running the full script.
+Only device enumeration and UI are mocked; signature probing/wiping is real.
+"""
+import json
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+ROOT = Path(__file__).resolve().parents[2]
+ENV = {**os.environ, 'PATH': os.environ.get('PATH', '') + ':/usr/sbin:/sbin', 'LC_ALL': 'C'}
+
+
+def run(*args, **kwargs):
+    return subprocess.run(args, env=ENV, text=True, capture_output=True, check=True, **kwargs)
+
+
+class PreservePartitionTables(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        for tool in ('blkid', 'sfdisk', 'wipefs', 'mkfs.ext4'):
+            if not shutil.which(tool, path=ENV['PATH']):
+                raise unittest.SkipTest(f'Missing {tool}')
+        source = (ROOT / 'scripts/storage/format-disk.sh').read_text()
+        start = source.index('    if [[ "$OPERATION_MODE" == "clean_sigs" ]]; then', source.index('main() {'))
+        end = source.index('    if [[ "$OPERATION_MODE" == "wipe_data" ]]; then', start)
+        cls.branch = source[start:end]
+
+    def setUp(self):
+        self.temp = tempfile.TemporaryDirectory(prefix='pmx-partition-test-')
+        self.addCleanup(self.temp.cleanup)
+        self.image = Path(self.temp.name) / 'disk.img'
+        with self.image.open('wb') as stream:
+            stream.truncate(16 * 1024 * 1024)
+
+    def clean(self, extra=''):
+        shell = '''
+translate() { printf '%s' "$*"; }
+msg_info() { :; }
+msg_warn() { printf 'WARNING: %s\\n' "$*"; }
+msg_error() { printf 'ERROR: %s\\n' "$*"; }
+msg_ok() { printf 'OK: %s\\n' "$*"; }
+msg_success() { :; }
+wait_for_enter_to_main() { :; }
+# No real device enumeration. The fixture is the whole-device target.
+lsblk() { printf 'fixture\\n'; }
+SELECTED_DISK="$1"
+OPERATION_MODE=clean_sigs
+'''
+        shell += extra + '\nmain() {\n' + self.branch + '\n}\nmain\n'
+        return subprocess.run(['bash', '--noprofile', '--norc', '-c', shell, 'test', str(self.image)],
+                              env=ENV, text=True, capture_output=True, timeout=10)
+
+    def test_gpt_layout_and_bytes_preserved(self):
+        self.assert_table_preserved('gpt')
+
+    def test_dos_layout_and_bytes_preserved(self):
+        self.assert_table_preserved('dos')
+
+    def test_partition_wipe_preserves_nested_table(self):
+        run('sfdisk', str(self.image), input='label: gpt\n,8M,L\n')
+        before = self.image.read_bytes()
+        # Redirect the partition invocation onto the regular-file fixture.
+        # The block-device predicate is the only source condition replaced.
+        original = self.branch
+        self.branch = self.branch.replace('[[ -b "/dev/$pname" ]]', 'true')
+        try:
+            result = self.clean('''
+lsblk() { printf 'fixture\\nfixturepart\\n'; }
+wipefs() {
+  local -a args=("$@")
+  if [[ "${args[-1]}" == /dev/fixturepart ]]; then
+    args[-1]="$SELECTED_DISK"
+  fi
+  command wipefs "${args[@]}"
+}
+''')
+        finally:
+            self.branch = original
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertEqual(self.image.read_bytes(), before, 'Nested partition table changed')
+
+    def test_unpartitioned_ext4_signature_removed(self):
+        run('mkfs.ext4', '-q', '-F', str(self.image))
+        before = json.loads(run('wipefs', '--json', str(self.image)).stdout)
+        self.assertIn('ext4', [s['type'] for s in before['signatures']])
+        result = self.clean()
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertEqual(json.loads(run('wipefs', '--json', str(self.image)).stdout)['signatures'], [])
+
+    def test_failed_or_empty_type_discovery_does_not_write(self):
+        for stub in ('blkid() { return 1; }', 'blkid() { return 0; }'):
+            with self.subTest(stub=stub):
+                result = self.clean(stub + '\nwipefs() { printf called > "$SELECTED_DISK.calls"; }')
+                self.assertNotEqual(result.returncode, 0)
+                self.assertFalse(Path(str(self.image) + '.calls').exists())
+                self.assertNotIn('Partition table preserved.', result.stdout)
+
+    def test_wipe_failure_is_reported(self):
+        result = self.clean('wipefs() { return 1; }')
+        self.assertIn('Some signatures could not be removed', result.stdout)
+        self.assertNotIn('OK:', result.stdout)
+
+    def assert_table_preserved(self, label):
+        run('sfdisk', str(self.image), input=f'label: {label}\n,8M,L\n')
+        before = self.image.read_bytes()
+        layout = json.loads(run('sfdisk', '--json', str(self.image)).stdout)
+        result = self.clean()
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertEqual(self.image.read_bytes(), before, 'Partition-table bytes changed')
+        self.assertEqual(json.loads(run('sfdisk', '--json', str(self.image)).stdout), layout)
+        self.assertIn('Partition table preserved.', result.stdout)
+
+
+if __name__ == '__main__':
+    unittest.main()