Allow LLM model deletion without replacement if unused

Updated backend logic and API schema to permit deleting an LLM model without specifying a replacement if no workflow nodes are using it. Adjusted tests to cover both cases (with and without usage), made replacement_model_slug optional in the response model, and updated OpenAPI spec accordingly.

autogpt_platform/backend/backend/api/features/admin/llm_routes_test.py

@@ -439,9 +439,53 @@ def test_delete_llm_model_validation_error(
     assert "Replacement model 'invalid' not found" in response.json()["detail"]
 
 
-def test_delete_llm_model_missing_replacement() -> None:
-    """Test deletion fails when replacement_model_slug is not provided"""
+def test_delete_llm_model_no_replacement_with_usage(
+    mocker: pytest_mock.MockFixture,
+) -> None:
+    """Test deletion fails when nodes exist but no replacement is provided"""
+    mocker.patch(
+        "backend.api.features.admin.llm_routes.llm_db.delete_model",
+        new=AsyncMock(
+            side_effect=ValueError(
+                "Cannot delete model 'test-model': 5 workflow node(s) are using it. "
+                "Please provide a replacement_model_slug to migrate them."
+            )
+        ),
+    )
+
     response = client.delete("/admin/llm/models/model-1")
 
-    # FastAPI will return 422 for missing required query params
-    assert response.status_code == 422
+    assert response.status_code == 400
+    assert "workflow node(s) are using it" in response.json()["detail"]
+
+
+def test_delete_llm_model_no_replacement_no_usage(
+    mocker: pytest_mock.MockFixture,
+) -> None:
+    """Test deletion succeeds when no nodes use the model and no replacement is provided"""
+    mock_response = llm_model.DeleteLlmModelResponse(
+        deleted_model_slug="unused-model",
+        deleted_model_display_name="Unused Model",
+        replacement_model_slug=None,
+        nodes_migrated=0,
+        message="Successfully deleted model 'Unused Model' (unused-model). No workflows were using this model.",
+    )
+
+    mocker.patch(
+        "backend.api.features.admin.llm_routes.llm_db.delete_model",
+        new=AsyncMock(return_value=mock_response),
+    )
+
+    mock_refresh = mocker.patch(
+        "backend.api.features.admin.llm_routes._refresh_runtime_state",
+        new=AsyncMock(),
+    )
+
+    response = client.delete("/admin/llm/models/model-1")
+
+    assert response.status_code == 200
+    response_data = response.json()
+    assert response_data["deleted_model_slug"] == "unused-model"
+    assert response_data["nodes_migrated"] == 0
+    assert response_data["replacement_model_slug"] is None
+    mock_refresh.assert_called_once()

autogpt_platform/backend/backend/server/v2/llm/db.py

@@ -493,7 +493,9 @@ async def delete_model(
     deleted_display_name = model.displayName
 
     # 2. Count affected nodes first to determine if replacement is needed
-    count_result = await prisma.models.prisma().query_raw(
+    import prisma as prisma_module
+
+    count_result = await prisma_module.get_client().query_raw(
         """
         SELECT COUNT(*) as count
         FROM "AgentNode"

autogpt_platform/backend/backend/server/v2/llm/model.py

@@ -173,7 +173,7 @@ class ToggleLlmModelResponse(pydantic.BaseModel):
 class DeleteLlmModelResponse(pydantic.BaseModel):
     deleted_model_slug: str
     deleted_model_display_name: str
-    replacement_model_slug: str
+    replacement_model_slug: Optional[str] = None
     nodes_migrated: int
     message: str
 

autogpt_platform/frontend/src/app/api/openapi.json

@@ -7930,7 +7930,7 @@
             "title": "Deleted Model Display Name"
           },
           "replacement_model_slug": {
-            "type": "string",
+            "anyOf": [{ "type": "string" }, { "type": "null" }],
             "title": "Replacement Model Slug"
           },
           "nodes_migrated": { "type": "integer", "title": "Nodes Migrated" },
@@ -7940,7 +7940,6 @@
         "required": [
           "deleted_model_slug",
           "deleted_model_display_name",
-          "replacement_model_slug",
           "nodes_migrated",
           "message"
         ],