diff --git a/docs/web-cad-implementation-plan.zh-CN.md b/docs/web-cad-implementation-plan.zh-CN.md
index f04057d..1c60e8d 100644
--- a/docs/web-cad-implementation-plan.zh-CN.md
+++ b/docs/web-cad-implementation-plan.zh-CN.md
@@ -1584,9 +1584,11 @@ P0 基线/治理
 | P0-02 运行时版本基线 | `IN PROGRESS` | `config/runtime-baseline.json` 已建立；Three.js 锁定为当前 npm 最新 `0.185.1`，其他内核版本待锁定 |
 | P0-03 兼容矩阵 | `DONE` | `config/compatibility-matrix.json` 覆盖 13 个工作台和命令状态 |
 | P1-01 Facade 最小合同 | `DONE` | `src/facade/types.ts` 定义 App/Gui/Command/Selection/Task/Viewport 合同 |
+| P1-02 命令状态和选择前置 | `DONE` | MockFacade 根据工作台、选择对象和命令清单返回 enabled/disabled 原因 |
+| P1-03 请求上下文、事件和诊断 | `DONE` | 命令事件携带 API 版本、请求 ID、文档 ID/版本和工作台；禁用命令生成结构化诊断 |
 | P1-05 MockFacadeAdapter | `DONE` | `src/facade/mockFacade.ts`，React 工作区已通过事件投影工作台、选择、文档树和通知 |
 | P1-06 Facade-only 依赖守卫 | `DONE` | `scripts/check-facade-boundary.mjs`，禁止 UI 绕过入口导入 Three.js/SQLite/OPFS/Worker |
 | P5-01 Three.js 视口适配器 | `IN PROGRESS` | `src/facade/threeViewport.ts` 使用 `three@0.185.1`，已挂载 WebGL2 场景和资源释放 |
-| P8-01 第一批自动化场景 | `IN PROGRESS` | `tests/facade.test.ts` 已覆盖初始化、事件、任务生命周期和禁用命令；E2E/黄金几何待补齐 |
+| P8-01 第一批自动化场景 | `IN PROGRESS` | `tests/facade.test.ts` 已覆盖初始化、事件、任务生命周期、禁用命令和请求上下文；E2E/黄金几何待补齐 |
 
 本迭代验证命令：`npm run check:facade-boundary`、`npm run test:facade`、`npm run build`。构建产物将 Three.js 拆为独立 chunk，避免把全部渲染库重复打入应用主 chunk。下一迭代继续完成 P0-01/P0-02 的精确锁定和 P1-02/P1-03 的命令状态、事件及诊断协议。
diff --git a/src/facade/mockFacade.ts b/src/facade/mockFacade.ts
index 7faf3f1..a2f3266 100644
--- a/src/facade/mockFacade.ts
+++ b/src/facade/mockFacade.ts
@@ -3,9 +3,11 @@ import type {
   BitBybitWebCadFacade,
   CommandState,
   DocumentSnapshot,
+  Diagnostic,
   ExecuteCommandInput,
   FacadeEvent,
   FacadeListener,
+  FacadeRequestContext,
   FacadeState,
   ModelTreeItem,
   TaskSnapshot,
@@ -27,41 +29,49 @@ const createDocument = (label = 'Pump Housing'): DocumentSnapshot => ({
   id: 'doc-pump-housing', label, version: 18, dirty: true, readOnly: false, units: 'mm', tree: initialTree.map((item) => ({ ...item, children: item.children ? [...item.children] : undefined })),
 })
 
-const commandState = (commandId: string, activeWorkbench: WorkbenchId): CommandState => {
+const selectionRequired = new Set(['pad', 'pocket', 'revolution', 'fillet', 'chamfer', 'hole', 'linear-pattern', 'polar-pattern', 'measure-distance', 'measure-angle', 'measure-area'])
+
+const commandState = (commandId: string, activeWorkbench: WorkbenchId, selectedObjectId: string): CommandState => {
   const known = Object.values(workbenchDefinitions).some((definition) => definition.groups.some((group) => group.commands.some((command) => command.id === commandId)))
   if (!known) return { id: commandId, status: 'disabled', reason: 'Command is not registered in the active manifest.' }
   if (commandId === 'pad' && activeWorkbench !== 'Part Design') return { id: commandId, status: 'disabled', reason: 'Switch to Part Design to use Pad.' }
+  if (selectionRequired.has(commandId) && !selectedObjectId) return { id: commandId, status: 'disabled', reason: 'Select a compatible object or sub-shape first.' }
   return { id: commandId, status: 'enabled' }
 }
 
