feat(api): add break-glass local authentication module

Implement LocalAuth module for emergency access without OIDC.
Endpoints: POST /api/auth/local/setup (first-time user creation with
BREAKGLASS_SETUP_TOKEN), POST /api/auth/local/login (email + password).
Both return 404 when ENABLE_LOCAL_AUTH != true. Uses bcrypt (12 rounds)
for password hashing and creates BetterAuth-compatible sessions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.mosaic/orchestrator/mission.json

@@ -65,5 +65,16 @@
       "completed_at": ""
     }
   ],
-  "sessions": []
+  "sessions": [
+    {
+      "session_id": "sess-001",
+      "runtime": "unknown",
+      "started_at": "2026-02-28T17:48:51Z",
+      "ended_at": "",
+      "ended_reason": "",
+      "milestone_at_end": "",
+      "tasks_completed": [],
+      "last_task_id": ""
+    }
+  ]
 }

.mosaic/orchestrator/session.lock

@@ -0,0 +1,8 @@
+{
+  "session_id": "sess-001",
+  "runtime": "unknown",
+  "pid": 2396592,
+  "started_at": "2026-02-28T17:48:51Z",
+  "project_path": "/tmp/ms21-api-003",
+  "milestone_id": ""
+}

apps/api/src/admin/admin.controller.spec.ts

@@ -0,0 +1,258 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { Test, TestingModule } from "@nestjs/testing";
+import { AdminController } from "./admin.controller";
+import { AdminService } from "./admin.service";
+import { AuthGuard } from "../auth/guards/auth.guard";
+import { AdminGuard } from "../auth/guards/admin.guard";
+import { WorkspaceMemberRole } from "@prisma/client";
+import type { ExecutionContext } from "@nestjs/common";
+
+describe("AdminController", () => {
+  let controller: AdminController;
+  let service: AdminService;
+
+  const mockAdminService = {
+    listUsers: vi.fn(),
+    inviteUser: vi.fn(),
+    updateUser: vi.fn(),
+    deactivateUser: vi.fn(),
+    createWorkspace: vi.fn(),
+    updateWorkspace: vi.fn(),
+  };
+
+  const mockAuthGuard = {
+    canActivate: vi.fn((context: ExecutionContext) => {
+      const request = context.switchToHttp().getRequest();
+      request.user = {
+        id: "550e8400-e29b-41d4-a716-446655440001",
+        email: "admin@example.com",
+        name: "Admin User",
+      };
+      return true;
+    }),
+  };
+
+  const mockAdminGuard = {
+    canActivate: vi.fn(() => true),
+  };
+
+  const mockAdminId = "550e8400-e29b-41d4-a716-446655440001";
+  const mockUserId = "550e8400-e29b-41d4-a716-446655440002";
+  const mockWorkspaceId = "550e8400-e29b-41d4-a716-446655440003";
+
+  const mockAdminUser = {
+    id: mockAdminId,
+    email: "admin@example.com",
+    name: "Admin User",
+  };
+
+  const mockUserResponse = {
+    id: mockUserId,
+    name: "Test User",
+    email: "test@example.com",
+    emailVerified: false,
+    image: null,
+    createdAt: new Date("2026-01-01"),
+    deactivatedAt: null,
+    isLocalAuth: false,
+    invitedAt: null,
+    invitedBy: null,
+    workspaceMemberships: [],
+  };
+
+  const mockWorkspaceResponse = {
+    id: mockWorkspaceId,
+    name: "Test Workspace",
+    ownerId: mockAdminId,
+    settings: {},
+    createdAt: new Date("2026-01-01"),
+    updatedAt: new Date("2026-01-01"),
+    memberCount: 1,
+  };
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      controllers: [AdminController],
+      providers: [
+        {
+          provide: AdminService,
+          useValue: mockAdminService,
+        },
+      ],
+    })
+      .overrideGuard(AuthGuard)
+      .useValue(mockAuthGuard)
+      .overrideGuard(AdminGuard)
+      .useValue(mockAdminGuard)
+      .compile();
+
+    controller = module.get<AdminController>(AdminController);
+    service = module.get<AdminService>(AdminService);
+
+    vi.clearAllMocks();
+  });
+
+  it("should be defined", () => {
+    expect(controller).toBeDefined();
+  });
+
+  describe("listUsers", () => {
+    it("should return paginated users", async () => {
+      const paginatedResult = {
+        data: [mockUserResponse],
+        meta: { total: 1, page: 1, limit: 50, totalPages: 1 },
+      };
+      mockAdminService.listUsers.mockResolvedValue(paginatedResult);
+
+      const result = await controller.listUsers({ page: 1, limit: 50 });
+
+      expect(result).toEqual(paginatedResult);
+      expect(service.listUsers).toHaveBeenCalledWith(1, 50);
+    });
+
+    it("should use default pagination", async () => {
+      const paginatedResult = {
+        data: [],
+        meta: { total: 0, page: 1, limit: 50, totalPages: 0 },
+      };
+      mockAdminService.listUsers.mockResolvedValue(paginatedResult);
+
+      await controller.listUsers({});
+
+      expect(service.listUsers).toHaveBeenCalledWith(undefined, undefined);
+    });
+  });
+
+  describe("inviteUser", () => {
+    it("should invite a user", async () => {
+      const inviteDto = { email: "new@example.com" };
+      const invitationResponse = {
+        userId: "new-id",
+        invitationToken: "token",
+        email: "new@example.com",
+        invitedAt: new Date(),
+      };
+      mockAdminService.inviteUser.mockResolvedValue(invitationResponse);
+
+      const result = await controller.inviteUser(inviteDto, mockAdminUser);
+
+      expect(result).toEqual(invitationResponse);
+      expect(service.inviteUser).toHaveBeenCalledWith(inviteDto, mockAdminId);
+    });
+
+    it("should invite a user with workspace and role", async () => {
+      const inviteDto = {
+        email: "new@example.com",
+        workspaceId: mockWorkspaceId,
+        role: WorkspaceMemberRole.ADMIN,
+      };
+      mockAdminService.inviteUser.mockResolvedValue({
+        userId: "new-id",
+        invitationToken: "token",
+        email: "new@example.com",
+        invitedAt: new Date(),
+      });
+
+      await controller.inviteUser(inviteDto, mockAdminUser);
+
+      expect(service.inviteUser).toHaveBeenCalledWith(inviteDto, mockAdminId);
+    });
+  });
+
+  describe("updateUser", () => {
+    it("should update a user", async () => {
+      const updateDto = { name: "Updated Name" };
+      mockAdminService.updateUser.mockResolvedValue({
+        ...mockUserResponse,
+        name: "Updated Name",
+      });
+
+      const result = await controller.updateUser(mockUserId, updateDto);
+
+      expect(result.name).toBe("Updated Name");
+      expect(service.updateUser).toHaveBeenCalledWith(mockUserId, updateDto);
+    });
+
+    it("should deactivate a user via update", async () => {
+      const deactivatedAt = "2026-02-28T00:00:00.000Z";
+      const updateDto = { deactivatedAt };
+      mockAdminService.updateUser.mockResolvedValue({
+        ...mockUserResponse,
+        deactivatedAt: new Date(deactivatedAt),
+      });
+
+      const result = await controller.updateUser(mockUserId, updateDto);
+
+      expect(result.deactivatedAt).toEqual(new Date(deactivatedAt));
+    });
+  });
+
+  describe("deactivateUser", () => {
+    it("should soft-delete a user", async () => {
+      mockAdminService.deactivateUser.mockResolvedValue({
+        ...mockUserResponse,
+        deactivatedAt: new Date(),
+      });
+
+      const result = await controller.deactivateUser(mockUserId);
+
+      expect(result.deactivatedAt).toBeDefined();
+      expect(service.deactivateUser).toHaveBeenCalledWith(mockUserId);
+    });
+  });
+
+  describe("createWorkspace", () => {
+    it("should create a workspace", async () => {
+      const createDto = { name: "New Workspace", ownerId: mockAdminId };
+      mockAdminService.createWorkspace.mockResolvedValue(mockWorkspaceResponse);
+
+      const result = await controller.createWorkspace(createDto);
+
+      expect(result).toEqual(mockWorkspaceResponse);
+      expect(service.createWorkspace).toHaveBeenCalledWith(createDto);
+    });
+
+    it("should create workspace with settings", async () => {
+      const createDto = {
+        name: "New Workspace",
+        ownerId: mockAdminId,
+        settings: { feature: true },
+      };
+      mockAdminService.createWorkspace.mockResolvedValue({
+        ...mockWorkspaceResponse,
+        settings: { feature: true },
+      });
+
+      const result = await controller.createWorkspace(createDto);
+
+      expect(result.settings).toEqual({ feature: true });
+    });
+  });
+
+  describe("updateWorkspace", () => {
+    it("should update a workspace", async () => {
+      const updateDto = { name: "Updated Workspace" };
+      mockAdminService.updateWorkspace.mockResolvedValue({
+        ...mockWorkspaceResponse,
+        name: "Updated Workspace",
+      });
+
+      const result = await controller.updateWorkspace(mockWorkspaceId, updateDto);
+
+      expect(result.name).toBe("Updated Workspace");
+      expect(service.updateWorkspace).toHaveBeenCalledWith(mockWorkspaceId, updateDto);
+    });
+
+    it("should update workspace settings", async () => {
+      const updateDto = { settings: { notifications: false } };
+      mockAdminService.updateWorkspace.mockResolvedValue({
+        ...mockWorkspaceResponse,
+        settings: { notifications: false },
+      });
+
+      const result = await controller.updateWorkspace(mockWorkspaceId, updateDto);
+
+      expect(result.settings).toEqual({ notifications: false });
+    });
+  });
+});

