diff --git a/src/pkg/session/session.go b/src/pkg/session/session.go
index c7a85813a..09640120d 100644
--- a/src/pkg/session/session.go
+++ b/src/pkg/session/session.go
@@ -2,6 +2,7 @@ package session
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 
@@ -78,6 +79,10 @@ func (sl *SessionLoader) loadStack(ctx context.Context) (*stacks.Parameters, str
 	}
 	stack, whence, err := sl.sm.GetStack(ctx, sl.opts.GetStackOpts)
 	if err != nil {
+		var notExistErr *stacks.ErrNotExist
+		if errors.As(err, &notExistErr) {
+			return nil, "", err
+		}
 		if sl.opts.ProviderID != "" {
 			whence = "--provider flag"
 		}
@@ -88,6 +93,9 @@ func (sl *SessionLoader) loadStack(ctx context.Context) (*stacks.Parameters, str
 		if whence == "" {
 			whence = "fallback stack"
 		}
+		if sl.opts.ProviderID == client.ProviderAuto {
+			sl.opts.ProviderID = client.ProviderDefang
+		}
 		return &stacks.Parameters{
 			Name:     stacks.DefaultBeta,
 			Provider: sl.opts.ProviderID,
diff --git a/src/pkg/session/session_test.go b/src/pkg/session/session_test.go
index 566a63e9e..ceb4ec3c9 100644
--- a/src/pkg/session/session_test.go
+++ b/src/pkg/session/session_test.go
@@ -94,6 +94,17 @@ func TestLoadSession(t *testing.T) {
 				Name: "beta",
 			},
 		},
+		{
+			name: "specified non-existing stack",
+			options: SessionLoaderOptions{
+				GetStackOpts: stacks.GetStackOpts{
+					Stack: "missingstack",
+				},
+			},
+
+			expectedError: "stack \"missingstack\" does not exist",
+			expectedEnv:   map[string]string{},
+		},
 		{
 			name: "specified existing stack",
 			options: SessionLoaderOptions{
@@ -151,7 +162,13 @@ func TestLoadSession(t *testing.T) {
 			sm := &mockStacksManager{}
 
 			if tt.existingStack == nil {
-				sm.On("GetStack", ctx, mock.Anything).Maybe().Return(nil, "", errors.New("stack not found"))
+				if tt.options.GetStackOpts.Stack != "" {
+					// For specified non-existing stack, return ErrNotExist
+					sm.On("GetStack", ctx, mock.Anything).Maybe().Return(nil, "", &stacks.ErrNotExist{StackName: tt.options.GetStackOpts.Stack})
+				} else {
+					// For empty stack (should fall back to beta), return a general error that's not ErrNotExist
+					sm.On("GetStack", ctx, mock.Anything).Maybe().Return(nil, "", errors.New("no default stack set for project"))
+				}
 			} else {
 				sm.On("GetStack", ctx, mock.Anything).Maybe().Return(tt.existingStack, "local", nil)
 			}
diff --git a/src/pkg/stacks/manager.go b/src/pkg/stacks/manager.go
index 34423d79a..9353b18bd 100644
--- a/src/pkg/stacks/manager.go
+++ b/src/pkg/stacks/manager.go
@@ -173,7 +173,7 @@ func (sm *manager) GetRemote(ctx context.Context, name string) (*Parameters, err
 		}
 	}
 	if remoteStack == nil {
-		return nil, fmt.Errorf("unable to find stack %q", name)
+		return nil, &ErrNotExist{StackName: name}
 	}
 
 	return &remoteStack.Parameters, nil
@@ -203,6 +203,14 @@ func (sl *manager) GetStack(ctx context.Context, opts GetStackOpts) (*Parameters
 	return sl.getDefaultStack(ctx)
 }
 
+type ErrNotExist struct {
+	StackName string
+}
+
+func (e *ErrNotExist) Error() string {
+	return fmt.Sprintf("stack %q does not exist", e.StackName)
+}
+
 func (sm *manager) getSpecifiedStack(ctx context.Context, name string) (*Parameters, string, error) {
 	whence := "--stack flag"
 	_, envSet := os.LookupEnv("DEFANG_STACK")
@@ -219,7 +227,7 @@ func (sm *manager) getSpecifiedStack(ctx context.Context, name string) (*Paramet
 	// the stack file does not exist locally; try loading remotely
 	stack, err = sm.GetRemote(ctx, name)
 	if err != nil {
-		return nil, "", fmt.Errorf("failed to find stack file or previously deployed stack: %w", err)
+		return nil, "", err
 	}
 	// persist the remote stack file to the local target directory
 	stackFilename, err := sm.Create(*stack)
@@ -257,7 +265,7 @@ func (sm *manager) getDefaultStack(ctx context.Context) (*Parameters, string, er
 		if connect.CodeOf(err) != connect.CodeNotFound {
 			return nil, "", err
 		}
-		term.Debugf("No default stack set for project %q; using default", sm.projectName)
+		term.Debugf("No default stack set for project %q; using fallback", sm.projectName)
 		return nil, "", errors.New("no default stack set for project")
 	}
 
diff --git a/src/pkg/stacks/manager_test.go b/src/pkg/stacks/manager_test.go
index 120de4f81..fef86a1d4 100644
--- a/src/pkg/stacks/manager_test.go
+++ b/src/pkg/stacks/manager_test.go
@@ -614,7 +614,7 @@ GOOGLE_REGION=us-central1
 	// Load should fail
 	_, err = manager.Load(t.Context(), "teststack")
 	require.Error(t, err, "Load() should fail when target directory is empty")
-	require.Contains(t, err.Error(), "unable to find stack \"teststack\"", "Expected specific error message about operation not allowed")
+	require.Contains(t, err.Error(), "stack \"teststack\" does not exist", "Expected specific error message about operation not allowed")
 }
 
 func TestManager_RemoteOperationsWorkRegardlessOfDirectory(t *testing.T) {
@@ -666,7 +666,7 @@ func TestGetStack(t *testing.T) {
 			options: GetStackOpts{
 				Stack: "missingstack",
 			},
-			expectedError: "unable to find stack",
+			expectedError: "stack \"missingstack\" does not exist",
 			expectedEnv:   map[string]string{},
 		},
 		{