@@ -18,6 +18,7 @@ package applications
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 
 	v1 "github.com/radius-project/radius/pkg/armrpc/api/v1"
@@ -36,6 +37,42 @@ const (
 	planeName   = "local"
 )
 
+// ComputeGraphResponse computes the application graph for the given application and environment IDs and
+// returns it wrapped in an OK rest.Response. It is shared by the Applications.Core and Radius.Core
+// implementations of the getGraph custom action.
+func ComputeGraphResponse(ctx context.Context, applicationID resources.ID, environmentID string, connection sdk.Connection) (rest.Response, error) {
+	// An application **MUST** have an environment id
+	parsedEnvironmentID, err := resources.ParseResource(environmentID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse environment ID %q: %w", environmentID, err)
+	}
+
+	clientOptions := sdk.NewClientOptions(connection)
+
+	ucpApplicationsManagementClient := &clients.UCPApplicationsManagementClient{
+		RootScope:     radiusPlane + planeName,
+		ClientOptions: clientOptions,
+	}
+
+	resourceTypes, err := ucpApplicationsManagementClient.ListAllResourceTypesNames(ctx, "local")
+	if err != nil {
+		return nil, err
+	}
+
+	applicationResources, err := listAllResourcesByApplication(ctx, applicationID, resourceTypes, clientOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	environmentResources, err := listAllResourcesByEnvironment(ctx, parsedEnvironmentID, resourceTypes, clientOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	graph := computeGraph(applicationResources, environmentResources)
+	return rest.NewOKResponse(graph), nil
+}
+
 var _ ctrl.Controller = (*GetGraph)(nil)
 
 // GetGraph is the controller implementation to get application graph.
@@ -71,33 +108,5 @@ func (ctrl *GetGraph) Run(ctx context.Context, w http.ResponseWriter, req *http.
 		return rest.NewNotFoundResponse(sCtx.ResourceID), nil
 	}
 	// An application **MUST** have an environment id
-	environmentID, err := resources.Parse(applicationResource.Properties.Environment)
-	if err != nil {
-		return nil, err
-	}
-
-	clientOptions := sdk.NewClientOptions(ctrl.connection)
-
-	ucpApplicationsManagementClient := &clients.UCPApplicationsManagementClient{
-		RootScope:     radiusPlane + planeName,
-		ClientOptions: clientOptions,
-	}
-
-	resourceTypes, err := ucpApplicationsManagementClient.ListAllResourceTypesNames(ctx, "local")
-	if err != nil {
-		return nil, err
-	}
-
-	applicationResources, err := listAllResourcesByApplication(ctx, applicationID, resourceTypes, clientOptions)
-	if err != nil {
-		return nil, err
-	}
-
-	environmentResources, err := listAllResourcesByEnvironment(ctx, environmentID, resourceTypes, clientOptions)
-	if err != nil {
-		return nil, err
-	}
-
-	graph := computeGraph(applicationResources, environmentResources)
-	return rest.NewOKResponse(graph), nil
+	return ComputeGraphResponse(ctx, applicationID, applicationResource.Properties.Environment, ctrl.connection)
 }
@@ -18,14 +18,20 @@ package applications
 
 import (
 	"context"
+	"errors"
+	"net/http"
 	"net/http/httptest"
 	"testing"
 
 	v1 "github.com/radius-project/radius/pkg/armrpc/api/v1"
 	ctrl "github.com/radius-project/radius/pkg/armrpc/frontend/controller"
+	"github.com/radius-project/radius/pkg/armrpc/rest"
 	"github.com/radius-project/radius/pkg/armrpc/rpctest"
 	"github.com/radius-project/radius/pkg/components/database"
+	"github.com/radius-project/radius/pkg/corerp/datamodel"
+	rpv1 "github.com/radius-project/radius/pkg/rp/v1"
 	"github.com/radius-project/radius/pkg/sdk"
+	"github.com/radius-project/radius/pkg/ucp/resources"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/mock/gomock"
 )
@@ -67,3 +73,204 @@ func TestGetGraphRun_20231001Preview(t *testing.T) {
 		require.NoError(t, err)
 	})
 }
+
+func TestComputeGraphResponse_InvalidEnvironmentID(t *testing.T) {
+	conn, err := sdk.NewDirectConnection("http://localhost:9000/apis/api.ucp.dev/v1alpha3")
+	require.NoError(t, err)
+
+	applicationID, err := resources.Parse("/planes/radius/local/resourceGroups/default/providers/Applications.Core/applications/myapp")
+	require.NoError(t, err)
+
+	// An empty/invalid environment ID string must surface as a parse error from
+	// resources.Parse and not a panic or a successful response.
+	resp, err := ComputeGraphResponse(context.Background(), applicationID, "not-a-valid-resource-id", conn)
+	require.Error(t, err)
+	require.Nil(t, resp)
+}
+
+// TestComputeGraphResponse_UCPProvidersError covers the error-propagation path from
+// ListAllResourceTypesNames (~lines 57-59) by returning a 500 from the UCP providers endpoint.