apps/api/src/admin/admin.controller.ts

@@ -0,0 +1,64 @@
+import {
+  Controller,
+  Get,
+  Post,
+  Patch,
+  Delete,
+  Body,
+  Param,
+  Query,
+  UseGuards,
+  ParseUUIDPipe,
+} from "@nestjs/common";
+import { AdminService } from "./admin.service";
+import { AuthGuard } from "../auth/guards/auth.guard";
+import { AdminGuard } from "../auth/guards/admin.guard";
+import { CurrentUser } from "../auth/decorators/current-user.decorator";
+import type { AuthUser } from "@mosaic/shared";
+import { InviteUserDto } from "./dto/invite-user.dto";
+import { UpdateUserDto } from "./dto/update-user.dto";
+import { CreateWorkspaceDto } from "./dto/create-workspace.dto";
+import { UpdateWorkspaceDto } from "./dto/update-workspace.dto";
+import { QueryUsersDto } from "./dto/query-users.dto";
+
+@Controller("admin")
+@UseGuards(AuthGuard, AdminGuard)
+export class AdminController {
+  constructor(private readonly adminService: AdminService) {}
+
+  @Get("users")
+  async listUsers(@Query() query: QueryUsersDto) {
+    return this.adminService.listUsers(query.page, query.limit);
+  }
+
+  @Post("users/invite")
+  async inviteUser(@Body() dto: InviteUserDto, @CurrentUser() user: AuthUser) {
+    return this.adminService.inviteUser(dto, user.id);
+  }
+
+  @Patch("users/:id")
+  async updateUser(
+    @Param("id", new ParseUUIDPipe({ version: "4" })) id: string,
+    @Body() dto: UpdateUserDto
+  ) {
+    return this.adminService.updateUser(id, dto);
+  }
+
+  @Delete("users/:id")
+  async deactivateUser(@Param("id", new ParseUUIDPipe({ version: "4" })) id: string) {
+    return this.adminService.deactivateUser(id);
+  }
+
+  @Post("workspaces")
+  async createWorkspace(@Body() dto: CreateWorkspaceDto) {
+    return this.adminService.createWorkspace(dto);
+  }
+
+  @Patch("workspaces/:id")
+  async updateWorkspace(
+    @Param("id", new ParseUUIDPipe({ version: "4" })) id: string,
+    @Body() dto: UpdateWorkspaceDto
+  ) {
+    return this.adminService.updateWorkspace(id, dto);
+  }
+}

apps/api/src/admin/admin.module.ts

@@ -0,0 +1,13 @@
+import { Module } from "@nestjs/common";
+import { AdminController } from "./admin.controller";
+import { AdminService } from "./admin.service";
+import { PrismaModule } from "../prisma/prisma.module";
+import { AuthModule } from "../auth/auth.module";
+
+@Module({
+  imports: [PrismaModule, AuthModule],
+  controllers: [AdminController],
+  providers: [AdminService],
+  exports: [AdminService],
+})
+export class AdminModule {}

