diff --git a/gns3server/api/routes/controller/appliances.py b/gns3server/api/routes/controller/appliances.py
index ad8645554..1d3f0e413 100644
--- a/gns3server/api/routes/controller/appliances.py
+++ b/gns3server/api/routes/controller/appliances.py
@@ -19,7 +19,7 @@ API routes for appliances.
 """
 
 import logging
-from typing import List, Optional, Union
+from typing import List, Optional
 from uuid import UUID
 
 from fastapi import APIRouter, Depends, status
@@ -85,9 +85,7 @@ def get_appliance(appliance_id: UUID) -> schemas.Appliance:
     status_code=status.HTTP_201_CREATED,
     dependencies=[Depends(has_privilege("Appliance.Allocate"))],
 )
-def add_appliance_version(
-    appliance_id: UUID, appliance_version: Union[schemas.ApplianceVersion, schemas.ApplianceVersionV8]
-) -> dict:
+def add_appliance_version(appliance_id: UUID, appliance_version: schemas.ApplianceVersionCreate) -> dict:
     """
     Add a version to an appliance.
 
@@ -109,7 +107,7 @@ def add_appliance_version(
         if version.get("name") == appliance_version.name:
             raise ControllerError(message=f"Appliance '{appliance_id}' already has version '{appliance_version.name}'")
 
-    appliance.versions.append(appliance_version.model_dump(exclude_unset=True))
+    appliance.versions.append(appliance_version.model_dump(exclude_unset=True, exclude={"registry_version"}))
     return appliance.asdict()
 
 
diff --git a/gns3server/api/routes/controller/links.py b/gns3server/api/routes/controller/links.py
index b67fd0790..d8625b9ad 100644
--- a/gns3server/api/routes/controller/links.py
+++ b/gns3server/api/routes/controller/links.py
@@ -20,7 +20,7 @@ API routes for links.
 
 import logging
 import os
-from typing import Any, List, Optional, Union
+from typing import Any, List, Optional
 from uuid import UUID, uuid4
 
 import aiohttp
@@ -539,7 +539,7 @@ async def update_marker(marker_name: str, marker_data: schemas.MarkerUpdate, lin
 
 @router.get(
     "/{link_id}/iface",
-    response_model=Union[schemas.UDPPortInfo, schemas.EthernetPortInfo],
+    response_model=schemas.LinkIfaceInfo,
     dependencies=[Depends(has_privilege("Link.Audit"))],
 )
 async def get_iface(link: Link = Depends(dep_link)) -> dict:
@@ -570,6 +570,7 @@ async def get_iface(link: Link = Depends(dep_link)) -> dict:
                 port_type = port.get("type", "")
                 if "udp" in port_type.lower():
                     ifaces_info = {
+                        "kind": "udp",
                         "node_id": node.id,
                         "type": f"{port_type}",
                         "lport": port["lport"],
@@ -578,6 +579,7 @@ async def get_iface(link: Link = Depends(dep_link)) -> dict:
                     }
                 else:
                     ifaces_info = {
+                        "kind": "ethernet",
                         "node_id": node.id,
                         "type": f"{port_type}",
                         "interface": port["interface"],
diff --git a/gns3server/schemas/__init__.py b/gns3server/schemas/__init__.py
index e8fd9c1f8..5338f5b57 100644
--- a/gns3server/schemas/__init__.py
+++ b/gns3server/schemas/__init__.py
@@ -17,7 +17,7 @@
 # General schemas
 from .common import ErrorMessage
 from .config import ServerConfig
-from .controller.appliances import Appliance, ApplianceVersion, ApplianceVersionV8
+from .controller.appliances import Appliance, ApplianceVersion, ApplianceVersionCreate, ApplianceVersionV8
 from .controller.computes import (
     AutoIdlePC,
     Compute,
@@ -41,6 +41,7 @@ from .controller.links import (
     LinkFilterParameter,
     LinkFilters,
     LinkFilterType,
+    LinkIfaceInfo,
     LinkUpdate,
     MarkerCreate,
     MarkerDefinitionCreate,
@@ -167,6 +168,7 @@ __all__ = [
     "ApiKeyCreate",
     "Appliance",
     "ApplianceVersion",
+    "ApplianceVersionCreate",
     "ApplianceVersionV8",
     "AutoIdlePC",
     "BatchNIOCreate",
@@ -253,6 +255,7 @@ __all__ = [
     "LinkFilterParameter",
     "LinkFilterType",
     "LinkFilters",
+    "LinkIfaceInfo",
     "LinkUpdate",
     "LoggedInUserUpdate",
     "MarkerCreate",
diff --git a/gns3server/schemas/controller/appliances.py b/gns3server/schemas/controller/appliances.py
index 4a5b48da1..ce1a71b98 100644
--- a/gns3server/schemas/controller/appliances.py
+++ b/gns3server/schemas/controller/appliances.py
@@ -20,7 +20,7 @@ from enum import Enum
 from typing import Annotated, List, Literal, Optional, Union
 from uuid import UUID
 
