diff --git a/koolook_setups.py b/koolook_setups.py
index 36dbd2f..68bcbb2 100644
--- a/koolook_setups.py
+++ b/koolook_setups.py
@@ -548,6 +548,8 @@ def _validate_persisted_setup_surface(
         items = surface.get(key)
         if isinstance(items, list):
             _validate_surface_entries(items, f"setupSurface.{key}", diagnostics)
+    if "app" in surface:
+        _validate_surface_app(surface["app"], "setupSurface.app", diagnostics)
 
 
 def _validate_surface_entries(
@@ -576,6 +578,77 @@ def _validate_surface_entries(
                     diagnostics.append(f"{node_path}.{field} must be non-empty text")
 
 
+def _validate_surface_app(app: Any, path: str, diagnostics: list[str]) -> None:
+    if not isinstance(app, dict):
+        diagnostics.append(f"{path} must be a JSON object")
+        return
+    for key in ("inputs", "outputs", "results"):
+        value = app.get(key)
+        if value is None:
+            continue
+        if not isinstance(value, list):
+            diagnostics.append(f"{path}.{key} must be a list")
+            continue
+        _validate_surface_app_fields(value, f"{path}.{key}", diagnostics)
+    if "switch" in app:
+        _validate_surface_app_switch(app["switch"], f"{path}.switch", diagnostics)
+
+
+def _validate_surface_app_fields(fields: list[Any], path: str, diagnostics: list[str]) -> None:
+    for field_index, field in enumerate(fields):
+        field_path = f"{path}[{field_index}]"
+        if not isinstance(field, dict):
+            diagnostics.append(f"{field_path} must be a JSON object")
+            continue
+        _validate_non_empty_text(field.get("key"), f"{field_path}.key", diagnostics)
+        _validate_non_empty_text(field.get("label"), f"{field_path}.label", diagnostics)
+        if "visible" in field and not isinstance(field["visible"], bool):
+            diagnostics.append(f"{field_path}.visible must be a boolean")
+        _validate_surface_app_target(field.get("target"), f"{field_path}.target", diagnostics)
+
+
+def _validate_surface_app_switch(switch: Any, path: str, diagnostics: list[str]) -> None:
+    if not isinstance(switch, dict):
+        diagnostics.append(f"{path} must be a JSON object")
+        return
+    _validate_non_empty_text(switch.get("key"), f"{path}.key", diagnostics)
+    _validate_non_empty_text(switch.get("label"), f"{path}.label", diagnostics)
+    if "visible" in switch and not isinstance(switch["visible"], bool):
+        diagnostics.append(f"{path}.visible must be a boolean")
+    _validate_surface_app_target(switch.get("target"), f"{path}.target", diagnostics)
+    default = switch.get("default")
+    if default is not None and (isinstance(default, bool) or not isinstance(default, int)):
+        diagnostics.append(f"{path}.default must be an integer")
+    options = switch.get("options")
+    if not isinstance(options, list):
+        diagnostics.append(f"{path}.options must be a list")
+        return
+    for option_index, option in enumerate(options):
+        option_path = f"{path}.options[{option_index}]"
+        if not isinstance(option, dict):
+            diagnostics.append(f"{option_path} must be a JSON object")
+            continue
+        if isinstance(option.get("value"), bool) or not isinstance(option.get("value"), int):
+            diagnostics.append(f"{option_path}.value must be an integer")
+        _validate_non_empty_text(option.get("label"), f"{option_path}.label", diagnostics)
+        _validate_non_empty_text(option.get("input"), f"{option_path}.input", diagnostics)
+        if "visible" in option and not isinstance(option["visible"], bool):
+            diagnostics.append(f"{option_path}.visible must be a boolean")
+
+
+def _validate_surface_app_target(target: Any, path: str, diagnostics: list[str]) -> None:
+    if not isinstance(target, dict):
+        diagnostics.append(f"{path} must be a JSON object")
+        return
+    _validate_non_empty_text(target.get("node"), f"{path}.node", diagnostics)
+    _validate_non_empty_text(target.get("input"), f"{path}.input", diagnostics)
+
+
+def _validate_non_empty_text(value: Any, path: str, diagnostics: list[str]) -> None:
+    if not isinstance(value, str) or not value.strip():
+        diagnostics.append(f"{path} must be non-empty text")
+
+
 def _uses_group_authored_surface(
     input_contract: dict[str, Any],
     output_contract: dict[str, Any],
diff --git a/tests/server/test_published_setup_registry.py b/tests/server/test_published_setup_registry.py
index d363854..e038d3e 100644
--- a/tests/server/test_published_setup_registry.py
+++ b/tests/server/test_published_setup_registry.py
@@ -196,6 +196,86 @@ def test_registry_omits_malformed_persisted_setup_surface() -> None:
     assert "ltx-director-demo: setupSurface.outputs must be a list" in registry.diagnostics
 