apps/api/src/admin/admin.service.spec.ts

@@ -0,0 +1,471 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { Test, TestingModule } from "@nestjs/testing";
+import { AdminService } from "./admin.service";
+import { PrismaService } from "../prisma/prisma.service";
+import { BadRequestException, ConflictException, NotFoundException } from "@nestjs/common";
+import { WorkspaceMemberRole } from "@prisma/client";
+
+describe("AdminService", () => {
+  let service: AdminService;
+
+  const mockPrismaService = {
+    user: {
+      findMany: vi.fn(),
+      findUnique: vi.fn(),
+      count: vi.fn(),
+      create: vi.fn(),
+      update: vi.fn(),
+    },
+    workspace: {
+      findUnique: vi.fn(),
+      create: vi.fn(),
+      update: vi.fn(),
+    },
+    workspaceMember: {
+      create: vi.fn(),
+    },
+    $transaction: vi.fn(),
+  };
+
+  const mockAdminId = "550e8400-e29b-41d4-a716-446655440001";
+  const mockUserId = "550e8400-e29b-41d4-a716-446655440002";
+  const mockWorkspaceId = "550e8400-e29b-41d4-a716-446655440003";
+
+  const mockUser = {
+    id: mockUserId,
+    name: "Test User",
+    email: "test@example.com",
+    emailVerified: false,
+    image: null,
+    createdAt: new Date("2026-01-01"),
+    updatedAt: new Date("2026-01-01"),
+    deactivatedAt: null,
+    isLocalAuth: false,
+    passwordHash: null,
+    invitedBy: null,
+    invitationToken: null,
+    invitedAt: null,
+    authProviderId: null,
+    preferences: {},
+    workspaceMemberships: [
+      {
+        workspaceId: mockWorkspaceId,
+        userId: mockUserId,
+        role: WorkspaceMemberRole.MEMBER,
+        joinedAt: new Date("2026-01-01"),
+        workspace: { id: mockWorkspaceId, name: "Test Workspace" },
+      },
+    ],
+  };
+
+  const mockWorkspace = {
+    id: mockWorkspaceId,
+    name: "Test Workspace",
+    ownerId: mockAdminId,
+    settings: {},
+    createdAt: new Date("2026-01-01"),
+    updatedAt: new Date("2026-01-01"),
+    matrixRoomId: null,
+  };
+
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [
+        AdminService,
+        {
+          provide: PrismaService,
+          useValue: mockPrismaService,
+        },
+      ],
+    }).compile();
+
+    service = module.get<AdminService>(AdminService);
+
+    vi.clearAllMocks();
+
+    mockPrismaService.$transaction.mockImplementation(async (fn: (tx: unknown) => unknown) => {
+      return fn(mockPrismaService);
+    });
+  });
+
+  it("should be defined", () => {
+    expect(service).toBeDefined();
+  });
+
+  describe("listUsers", () => {
+    it("should return paginated users with memberships", async () => {
+      mockPrismaService.user.findMany.mockResolvedValue([mockUser]);
+      mockPrismaService.user.count.mockResolvedValue(1);
+
+      const result = await service.listUsers(1, 50);
+
+      expect(result.data).toHaveLength(1);
+      expect(result.data[0]?.id).toBe(mockUserId);
+      expect(result.data[0]?.workspaceMemberships).toHaveLength(1);
+      expect(result.meta).toEqual({
+        total: 1,
+        page: 1,
+        limit: 50,
+        totalPages: 1,
+      });
+    });
+
+    it("should use default pagination when not provided", async () => {
+      mockPrismaService.user.findMany.mockResolvedValue([]);
+      mockPrismaService.user.count.mockResolvedValue(0);
+
+      await service.listUsers();
+
+      expect(mockPrismaService.user.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          skip: 0,
+          take: 50,
+        })
+      );
+    });
+
+    it("should calculate pagination correctly", async () => {
+      mockPrismaService.user.findMany.mockResolvedValue([]);
+      mockPrismaService.user.count.mockResolvedValue(150);
+
+      const result = await service.listUsers(3, 25);
+
+      expect(mockPrismaService.user.findMany).toHaveBeenCalledWith(
+        expect.objectContaining({
+          skip: 50,
+          take: 25,
+        })
+      );
+      expect(result.meta.totalPages).toBe(6);
+    });
+  });
+
+  describe("inviteUser", () => {
+    it("should create a user with invitation token", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+      const createdUser = {
+        id: "new-user-id",
+        email: "new@example.com",
+        name: "new",
+        invitationToken: "some-token",
+      };
+      mockPrismaService.user.create.mockResolvedValue(createdUser);
+
+      const result = await service.inviteUser({ email: "new@example.com" }, mockAdminId);
+
+      expect(result.email).toBe("new@example.com");
+      expect(result.invitationToken).toBeDefined();
+      expect(result.userId).toBe("new-user-id");
+      expect(mockPrismaService.user.create).toHaveBeenCalledWith(
+        expect.objectContaining({
+          data: expect.objectContaining({
+            email: "new@example.com",
+            invitedBy: mockAdminId,
+            invitationToken: expect.any(String),
+          }),
+        })
+      );
+    });
+
+    it("should add user to workspace when workspaceId provided", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+      mockPrismaService.workspace.findUnique.mockResolvedValue(mockWorkspace);
+      const createdUser = { id: "new-user-id", email: "new@example.com", name: "new" };
+      mockPrismaService.user.create.mockResolvedValue(createdUser);
+
+      await service.inviteUser(
+        {
+          email: "new@example.com",
+          workspaceId: mockWorkspaceId,
+          role: WorkspaceMemberRole.ADMIN,
+        },
+        mockAdminId
+      );
+
+      expect(mockPrismaService.workspaceMember.create).toHaveBeenCalledWith({
+        data: {
+          workspaceId: mockWorkspaceId,
+          userId: "new-user-id",
+          role: WorkspaceMemberRole.ADMIN,
+        },
+      });
+    });
+
+    it("should throw ConflictException if email already exists", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+
+      await expect(service.inviteUser({ email: "test@example.com" }, mockAdminId)).rejects.toThrow(
+        ConflictException
+      );
+    });
+
+    it("should throw NotFoundException if workspace does not exist", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+      mockPrismaService.workspace.findUnique.mockResolvedValue(null);
+
+      await expect(
+        service.inviteUser({ email: "new@example.com", workspaceId: "non-existent" }, mockAdminId)
+      ).rejects.toThrow(NotFoundException);
+    });
+
+    it("should use email prefix as default name", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+      const createdUser = { id: "new-user-id", email: "jane.doe@example.com", name: "jane.doe" };
+      mockPrismaService.user.create.mockResolvedValue(createdUser);
+
+      await service.inviteUser({ email: "jane.doe@example.com" }, mockAdminId);
+
+      expect(mockPrismaService.user.create).toHaveBeenCalledWith(
+        expect.objectContaining({
+          data: expect.objectContaining({
+            name: "jane.doe",
+          }),
+        })
+      );
+    });
+
+    it("should use provided name when given", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+      const createdUser = { id: "new-user-id", email: "j@example.com", name: "Jane Doe" };
+      mockPrismaService.user.create.mockResolvedValue(createdUser);
+
+      await service.inviteUser({ email: "j@example.com", name: "Jane Doe" }, mockAdminId);
+
+      expect(mockPrismaService.user.create).toHaveBeenCalledWith(
+        expect.objectContaining({
+          data: expect.objectContaining({
+            name: "Jane Doe",
+          }),
+        })
+      );
+    });
+  });
+
+  describe("updateUser", () => {
+    it("should update user fields", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.user.update.mockResolvedValue({
+        ...mockUser,
+        name: "Updated Name",
+      });
+
+      const result = await service.updateUser(mockUserId, { name: "Updated Name" });
+
+      expect(result.name).toBe("Updated Name");
+      expect(mockPrismaService.user.update).toHaveBeenCalledWith(
+        expect.objectContaining({
+          where: { id: mockUserId },
+          data: { name: "Updated Name" },
+        })
+      );
+    });
+
+    it("should set deactivatedAt when provided", async () => {
+      const deactivatedAt = "2026-02-28T00:00:00.000Z";
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.user.update.mockResolvedValue({
+        ...mockUser,
+        deactivatedAt: new Date(deactivatedAt),
+      });
+
+      const result = await service.updateUser(mockUserId, { deactivatedAt });
+
+      expect(result.deactivatedAt).toEqual(new Date(deactivatedAt));
+    });
+
+    it("should clear deactivatedAt when set to null", async () => {
+      const deactivatedUser = { ...mockUser, deactivatedAt: new Date() };
+      mockPrismaService.user.findUnique.mockResolvedValue(deactivatedUser);
+      mockPrismaService.user.update.mockResolvedValue({
+        ...deactivatedUser,
+        deactivatedAt: null,
+      });
+
+      const result = await service.updateUser(mockUserId, { deactivatedAt: null });
+
+      expect(result.deactivatedAt).toBeNull();
+    });
+
+    it("should throw NotFoundException if user does not exist", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+
+      await expect(service.updateUser("non-existent", { name: "Test" })).rejects.toThrow(
+        NotFoundException
+      );
+    });
+
+    it("should update emailVerified", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.user.update.mockResolvedValue({
+        ...mockUser,
+        emailVerified: true,
+      });
+
+      const result = await service.updateUser(mockUserId, { emailVerified: true });
+
+      expect(result.emailVerified).toBe(true);
+    });
+
+    it("should update preferences", async () => {
+      const prefs = { theme: "dark" };
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.user.update.mockResolvedValue({
+        ...mockUser,
+        preferences: prefs,
+      });
+
+      await service.updateUser(mockUserId, { preferences: prefs });
+
+      expect(mockPrismaService.user.update).toHaveBeenCalledWith(
+        expect.objectContaining({
+          data: expect.objectContaining({ preferences: prefs }),
+        })
+      );
+    });
+  });
+
+  describe("deactivateUser", () => {
+    it("should set deactivatedAt on the user", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.user.update.mockResolvedValue({
+        ...mockUser,
+        deactivatedAt: new Date(),
+      });
+
+      const result = await service.deactivateUser(mockUserId);
+
+      expect(result.deactivatedAt).toBeDefined();
+      expect(mockPrismaService.user.update).toHaveBeenCalledWith(
+        expect.objectContaining({
+          where: { id: mockUserId },
+          data: { deactivatedAt: expect.any(Date) },
+        })
+      );
+    });
+
+    it("should throw NotFoundException if user does not exist", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+
+      await expect(service.deactivateUser("non-existent")).rejects.toThrow(NotFoundException);
+    });
+
+    it("should throw BadRequestException if user is already deactivated", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue({
+        ...mockUser,
+        deactivatedAt: new Date(),
+      });
+
+      await expect(service.deactivateUser(mockUserId)).rejects.toThrow(BadRequestException);
+    });
+  });
+
+  describe("createWorkspace", () => {
+    it("should create a workspace with owner membership", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.workspace.create.mockResolvedValue(mockWorkspace);
+
+      const result = await service.createWorkspace({
+        name: "New Workspace",
+        ownerId: mockAdminId,
+      });
+
+      expect(result.name).toBe("Test Workspace");
+      expect(result.memberCount).toBe(1);
+      expect(mockPrismaService.workspace.create).toHaveBeenCalled();
+      expect(mockPrismaService.workspaceMember.create).toHaveBeenCalledWith({
+        data: {
+          workspaceId: mockWorkspace.id,
+          userId: mockAdminId,
+          role: WorkspaceMemberRole.OWNER,
+        },
+      });
+    });
+
+    it("should throw NotFoundException if owner does not exist", async () => {
+      mockPrismaService.user.findUnique.mockResolvedValue(null);
+
+      await expect(
+        service.createWorkspace({ name: "New Workspace", ownerId: "non-existent" })
+      ).rejects.toThrow(NotFoundException);
+    });
+
+    it("should pass settings when provided", async () => {
+      const settings = { theme: "dark", features: ["chat"] };
+      mockPrismaService.user.findUnique.mockResolvedValue(mockUser);
+      mockPrismaService.workspace.create.mockResolvedValue({
+        ...mockWorkspace,
+        settings,
+      });
+
+      await service.createWorkspace({
+        name: "New Workspace",
+        ownerId: mockAdminId,
+        settings,
+      });
+
+      expect(mockPrismaService.workspace.create).toHaveBeenCalledWith(
+        expect.objectContaining({
+          data: expect.objectContaining({ settings }),
+        })
+      );
+    });
+  });
+
+  describe("updateWorkspace", () => {
+    it("should update workspace name", async () => {
+      mockPrismaService.workspace.findUnique.mockResolvedValue(mockWorkspace);
+      mockPrismaService.workspace.update.mockResolvedValue({
+        ...mockWorkspace,
+        name: "Updated Workspace",
+        _count: { members: 3 },
+      });
+
+      const result = await service.updateWorkspace(mockWorkspaceId, {
+        name: "Updated Workspace",
+      });
+
+      expect(result.name).toBe("Updated Workspace");
+      expect(result.memberCount).toBe(3);
+    });
+
+    it("should update workspace settings", async () => {
+      const newSettings = { notifications: true };
+      mockPrismaService.workspace.findUnique.mockResolvedValue(mockWorkspace);
+      mockPrismaService.workspace.update.mockResolvedValue({
+        ...mockWorkspace,
+        settings: newSettings,
+        _count: { members: 1 },
+      });
+
+      const result = await service.updateWorkspace(mockWorkspaceId, {
+        settings: newSettings,
+      });
+
+      expect(result.settings).toEqual(newSettings);
+    });
+
+    it("should throw NotFoundException if workspace does not exist", async () => {
+      mockPrismaService.workspace.findUnique.mockResolvedValue(null);
+
+      await expect(service.updateWorkspace("non-existent", { name: "Test" })).rejects.toThrow(
+        NotFoundException
+      );
+    });
+
+    it("should only update provided fields", async () => {
+      mockPrismaService.workspace.findUnique.mockResolvedValue(mockWorkspace);
+      mockPrismaService.workspace.update.mockResolvedValue({
+        ...mockWorkspace,
+        _count: { members: 1 },
+      });
+
+      await service.updateWorkspace(mockWorkspaceId, { name: "Only Name" });
+
+      expect(mockPrismaService.workspace.update).toHaveBeenCalledWith(
+        expect.objectContaining({
+          data: { name: "Only Name" },
+        })
+      );
+    });
+  });
+});

