diff --git a/apps/stage-tamagotchi/src/main/services/airi/widgets/index.ts b/apps/stage-tamagotchi/src/main/services/airi/widgets/index.ts
index eca23a6fc..913a5e206 100644
--- a/apps/stage-tamagotchi/src/main/services/airi/widgets/index.ts
+++ b/apps/stage-tamagotchi/src/main/services/airi/widgets/index.ts
@@ -6,6 +6,12 @@ import type { WidgetsWindowManager } from '../../../windows/widgets'
 import { defineInvokeHandlers } from '@moeru/eventa'
 
 import { widgetsAdd, widgetsClear, widgetsFetch, widgetsOpenWindow, widgetsPrepareWindow, widgetsRemove, widgetsUpdate } from '../../../../shared/eventa'
+import {
+  normalizeOptionalWidgetId,
+  normalizeRequiredWidgetId,
+  validateWidgetsAddPayload,
+  validateWidgetsUpdatePayload,
+} from './validation'
 
 interface InvokeOptions {
   raw?: { ipcMainEvent?: IpcMainEvent }
@@ -18,6 +24,27 @@ function isFromWindow(options: InvokeOptions | undefined, window: BrowserWindow)
   return sender.id === window.webContents.id
 }
 
+/**
+ * Registers widget-related Electron invoke handlers for one window context.
+ *
+ * Use when:
+ * - A main-process window should expose widget management invokes to its renderer
+ * - Widget requests must be validated before reaching {@link WidgetsWindowManager}
+ *
+ * Expects:
+ * - `context` is an Eventa context bound to the target Electron window
+ * - `window` is the only renderer allowed to use the registered invokes
+ *
+ * Returns:
+ * - Registers handlers on the provided context and does not return a value
+ *
+ * Call stack:
+ *
+ * createWidgetsService (./index)
+ *   -> {@link defineInvokeHandlers}
+ *     -> {@link validateWidgetsAddPayload}
+ *       -> {@link WidgetsWindowManager.pushWidget}
+ */
 export function createWidgetsService(params: { context: ReturnType<typeof createContext>['context'], widgetsManager: WidgetsWindowManager, window: BrowserWindow }) {
   defineInvokeHandlers(params.context, {
     widgetsPrepareWindow,
@@ -31,37 +58,43 @@ export function createWidgetsService(params: { context: ReturnType<typeof create
     widgetsPrepareWindow: async (payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return params.widgetsManager!.prepareWidgetWindow(payload ?? undefined)
+      const id = normalizeOptionalWidgetId(payload?.id)
+      return params.widgetsManager.prepareWidgetWindow(id ? { id } : undefined)
     },
     widgetsOpenWindow: async (payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return params.widgetsManager!.openWindow(payload ?? undefined)
+      const id = normalizeOptionalWidgetId(payload?.id)
+      return params.widgetsManager.openWindow(id ? { id } : undefined)
     },
     widgetsAdd: async (payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return payload ? params.widgetsManager!.pushWidget(payload) : undefined
+      return params.widgetsManager.pushWidget(validateWidgetsAddPayload(payload))
     },
     widgetsUpdate: async (payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return payload ? params.widgetsManager!.updateWidget(payload) : undefined
+      return params.widgetsManager.updateWidget(validateWidgetsUpdatePayload(payload))
     },
     widgetsRemove: async (payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return payload?.id ? params.widgetsManager!.removeWidget(payload.id) : undefined
+      return params.widgetsManager.removeWidget(
+        normalizeRequiredWidgetId(payload?.id, 'id is required to remove a widget.'),
+      )
     },
     widgetsClear: async (_payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return params.widgetsManager!.clearWidgets()
+      return params.widgetsManager.clearWidgets()
     },
     widgetsFetch: async (payload, options) => {