-from pydantic import AnyUrl, BaseModel, Discriminator, EmailStr, Field, Tag
+from pydantic import AnyUrl, BaseModel, BeforeValidator, Discriminator, EmailStr, Field, Tag
 
 from ..common import ExtraConfig
 
@@ -648,6 +648,39 @@ class ApplianceVersionV8(BaseModel):
     images: Optional[ApplianceVersionImages] = Field(None, title="Images used for this version")
 
 
+_V8_VERSION_ONLY_FIELDS = frozenset(set(ApplianceVersionV8.model_fields) - set(ApplianceVersion.model_fields))
+
+
+class ApplianceVersionCreateV1_6(ApplianceVersion):
+    """Request body to add a version to an appliance with registry version 1-6"""
+
+    registry_version: Literal[1, 2, 3, 4, 5, 6] = Field(
+        1, title="Version of the registry compatible with the appliance receiving the version"
+    )
+
+
+class ApplianceVersionCreateV8(ApplianceVersionV8):
+    """Request body to add a version to an appliance with registry version 8"""
+
+    registry_version: Literal[8] = Field(
+        8, title="Version of the registry compatible with the appliance receiving the version"
+    )
+
+
+def _infer_version_registry_version(data):
+    if isinstance(data, dict) and "registry_version" not in data:
+        data = dict(data)
+        data["registry_version"] = 8 if _V8_VERSION_ONLY_FIELDS.intersection(data) else 1
+    return data
+
+
+ApplianceVersionCreate = Annotated[
+    Union[ApplianceVersionCreateV1_6, ApplianceVersionCreateV8],
+    BeforeValidator(_infer_version_registry_version),
+    Discriminator("registry_version"),
+]
+
+
 # ============================================================================
 # Child Models with Discriminated Union
 # ============================================================================
diff --git a/gns3server/schemas/controller/links.py b/gns3server/schemas/controller/links.py
index a1b741440..f74635b8c 100644
--- a/gns3server/schemas/controller/links.py
+++ b/gns3server/schemas/controller/links.py
@@ -15,10 +15,10 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from enum import Enum
-from typing import Annotated, List, Literal, Optional, Tuple
+from typing import Annotated, List, Literal, Optional, Tuple, Union
 from uuid import UUID, uuid4
 
-from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
+from pydantic import BaseModel, ConfigDict, Discriminator, Field, field_validator, model_validator
 
 from ..update import PartialUpdateModel
 from .labels import Label
@@ -205,6 +205,7 @@ class UDPPortInfo(BaseModel):
     rhost: str
     rport: int
     type: str
+    kind: Literal["udp"]
 
 
 class EthernetPortInfo(BaseModel):
@@ -215,6 +216,10 @@ class EthernetPortInfo(BaseModel):
     node_id: UUID
     interface: str
     type: str
+    kind: Literal["ethernet"]
+
+
+LinkIfaceInfo = Annotated[Union[UDPPortInfo, EthernetPortInfo], Discriminator("kind")]
 