apps/api/src/admin/admin.service.ts

@@ -0,0 +1,306 @@
+import {
+  BadRequestException,
+  ConflictException,
+  Injectable,
+  Logger,
+  NotFoundException,
+} from "@nestjs/common";
+import { Prisma, WorkspaceMemberRole } from "@prisma/client";
+import { randomUUID } from "node:crypto";
+import { PrismaService } from "../prisma/prisma.service";
+import type { InviteUserDto } from "./dto/invite-user.dto";
+import type { UpdateUserDto } from "./dto/update-user.dto";
+import type { CreateWorkspaceDto } from "./dto/create-workspace.dto";
+import type {
+  AdminUserResponse,
+  AdminWorkspaceResponse,
+  InvitationResponse,
+  PaginatedResponse,
+} from "./types/admin.types";
+
+@Injectable()
+export class AdminService {
+  private readonly logger = new Logger(AdminService.name);
+
+  constructor(private readonly prisma: PrismaService) {}
+
+  async listUsers(page = 1, limit = 50): Promise<PaginatedResponse<AdminUserResponse>> {
+    const skip = (page - 1) * limit;
+
+    const [users, total] = await Promise.all([
+      this.prisma.user.findMany({
+        include: {
+          workspaceMemberships: {
+            include: {
+              workspace: { select: { id: true, name: true } },
+            },
+          },
+        },
+        orderBy: { createdAt: "desc" },
+        skip,
+        take: limit,
+      }),
+      this.prisma.user.count(),
+    ]);
+
+    return {
+      data: users.map((user) => ({
+        id: user.id,
+        name: user.name,
+        email: user.email,
+        emailVerified: user.emailVerified,
+        image: user.image,
+        createdAt: user.createdAt,
+        deactivatedAt: user.deactivatedAt,
+        isLocalAuth: user.isLocalAuth,
+        invitedAt: user.invitedAt,
+        invitedBy: user.invitedBy,
+        workspaceMemberships: user.workspaceMemberships.map((m) => ({
+          workspaceId: m.workspaceId,
+          workspaceName: m.workspace.name,
+          role: m.role,
+          joinedAt: m.joinedAt,
+        })),
+      })),
+      meta: {
+        total,
+        page,
+        limit,
+        totalPages: Math.ceil(total / limit),
+      },
+    };
+  }
+
+  async inviteUser(dto: InviteUserDto, inviterId: string): Promise<InvitationResponse> {
+    const existing = await this.prisma.user.findUnique({
+      where: { email: dto.email },
+    });
+
+    if (existing) {
+      throw new ConflictException(`User with email ${dto.email} already exists`);
+    }
+
+    if (dto.workspaceId) {
+      const workspace = await this.prisma.workspace.findUnique({
+        where: { id: dto.workspaceId },
+      });
+      if (!workspace) {
+        throw new NotFoundException(`Workspace ${dto.workspaceId} not found`);
+      }
+    }
+
+    const invitationToken = randomUUID();
+    const now = new Date();
+
+    const user = await this.prisma.$transaction(async (tx) => {
+      const created = await tx.user.create({
+        data: {
+          email: dto.email,
+          name: dto.name ?? dto.email.split("@")[0] ?? dto.email,
+          emailVerified: false,
+          invitedBy: inviterId,
+          invitationToken,
+          invitedAt: now,
+        },
+      });
+
+      if (dto.workspaceId) {
+        await tx.workspaceMember.create({
+          data: {
+            workspaceId: dto.workspaceId,
+            userId: created.id,
+            role: dto.role ?? WorkspaceMemberRole.MEMBER,
+          },
+        });
+      }
+
+      return created;
+    });
+
+    this.logger.log(`User invited: ${user.email} by ${inviterId}`);
+
+    return {
+      userId: user.id,
+      invitationToken,
+      email: user.email,
+      invitedAt: now,
+    };
+  }
+
+  async updateUser(id: string, dto: UpdateUserDto): Promise<AdminUserResponse> {
+    const existing = await this.prisma.user.findUnique({ where: { id } });
+    if (!existing) {
+      throw new NotFoundException(`User ${id} not found`);
+    }
+
+    const data: Prisma.UserUpdateInput = {};
+
+    if (dto.name !== undefined) {
+      data.name = dto.name;
+    }
+    if (dto.emailVerified !== undefined) {
+      data.emailVerified = dto.emailVerified;
+    }
+    if (dto.preferences !== undefined) {
+      data.preferences = dto.preferences as Prisma.InputJsonValue;
+    }
+    if (dto.deactivatedAt !== undefined) {
+      data.deactivatedAt = dto.deactivatedAt ? new Date(dto.deactivatedAt) : null;
+    }
+
+    const user = await this.prisma.user.update({
+      where: { id },
+      data,
+      include: {
+        workspaceMemberships: {
+          include: {
+            workspace: { select: { id: true, name: true } },
+          },
+        },
+      },
+    });
+
+    this.logger.log(`User updated: ${id}`);
+
+    return {
+      id: user.id,
+      name: user.name,
+      email: user.email,
+      emailVerified: user.emailVerified,
+      image: user.image,
+      createdAt: user.createdAt,
+      deactivatedAt: user.deactivatedAt,
+      isLocalAuth: user.isLocalAuth,
+      invitedAt: user.invitedAt,
+      invitedBy: user.invitedBy,
+      workspaceMemberships: user.workspaceMemberships.map((m) => ({
+        workspaceId: m.workspaceId,
+        workspaceName: m.workspace.name,
+        role: m.role,
+        joinedAt: m.joinedAt,
+      })),
+    };
+  }
+
+  async deactivateUser(id: string): Promise<AdminUserResponse> {
+    const existing = await this.prisma.user.findUnique({ where: { id } });
+    if (!existing) {
+      throw new NotFoundException(`User ${id} not found`);
+    }
+
+    if (existing.deactivatedAt) {
+      throw new BadRequestException(`User ${id} is already deactivated`);
+    }
+
+    const user = await this.prisma.user.update({
+      where: { id },
+      data: { deactivatedAt: new Date() },
+      include: {
+        workspaceMemberships: {
+          include: {
+            workspace: { select: { id: true, name: true } },
+          },
+        },
+      },
+    });
+
+    this.logger.log(`User deactivated: ${id}`);
+
+    return {
+      id: user.id,
+      name: user.name,
+      email: user.email,
+      emailVerified: user.emailVerified,
+      image: user.image,
+      createdAt: user.createdAt,
+      deactivatedAt: user.deactivatedAt,
+      isLocalAuth: user.isLocalAuth,
+      invitedAt: user.invitedAt,
+      invitedBy: user.invitedBy,
+      workspaceMemberships: user.workspaceMemberships.map((m) => ({
+        workspaceId: m.workspaceId,
+        workspaceName: m.workspace.name,
+        role: m.role,
+        joinedAt: m.joinedAt,
+      })),
+    };
+  }
+
+  async createWorkspace(dto: CreateWorkspaceDto): Promise<AdminWorkspaceResponse> {
+    const owner = await this.prisma.user.findUnique({ where: { id: dto.ownerId } });
+    if (!owner) {
+      throw new NotFoundException(`User ${dto.ownerId} not found`);
+    }
+
+    const workspace = await this.prisma.$transaction(async (tx) => {
+      const created = await tx.workspace.create({
+        data: {
+          name: dto.name,
+          ownerId: dto.ownerId,
+          settings: dto.settings ? (dto.settings as Prisma.InputJsonValue) : {},
+        },
+      });
+
+      await tx.workspaceMember.create({
+        data: {
+          workspaceId: created.id,
+          userId: dto.ownerId,
+          role: WorkspaceMemberRole.OWNER,
+        },
+      });
+
+      return created;
+    });
+
+    this.logger.log(`Workspace created: ${workspace.id} with owner ${dto.ownerId}`);
+
+    return {
+      id: workspace.id,
+      name: workspace.name,
+      ownerId: workspace.ownerId,
+      settings: workspace.settings as Record<string, unknown>,
+      createdAt: workspace.createdAt,
+      updatedAt: workspace.updatedAt,
+      memberCount: 1,
+    };
+  }
+
+  async updateWorkspace(
+    id: string,
+    dto: { name?: string; settings?: Record<string, unknown> }
+  ): Promise<AdminWorkspaceResponse> {
+    const existing = await this.prisma.workspace.findUnique({ where: { id } });
+    if (!existing) {
+      throw new NotFoundException(`Workspace ${id} not found`);
+    }
+
+    const data: Prisma.WorkspaceUpdateInput = {};
+
+    if (dto.name !== undefined) {
+      data.name = dto.name;
+    }
+    if (dto.settings !== undefined) {
+      data.settings = dto.settings as Prisma.InputJsonValue;
+    }
+
+    const workspace = await this.prisma.workspace.update({
+      where: { id },
+      data,
+      include: {
+        _count: { select: { members: true } },
+      },
+    });
+
+    this.logger.log(`Workspace updated: ${id}`);
+
+    return {
+      id: workspace.id,
+      name: workspace.name,
+      ownerId: workspace.ownerId,
+      settings: workspace.settings as Record<string, unknown>,
+      createdAt: workspace.createdAt,
+      updatedAt: workspace.updatedAt,
+      memberCount: workspace._count.members,
+    };
+  }
+}