       if (!isFromWindow(options as InvokeOptions, params.window))
         return undefined
-      return payload?.id ? params.widgetsManager!.getWidgetSnapshot(payload.id) : undefined
+      return params.widgetsManager.getWidgetSnapshot(
+        normalizeRequiredWidgetId(payload?.id, 'id is required to fetch a widget snapshot.'),
+      )
     },
   })
 }
diff --git a/apps/stage-tamagotchi/src/main/services/airi/widgets/validation.test.ts b/apps/stage-tamagotchi/src/main/services/airi/widgets/validation.test.ts
new file mode 100644
index 000000000..d62b5172d
--- /dev/null
+++ b/apps/stage-tamagotchi/src/main/services/airi/widgets/validation.test.ts
@@ -0,0 +1,100 @@
+import { describe, expect, it } from 'vitest'
+
+import {
+  normalizeOptionalWidgetId,
+  normalizeRequiredWidgetId,
+  validateWidgetsAddPayload,
+  validateWidgetsUpdatePayload,
+} from './validation'
+
+describe('widget invoke validation', () => {
+  describe('validateWidgetsAddPayload', () => {
+    it('normalizes add payloads for the widgets manager', () => {
+      expect(validateWidgetsAddPayload({
+        id: ' widget-1 ',
+        componentName: ' weather ',
+        componentProps: { city: 'Tokyo' },
+        ttlMs: 2500.9,
+        windowSize: {
+          width: 620.8,
+          height: 480.2,
+          minWidth: 320.9,
+        },
+      })).toEqual({
+        id: 'widget-1',
+        componentName: 'weather',
+        componentProps: { city: 'Tokyo' },
+        ttlMs: 2500,
+        windowSize: {
+          width: 620,
+          height: 480,
+          minWidth: 320,
+        },
+      })
+    })
+
+    it('rejects empty component names and invalid payload fields', () => {
+      expect(() => validateWidgetsAddPayload({
+        componentName: '   ',
+      } as any)).toThrow('componentName is required to spawn a widget.')
+
+      expect(() => validateWidgetsAddPayload({
+        componentName: 'weather',
+        componentProps: [] as any,
+      })).toThrow('componentProps must be a plain object.')
+
+      expect(() => validateWidgetsAddPayload({
+        componentName: 'weather',
+        ttlMs: -1,
+      })).toThrow('ttlMs must be a non-negative finite number.')
+
+      expect(() => validateWidgetsAddPayload({
+        componentName: 'weather',
+        windowSize: { width: 0, height: 320 },
+      } as any)).toThrow('windowSize must contain a positive finite width and height.')
+    })
+  })
+
+  describe('validateWidgetsUpdatePayload', () => {
+    it('normalizes widget updates and keeps optional fields optional', () => {
+      expect(validateWidgetsUpdatePayload({
+        id: ' widget-1 ',
+        componentProps: { city: 'Taipei' },
+        ttlMs: 1500.4,
+      })).toEqual({
+        id: 'widget-1',
+        componentProps: { city: 'Taipei' },
+        ttlMs: 1500,
+        windowSize: undefined,
+      })
+    })
+
+    it('rejects missing ids and malformed update fields', () => {
+      expect(() => validateWidgetsUpdatePayload({
+        id: '   ',
+      } as any)).toThrow('id is required to update a widget.')
+
+      expect(() => validateWidgetsUpdatePayload({
+        id: 'widget-1',
+        componentProps: [] as any,
+      })).toThrow('componentProps must be a plain object.')
+
+      expect(() => validateWidgetsUpdatePayload({
+        id: 'widget-1',
+        windowSize: { width: Number.NaN, height: 400 },
+      } as any)).toThrow('windowSize must contain a positive finite width and height.')
+    })
+  })
+
+  describe('widget id normalization helpers', () => {
+    it('normalizes optional ids for open/prepare flows', () => {
+      expect(normalizeOptionalWidgetId(' widget-1 ')).toBe('widget-1')
