feat(lora): the LoRA save takes the settings revision

POST /prompt_manager/lora/enable accepts the optional expected_revision
that GET /settings returns, so the System Save row refuses to write over
a config.json changed elsewhere (settings-changed, nothing written). The
legacy page sends none and still merges into what is on disk.

py/api/lora_integration.py

@@ -168,6 +168,9 @@ class LoraIntegrationMixin:
     async def lora_enable(self, request):
         """Enable or disable LoraManager integration and save it to config.json.
 
+        ``expected_revision`` (optional, GET /settings' ``revision``) refuses
+        a save over a config.json changed meanwhile (``settings-changed``).
+
         The values are committed through the config store first (#220) and
         published at runtime only once config.json holds them; a save that
         cannot be written reports ``persisted: false`` and changes nothing.
@@ -180,6 +183,11 @@ class LoraIntegrationMixin:
             for flag in _LORA_FLAGS:
                 if flag in data and not isinstance(data[flag], bool):
                     return self._bad_lora_request(f"{flag} must be true or false")
+            # The System Save row sends the revision it read (#220); the
+            # legacy page sends none and merges into what is on disk.
+            expected_revision = data.get("expected_revision")
+            if expected_revision is not None and not isinstance(expected_revision, str):
+                return self._bad_lora_request("expected_revision must be a string")
             enabled = data.get("enabled", False)
             path = data.get("path", "")
             trigger_words = data.get("trigger_words_enabled", False)
@@ -226,7 +234,7 @@ class LoraIntegrationMixin:
                 _saved, revision = await self._run_in_executor(
                     get_config_store().commit,
                     _lora_settings_mutation(values),
-                    expected_revision=None,
+                    expected_revision=expected_revision,
                     publish=publish,
                 )
             except (ConfigUnreadable, RevisionConflict, OSError) as exc:

tests/test_api_lora.py

@@ -528,6 +528,48 @@ class TestLoraEnableRoute(LoraAPITestCase):
         self.assertEqual(self.config_file.read_bytes(), b"{not json")
         self.assertFalse(IntegrationConfig.LORA_TRIGGER_WORDS_ENABLED)
 
+    async def test_enable_with_a_stale_revision_changes_nothing(self):
+        # System S10: the Save row sends the revision it read; a file changed
+        # since is a settings-changed conflict and nothing is written.
+        self.config_file.write_text(json.dumps({"web_ui": {"result_timeout": 9}}))
+        resp = await self.client.request("GET", "/prompt_manager/settings")
+        revision = (await resp.json())["revision"]
+        self.config_file.write_text(json.dumps({"web_ui": {"result_timeout": 10}}))
+        before = self.config_file.read_bytes()
+
+        resp = await self._post_json(
+            "/prompt_manager/lora/enable",
+            {
+                "enabled": False,
+                "trigger_words_enabled": True,
+                "expected_revision": revision,
+            },
+        )
+        body = await resp.json()
+
+        self.assertEqual((resp.status, body["code"]), (409, "settings-changed"))
+        self.assertEqual(self.config_file.read_bytes(), before)
+        self.assertFalse(IntegrationConfig.LORA_TRIGGER_WORDS_ENABLED)
+
+        resp = await self._post_json(
+            "/prompt_manager/lora/enable",
+            {
+                "enabled": False,
+                "trigger_words_enabled": True,
+                "expected_revision": body["revision"],
+            },
+        )
+        saved = await resp.json()
+        self.assertEqual(resp.status, 200)
+        self.assertTrue(saved["revision"].startswith("sha256:"))
+        self.assertTrue(IntegrationConfig.LORA_TRIGGER_WORDS_ENABLED)
+
+        resp = await self._post_json(
+            "/prompt_manager/lora/enable",
+            {"enabled": False, "expected_revision": 7},
+        )
+        self.assertEqual(resp.status, 400)
+
     async def test_enable_requires_boolean_flags_and_body_cap(self):
         for body in (
             {"enabled": "yes"},