apps/api/src/admin/dto/create-workspace.dto.ts

@@ -0,0 +1,15 @@
+import { IsObject, IsOptional, IsString, IsUUID, MaxLength, MinLength } from "class-validator";
+
+export class CreateWorkspaceDto {
+  @IsString({ message: "name must be a string" })
+  @MinLength(1, { message: "name must not be empty" })
+  @MaxLength(255, { message: "name must not exceed 255 characters" })
+  name!: string;
+
+  @IsUUID("4", { message: "ownerId must be a valid UUID" })
+  ownerId!: string;
+
+  @IsOptional()
+  @IsObject({ message: "settings must be an object" })
+  settings?: Record<string, unknown>;
+}

apps/api/src/admin/dto/invite-user.dto.ts

@@ -0,0 +1,20 @@
+import { WorkspaceMemberRole } from "@prisma/client";
+import { IsEmail, IsEnum, IsOptional, IsString, IsUUID, MaxLength } from "class-validator";
+
+export class InviteUserDto {
+  @IsEmail({}, { message: "email must be a valid email address" })
+  email!: string;
+
+  @IsOptional()
+  @IsString({ message: "name must be a string" })
+  @MaxLength(255, { message: "name must not exceed 255 characters" })
+  name?: string;
+
+  @IsOptional()
+  @IsUUID("4", { message: "workspaceId must be a valid UUID" })
+  workspaceId?: string;
+
+  @IsOptional()
+  @IsEnum(WorkspaceMemberRole, { message: "role must be a valid WorkspaceMemberRole" })
+  role?: WorkspaceMemberRole;
+}

apps/api/src/admin/dto/manage-member.dto.ts

@@ -0,0 +1,15 @@
+import { WorkspaceMemberRole } from "@prisma/client";
+import { IsEnum, IsUUID } from "class-validator";
+
+export class AddMemberDto {
+  @IsUUID("4", { message: "userId must be a valid UUID" })
+  userId!: string;
+
+  @IsEnum(WorkspaceMemberRole, { message: "role must be a valid WorkspaceMemberRole" })
+  role!: WorkspaceMemberRole;
+}
+
+export class UpdateMemberRoleDto {
+  @IsEnum(WorkspaceMemberRole, { message: "role must be a valid WorkspaceMemberRole" })
+  role!: WorkspaceMemberRole;
+}

apps/api/src/admin/dto/query-users.dto.ts

@@ -0,0 +1,17 @@
+import { IsInt, IsOptional, Max, Min } from "class-validator";
+import { Type } from "class-transformer";
+
+export class QueryUsersDto {
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "page must be an integer" })
+  @Min(1, { message: "page must be at least 1" })
+  page?: number;
+
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt({ message: "limit must be an integer" })
+  @Min(1, { message: "limit must be at least 1" })
+  @Max(100, { message: "limit must not exceed 100" })
+  limit?: number;
+}

apps/api/src/admin/dto/update-user.dto.ts

@@ -0,0 +1,27 @@
+import {
+  IsBoolean,
+  IsDateString,
+  IsObject,
+  IsOptional,
+  IsString,
+  MaxLength,
+} from "class-validator";
+
+export class UpdateUserDto {
+  @IsOptional()
+  @IsString({ message: "name must be a string" })
+  @MaxLength(255, { message: "name must not exceed 255 characters" })
+  name?: string;
+
+  @IsOptional()
+  @IsDateString({}, { message: "deactivatedAt must be a valid ISO 8601 date string" })
+  deactivatedAt?: string | null;
+
+  @IsOptional()
+  @IsBoolean({ message: "emailVerified must be a boolean" })
+  emailVerified?: boolean;
+
+  @IsOptional()
+  @IsObject({ message: "preferences must be an object" })
+  preferences?: Record<string, unknown>;
+}

apps/api/src/admin/dto/update-workspace.dto.ts

@@ -0,0 +1,13 @@
+import { IsObject, IsOptional, IsString, MaxLength, MinLength } from "class-validator";
+
+export class UpdateWorkspaceDto {
+  @IsOptional()
+  @IsString({ message: "name must be a string" })
+  @MinLength(1, { message: "name must not be empty" })
+  @MaxLength(255, { message: "name must not exceed 255 characters" })
+  name?: string;
+
+  @IsOptional()
+  @IsObject({ message: "settings must be an object" })
+  settings?: Record<string, unknown>;
+}

apps/api/src/admin/types/admin.types.ts

@@ -0,0 +1,49 @@
+import type { WorkspaceMemberRole } from "@prisma/client";
+
+export interface AdminUserResponse {
+  id: string;
+  name: string;
+  email: string;
+  emailVerified: boolean;
+  image: string | null;
+  createdAt: Date;
+  deactivatedAt: Date | null;
+  isLocalAuth: boolean;
+  invitedAt: Date | null;
+  invitedBy: string | null;
+  workspaceMemberships: WorkspaceMembershipResponse[];
+}
+
+export interface WorkspaceMembershipResponse {
+  workspaceId: string;
+  workspaceName: string;
+  role: WorkspaceMemberRole;
+  joinedAt: Date;
+}
+
+export interface PaginatedResponse<T> {
+  data: T[];
+  meta: {
+    total: number;
+    page: number;
+    limit: number;
+    totalPages: number;
+  };
+}
+
+export interface InvitationResponse {
+  userId: string;
+  invitationToken: string;
+  email: string;
+  invitedAt: Date;
+}
+
+export interface AdminWorkspaceResponse {
+  id: string;
+  name: string;
+  ownerId: string;
+  settings: Record<string, unknown>;
+  createdAt: Date;
+  updatedAt: Date;
+  memberCount: number;
+}

apps/api/src/app.module.ts

@@ -43,6 +43,7 @@ import { DashboardModule } from "./dashboard/dashboard.module";
 import { TerminalModule } from "./terminal/terminal.module";
 import { PersonalitiesModule } from "./personalities/personalities.module";
 import { WorkspacesModule } from "./workspaces/workspaces.module";
+import { AdminModule } from "./admin/admin.module";
 import { RlsContextInterceptor } from "./common/interceptors/rls-context.interceptor";
 