+      expect(normalizeOptionalWidgetId('   ')).toBeUndefined()
+    })
+
+    it('enforces required ids for destructive flows', () => {
+      expect(normalizeRequiredWidgetId(' widget-1 ', 'id required')).toBe('widget-1')
+      expect(() => normalizeRequiredWidgetId('   ', 'id required')).toThrow('id required')
+    })
+  })
+})
diff --git a/apps/stage-tamagotchi/src/main/services/airi/widgets/validation.ts b/apps/stage-tamagotchi/src/main/services/airi/widgets/validation.ts
new file mode 100644
index 000000000..9bc48ce79
--- /dev/null
+++ b/apps/stage-tamagotchi/src/main/services/airi/widgets/validation.ts
@@ -0,0 +1,151 @@
+import type {
+  WidgetsAddPayload,
+  WidgetsUpdatePayload,
+} from '../../../../shared/eventa'
+
+import { isPlainObject } from 'es-toolkit'
+
+import { normalizeWidgetWindowSize } from '../../../../shared/utils/electron/windows/window-size'
+
+function normalizeWidgetId(value?: string): string | undefined {
+  if (!value)
+    return undefined
+
+  const normalized = value.trim()
+  return normalized || undefined
+}
+
+function normalizeTtlMs(ttlMs?: number): number {
+  if (ttlMs === undefined)
+    return 0
+
+  if (!Number.isFinite(ttlMs) || ttlMs < 0)
+    throw new Error('ttlMs must be a non-negative finite number.')
+
+  return Math.floor(ttlMs)
+}
+
+function normalizeComponentProps(componentProps?: Record<string, unknown>): Record<string, unknown> {
+  if (componentProps === undefined)
+    return {}
+
+  if (!isPlainObject(componentProps))
+    throw new Error('componentProps must be a plain object.')
+
+  return componentProps
+}
+
+/**
+ * Validates and normalizes widget spawn payloads at the Electron invoke boundary.
+ *
+ * Use when:
+ * - `defineInvokeHandler(...)` receives a widgets add request from a renderer
+ *
+ * Expects:
+ * - `componentName` is a non-empty string
+ * - `componentProps`, when provided, is a plain object
+ * - `ttlMs`, when provided, is a non-negative finite number
+ *
+ * Returns:
+ * - A normalized payload safe to pass into the widgets manager
+ */
+export function validateWidgetsAddPayload(payload?: WidgetsAddPayload): WidgetsAddPayload {
+  if (!payload)
+    throw new Error('widgets.add requires a payload.')
+
+  const componentName = payload.componentName?.trim()
+  if (!componentName)
+    throw new Error('componentName is required to spawn a widget.')
+
+  const normalizedWindowSize = payload.windowSize === undefined
+    ? undefined
+    : normalizeWidgetWindowSize(payload.windowSize)
+
+  if (payload.windowSize !== undefined && !normalizedWindowSize)
+    throw new Error('windowSize must contain a positive finite width and height.')
+
+  return {
+    ...payload,
+    id: normalizeWidgetId(payload.id),
+    componentName,
+    componentProps: normalizeComponentProps(payload.componentProps),
+    ttlMs: normalizeTtlMs(payload.ttlMs),
+    windowSize: normalizedWindowSize,
+  }
+}
+
+/**
+ * Validates and normalizes widget update payloads at the Electron invoke boundary.
+ *
+ * Use when:
+ * - `defineInvokeHandler(...)` receives a widgets update request from a renderer
+ *
+ * Expects:
+ * - `id` is a non-empty string after trimming
+ * - `componentProps`, when provided, is a plain object
+ *
+ * Returns:
+ * - A normalized payload safe to pass into the widgets manager
+ */
+export function validateWidgetsUpdatePayload(payload?: WidgetsUpdatePayload): WidgetsUpdatePayload {
+  if (!payload)
+    throw new Error('widgets.update requires a payload.')
+
+  const id = normalizeWidgetId(payload.id)
+  if (!id)
+    throw new Error('id is required to update a widget.')
+
+  const normalizedWindowSize = payload.windowSize === undefined
+    ? undefined
