diff --git a/api/ddns_manager.py b/api/ddns_manager.py
index 8b508bc..d5e3d76 100644
--- a/api/ddns_manager.py
+++ b/api/ddns_manager.py
@@ -112,6 +112,14 @@ class PicNgoDDNS(DDNSProvider):
     # Public interface
     # ------------------------------------------------------------------
 
+    def release(self, token: str) -> bool:
+        """DELETE /api/v1/registration — release the subdomain owned by token."""
+        url = f'{self.api_base_url}/api/v1/registration'
+        resp = requests.delete(url, json={'token': token},
+                               headers=self._headers(), timeout=self.TIMEOUT)
+        self._raise_for_status(resp, 'release')
+        return True
+
     def register(self, name: str, ip: str) -> dict:
         """POST /api/v1/register — register subdomain, returns token + subdomain."""
         url = f'{self.api_base_url}/api/v1/register'
@@ -398,6 +406,18 @@ class DDNSManager(BaseServiceManager):
         if not ip:
             ip = _get_public_ip() or ''
 
+        # Release the old subdomain if the name is changing and we hold a token
+        if self.config_manager is not None and hasattr(provider, 'release'):
+            old_token = self._ddns_cfg().get('token', '')
+            old_domain = self._identity().get('domain_name', '')
+            old_name = old_domain.replace('.pic.ngo', '') if old_domain else ''
+            if old_token and old_name and old_name != name:
+                try:
+                    provider.release(old_token)
+                    logger.info("DDNS released old subdomain %r before registering %r", old_name, name)
+                except Exception as exc:
+                    logger.warning("DDNS could not release old subdomain %r: %s", old_name, exc)
+
         result = provider.register(name, ip)
 
         if self.config_manager is not None:
diff --git a/tests/test_ddns_manager.py b/tests/test_ddns_manager.py
index 43c8d08..9eb4744 100644
--- a/tests/test_ddns_manager.py
+++ b/tests/test_ddns_manager.py
@@ -352,6 +352,60 @@ class TestRegister(unittest.TestCase):
         mock_ip.assert_not_called()
         mock_provider.register.assert_called_once_with('alpha', '1.2.3.4')
 
+    def test_register_releases_old_name_when_changing(self):
+        cm = _make_config_manager(ddns_cfg={'provider': 'pic_ngo', 'token': 'old_tok'})
+        cm.get_identity.return_value = {'domain_name': 'oldname.pic.ngo'}
+        mgr = DDNSManager(config_manager=cm)
+
+        mock_provider = MagicMock()
+        mock_provider.register.return_value = {'token': 'new_tok', 'subdomain': 'newname.pic.ngo'}
+        mgr.get_provider = MagicMock(return_value=mock_provider)
+
+        mgr.register('newname', '1.2.3.4')
+
+        mock_provider.release.assert_called_once_with('old_tok')
+        mock_provider.register.assert_called_once_with('newname', '1.2.3.4')
+
+    def test_register_skips_release_when_name_unchanged(self):
+        cm = _make_config_manager(ddns_cfg={'provider': 'pic_ngo', 'token': 'tok'})
+        cm.get_identity.return_value = {'domain_name': 'alpha.pic.ngo'}
+        mgr = DDNSManager(config_manager=cm)
+
+        mock_provider = MagicMock()
+        mock_provider.register.return_value = {'token': 'tok2', 'subdomain': 'alpha.pic.ngo'}
+        mgr.get_provider = MagicMock(return_value=mock_provider)
+
+        mgr.register('alpha', '1.2.3.4')
+
+        mock_provider.release.assert_not_called()
+
+    def test_register_skips_release_when_no_old_token(self):
+        cm = _make_config_manager(ddns_cfg={'provider': 'pic_ngo'})
+        cm.get_identity.return_value = {'domain_name': 'oldname.pic.ngo'}
+        mgr = DDNSManager(config_manager=cm)
+
+        mock_provider = MagicMock()
+        mock_provider.register.return_value = {'token': 'new_tok', 'subdomain': 'newname.pic.ngo'}
+        mgr.get_provider = MagicMock(return_value=mock_provider)
+
+        mgr.register('newname', '1.2.3.4')
+
+        mock_provider.release.assert_not_called()
+
+    def test_register_continues_if_release_fails(self):
+        cm = _make_config_manager(ddns_cfg={'provider': 'pic_ngo', 'token': 'old_tok'})
+        cm.get_identity.return_value = {'domain_name': 'oldname.pic.ngo'}
+        mgr = DDNSManager(config_manager=cm)
+
+        mock_provider = MagicMock()
+        mock_provider.release.side_effect = DDNSError("server down")
+        mock_provider.register.return_value = {'token': 'new_tok', 'subdomain': 'newname.pic.ngo'}
+        mgr.get_provider = MagicMock(return_value=mock_provider)
+
+        result = mgr.register('newname', '1.2.3.4')
+        self.assertEqual(result['token'], 'new_tok')
+        mock_provider.register.assert_called_once()
+
     def test_register_raises_when_no_provider(self):
         cm = _make_config_manager()
         mgr = DDNSManager(config_manager=cm)