 
 class LinkCapture(BaseModel):
diff --git a/tests/api/routes/controller/test_appliances.py b/tests/api/routes/controller/test_appliances.py
index 94e7673f7..193557e35 100644
--- a/tests/api/routes/controller/test_appliances.py
+++ b/tests/api/routes/controller/test_appliances.py
@@ -101,3 +101,33 @@ class TestApplianceRoutes:
             app.url_path_for("add_appliance_version", appliance_id=appliance_id), json=new_version
         )
         assert response.status_code == status.HTTP_409_CONFLICT
+
+    async def test_add_v8_version_appliance(self, app: FastAPI, client: AsyncClient) -> None:
+
+        appliance_id = "1cfdf900-7c30-4cb7-8f03-3f61d2581633"  # Empty VM appliance
+        new_version = {"name": "v8-99G", "category": "guest", "images": {"hda_disk_image": "empty99G.qcow2"}}
+        response = await client.post(
+            app.url_path_for("add_appliance_version", appliance_id=appliance_id), json=new_version
+        )
+        assert response.status_code == status.HTTP_201_CREATED
+        assert new_version in response.json()["versions"]
+
+    async def test_add_version_appliance_with_registry_version(self, app: FastAPI, client: AsyncClient) -> None:
+
+        appliance_id = "1cfdf900-7c30-4cb7-8f03-3f61d2581633"  # Empty VM appliance
+        stored_version = {"name": "explicit-99G", "images": {"hda_disk_image": "empty99G.qcow2"}}
+        response = await client.post(
+            app.url_path_for("add_appliance_version", appliance_id=appliance_id),
+            json=dict(stored_version, registry_version=3),
+        )
+        assert response.status_code == status.HTTP_201_CREATED
+        assert stored_version in response.json()["versions"]
+
+    async def test_add_version_appliance_unknown_registry_version(self, app: FastAPI, client: AsyncClient) -> None:
+
+        appliance_id = "1cfdf900-7c30-4cb7-8f03-3f61d2581633"  # Empty VM appliance
+        response = await client.post(
+            app.url_path_for("add_appliance_version", appliance_id=appliance_id),
+            json={"name": "bad", "registry_version": 7, "images": {"hda_disk_image": "empty99G.qcow2"}},
+        )
+        assert response.status_code == status.HTTP_422_UNPROCESSABLE_ENTITY
diff --git a/tests/api/routes/controller/test_links.py b/tests/api/routes/controller/test_links.py
index ba1d018d0..d7daded0e 100644
--- a/tests/api/routes/controller/test_links.py
+++ b/tests/api/routes/controller/test_links.py
@@ -608,6 +608,7 @@ class TestLinkRoutes:
         assert result["rhost"] == "127.0.0.1"
         assert result["rport"] == 30000
         assert result["type"] == "udp"
+        assert result["kind"] == "udp"
 
     async def test_get_ethernet_interface(self, app: FastAPI, client: AsyncClient, project: Project) -> None:
         """
@@ -638,3 +639,4 @@ class TestLinkRoutes:
         assert result["node_id"] == cloud_node.id
         assert result["interface"] == "eth0"
         assert result["type"] == "ethernet"
+        assert result["kind"] == "ethernet"
diff --git a/tests/api/test_openapi_discriminators.py b/tests/api/test_openapi_discriminators.py
new file mode 100644
index 000000000..2a1bca86a
--- /dev/null
+++ b/tests/api/test_openapi_discriminators.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2026 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import pytest
+from fastapi import FastAPI
+
+pytestmark = pytest.mark.asyncio
+
+
+@pytest.fixture
+def openapi(app: FastAPI) -> dict:
+    return app.openapi()
+
+
+def _ref(name: str) -> str:
+    return f"#/components/schemas/{name}"
+
+
+def _assert_discriminated(schema: dict, property_name: str, mapping: dict) -> None:
+    assert [item["$ref"] for item in schema["oneOf"]] == [_ref(name) for name in dict.fromkeys(mapping.values())]
+    assert schema["discriminator"]["propertyName"] == property_name
+    assert schema["discriminator"]["mapping"] == {key: _ref(name) for key, name in mapping.items()}
+
+
+async def test_link_iface_response_is_discriminated(openapi: dict) -> None:
+    path = "/v3/projects/{project_id}/links/{link_id}/iface"
+    schema = openapi["paths"][path]["get"]["responses"]["200"]["content"]["application/json"]["schema"]
+    _assert_discriminated(schema, "kind", {"udp": "UDPPortInfo", "ethernet": "EthernetPortInfo"})
+
+
+async def test_appliance_version_request_is_discriminated(openapi: dict) -> None:
+    schema = openapi["paths"]["/v3/appliances/{appliance_id}/version"]["post"]["requestBody"]["content"][
+        "application/json"
+    ]["schema"]
+    mapping = {str(version): "ApplianceVersionCreateV1_6" for version in range(1, 7)}
+    mapping["8"] = "ApplianceVersionCreateV8"
+    _assert_discriminated(schema, "registry_version", mapping)
+
+
+async def test_appliance_settings_are_discriminated(openapi: dict) -> None:
+    schema = openapi["components"]["schemas"]["ApplianceV8"]["properties"]["settings"]["items"]
+    _assert_discriminated(
+        schema,
+        "template_type",
+        {
+            "qemu": "QemuTemplateSetting",
+            "dynamips": "DynamipsTemplateSetting",
+            "iou": "IouTemplateSetting",
+            "docker": "DockerTemplateSetting",
+        },
+    )
diff --git a/tests/controller/test_appliance.py b/tests/controller/test_appliance.py
index 0ec004e20..89f58f802 100644
--- a/tests/controller/test_appliance.py
+++ b/tests/controller/test_appliance.py
@@ -17,10 +17,21 @@
 