+    : normalizeWidgetWindowSize(payload.windowSize)
+
+  if (payload.windowSize !== undefined && !normalizedWindowSize)
+    throw new Error('windowSize must contain a positive finite width and height.')
+
+  return {
+    ...payload,
+    id,
+    componentProps: payload.componentProps === undefined
+      ? undefined
+      : normalizeComponentProps(payload.componentProps),
+    ttlMs: payload.ttlMs === undefined
+      ? undefined
+      : normalizeTtlMs(payload.ttlMs),
+    windowSize: normalizedWindowSize,
+  }
+}
+
+/**
+ * Validates widget ids for remove/fetch/open operations at the Electron boundary.
+ *
+ * Use when:
+ * - A widget operation requires an existing widget id
+ *
+ * Expects:
+ * - `id` is a string or `undefined`
+ *
+ * Returns:
+ * - The trimmed id, or `undefined` for empty input
+ */
+export function normalizeRequiredWidgetId(id?: string, reason = 'id is required.'): string {
+  const normalized = normalizeWidgetId(id)
+  if (!normalized)
+    throw new Error(reason)
+
+  return normalized
+}
+
+/**
+ * Normalizes optional widget ids for open/prepare operations.
+ *
+ * Before:
+ * - `"  widget-1  "`
+ * - `""`
+ *
+ * After:
+ * - `"widget-1"`
+ * - `undefined`
+ */
+export function normalizeOptionalWidgetId(id?: string): string | undefined {
+  return normalizeWidgetId(id)
+}
diff --git a/apps/stage-tamagotchi/src/main/windows/widgets/index.test.ts b/apps/stage-tamagotchi/src/main/windows/widgets/index.test.ts
new file mode 100644
index 000000000..560ae0b2e
--- /dev/null
+++ b/apps/stage-tamagotchi/src/main/windows/widgets/index.test.ts
@@ -0,0 +1,53 @@
+import type { WidgetWindowSize } from '../../../shared/eventa'
+
+import { describe, expect, it } from 'vitest'
+
+import { normalizeWidgetWindowSize } from '../../../shared/utils/electron/windows/window-size'
+
+describe('normalizeWidgetWindowSize', () => {
+  it('returns undefined for missing or unusable base sizes', () => {
+    expect(normalizeWidgetWindowSize()).toBeUndefined()
+    expect(normalizeWidgetWindowSize({ width: 0, height: 320 })).toBeUndefined()
+    expect(normalizeWidgetWindowSize({ width: 320, height: -1 })).toBeUndefined()
+    expect(normalizeWidgetWindowSize({ width: Number.NaN, height: 320 })).toBeUndefined()
+    expect(normalizeWidgetWindowSize({ width: 320, height: Number.POSITIVE_INFINITY })).toBeUndefined()
+  })
+
+  it('floors valid dimensions and strips invalid optional constraints', () => {
+    const input: WidgetWindowSize = {
+      width: 620.9,
+      height: 480.4,
+      minWidth: -10,
+      minHeight: Number.NaN,
+      maxWidth: 1280.6,
+      maxHeight: 720.1,
+    }
+
+    expect(normalizeWidgetWindowSize(input)).toEqual({
+      width: 620,
+      height: 480,
+      maxWidth: 1280,
+      maxHeight: 720,
+    })
+  })
+
+  it('keeps contradictory but numerically valid constraints for later display clamping', () => {
+    const input: WidgetWindowSize = {
+      width: 900,
+      height: 700,
+      minWidth: 1200,
+      maxWidth: 800,
+      minHeight: 900,
+      maxHeight: 600,
+    }
+
+    expect(normalizeWidgetWindowSize(input)).toEqual({
+      width: 900,
+      height: 700,
+      minWidth: 1200,
+      maxWidth: 800,
+      minHeight: 900,
+      maxHeight: 600,
+    })
+  })
+})
diff --git a/apps/stage-tamagotchi/src/main/windows/widgets/index.ts b/apps/stage-tamagotchi/src/main/windows/widgets/index.ts
index 360d22bf7..8425262f9 100644
--- a/apps/stage-tamagotchi/src/main/windows/widgets/index.ts
+++ b/apps/stage-tamagotchi/src/main/windows/widgets/index.ts
@@ -1,7 +1,12 @@
 import type { BrowserWindow, Rectangle } from 'electron'
 import type { InferOutput } from 'valibot'
 