 @Module({
@@ -109,6 +110,7 @@ import { RlsContextInterceptor } from "./common/interceptors/rls-context.interce
     TerminalModule,
     PersonalitiesModule,
     WorkspacesModule,
+    AdminModule,
   ],
   controllers: [AppController, CsrfController],
   providers: [

apps/api/src/workspaces/dto/add-member.dto.ts

@@ -0,0 +1,13 @@
+import { WorkspaceMemberRole } from "@prisma/client";
+import { IsEnum, IsUUID } from "class-validator";
+
+/**
+ * DTO for adding a user to a workspace.
+ */
+export class AddMemberDto {
+  @IsUUID("4", { message: "userId must be a valid UUID" })
+  userId!: string;
+
+  @IsEnum(WorkspaceMemberRole, { message: "role must be a valid WorkspaceMemberRole" })
+  role!: WorkspaceMemberRole;
+}

apps/api/src/workspaces/dto/index.ts

@@ -1 +1,3 @@
+export { AddMemberDto } from "./add-member.dto";
+export { UpdateMemberRoleDto } from "./update-member-role.dto";
 export { WorkspaceResponseDto } from "./workspace-response.dto";

apps/api/src/workspaces/dto/update-member-role.dto.ts

@@ -0,0 +1,10 @@
+import { WorkspaceMemberRole } from "@prisma/client";
+import { IsEnum } from "class-validator";
+
+/**
+ * DTO for updating a workspace member's role.
+ */
+export class UpdateMemberRoleDto {
+  @IsEnum(WorkspaceMemberRole, { message: "role must be a valid WorkspaceMemberRole" })
+  role!: WorkspaceMemberRole;
+}

apps/api/src/workspaces/workspaces.controller.spec.ts

@@ -3,6 +3,7 @@ import { Test, TestingModule } from "@nestjs/testing";
 import { WorkspacesController } from "./workspaces.controller";
 import { WorkspacesService } from "./workspaces.service";
 import { AuthGuard } from "../auth/guards/auth.guard";
+import { WorkspaceGuard, PermissionGuard } from "../common/guards";
 import { WorkspaceMemberRole } from "@prisma/client";
 import type { AuthUser } from "@mosaic/shared";
 
@@ -12,6 +13,9 @@ describe("WorkspacesController", () => {
 
   const mockWorkspacesService = {
     getUserWorkspaces: vi.fn(),
+    addMember: vi.fn(),
+    updateMemberRole: vi.fn(),
+    removeMember: vi.fn(),
   };
 
   const mockUser: AuthUser = {
@@ -32,6 +36,10 @@ describe("WorkspacesController", () => {
     })
       .overrideGuard(AuthGuard)
       .useValue({ canActivate: () => true })
+      .overrideGuard(WorkspaceGuard)
+      .useValue({ canActivate: () => true })
+      .overrideGuard(PermissionGuard)
+      .useValue({ canActivate: () => true })
       .compile();
 
     controller = module.get<WorkspacesController>(WorkspacesController);
@@ -72,4 +80,70 @@ describe("WorkspacesController", () => {
       await expect(controller.getUserWorkspaces(mockUser)).rejects.toThrow("Database error");
     });
   });
+
+  describe("POST /api/workspaces/:id/members", () => {
+    it("should call service with workspace id, actor id, and add member dto", async () => {
+      const workspaceId = "ws-1";
+      const addMemberDto = {
+        userId: "user-2",
+        role: WorkspaceMemberRole.MEMBER,
+      };
+      const mockMember = {
+        workspaceId,
+        userId: "user-2",
+        role: WorkspaceMemberRole.MEMBER,
+        joinedAt: new Date("2026-02-01"),
+      };
+      mockWorkspacesService.addMember.mockResolvedValueOnce(mockMember);
+
+      const result = await controller.addMember(workspaceId, addMemberDto, mockUser);
+
+      expect(result).toEqual(mockMember);
+      expect(service.addMember).toHaveBeenCalledWith(workspaceId, mockUser.id, addMemberDto);
+    });
+  });
+
+  describe("PATCH /api/workspaces/:id/members/:userId", () => {
+    it("should call service with workspace id, actor id, target user id, and role dto", async () => {
+      const workspaceId = "ws-1";
+      const targetUserId = "user-2";
+      const updateRoleDto = {
+        role: WorkspaceMemberRole.ADMIN,
+      };
+      const mockMember = {
+        workspaceId,
+        userId: targetUserId,
+        role: WorkspaceMemberRole.ADMIN,
+        joinedAt: new Date("2026-02-01"),
+      };
+      mockWorkspacesService.updateMemberRole.mockResolvedValueOnce(mockMember);
+
+      const result = await controller.updateMemberRole(
+        workspaceId,
+        targetUserId,
+        updateRoleDto,
+        mockUser
+      );
+
+      expect(result).toEqual(mockMember);
+      expect(service.updateMemberRole).toHaveBeenCalledWith(
+        workspaceId,
+        mockUser.id,
+        targetUserId,
+        updateRoleDto
+      );
+    });
+  });
+
+  describe("DELETE /api/workspaces/:id/members/:userId", () => {
+    it("should call service with workspace id, actor id, and target user id", async () => {
+      const workspaceId = "ws-1";
+      const targetUserId = "user-2";
+      mockWorkspacesService.removeMember.mockResolvedValueOnce(undefined);
+
+      await controller.removeMember(workspaceId, targetUserId, mockUser);
+
+      expect(service.removeMember).toHaveBeenCalledWith(workspaceId, mockUser.id, targetUserId);
+    });
+  });
 });

apps/api/src/workspaces/workspaces.controller.ts

@@ -1,9 +1,12 @@
-import { Controller, Get, UseGuards } from "@nestjs/common";
+import { Body, Controller, Delete, Get, Param, Patch, Post, UseGuards } from "@nestjs/common";
 import { WorkspacesService } from "./workspaces.service";
 import { AuthGuard } from "../auth/guards/auth.guard";
 import { CurrentUser } from "../auth/decorators/current-user.decorator";
-import type { AuthUser } from "@mosaic/shared";
-import type { WorkspaceResponseDto } from "./dto";
+import { WorkspaceGuard, PermissionGuard } from "../common/guards";
+import { Permission, RequirePermission } from "../common/decorators";
+import type { WorkspaceMember } from "@prisma/client";
+import type { AuthenticatedUser } from "../common/types/user.types";
+import type { AddMemberDto, UpdateMemberRoleDto, WorkspaceResponseDto } from "./dto";
 
 /**
  * User-scoped workspace operations.
@@ -22,7 +25,61 @@ export class WorkspacesController {
    * Auto-provisions a default workspace if the user has none.
    */
   @Get()
-  async getUserWorkspaces(@CurrentUser() user: AuthUser): Promise<WorkspaceResponseDto[]> {
+  async getUserWorkspaces(@CurrentUser() user: AuthenticatedUser): Promise<WorkspaceResponseDto[]> {
     return this.workspacesService.getUserWorkspaces(user.id);
   }
+
+  /**
+   * POST /api/workspaces/:workspaceId/members
+   * Add a member to a workspace with the specified role.
+   * Requires: ADMIN role or higher.
+   */
+  @Post(":workspaceId/members")
+  @UseGuards(WorkspaceGuard, PermissionGuard)
+  @RequirePermission(Permission.WORKSPACE_ADMIN)
+  async addMember(
+    @Param("workspaceId") workspaceId: string,
+    @Body() addMemberDto: AddMemberDto,
+    @CurrentUser() user: AuthenticatedUser
+  ): Promise<WorkspaceMember> {
+    return this.workspacesService.addMember(workspaceId, user.id, addMemberDto);
+  }
+
+  /**
+   * PATCH /api/workspaces/:workspaceId/members/:userId
+   * Change a member role in a workspace.
+   * Requires: ADMIN role or higher.
+   */
+  @Patch(":workspaceId/members/:userId")
+  @UseGuards(WorkspaceGuard, PermissionGuard)
+  @RequirePermission(Permission.WORKSPACE_ADMIN)
+  async updateMemberRole(
+    @Param("workspaceId") workspaceId: string,
+    @Param("userId") targetUserId: string,
+    @Body() updateMemberRoleDto: UpdateMemberRoleDto,
+    @CurrentUser() user: AuthenticatedUser
+  ): Promise<WorkspaceMember> {
+    return this.workspacesService.updateMemberRole(
+      workspaceId,
+      user.id,
+      targetUserId,
+      updateMemberRoleDto
+    );
+  }
+
+  /**
+   * DELETE /api/workspaces/:workspaceId/members/:userId
+   * Remove a member from a workspace.
+   * Requires: ADMIN role or higher.
+   */
+  @Delete(":workspaceId/members/:userId")
+  @UseGuards(WorkspaceGuard, PermissionGuard)
+  @RequirePermission(Permission.WORKSPACE_ADMIN)
+  async removeMember(
+    @Param("workspaceId") workspaceId: string,
+    @Param("userId") targetUserId: string,
+    @CurrentUser() user: AuthenticatedUser
+  ): Promise<void> {
+    await this.workspacesService.removeMember(workspaceId, user.id, targetUserId);
+  }
 }

