fix: dedupe and report automatic template creation from images

install_appliances_from_image relied on the name+version pair check in
TemplatesService, so the same appliance reached through a second image
(the CSR1000v case) created a second template sharing the name. The auto
path now skips when any template with the same name exists, whatever the
version, and returns a manifest of created and skipped candidates;
POST /images/install replies 200 with that manifest instead of an empty
204, and the image_install MCP tool surfaces it.

gns3server/agent/mcp/__init__.py

@@ -1435,7 +1435,9 @@ async def image_install() -> list[dict[str, Any]]:
 
     This is NOT for downloading images. Images must be uploaded first (via the GNS3 Web UI).
     If an uploaded image matches a known appliance, a template is automatically created.
-    Images already referenced by existing templates are skipped.
+    Returns {"created": [...], "skipped": [...]}: images already referenced by existing
+    templates are skipped, and no template is auto-created when one with the same name
+    already exists (regardless of version).
     """
     return await asyncio.to_thread(_run_handler_sync, install_images_handler, {})
 

gns3server/agent/mcp/images.py

@@ -72,6 +72,9 @@ def prune_images_handler(params: dict[str, Any], gns3_ctx: dict[str, Any]) -> di
 
 def install_images_handler(params: dict[str, Any], gns3_ctx: dict[str, Any]) -> dict[str, Any]:
     conn = _get_connector(gns3_ctx)
-    # Returns 204 No Content on success (empty body, no .json())
+    response = conn.http_call("post", f"{conn.base_url}/images/install")
-    conn.http_call("post", f"{conn.base_url}/images/install")
+    if response.content:
+        # the install endpoint reports which templates were created or skipped
+        return response.json()
+    # tolerate an empty body in case an older server still replies with 204
     return {"message": "Image installation completed"}

gns3server/api/routes/controller/images.py

@@ -206,19 +206,24 @@ async def prune_images(
 
 @router.post(
     "/install",
-    status_code=status.HTTP_204_NO_CONTENT,
+    status_code=status.HTTP_200_OK,
     dependencies=[Depends(has_privilege("Image.Allocate"))]
 )
 async def install_images(
         images_repo: ImagesRepository = Depends(get_repository(ImagesRepository)),
         templates_repo: TemplatesRepository = Depends(get_repository(TemplatesRepository))
-) -> None:
+) -> dict:
     """
     Attempt to automatically create templates based on image checksums.
 
+    Returns the list of created templates and the list of skipped
+    candidates (with the reason why they were skipped).
+
     Required privilege: Image.Allocate
     """
 
+    created = []
+    skipped = []
     skip_images = get_builtin_disks()
     images = await images_repo.get_images()
     for image in images:
@@ -229,8 +234,12 @@ async def install_images(
         if templates:
             # the image is already used by a template
             log.warning(f"Image '{image.path}' is used by one or more templates")
+            skipped.append({
+                "name": image.filename,
+                "reason": "image is already used by one or more templates",
+            })
             continue
-        await Controller.instance().appliance_manager.install_appliances_from_image(
+        results = await Controller.instance().appliance_manager.install_appliances_from_image(
             image.path,
             image.checksum,
             images_repo,
@@ -239,6 +248,12 @@ async def install_images(
             None,
             os.path.dirname(image.path)
         )
+        for result in results:
+            if result.get("status") == "created":
+                created.append({k: v for k, v in result.items() if k != "status"})
+            else:
+                skipped.append({k: v for k, v in result.items() if k != "status"})
+    return {"created": created, "skipped": skipped}
 
 
 @router.get(

gns3server/controller/appliance_manager.py

@@ -245,11 +245,16 @@ class ApplianceManager:
             rbac_repo: RbacRepository,
             current_user: schemas.User,
             image_dir: str
-    ) -> None:
+    ) -> List[dict]:
         """
-        Install appliances using an image checksum
+        Install appliances using an image checksum.
+
+        Returns a manifest of what happened: one entry per attempted template,
+        either {"status": "created", ...template fields} or
+        {"status": "skipped", "name", "reason"}.
         """
 
+        results: List[dict] = []
         appliances_info = self._find_appliances_from_image_checksum(image_checksum)
         for appliance, image_version in appliances_info:
             try:
@@ -257,15 +262,48 @@ class ApplianceManager:
                 ApplianceModel.model_validate(appliance.asdict())
             except ValidationError as e:
                 log.warning(f"Could not validate appliance '{appliance.id}': {e}")
+                results.append({
+                    "status": "skipped",
+                    "name": appliance.name,
+                    "reason": f"could not validate appliance '{appliance.id}': {e}",
+                })
+                continue
             if appliance.versions:
                 for version in appliance.versions:
                     if version.get("name") == image_version:
                         try:
                             await self._find_appliance_version_images(appliance, version, images_repo, image_dir)
                             template_data = await self._appliance_to_template(appliance, version)
-                            await self._create_template(template_data, templates_repo, rbac_repo, current_user)
+                            name = template_data.get("name")
+                            existing = await templates_repo.get_template_by_name(name) if name else None
+                            if existing is not None:
+                                # never automatically create a second template with the same
+                                # name: the name+version check in TemplatesService would allow
+                                # duplicates when the appliance version differs, but two
+                                # templates sharing a name is never what the user asked for here
+                                log.warning(f"Template '{name}' already exists, skipping automatic template creation")
+                                results.append({
+                                    "status": "skipped",
+                                    "name": name,
+                                    "reason": f"a template named '{name}' already exists",
+                                })
+                                continue
+                            template = await self._create_template(template_data, templates_repo, rbac_repo, current_user)
+                            results.append({
+                                "status": "created",
+                                "template_id": str(template.get("template_id")),
+                                "name": template.get("name"),
+                                "version": template.get("version"),
+                                "template_type": template.get("template_type"),
+                            })
                         except (ControllerError, InvalidImageError) as e:
                             log.warning(f"Could not automatically create template using image '{image_path}': {e}")
+                            results.append({
+                                "status": "skipped",
+                                "name": appliance.name,
+                                "reason": str(e),
+                            })
+        return results
 