-import type { WidgetsAddPayload, WidgetSnapshot } from '../../../shared/eventa'
+import type {
+  PluginModuleWidgetPayload,
+  WidgetsAddPayload,
+  WidgetSnapshot,
+  WidgetsUpdatePayload,
+} from '../../../shared/eventa'
 import type { I18n } from '../../libs/i18n'
 import type { ServerChannel } from '../../services/airi/channel-server'
 
@@ -10,26 +15,140 @@ import { join, resolve } from 'node:path'
 import { createContext } from '@moeru/eventa/adapters/electron/main'
 import { safeClose } from '@proj-airi/electron-vueuse/main'
 import { BrowserWindow as ElectronBrowserWindow, ipcMain, screen, shell } from 'electron'
+import { clamp } from 'es-toolkit/math'
 import { isMacOS } from 'std-env'
 import { number, object, optional } from 'valibot'
 
 import icon from '../../../../resources/icon.png?asset'
 
 import { widgetsClearEvent, widgetsRemoveEvent, widgetsRenderEvent, widgetsUpdateEvent } from '../../../shared/eventa'
+import { normalizeWidgetWindowSize } from '../../../shared/utils/electron/windows/window-size'
 import { baseUrl, getElectronMainDirname, load, withHashRoute } from '../../libs/electron/location'
 import { createConfig } from '../../libs/electron/persistence'
 import { createReusableWindow } from '../../libs/electron/window-manager'
 import { spotlightLikeWindowConfig, transparentWindowConfig } from '../shared/window'
 import { setupWidgetsWindowInvokes } from './rpc/index.electron'
 
+/**
+ * Controls the overlay widget window lifecycle and widget registry.
+ *
+ * Use when:
+ * - Electron services need to spawn or update overlay widgets
+ * - Renderer invokes need a stable window-management bridge
+ *
+ * Expects:
+ * - A reusable Electron widget window managed by {@link setupWidgetsWindowManager}
+ * - Widget ids remain stable across updates for the same widget surface
+ *
+ * Returns:
+ * - An imperative manager for opening the widget window and mutating widget state
+ */
 export interface WidgetsWindowManager {
+  /**
+   * Resolves the shared widgets window instance.
+   *
+   * Use when:
+   * - A caller needs direct access to the backing Electron window
+   *
+   * Expects:
+   * - The window manager has already been initialized
+   *
+   * Returns:
+   * - The live widgets {@link BrowserWindow}, creating it if necessary
+   */
   getWindow: () => Promise<BrowserWindow>
+  /**
+   * Opens the widgets window, optionally focusing a prepared widget route.
+   *
+   * Use when:
+   * - The caller wants to show the widgets surface without pushing a new widget payload yet
+   * - A prepared widget id should restore its dedicated route and layout
+   *
+   * Expects:
+   * - `params.id`, when provided, matches a widget prepared through {@link WidgetsWindowManager.prepareWidgetWindow}
+   *
+   * Returns:
+   * - Resolves after the target window route has been shown
+   */
   openWindow: (params?: { id?: string }) => Promise<void>
+  /**
+   * Inserts or replaces a widget snapshot and renders it in the widgets window.
+   *
+   * Use when:
+   * - A renderer or tool wants to spawn a new overlay widget
+   * - A caller has already prepared an id and wants to attach widget content to it
+   *
+   * Expects:
+   * - `payload.componentName` identifies a registered renderer widget
+   *
+   * Returns:
+   * - The resolved widget id used for subsequent updates or removal
+   */
   pushWidget: (payload: WidgetsAddPayload) => Promise<string>
-  updateWidget: (payload: { id: string, componentProps?: Record<string, any> }) => Promise<void>
+  /**
+   * Applies partial widget changes to an existing widget snapshot.
+   *
+   * Use when:
+   * - A widget's props, size, or time-to-live must change without respawning it
+   *
+   * Expects:
+   * - `payload.id` references an existing widget managed by this instance
+   *
+   * Returns:
+   * - Resolves after in-memory state and renderer events have been updated
+   */
+  updateWidget: (payload: WidgetsUpdatePayload) => Promise<void>
+  /**
+   * Removes a single widget from the registry and renderer surface.
+   *
+   * Use when:
+   * - A specific widget should disappear immediately
+   *
+   * Expects:
+   * - `id` matches a widget previously created or prepared through this manager
+   *
+   * Returns:
+   * - Resolves after the widget has been removed and the renderer notified
+   */
   removeWidget: (id: string) => Promise<void>
+  /**
+   * Removes all widgets and closes any live widget windows.
+   *
+   * Use when:
+   * - The overlay surface should reset to an empty state
+   *
+   * Expects:
+   * - No additional input
+   *
+   * Returns:
+   * - Resolves after the registry, renderer, and child windows have been cleared
+   */
   clearWidgets: () => Promise<void>
+  /**
+   * Reads the current snapshot for a single widget id.
+   *
+   * Use when:
+   * - Another service needs to inspect a widget before opening or mutating it
+   *
+   * Expects:
+   * - `id` is the widget identifier to inspect
+   *
+   * Returns:
+   * - The current snapshot, or `undefined` when the widget is unknown
+   */
   getWidgetSnapshot: (id: string) => WidgetSnapshot | undefined
+  /**
+   * Reserves a widget id before content is pushed into the widgets window.
+   *
+   * Use when:
+   * - The caller wants a stable route or window context before rendering
+   *
+   * Expects:
+   * - `options.id`, when provided, should be stable for later reuse
+   *
+   * Returns:
+   * - The prepared widget id bound to a future window context
+   */
   prepareWidgetWindow: (options?: { id?: string }) => string
 }
 