apps/api/src/workspaces/workspaces.service.spec.ts

@@ -3,11 +3,19 @@ import { Test, TestingModule } from "@nestjs/testing";
 import { WorkspacesService } from "./workspaces.service";
 import { PrismaService } from "../prisma/prisma.service";
 import { WorkspaceMemberRole } from "@prisma/client";
+import {
+  BadRequestException,
+  ConflictException,
+  ForbiddenException,
+  NotFoundException,
+} from "@nestjs/common";
 
 describe("WorkspacesService", () => {
   let service: WorkspacesService;
 
   const mockUserId = "550e8400-e29b-41d4-a716-446655440001";
+  const mockAdminUserId = "550e8400-e29b-41d4-a716-446655440010";
+  const mockMemberUserId = "550e8400-e29b-41d4-a716-446655440011";
   const mockWorkspaceId = "550e8400-e29b-41d4-a716-446655440002";
 
   const mockWorkspace = {
@@ -36,11 +44,18 @@ describe("WorkspacesService", () => {
   const mockPrismaService = {
     workspaceMember: {
       findMany: vi.fn(),
+      findUnique: vi.fn(),
+      count: vi.fn(),
       create: vi.fn(),
+      update: vi.fn(),
+      delete: vi.fn(),
     },
     workspace: {
       create: vi.fn(),
     },
+    user: {
+      findUnique: vi.fn(),
+    },
     $transaction: vi.fn(),
   };
 
@@ -58,6 +73,11 @@ describe("WorkspacesService", () => {
     service = module.get<WorkspacesService>(WorkspacesService);
 
     vi.clearAllMocks();
+
+    mockPrismaService.$transaction.mockImplementation(
+      async (fn: (tx: typeof mockPrismaService) => Promise<unknown>) =>
+        fn(mockPrismaService as unknown as typeof mockPrismaService)
+    );
   });
 
   describe("getUserWorkspaces", () => {
@@ -226,4 +246,271 @@ describe("WorkspacesService", () => {
       );
     });
   });
+
+  describe("addMember", () => {
+    const addMemberDto = {
+      userId: mockMemberUserId,
+      role: WorkspaceMemberRole.MEMBER,
+    };
+
+    it("should add a new member to the workspace", async () => {
+      const createdMembership = {
+        workspaceId: mockWorkspaceId,
+        userId: mockMemberUserId,
+        role: WorkspaceMemberRole.MEMBER,
+        joinedAt: new Date("2026-02-02"),
+      };
+      mockPrismaService.user.findUnique.mockResolvedValueOnce({ id: mockMemberUserId });
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockAdminUserId,
+          role: WorkspaceMemberRole.ADMIN,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce(null);
+      mockPrismaService.workspaceMember.create.mockResolvedValueOnce(createdMembership);
+
+      const result = await service.addMember(mockWorkspaceId, mockAdminUserId, addMemberDto);
+
+      expect(result).toEqual(createdMembership);
+      expect(mockPrismaService.workspaceMember.create).toHaveBeenCalledWith({
+        data: {
+          workspaceId: mockWorkspaceId,
+          userId: mockMemberUserId,
+          role: WorkspaceMemberRole.MEMBER,
+        },
+      });
+    });
+
+    it("should throw NotFoundException when user does not exist", async () => {
+      mockPrismaService.workspaceMember.findUnique.mockResolvedValueOnce({
+        workspaceId: mockWorkspaceId,
+        userId: mockAdminUserId,
+        role: WorkspaceMemberRole.ADMIN,
+        joinedAt: new Date("2026-01-01"),
+      });
+      mockPrismaService.user.findUnique.mockResolvedValueOnce(null);
+
+      await expect(
+        service.addMember(mockWorkspaceId, mockAdminUserId, addMemberDto)
+      ).rejects.toThrow(NotFoundException);
+    });
+
+    it("should throw ConflictException when user is already a member", async () => {
+      mockPrismaService.workspaceMember.findUnique.mockResolvedValueOnce({
+        workspaceId: mockWorkspaceId,
+        userId: mockAdminUserId,
+        role: WorkspaceMemberRole.ADMIN,
+        joinedAt: new Date("2026-01-01"),
+      });
+      mockPrismaService.user.findUnique.mockResolvedValueOnce({ id: mockMemberUserId });
+      mockPrismaService.workspaceMember.findUnique.mockResolvedValueOnce({
+        workspaceId: mockWorkspaceId,
+        userId: mockMemberUserId,
+        role: WorkspaceMemberRole.MEMBER,
+        joinedAt: new Date("2026-01-02"),
+      });
+
+      await expect(
+        service.addMember(mockWorkspaceId, mockAdminUserId, addMemberDto)
+      ).rejects.toThrow(ConflictException);
+    });
+
+    it("should throw ForbiddenException when admin tries to assign OWNER role", async () => {
+      mockPrismaService.workspaceMember.findUnique.mockResolvedValueOnce({
+        workspaceId: mockWorkspaceId,
+        userId: mockAdminUserId,
+        role: WorkspaceMemberRole.ADMIN,
+        joinedAt: new Date("2026-01-01"),
+      });
+
+      await expect(
+        service.addMember(mockWorkspaceId, mockAdminUserId, {
+          userId: mockMemberUserId,
+          role: WorkspaceMemberRole.OWNER,
+        })
+      ).rejects.toThrow(ForbiddenException);
+    });
+  });
+
+  describe("updateMemberRole", () => {
+    it("should update a member role", async () => {
+      const updatedMembership = {
+        workspaceId: mockWorkspaceId,
+        userId: mockMemberUserId,
+        role: WorkspaceMemberRole.ADMIN,
+        joinedAt: new Date("2026-01-02"),
+      };
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockMemberUserId,
+          role: WorkspaceMemberRole.MEMBER,
+          joinedAt: new Date("2026-01-02"),
+        });
+      mockPrismaService.workspaceMember.update.mockResolvedValueOnce(updatedMembership);
+
+      const result = await service.updateMemberRole(mockWorkspaceId, mockUserId, mockMemberUserId, {
+        role: WorkspaceMemberRole.ADMIN,
+      });
+
+      expect(result).toEqual(updatedMembership);
+      expect(mockPrismaService.workspaceMember.update).toHaveBeenCalledWith({
+        where: {
+          workspaceId_userId: {
+            workspaceId: mockWorkspaceId,
+            userId: mockMemberUserId,
+          },
+        },
+        data: {
+          role: WorkspaceMemberRole.ADMIN,
+        },
+      });
+    });
+
+    it("should throw NotFoundException when target member does not exist", async () => {
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce(null);
+
+      await expect(
+        service.updateMemberRole(mockWorkspaceId, mockUserId, mockMemberUserId, {
+          role: WorkspaceMemberRole.ADMIN,
+        })
+      ).rejects.toThrow(NotFoundException);
+    });
+
+    it("should throw BadRequestException when sole owner attempts self-demotion", async () => {
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        });
+      mockPrismaService.workspaceMember.count.mockResolvedValueOnce(1);
+
+      await expect(
+        service.updateMemberRole(mockWorkspaceId, mockUserId, mockUserId, {
+          role: WorkspaceMemberRole.ADMIN,
+        })
+      ).rejects.toThrow(BadRequestException);
+    });
+
+    it("should throw ForbiddenException when actor tries to change role of higher-ranked member", async () => {
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockAdminUserId,
+          role: WorkspaceMemberRole.ADMIN,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        });
+
+      await expect(
+        service.updateMemberRole(mockWorkspaceId, mockAdminUserId, mockUserId, {
+          role: WorkspaceMemberRole.MEMBER,
+        })
+      ).rejects.toThrow(ForbiddenException);
+    });
+  });
+
+  describe("removeMember", () => {
+    it("should remove a workspace member", async () => {
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockMemberUserId,
+          role: WorkspaceMemberRole.MEMBER,
+          joinedAt: new Date("2026-01-02"),
+        });
+      mockPrismaService.workspaceMember.delete.mockResolvedValueOnce({
+        workspaceId: mockWorkspaceId,
+        userId: mockMemberUserId,
+        role: WorkspaceMemberRole.MEMBER,
+        joinedAt: new Date("2026-01-02"),
+      });
+
+      await service.removeMember(mockWorkspaceId, mockUserId, mockMemberUserId);
+
+      expect(mockPrismaService.workspaceMember.delete).toHaveBeenCalledWith({
+        where: {
+          workspaceId_userId: {
+            workspaceId: mockWorkspaceId,
+            userId: mockMemberUserId,
+          },
+        },
+      });
+    });
+
+    it("should throw BadRequestException when trying to remove the last owner", async () => {
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        });
+      mockPrismaService.workspaceMember.count.mockResolvedValueOnce(1);
+
+      await expect(service.removeMember(mockWorkspaceId, mockUserId, mockUserId)).rejects.toThrow(
+        BadRequestException
+      );
+    });
+
+    it("should throw ForbiddenException when admin attempts to remove an owner", async () => {
+      mockPrismaService.workspaceMember.findUnique
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockAdminUserId,
+          role: WorkspaceMemberRole.ADMIN,
+          joinedAt: new Date("2026-01-01"),
+        })
+        .mockResolvedValueOnce({
+          workspaceId: mockWorkspaceId,
+          userId: mockUserId,
+          role: WorkspaceMemberRole.OWNER,
+          joinedAt: new Date("2026-01-01"),
+        });
+
+      await expect(
+        service.removeMember(mockWorkspaceId, mockAdminUserId, mockUserId)
+      ).rejects.toThrow(ForbiddenException);
+    });
+  });
 });