 export function createMockFacade(): BitBybitWebCadFacade {
-  let state: FacadeState = { apiVersion: '0.1', activeWorkbench: 'Part Design', selectedObjectId: 'pad', document: createDocument(), task: null, lastNotice: '' }
+  let state: FacadeState = { apiVersion: '0.1', activeWorkbench: 'Part Design', selectedObjectId: 'pad', document: createDocument(), task: null, lastNotice: '', diagnostics: [] }
   const listeners = new Set<FacadeListener>()
   let requestSequence = 0
 
   const emit = (event: FacadeEvent) => listeners.forEach((listener) => listener(event))
   const emitState = () => emit({ type: 'state.changed', state: getState() })
-  const getState = () => ({ ...state, document: { ...state.document, tree: state.document.tree.map((item) => ({ ...item, children: item.children ? [...item.children] : undefined })) }, task: state.task ? { ...state.task, draft: { ...state.task.draft } } : null })
+  const getState = () => ({ ...state, diagnostics: state.diagnostics.map((diagnostic) => ({ ...diagnostic })), document: { ...state.document, tree: state.document.tree.map((item) => ({ ...item, children: item.children ? [...item.children] : undefined })) }, task: state.task ? { ...state.task, draft: { ...state.task.draft } } : null })
   const notify = (message: string) => { state = { ...state, lastNotice: message }; emit({ type: 'notice', message }); emitState() }
   const setActive = (id: WorkbenchId) => { state = { ...state, activeWorkbench: id }; emitState(); notify(`${id} workbench loaded`) }
   const select = (objectId: string) => { state = { ...state, selectedObjectId: objectId }; emitState() }
   const beginTask = (commandId: string, draft: Record<string, unknown> = {}) => { const task: TaskSnapshot = { id: `task-${++requestSequence}`, commandId, title: workbenchDefinitions[state.activeWorkbench].taskTitle, status: 'preview', draft }; state = { ...state, task }; emitState(); return task }
   const execute = ({ commandId, payload }: ExecuteCommandInput) => {
     const requestId = `req-${++requestSequence}`
-    const status = commandState(commandId, state.activeWorkbench)
-    if (status.status === 'disabled') { emit({ type: 'command.failed', commandId, requestId, message: status.reason }); notify(status.reason || 'Command is disabled'); return requestId }
-    emit({ type: 'command.started', commandId, requestId })
+    const context: FacadeRequestContext = { apiVersion: state.apiVersion, requestId, documentId: state.document.id, documentVersion: state.document.version, workbench: state.activeWorkbench }
+    const status = commandState(commandId, state.activeWorkbench, state.selectedObjectId)
+    if (status.status === 'disabled') {
+      const diagnostic: Diagnostic = { id: `diag-${++requestSequence}`, severity: 'warning', code: 'COMMAND_DISABLED', message: status.reason || 'Command is disabled', objectId: state.selectedObjectId || undefined, requestId }
+      state = { ...state, diagnostics: [...state.diagnostics, diagnostic] }
+      emit({ type: 'diagnostic.added', diagnostic, context }); emit({ type: 'command.failed', commandId, context, message: status.reason }); notify(status.reason || 'Command is disabled'); return requestId
+    }
+    emit({ type: 'command.started', commandId, context })
     if (commandId === 'new-document') state = { ...state, document: createDocument('Untitled document') }
     else if (commandId === 'save') state = { ...state, document: { ...state.document, dirty: false, version: state.document.version + 1 } }
     else if (commandId === 'select-object' && typeof payload?.objectId === 'string') select(payload.objectId)
     else if (commandId === 'create-body') beginTask('create-body')
     else if (commandId === 'create-sketch') beginTask('create-sketch')
-    emit({ type: 'command.completed', commandId, requestId }); emitState(); return requestId
+    emit({ type: 'command.completed', commandId, context }); emitState(); return requestId
   }
 