@@ -53,6 +172,18 @@ function computeDefaultBounds(): Rectangle {
   return { x, y, width, height }
 }
 
+function resolveWindowSizeFromPayload(payload: Pick<WidgetsAddPayload, 'componentName' | 'componentProps' | 'windowSize'>) {
+  const explicitWindowSize = normalizeWidgetWindowSize(payload.windowSize)
+  if (explicitWindowSize)
+    return explicitWindowSize
+
+  if (payload.componentName?.trim().toLowerCase() !== 'plugin-module')
+    return undefined
+
+  const pluginModulePayload = payload.componentProps as PluginModuleWidgetPayload | undefined
+  return normalizeWidgetWindowSize(pluginModulePayload?.windowSize)
+}
+
 function createWidgetsWindow() {
   const window = new ElectronBrowserWindow({
     title: 'Widgets',
@@ -96,6 +227,27 @@ interface WidgetWindowContext {
   window?: BrowserWindow
 }
 
+/**
+ * Creates the Electron widgets window manager and its widget registry bridge.
+ *
+ * Use when:
+ * - Main-process services need to spawn, update, or remove overlay widgets
+ * - Widget window RPC handlers need a stable manager instance
+ *
+ * Expects:
+ * - `serverChannel` and `i18n` are already initialized for the main process
+ * - Renderer widget routes are available under the widgets page
+ *
+ * Returns:
+ * - A {@link WidgetsWindowManager} that coordinates widget state and window reuse
+ *
+ * Call stack:
+ *
+ * setupWidgetsWindowManager (./index)
+ *   -> {@link createReusableWindow}
+ *     -> {@link setupWidgetsWindowInvokes}
+ *       -> {@link createContext}
+ */
 export function setupWidgetsWindowManager(params: {
   serverChannel: ServerChannel
   i18n: I18n
@@ -117,6 +269,7 @@ export function setupWidgetsWindowManager(params: {
   let pendingRoute: string | undefined
   let currentRoute: string | undefined
   let activeWidgetsWindow: BrowserWindow | undefined
+  let persistWindowBounds = true
 
   let widgetsManager: WidgetsWindowManager | undefined
 
@@ -146,7 +299,11 @@ export function setupWidgetsWindowManager(params: {
       window.setBounds(computeDefaultBounds())
     }
 
-    const persist = () => update({ bounds: window.getBounds() })
+    const persist = () => {
+      if (!persistWindowBounds)
+        return
+      update({ bounds: window.getBounds() })
+    }
     window.on('resize', persist)
     window.on('move', persist)
 
@@ -175,6 +332,19 @@ export function setupWidgetsWindowManager(params: {
     return window
   })
 
+  /**
+   * Reserves a widget id and its window context before rendering.
+   *
+   * Use when:
+   * - The caller wants a stable route for a widget before pushing content
+   * - `openWindow({ id })` should target a dedicated widget route
+   *
+   * Expects:
+   * - `options.id`, when supplied, should be reused for future updates
+   *
+   * Returns:
+   * - The prepared widget id
+   */
   function prepareWidgetWindow(options?: { id?: string }): string {
     const id = options?.id ?? Math.random().toString(36).slice(2, 10)
     if (!windowContexts.has(id)) {
@@ -227,6 +397,57 @@ export function setupWidgetsWindowManager(params: {
     currentRoute = route
   }
 