+func TestComputeGraphResponse_UCPProvidersError(t *testing.T) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/planes/radius/local/providers", func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "boom", http.StatusInternalServerError)
+	})
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	conn, err := sdk.NewDirectConnection(server.URL)
+	require.NoError(t, err)
+
+	applicationID, err := resources.Parse("/planes/radius/local/resourceGroups/default/providers/Applications.Core/applications/myapp")
+	require.NoError(t, err)
+
+	resp, err := ComputeGraphResponse(
+		context.Background(),
+		applicationID,
+		"/planes/radius/local/resourceGroups/default/providers/Applications.Core/environments/myenv",
+		conn,
+	)
+	require.Error(t, err)
+	require.Nil(t, resp)
+}
+
+// TestComputeGraphResponse_ListByApplicationError covers lines 62-63: the error-propagation path
+// from listAllResourcesByApplication when getAPIVersionForResourceType fails.
+func TestComputeGraphResponse_ListByApplicationError(t *testing.T) {
+	mux := http.NewServeMux()
+	// Return a provider with one resource type so the list is non-empty.
+	mux.HandleFunc("/planes/radius/local/providers", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"value":[{"name":"Applications.Core","resourceTypes":{"containers":{"apiVersions":{},"defaultApiVersion":"2023-10-01-preview"}}}]}`))
+	})
+	// GetProviderSummary for the resource type returns a 500 so listAllResourcesByApplication fails.
+	mux.HandleFunc("/planes/radius/local/providers/Applications.Core", func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "provider error", http.StatusInternalServerError)
+	})
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	conn, err := sdk.NewDirectConnection(server.URL)
+	require.NoError(t, err)
+
+	applicationID, err := resources.Parse("/planes/radius/local/resourceGroups/app-rg/providers/Applications.Core/applications/myapp")
+	require.NoError(t, err)
+
+	resp, err := ComputeGraphResponse(
+		context.Background(),
+		applicationID,
+		"/planes/radius/local/resourceGroups/env-rg/providers/Applications.Core/environments/myenv",
+		conn,
+	)
+	require.Error(t, err)
+	require.Nil(t, resp)
+}
+
+// TestComputeGraphResponse_ListByEnvironmentError covers lines 67-68: the error-propagation path
+// from listAllResourcesByEnvironment when the environment-scoped resource listing fails.
+func TestComputeGraphResponse_ListByEnvironmentError(t *testing.T) {
+	mux := http.NewServeMux()
+	// Return a provider with one resource type.
+	mux.HandleFunc("/planes/radius/local/providers", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"value":[{"name":"Applications.Core","resourceTypes":{"containers":{"apiVersions":{"2023-10-01-preview":{}},"defaultApiVersion":"2023-10-01-preview"}}}]}`))
+	})
+	// GetProviderSummary succeeds with a valid API version.
+	mux.HandleFunc("/planes/radius/local/providers/Applications.Core", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"name":"Applications.Core","resourceTypes":{"containers":{"apiVersions":{"2023-10-01-preview":{}},"defaultApiVersion":"2023-10-01-preview"}}}`))
+	})
+	// Application-scoped listing succeeds (empty list).
+	mux.HandleFunc("/planes/radius/local/resourceGroups/app-rg/providers/Applications.Core/containers", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"value":[]}`))
+	})
+	// Environment-scoped listing fails.
+	mux.HandleFunc("/planes/radius/local/resourceGroups/env-rg/providers/Applications.Core/containers", func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "env listing error", http.StatusInternalServerError)
+	})
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	conn, err := sdk.NewDirectConnection(server.URL)
+	require.NoError(t, err)
+
+	applicationID, err := resources.Parse("/planes/radius/local/resourceGroups/app-rg/providers/Applications.Core/applications/myapp")
+	require.NoError(t, err)
+
+	resp, err := ComputeGraphResponse(
+		context.Background(),
+		applicationID,
+		"/planes/radius/local/resourceGroups/env-rg/providers/Applications.Core/environments/myenv",
+		conn,
+	)
+	require.Error(t, err)
+	require.Nil(t, resp)
+}
+
+// TestGetGraphRun_DatabaseError covers the error path from GetResource (line ~104) where the
+// database client returns a non-NotFound error and the controller propagates it.
+func TestGetGraphRun_DatabaseError(t *testing.T) {
+	mctrl := gomock.NewController(t)
+	defer mctrl.Finish()
+
+	databaseClient := database.NewMockClient(mctrl)
+	req, err := rpctest.NewHTTPRequestWithContent(
+		context.Background(),
+		v1.OperationPost.HTTPMethod(),
+		"http://localhost:8080/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/radius-test-rg/providers/Applications.Core/Applications/myapp/getGraph?api-version=2023-10-01-preview", nil)
+	require.NoError(t, err)
+
+	databaseClient.
+		EXPECT().
+		Get(gomock.Any(), gomock.Any()).
