diff --git a/apps/backend/internal/task/service/service_resources.go b/apps/backend/internal/task/service/service_resources.go
index f7614948d3..e1e381b037 100644
--- a/apps/backend/internal/task/service/service_resources.go
+++ b/apps/backend/internal/task/service/service_resources.go
@@ -16,6 +16,7 @@ import (
 )
 
 const spritesTokenEnvKey = "SPRITES_API_TOKEN"
+const workspaceDeletePageSize = 500
 
 // Workspace operations
 
@@ -90,6 +91,30 @@ func (s *Service) DeleteWorkspace(ctx context.Context, id string) error {
 	if err != nil {
 		return err
 	}
+	tasks, err := s.listAllTasksForWorkspaceDelete(ctx, id)
+	if err != nil {
+		return err
+	}
+	for _, task := range tasks {
+		if task == nil || task.ID == "" {
+			continue
+		}
+		if err := s.DeleteTask(ctx, task.ID); err != nil {
+			return fmt.Errorf("delete task %s: %w", task.ID, err)
+		}
+	}
+	workflows, err := s.workflows.ListWorkflows(ctx, id, true)
+	if err != nil {
+		return fmt.Errorf("list workspace workflows: %w", err)
+	}
+	for _, workflow := range workflows {
+		if workflow == nil || workflow.ID == "" {
+			continue
+		}
+		if err := s.DeleteWorkflow(ctx, workflow.ID); err != nil {
+			return fmt.Errorf("delete workflow %s: %w", workflow.ID, err)
+		}
+	}
 	if err := s.workspaces.DeleteWorkspace(ctx, id); err != nil {
 		s.logger.Error("failed to delete workspace", zap.String("workspace_id", id), zap.Error(err))
 		return err
@@ -99,6 +124,22 @@ func (s *Service) DeleteWorkspace(ctx context.Context, id string) error {
 	return nil
 }
 
+func (s *Service) listAllTasksForWorkspaceDelete(ctx context.Context, workspaceID string) ([]*models.Task, error) {
+	var all []*models.Task
+	for page := 1; ; page++ {
+		tasks, total, err := s.tasks.ListTasksByWorkspace(
+			ctx, workspaceID, "", "", "", page, workspaceDeletePageSize, true, true, false, false,
+		)
+		if err != nil {
+			return nil, fmt.Errorf("list workspace tasks: %w", err)
+		}
+		all = append(all, tasks...)
+		if len(all) >= total || len(tasks) == 0 {
+			return all, nil
+		}
+	}
+}
+
 func normalizeOptionalID(value *string) *string {
 	if value == nil {
 		return nil
diff --git a/apps/backend/internal/task/service/service_resources_test.go b/apps/backend/internal/task/service/service_resources_test.go
index c77677b3e5..05dcc89ebd 100644
--- a/apps/backend/internal/task/service/service_resources_test.go
+++ b/apps/backend/internal/task/service/service_resources_test.go
@@ -129,6 +129,46 @@ func TestService_GetOfficeWorkflowIDs_DBError(t *testing.T) {
 	}
 }
 
+func TestService_DeleteWorkspaceDeletesWorkspaceOwnedTasksAndWorkflows(t *testing.T) {
+	svc, _, repo := createTestService(t)
+	ctx := context.Background()
+
+	_ = repo.CreateWorkspace(ctx, &models.Workspace{ID: "ws-delete", Name: "Delete Me"})
+	_ = repo.CreateWorkspace(ctx, &models.Workspace{ID: "ws-keep", Name: "Keep Me"})
+	_ = repo.CreateWorkflow(ctx, &models.Workflow{ID: "wf-delete", WorkspaceID: "ws-delete", Name: "Doomed"})
+	_ = repo.CreateWorkflow(ctx, &models.Workflow{ID: "wf-keep", WorkspaceID: "ws-keep", Name: "Keep"})
+	if err := repo.CreateTask(ctx, &models.Task{
+		ID:             "task-delete",
+		WorkspaceID:    "ws-delete",
+		WorkflowID:     "wf-delete",
+		WorkflowStepID: "step-delete",
+		Title:          "Delete task",
+	}); err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+
+	if err := svc.DeleteWorkspace(ctx, "ws-delete"); err != nil {
+		t.Fatalf("DeleteWorkspace: %v", err)
+	}
+
+	if _, err := repo.GetWorkspace(ctx, "ws-delete"); err == nil {
+		t.Fatalf("workspace should be deleted")
+	}
+	if _, err := repo.GetTask(ctx, "task-delete"); err == nil {
+		t.Fatalf("workspace task should be deleted")
+	}
+	workflows, err := repo.ListWorkflows(ctx, "ws-delete", true)
+	if err != nil {
+		t.Fatalf("ListWorkflows: %v", err)
+	}
+	if len(workflows) != 0 {
+		t.Fatalf("workspace workflows should be deleted, got %d", len(workflows))
+	}
+	if _, err := repo.GetWorkflow(ctx, "wf-keep"); err != nil {
+		t.Fatalf("unrelated workflow should remain: %v", err)
+	}
+}
+
 // TestService_DeleteWorkflow_ArchivesChildTasks verifies the cascade fix for
 // issue #1279: workflow deletion archives any active child tasks instead of
 // leaving them with a dangling workflow_id (tasks.workflow_id has no FK, so
diff --git a/apps/web/app/actions/workspaces.test.ts b/apps/web/app/actions/workspaces.test.ts
index b7600ea782..3d6fb5287c 100644
--- a/apps/web/app/actions/workspaces.test.ts
+++ b/apps/web/app/actions/workspaces.test.ts
@@ -63,7 +63,7 @@ describe("deleteWorkspaceAction", () => {
     expect(fetchMock).toHaveBeenCalledTimes(1);
 
     const [url, init] = fetchMock.mock.calls[0];
-    expect(url).toBe("http://backend.test/api/v1/office/workspaces/ws-1");
+    expect(url).toBe("http://backend.test/api/v1/workspaces/ws-1");
     expect(init.method).toBe("DELETE");
     expect(JSON.parse(init.body as string)).toEqual({ confirm_name: "My Workspace" });
   });
diff --git a/apps/web/app/actions/workspaces.ts b/apps/web/app/actions/workspaces.ts
index 46790af4c1..fc3563dbc1 100644
--- a/apps/web/app/actions/workspaces.ts
+++ b/apps/web/app/actions/workspaces.ts
@@ -97,7 +97,7 @@ export async function updateWorkspaceAction(
 }
 
 export async function deleteWorkspaceAction(id: string, confirmName: string) {
-  await fetchJson<void>(`${apiBaseUrl}/api/v1/office/workspaces/${id}`, {
+  await fetchJson<void>(`${apiBaseUrl}/api/v1/workspaces/${id}`, {
     method: "DELETE",
     body: JSON.stringify({ confirm_name: confirmName }),
   });