 import pydantic
 import pytest
+from pydantic import TypeAdapter
 
 from gns3server.controller.appliance import Appliance
 from gns3server.controller.appliance_to_template import ApplianceToTemplate
-from gns3server.schemas.controller.appliances import ApplianceModel
+from gns3server.schemas.controller.appliances import (
+    ApplianceModel,
+    ApplianceVersionCreate,
+    ApplianceVersionCreateV1_6,
+    ApplianceVersionCreateV8,
+    DockerTemplateSetting,
+    DynamipsTemplateSetting,
+    IouTemplateSetting,
+    QemuTemplateSetting,
+    TemplateSetting,
+)
 
 # v8 mirror of the XRd Control Plane appliance shape (docker, custom_adapters, no versions)
 XRD_V8 = {
@@ -242,3 +253,44 @@ def test_v8_netmiko_device_type_empty_string_clears():
     appliance = dict(XRD_V8, netmiko_device_type="")
     model = ApplianceModel.model_validate(appliance)
     assert model.netmiko_device_type == ""
+
+
+@pytest.mark.parametrize(
+    "template_type, properties, expected",
+    [
+        ("qemu", {"ram": 512}, QemuTemplateSetting),
+        ("dynamips", {"platform": "c7200", "ram": 256}, DynamipsTemplateSetting),
+        ("iou", {"ram": 256}, IouTemplateSetting),
+        ("docker", {"image": "alpine:latest"}, DockerTemplateSetting),
+    ],
+)
+def test_template_setting_decoded_through_discriminator(template_type, properties, expected):
+    setting = TypeAdapter(TemplateSetting).validate_python(
+        {"name": "a", "template_type": template_type, "template_properties": properties}
+    )
+    assert type(setting) is expected
+    assert setting.template_type == template_type
+
+
+def test_template_setting_unknown_template_type_rejected():
+    with pytest.raises(pydantic.ValidationError):
+        TypeAdapter(TemplateSetting).validate_python({"template_type": "vpcs", "template_properties": {}})
+
+
+@pytest.mark.parametrize(
+    "data, expected",
+    [
+        ({"name": "1", "registry_version": 1}, ApplianceVersionCreateV1_6),
+        ({"name": "6", "registry_version": 6}, ApplianceVersionCreateV1_6),
+        ({"name": "8", "registry_version": 8}, ApplianceVersionCreateV8),
+        ({"name": "plain", "images": {"hda_disk_image": "a.qcow2"}}, ApplianceVersionCreateV1_6),
+        ({"name": "v8", "category": "guest"}, ApplianceVersionCreateV8),
+    ],
+)
+def test_appliance_version_decoded_through_discriminator(data, expected):
+    assert type(TypeAdapter(ApplianceVersionCreate).validate_python(data)) is expected
+
+
+def test_appliance_version_unknown_registry_version_rejected():
+    with pytest.raises(pydantic.ValidationError):
+        TypeAdapter(ApplianceVersionCreate).validate_python({"name": "x", "registry_version": 7})