 
+def test_registry_omits_malformed_persisted_setup_surface_app() -> None:
+    setup = deepcopy(_valid_setup())
+    setup["inputContract"] = {"inputs": []}
+    setup["outputContract"] = {"outputs": []}
+    setup["setupSurface"] = {
+        "sourceInputs": [
+            {
+                "group": "Koolook Input",
+                "nodes": [{"id": "12", "type": "Koolook_PublishInput", "title": "Input"}],
+            }
+        ],
+        "outputs": [
+            {
+                "group": "Koolook Output",
+                "nodes": [{"id": "20", "type": "Koolook_PublishOutput", "title": "Output"}],
+            }
+        ],
+        "controls": [],
+        "app": "not-object",
+    }
+    registry = PublishedSetupRegistry(StaticSetupStorage([setup]))
+
+    assert registry.getSetup("ltx-director-demo") is None
+    assert "ltx-director-demo: setupSurface.app must be a JSON object" in registry.diagnostics
+
+
+def test_registry_omits_malformed_persisted_setup_surface_app_fields() -> None:
+    setup = deepcopy(_valid_setup())
+    setup["inputContract"] = {"inputs": []}
+    setup["outputContract"] = {"outputs": []}
+    setup["setupSurface"] = {
+        "sourceInputs": [
+            {
+                "group": "Koolook Input",
+                "nodes": [{"id": "12", "type": "Koolook_PublishInput", "title": "Input"}],
+            }
+        ],
+        "outputs": [
+            {
+                "group": "Koolook Output",
+                "nodes": [{"id": "20", "type": "Koolook_PublishOutput", "title": "Output"}],
+            }
+        ],
+        "controls": [],
+        "app": {
+            "inputs": [
+                {
+                    "key": "single_file",
+                    "label": "Single file",
+                    "visible": True,
+                    "target": {"node": "12"},
+                    "default": "/image.png",
+                }
+            ],
+            "outputs": "not-list",
+            "results": [],
+            "switch": {
+                "key": "switch",
+                "label": "Input type",
+                "visible": True,
+                "target": {"node": "12", "input": "mode"},
+                "default": 2,
+                "options": [{"value": True, "label": "Img", "visible": True, "input": "single_file"}],
+            },
+        },
+    }
+    registry = PublishedSetupRegistry(StaticSetupStorage([setup]))
+
+    assert registry.getSetup("ltx-director-demo") is None
+    assert "ltx-director-demo: setupSurface.app.outputs must be a list" in registry.diagnostics
+    assert (
+        "ltx-director-demo: setupSurface.app.inputs[0].target.input must be non-empty text"
+        in registry.diagnostics
+    )
+    assert (
+        "ltx-director-demo: setupSurface.app.switch.options[0].value must be an integer"
+        in registry.diagnostics
+    )
+
+
 def test_file_storage_loads_setups_object_and_uses_sample_fallback(tmp_path) -> None:
     primary = tmp_path / "setups.json"
     fallback = tmp_path / "sample.json"