+  function applyStoredOrDefaultBounds(window: BrowserWindow) {
+    const saved = getConfig().bounds
+    if (saved) {
+      const work = screen.getDisplayMatching(saved).workArea
+      const width = Math.min(saved.width, work.width)
+      const height = Math.min(saved.height, work.height)
+      const clamped: Rectangle = {
+        x: clamp(saved.x, work.x, work.x + work.width - width),
+        y: clamp(saved.y, work.y, work.y + work.height - height),
+        width,
+        height,
+      }
+      window.setBounds(clamped)
+      return
+    }
+
+    window.setBounds(computeDefaultBounds())
+  }
+
+  function applyWindowLayout(window: BrowserWindow, snapshot?: Pick<WidgetSnapshot, 'windowSize'>) {
+    const display = screen.getDisplayMatching(window.getBounds())
+    const work = display.workArea
+    const windowSize = normalizeWidgetWindowSize(snapshot?.windowSize)
+
+    if (!windowSize) {
+      persistWindowBounds = true
+      window.setMinimumSize(0, 0)
+      window.setMaximumSize(work.width, work.height)
+      applyStoredOrDefaultBounds(window)
+      return
+    }
+
+    persistWindowBounds = false
+    const minWidth = clamp(windowSize.minWidth ?? 240, 1, work.width)
+    const minHeight = clamp(windowSize.minHeight ?? 160, 1, work.height)
+    const maxWidth = clamp(windowSize.maxWidth ?? work.width, minWidth, work.width)
+    const maxHeight = clamp(windowSize.maxHeight ?? work.height, minHeight, work.height)
+    const width = clamp(windowSize.width, minWidth, maxWidth)
+    const height = clamp(windowSize.height, minHeight, maxHeight)
+    const currentBounds = window.getBounds()
+
+    window.setMinimumSize(minWidth, minHeight)
+    window.setMaximumSize(maxWidth, maxHeight)
+    window.setBounds({
+      x: clamp(currentBounds.x, work.x, work.x + work.width - width),
+      y: clamp(currentBounds.y, work.y, work.y + work.height - height),
+      width,
+      height,
+    })
+  }
+
   async function getWindowFromContext(context?: WidgetWindowContext): Promise<BrowserWindow> {
     if (!context)
       return getWindow()
@@ -237,10 +458,11 @@ export function setupWidgetsWindowManager(params: {
     return resolved
   }
 
-  async function showWindowWithRoute(route: string, context?: WidgetWindowContext) {
+  async function showWindowWithRoute(route: string, context?: WidgetWindowContext, snapshot?: Pick<WidgetSnapshot, 'windowSize'>) {
     pendingRoute = route
     const window = await getWindowFromContext(context)
     pendingRoute = undefined
+    applyWindowLayout(window, snapshot)
     if (currentRoute !== route)
       await loadWithRoute(window, route)
     window.show()
@@ -249,17 +471,54 @@ export function setupWidgetsWindowManager(params: {
     return window
   }
 
+  /**
+   * Resolves the shared widgets window instance for callers that need direct access.
+   *
+   * Use when:
+   * - Another service needs the backing Electron window without changing widget state
+   *
+   * Expects:
+   * - The reusable window factory is available
+   *
+   * Returns:
+   * - The widgets {@link BrowserWindow}
+   */
   async function getWindow(): Promise<BrowserWindow> {
     return reusable.getWindow()
   }
 
+  /**
+   * Opens the widgets window and restores a prepared widget route when available.
+   *
+   * Use when:
+   * - The caller wants to reveal the widgets surface without pushing new content
+   *
+   * Expects:
+   * - `params.id`, when provided, references a prepared widget id
+   *
+   * Returns:
+   * - Resolves after the window has been shown
+   */
   async function openWindow(params?: { id?: string }) {
     const id = params?.id ? prepareWidgetWindow({ id: params.id }) : undefined
     const route = id ? `${defaultRoute}?id=${id}` : defaultRoute
     const context = id ? windowContexts.get(id) : undefined
-    await showWindowWithRoute(route, context)
+    const snapshot = id ? widgetRecords.get(id) : undefined
+    await showWindowWithRoute(route, context, snapshot)
   }
 
