diff --git a/apps/web/src/api/assets.ts b/apps/web/src/api/assets.ts
index 56a20468d..b95c736fb 100644
--- a/apps/web/src/api/assets.ts
+++ b/apps/web/src/api/assets.ts
@@ -3,6 +3,7 @@
  * Phase 1 重构：去掉 project_id，素材直接归属用户
  */
 import apiClient from './client';
+import { getOrCreateDefaultProject } from './projects';
 
 /** 素材条目 */
 export interface AssetItem {
@@ -93,12 +94,17 @@ export const getAssetLibraries = async (): Promise<AssetLibraryItem[]> => {
   return response.data.items || [];
 };
 
-/** 创建素材库 */
+/** 创建素材库（自动获取或创建默认项目以提供 project_id） */
 export const createAssetLibrary = async (data: {
   name: string;
   kind: 'video' | 'voice' | 'image';
 }): Promise<AssetLibraryItem> => {
-  const response = await apiClient.post('/asset-libraries', data);
+  // 后端要求 project_id，前端自动管理默认项目
+  const project = await getOrCreateDefaultProject();
+  const response = await apiClient.post('/asset-libraries', {
+    project_id: project.id,
+    ...data,
+  });
   return response.data;
 };
 
diff --git a/apps/web/src/api/projects.ts b/apps/web/src/api/projects.ts
new file mode 100644
index 000000000..fb3d73bb1
--- /dev/null
+++ b/apps/web/src/api/projects.ts
@@ -0,0 +1,60 @@
+/**
+ * 项目相关 API
+ * 素材库需要 project_id，前端自动管理默认项目
+ */
+import apiClient from './client';
+
+export interface ProjectItem {
+  id: string;
+  name: string;
+  description: string;
+}
+
+/** 后端 ProjectResponse 只返回 id, name, description */
+interface BackendProjectResponse {
+  id: string;
+  name: string;
+  description: string;
+}
+
+/** 后端 ListProjectsResponse 返回 { items: [...] } */
+interface BackendListProjectsResponse {
+  items: BackendProjectResponse[];
+}
+
+const toProjectItem = (item: BackendProjectResponse): ProjectItem => ({
+  id: item.id,
+  name: item.name,
+  description: item.description,
+});
+
+/** 获取当前用户的项目列表 */
+export const getProjects = async (): Promise<ProjectItem[]> => {
+  const response = await apiClient.get<BackendListProjectsResponse>('/projects');
+  return (response.data.items || []).map(toProjectItem);
+};
+
+/** 创建项目 */
+export const createProject = async (data: {
+  name: string;
+  description?: string;
+}): Promise<ProjectItem> => {
+  const response = await apiClient.post<BackendProjectResponse>('/projects', {
+    name: data.name,
+    description: data.description || '',
+  });
+  return toProjectItem(response.data);
+};
+
+/** 获取或创建默认项目（素材库需要 project_id） */
+export const getOrCreateDefaultProject = async (): Promise<ProjectItem> => {
+  const projects = await getProjects();
+  if (projects.length > 0) {
+    return projects[0];
+  }
+  // 没有项目时自动创建默认项目
+  return createProject({
+    name: '默认项目',
+    description: '系统自动创建的默认项目',
+  });
+};