   const facade: BitBybitWebCadFacade = {
     app: { document: { getActive: () => getState().document, create: (label) => { state = { ...state, document: createDocument(label), selectedObjectId: '' }; emitState(); return getState().document }, markDirty: () => { state = { ...state, document: { ...state.document, dirty: true } }; emitState() } } },
-    gui: { workbench: { list: () => Object.keys(workbenchDefinitions) as WorkbenchId[], getActive: () => state.activeWorkbench, setActive }, command: { getState: (commandId) => commandState(commandId, state.activeWorkbench), list: (workbench) => workbenchDefinitions[workbench].groups.flatMap((group) => group.commands), execute } },
+    gui: { workbench: { list: () => Object.keys(workbenchDefinitions) as WorkbenchId[], getActive: () => state.activeWorkbench, setActive }, command: { getState: (commandId) => commandState(commandId, state.activeWorkbench, state.selectedObjectId), list: (workbench) => workbenchDefinitions[workbench].groups.flatMap((group) => group.commands), execute } },
     selection: { getObjectId: () => state.selectedObjectId, select, clear: () => select('') },
     task: { getActive: () => getState().task, begin: beginTask, update: (draft) => { if (state.task) state = { ...state, task: { ...state.task, draft: { ...state.task.draft, ...draft } } }; emitState() }, apply: () => { if (state.task) state = { ...state, task: { ...state.task, status: 'completed' } }; emitState() }, cancel: () => { if (state.task) state = { ...state, task: { ...state.task, status: 'cancelled' } }; emitState() } },
     viewport: { createAdapter: () => new ThreeViewportAdapter() },
diff --git a/src/facade/types.ts b/src/facade/types.ts
index faa7e06..da0129a 100644
--- a/src/facade/types.ts
+++ b/src/facade/types.ts
@@ -25,6 +25,23 @@ export type CommandState = {
   reason?: string
 }
 
+export type FacadeRequestContext = {
+  apiVersion: '0.1'
+  requestId: string
+  documentId: string
+  documentVersion: number
+  workbench: WorkbenchId
+}
+
+export type Diagnostic = {
+  id: string
+  severity: 'info' | 'warning' | 'error'
+  code: string
+  message: string
+  objectId?: string
+  requestId?: string
+}
+
 export type TaskSnapshot = {
   id: string
   commandId: string
@@ -40,12 +57,14 @@ export type FacadeState = {
   document: DocumentSnapshot
   task: TaskSnapshot | null
   lastNotice: string
+  diagnostics: Diagnostic[]
 }
 
 export type FacadeEvent =
   | { type: 'state.changed'; state: FacadeState }
   | { type: 'notice'; message: string }
-  | { type: 'command.started' | 'command.completed' | 'command.failed'; commandId: string; requestId: string; message?: string }
+  | { type: 'command.started' | 'command.completed' | 'command.failed'; commandId: string; context: FacadeRequestContext; message?: string }
+  | { type: 'diagnostic.added'; diagnostic: Diagnostic; context: FacadeRequestContext }
 
 export type FacadeListener = (event: FacadeEvent) => void
 export type Unsubscribe = () => void
diff --git a/tests/facade.test.ts b/tests/facade.test.ts
index 38086d1..c7a362b 100644
--- a/tests/facade.test.ts
+++ b/tests/facade.test.ts
@@ -39,9 +39,23 @@ test('disabled commands return a reason instead of mutating the document', () =>
   const before = facade.getState().document.version
   const state = facade.gui.command.getState('pad')
   assert.equal(state.status, 'enabled')
+  facade.selection.clear()
   facade.gui.workbench.setActive('Sketcher')
   const disabled = facade.gui.command.getState('pad')
   assert.equal(disabled.status, 'disabled')
-  assert.match(disabled.reason || '', /Part Design/)
+  assert.match(disabled.reason || '', /Part Design|compatible object/)
+  facade.gui.command.execute({ commandId: 'pad' })
+  assert.equal(facade.getState().diagnostics.at(-1)?.code, 'COMMAND_DISABLED')
   assert.equal(facade.getState().document.version, before)
 })
+
+test('command events carry a document-scoped request context', () => {
+  const facade = createMockFacade()
+  const events: string[] = []
+  let requestId = ''
+  facade.subscribe((event) => { events.push(event.type); if (event.type === 'command.started') requestId = event.context.requestId })
+  facade.gui.command.execute({ commandId: 'create-sketch' })
+  assert.ok(events.includes('command.started'))
+  assert.ok(events.includes('command.completed'))
+  assert.match(requestId, /^req-/)
+})