     async def install_appliance(
             self,

gns3server/db/repositories/templates.py

@@ -71,6 +71,17 @@ class TemplatesRepository(BaseRepository):
         result = await self._db_session.execute(query)
         return result.scalars().first()
 
+    async def get_template_by_name(self, name: str) -> Union[None, models.Template]:
+        """
+        Return the first template with this name, regardless of version.
+        """
+
+        query = select(models.Template).\
+            options(selectinload(models.Template.images)).\
+            where(models.Template.name == name)
+        result = await self._db_session.execute(query)
+        return result.scalars().first()
+
     async def get_templates(self) -> List[models.Template]:
 
         query = select(models.Template).options(selectinload(models.Template.images))

tests/agent/mcp/test_handlers.py

@@ -523,6 +523,36 @@ class TestTemplate:
             assert "deleted" in str(result).lower()
 
 
+# ── Image ───────────────────────────────────────────────────────────────
+
+
+class TestImage:
+
+    mod = "images"
+
+    def test_install_manifest(self, ctx):
+        from gns3server.agent.mcp.images import install_images_handler
+        with patch(f"{BASE}.{self.mod}._get_connector") as m:
+            conn = _mock_conn({
+                "created": [{"template_id": "t1", "name": "Empty VM", "version": "100G", "template_type": "qemu"}],
+                "skipped": [{"name": "csr1000v.qcow2", "reason": "image is already used by one or more templates"}],
+            })
+            m.return_value = conn
+            result = install_images_handler({}, ctx)
+            assert result["created"][0]["name"] == "Empty VM"
+            assert result["skipped"][0]["name"] == "csr1000v.qcow2"
+
+    def test_install_empty_body(self, ctx):
+        from gns3server.agent.mcp.images import install_images_handler
+        with patch(f"{BASE}.{self.mod}._get_connector") as m:
+            conn = _mock_conn()
+            conn.http_call.return_value.content = b""
+            conn.http_call.return_value.json.side_effect = json.JSONDecodeError("Expecting value", "", 0)
+            m.return_value = conn
+            result = install_images_handler({}, ctx)
+            assert result == {"message": "Image installation completed"}
+
+
 # ── Marker (traffic-insight) ────────────────────────────────────────────
 
 

tests/api/routes/controller/test_images.py

@@ -328,10 +328,54 @@ class TestImageRoutes:
         with asyncio_patch("gns3server.api.routes.controller.images.get_builtin_disks", return_value=[]) as mock:
             response = await client.post(app.url_path_for("install_images"))
             assert mock.called
-            assert response.status_code == status.HTTP_204_NO_CONTENT
+            assert response.status_code == status.HTTP_200_OK
+            created = response.json()["created"]
+            assert len(created) == 1
+            assert created[0]["name"] == "Empty VM"
+            assert created[0]["version"] == "100G"
 
         templates_repo = TemplatesRepository(db_session)
         templates = await templates_repo.get_templates()
         assert len(templates) == 1
         assert templates[0].name == "Empty VM"
-        assert templates[0].version == "100G"
+        assert templates[0].version == "100G"
+        await templates_repo.delete_template(templates[0].template_id)
+
+    async def test_install_all_skips_existing_template_name(
+            self, app: FastAPI,
+            client: AsyncClient,
+            db_session: AsyncSession,
+            controller: Controller
+    ) -> None:
+        # two images matching two versions of the same appliance must not
+        # produce two templates with the same name
+        #
+        # earlier tests in this class uploaded the same filenames from different
+        # (function-scoped) images directories; drop those stale rows so the
+        # install route only sees this test's uploads
+        images_repo = ImagesRepository(db_session)
+        for image_name in ("empty30G.qcow2", "empty100G.qcow2"):
+            await images_repo.delete_image(image_name)
+        for image_path in ("tests/resources/empty30G.qcow2", "tests/resources/empty100G.qcow2"):
+            with open(image_path, "rb") as f:
+                image_data = f.read()
+            response = await client.post(
+                app.url_path_for("upload_image", image_path=os.path.basename(image_path)),
+                content=image_data)
+            assert response.status_code == status.HTTP_201_CREATED
+
+        controller.appliance_manager.load_appliances()  # make sure appliances are loaded
+        with asyncio_patch("gns3server.api.routes.controller.images.get_builtin_disks", return_value=[]):
+            response = await client.post(app.url_path_for("install_images"))
+            assert response.status_code == status.HTTP_200_OK
+
+        manifest = response.json()
+        assert len(manifest["created"]) == 1
+        assert manifest["created"][0]["name"] == "Empty VM"
+        assert any("already exists" in skipped["reason"] for skipped in manifest["skipped"])
+
+        templates_repo = TemplatesRepository(db_session)
+        templates = await templates_repo.get_templates()
+        assert len(templates) == 1
+        assert templates[0].name == "Empty VM"
+        await templates_repo.delete_template(templates[0].template_id)