+		Return(nil, errors.New("boom"))
+
+	ctx := rpctest.NewARMRequestContext(req)
+	conn, err := sdk.NewDirectConnection("http://localhost:9000/apis/api.ucp.dev/v1alpha3")
+	require.NoError(t, err)
+
+	ctl, err := NewGetGraph(ctrl.Options{DatabaseClient: databaseClient}, conn)
+	require.NoError(t, err)
+
+	w := httptest.NewRecorder()
+	resp, err := ctl.Run(ctx, w, req)
+	require.Error(t, err)
+	require.Nil(t, resp)
+}
+
+// TestGetGraphRun_ComputeGraphSuccess covers the success path through the controller's Run into
+// ComputeGraphResponse (line ~110 and the body of ComputeGraphResponse) by serving an empty UCP
+// resource-providers list from an httptest server, which yields an empty graph.
+func TestGetGraphRun_ComputeGraphSuccess(t *testing.T) {
+	mctrl := gomock.NewController(t)
+	defer mctrl.Finish()
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/planes/radius/local/providers", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"value":[]}`))
+	})
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	const appIDStr = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/radius-test-rg/providers/Applications.Core/applications/myapp"
+	const envIDStr = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/radius-test-rg/providers/Applications.Core/environments/myenv"
+
+	databaseClient := database.NewMockClient(mctrl)
+	databaseClient.
+		EXPECT().
+		Get(gomock.Any(), gomock.Any()).
+		Return(rpctest.FakeStoreObject(&datamodel.Application{
+			BaseResource: v1.BaseResource{
+				TrackedResource: v1.TrackedResource{ID: appIDStr},
+			},
+			Properties: datamodel.ApplicationProperties{
+				BasicResourceProperties: rpv1.BasicResourceProperties{Environment: envIDStr},
+			},
+		}), nil)
+
+	req, err := rpctest.NewHTTPRequestWithContent(
+		context.Background(),
+		v1.OperationPost.HTTPMethod(),
+		"http://localhost:8080"+appIDStr+"/getGraph?api-version=2023-10-01-preview", nil)
+	require.NoError(t, err)
+
+	ctx := rpctest.NewARMRequestContext(req)
+	conn, err := sdk.NewDirectConnection(server.URL)
+	require.NoError(t, err)
+
+	ctl, err := NewGetGraph(ctrl.Options{DatabaseClient: databaseClient}, conn)
+	require.NoError(t, err)
+
+	w := httptest.NewRecorder()
+	resp, err := ctl.Run(ctx, w, req)
+	require.NoError(t, err)
+	_, ok := resp.(*rest.OKResponse)
+	require.True(t, ok, "expected an OK response, got %T", resp)
+}
@@ -0,0 +1,72 @@
+/*
+Copyright 2023 The Radius Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package v20250801preview
+
+import (
+	"context"
+	"net/http"
+
+	v1 "github.com/radius-project/radius/pkg/armrpc/api/v1"
+	ctrl "github.com/radius-project/radius/pkg/armrpc/frontend/controller"
+	"github.com/radius-project/radius/pkg/armrpc/rest"
+	"github.com/radius-project/radius/pkg/corerp/datamodel"
+	"github.com/radius-project/radius/pkg/corerp/datamodel/converter"
+	app_ctrl "github.com/radius-project/radius/pkg/corerp/frontend/controller/applications"
+	"github.com/radius-project/radius/pkg/sdk"
+)
+
+var _ ctrl.Controller = (*GetGraphv20250801preview)(nil)
+
+// GetGraphv20250801preview is the controller implementation to get the application graph for
+// Radius.Core/applications resources.
+type GetGraphv20250801preview struct {
+	ctrl.Operation[*datamodel.Application_v20250801preview, datamodel.Application_v20250801preview]
+	connection sdk.Connection
+}
+
+// NewGetGraphv20250801preview creates a new instance of the GetGraphv20250801preview controller.
+func NewGetGraphv20250801preview(opts ctrl.Options, connection sdk.Connection) (ctrl.Controller, error) {
+	return &GetGraphv20250801preview{
+		ctrl.NewOperation(opts,
+			ctrl.ResourceOptions[datamodel.Application_v20250801preview]{
+				RequestConverter:  converter.Application20250801DataModelFromVersioned,
+				ResponseConverter: converter.Application20250801DataModelToVersioned,
+			},
+		),
+		connection,
+	}, nil
+}
+
+// Run handles the getGraph custom action for Radius.Core/applications. It looks up the application,
+// resolves its environment, lists application- and environment-scoped resources, and returns the
+// computed application graph.
+func (ctrl *GetGraphv20250801preview) Run(ctx context.Context, w http.ResponseWriter, req *http.Request) (rest.Response, error) {
+	sCtx := v1.ARMRequestContextFromContext(ctx)
+
+	// Request route for getGraph has the operation name as suffix which must be removed to get the resource id.
+	// route id format: /planes/radius/local/resourcegroups/default/providers/Radius.Core/applications/<app>/getGraph
+	applicationID := sCtx.ResourceID.Truncate()
+	applicationResource, _, err := ctrl.GetResource(ctx, applicationID)
+	if err != nil {
+		return nil, err
+	}
+	if applicationResource == nil {
+		return rest.NewNotFoundResponse(sCtx.ResourceID), nil
+	}
+
+	return app_ctrl.ComputeGraphResponse(ctx, applicationID, applicationResource.Properties.Environment, ctrl.connection)
+}