apps/api/src/workspaces/workspaces.service.ts

@@ -1,7 +1,22 @@
-import { Injectable, Logger } from "@nestjs/common";
-import { WorkspaceMemberRole } from "@prisma/client";
+import {
+  BadRequestException,
+  ConflictException,
+  ForbiddenException,
+  Injectable,
+  Logger,
+  NotFoundException,
+} from "@nestjs/common";
+import { Prisma, WorkspaceMemberRole } from "@prisma/client";
+import type { WorkspaceMember } from "@prisma/client";
 import { PrismaService } from "../prisma/prisma.service";
-import type { WorkspaceResponseDto } from "./dto";
+import type { AddMemberDto, UpdateMemberRoleDto, WorkspaceResponseDto } from "./dto";
+
+const WORKSPACE_ROLE_RANK: Record<WorkspaceMemberRole, number> = {
+  [WorkspaceMemberRole.GUEST]: 1,
+  [WorkspaceMemberRole.MEMBER]: 2,
+  [WorkspaceMemberRole.ADMIN]: 3,
+  [WorkspaceMemberRole.OWNER]: 4,
+};
 
 @Injectable()
 export class WorkspacesService {
@@ -94,4 +109,237 @@ export class WorkspacesService {
       },
     ];
   }
+
+  /**
+   * Add a member to a workspace.
+   */
+  async addMember(
+    workspaceId: string,
+    actorUserId: string,
+    addMemberDto: AddMemberDto
+  ): Promise<WorkspaceMember> {
+    const actorMembership = await this.prisma.workspaceMember.findUnique({
+      where: {
+        workspaceId_userId: {
+          workspaceId,
+          userId: actorUserId,
+        },
+      },
+      select: {
+        role: true,
+      },
+    });
+
+    if (!actorMembership) {
+      throw new ForbiddenException("You are not a member of this workspace");
+    }
+
+    this.assertCanAssignRole(actorMembership.role, addMemberDto.role);
+
+    const user = await this.prisma.user.findUnique({
+      where: { id: addMemberDto.userId },
+      select: { id: true },
+    });
+
+    if (!user) {
+      throw new NotFoundException(`User with ID ${addMemberDto.userId} not found`);
+    }
+
+    const existingMembership = await this.prisma.workspaceMember.findUnique({
+      where: {
+        workspaceId_userId: {
+          workspaceId,
+          userId: addMemberDto.userId,
+        },
+      },
+      select: {
+        workspaceId: true,
+        userId: true,
+      },
+    });
+
+    if (existingMembership) {
+      throw new ConflictException("User is already a member of this workspace");
+    }
+
+    try {
+      return await this.prisma.workspaceMember.create({
+        data: {
+          workspaceId,
+          userId: addMemberDto.userId,
+          role: addMemberDto.role,
+        },
+      });
+    } catch (error) {
+      if (this.isUniqueConstraintError(error)) {
+        throw new ConflictException("User is already a member of this workspace");
+      }
+      throw error;
+    }
+  }
+
+  /**
+   * Update the role of an existing workspace member.
+   */
+  async updateMemberRole(
+    workspaceId: string,
+    actorUserId: string,
+    targetUserId: string,
+    updateMemberRoleDto: UpdateMemberRoleDto
+  ): Promise<WorkspaceMember> {
+    return this.prisma.$transaction(async (tx) => {
+      const actorMembership = await tx.workspaceMember.findUnique({
+        where: {
+          workspaceId_userId: {
+            workspaceId,
+            userId: actorUserId,
+          },
+        },
+        select: {
+          role: true,
+        },
+      });
+
+      if (!actorMembership) {
+        throw new ForbiddenException("You are not a member of this workspace");
+      }
+
+      const targetMembership = await tx.workspaceMember.findUnique({
+        where: {
+          workspaceId_userId: {
+            workspaceId,
+            userId: targetUserId,
+          },
+        },
+        select: {
+          role: true,
+        },
+      });
+
+      if (!targetMembership) {
+        throw new NotFoundException(`User ${targetUserId} is not a member of this workspace`);
+      }
+
+      this.assertCanManageTargetMember(actorMembership.role, targetMembership.role);
+      this.assertCanAssignRole(actorMembership.role, updateMemberRoleDto.role);
+
+      if (targetMembership.role === WorkspaceMemberRole.OWNER) {
+        const isDemotion = updateMemberRoleDto.role !== WorkspaceMemberRole.OWNER;
+        if (isDemotion) {
+          const ownerCount = await tx.workspaceMember.count({
+            where: {
+              workspaceId,
+              role: WorkspaceMemberRole.OWNER,
+            },
+          });
+          if (ownerCount <= 1) {
+            if (actorUserId === targetUserId) {
+              throw new BadRequestException("Cannot self-demote if you are the sole owner");
+            }
+            throw new BadRequestException("Cannot remove the last owner from a workspace");
+          }
+        }
+      }
+
+      return tx.workspaceMember.update({
+        where: {
+          workspaceId_userId: {
+            workspaceId,
+            userId: targetUserId,
+          },
+        },
+        data: {
+          role: updateMemberRoleDto.role,
+        },
+      });
+    });
+  }
+
+  /**
+   * Remove a member from a workspace.
+   */
+  async removeMember(
+    workspaceId: string,
+    actorUserId: string,
+    targetUserId: string
+  ): Promise<void> {
+    await this.prisma.$transaction(async (tx) => {
+      const actorMembership = await tx.workspaceMember.findUnique({
+        where: {
+          workspaceId_userId: {
+            workspaceId,
+            userId: actorUserId,
+          },
+        },
+        select: {
+          role: true,
+        },
+      });
+
+      if (!actorMembership) {
+        throw new ForbiddenException("You are not a member of this workspace");
+      }
+
+      const targetMembership = await tx.workspaceMember.findUnique({
+        where: {
+          workspaceId_userId: {
+            workspaceId,
+            userId: targetUserId,
+          },
+        },
+        select: {
+          role: true,
+        },
+      });
+
+      if (!targetMembership) {
+        throw new NotFoundException(`User ${targetUserId} is not a member of this workspace`);
+      }
+
+      this.assertCanManageTargetMember(actorMembership.role, targetMembership.role);
+
+      if (targetMembership.role === WorkspaceMemberRole.OWNER) {
+        const ownerCount = await tx.workspaceMember.count({
+          where: {
+            workspaceId,
+            role: WorkspaceMemberRole.OWNER,
+          },
+        });
+        if (ownerCount <= 1) {
+          throw new BadRequestException("Cannot remove the last owner from a workspace");
+        }
+      }
+
+      await tx.workspaceMember.delete({
+        where: {
+          workspaceId_userId: {
+            workspaceId,
+            userId: targetUserId,
+          },
+        },
+      });
+    });
+  }
+
+  private assertCanAssignRole(
+    actorRole: WorkspaceMemberRole,
+    requestedRole: WorkspaceMemberRole
+  ): void {
+    if (WORKSPACE_ROLE_RANK[actorRole] < WORKSPACE_ROLE_RANK[requestedRole]) {
+      throw new ForbiddenException("You cannot assign a role higher than your own");
+    }
+  }
+
+  private assertCanManageTargetMember(
+    actorRole: WorkspaceMemberRole,
+    targetRole: WorkspaceMemberRole
+  ): void {
+    if (WORKSPACE_ROLE_RANK[actorRole] < WORKSPACE_ROLE_RANK[targetRole]) {
+      throw new ForbiddenException("You cannot manage a member with a higher role");
+    }
+  }
+
+  private isUniqueConstraintError(error: unknown): error is Prisma.PrismaClientKnownRequestError {
+    return error instanceof Prisma.PrismaClientKnownRequestError && error.code === "P2002";
+  }
 }