+  /**
+   * Creates or replaces a widget snapshot and renders it in the widget window.
+   *
+   * Use when:
+   * - A renderer or tool wants to spawn overlay content
+   *
+   * Expects:
+   * - `payload.componentName` matches a renderer component known by the widgets page
+   *
+   * Returns:
+   * - The stable widget id that was rendered
+   */
   async function pushWidget(payload: WidgetsAddPayload): Promise<string> {
     const id = prepareWidgetWindow({ id: payload.id })
     const snapshot: WidgetSnapshot = {
@@ -267,17 +526,30 @@ export function setupWidgetsWindowManager(params: {
       componentName: payload.componentName,
       componentProps: payload.componentProps ?? {},
       size: payload.size ?? 'm',
+      windowSize: resolveWindowSizeFromPayload(payload),
       ttlMs: payload.ttlMs ?? 0,
     }
     upsertRecord(snapshot)
     const context = windowContexts.get(id)
-    await showWindowWithRoute(`${defaultRoute}?id=${id}`, context)
+    await showWindowWithRoute(`${defaultRoute}?id=${id}`, context, snapshot)
     eventaContext?.emit(widgetsRenderEvent, snapshot)
 
     return id
   }
 
-  async function updateWidget(payload: { id: string, componentProps?: Record<string, any> }) {
+  /**
+   * Applies partial widget mutations to an existing widget snapshot.
+   *
+   * Use when:
+   * - Props, size, or time-to-live need to change without recreating the widget id
+   *
+   * Expects:
+   * - `payload.id` references an existing widget
+   *
+   * Returns:
+   * - Resolves after internal state and renderer events have been updated
+   */
+  async function updateWidget(payload: WidgetsUpdatePayload) {
     if (!payload?.id)
       return
 
@@ -288,13 +560,39 @@ export function setupWidgetsWindowManager(params: {
     const nextSnapshot: WidgetSnapshot = {
       ...toSnapshot(existing),
       componentProps: payload.componentProps ?? existing.componentProps,
+      size: payload.size ?? existing.size,
+      windowSize: normalizeWidgetWindowSize(payload.windowSize) ?? existing.windowSize,
+      ttlMs: payload.ttlMs ?? existing.ttlMs,
     }
 
     upsertRecord(nextSnapshot)
 
-    eventaContext?.emit(widgetsUpdateEvent, { id: nextSnapshot.id, componentProps: nextSnapshot.componentProps })
+    const context = windowContexts.get(payload.id)
+    const window = context?.window
+    if (window && !window.isDestroyed())
+      applyWindowLayout(window, nextSnapshot)
+
+    eventaContext?.emit(widgetsUpdateEvent, {
+      id: nextSnapshot.id,
+      componentProps: nextSnapshot.componentProps,
+      size: nextSnapshot.size,
+      windowSize: nextSnapshot.windowSize,
+      ttlMs: nextSnapshot.ttlMs,
+    })
   }
 
+  /**
+   * Removes one widget and emits the corresponding renderer event.
+   *
+   * Use when:
+   * - A caller needs to dismiss a single widget immediately
+   *
+   * Expects:
+   * - `id` references a widget managed by this instance
+   *
+   * Returns:
+   * - Resolves after the widget has been removed from memory and renderer state
+   */
   async function removeWidget(id: string) {
     if (!id)
       return
@@ -302,6 +600,18 @@ export function setupWidgetsWindowManager(params: {
     eventaContext?.emit(widgetsRemoveEvent, { id })
   }
 
+  /**
+   * Clears every widget and closes all widget windows owned by this manager.
+   *
+   * Use when:
+   * - The overlay surface must reset completely
+   *
+   * Expects:
+   * - No input
+   *
+   * Returns:
+   * - Resolves after state, renderer events, and windows have been cleared
+   */
   async function clearWidgets() {
     const ids = [...widgetRecords.keys()]
     for (const id of ids)
@@ -324,6 +634,18 @@ export function setupWidgetsWindowManager(params: {
     windowContexts.clear()
   }
 
+  /**
+   * Reads the current widget snapshot without mutating widget state.
+   *
+   * Use when:
+   * - Another service needs to inspect a widget before deciding what to do next
+   *
+   * Expects:
+   * - `id` is the widget identifier to read
+   *
+   * Returns:
+   * - The widget snapshot, or `undefined` when not found
+   */
   function getWidgetSnapshot(id: string) {
     const record = widgetRecords.get(id)
     if (!record)
diff --git a/apps/stage-tamagotchi/src/renderer/pages/devtools/widgets-calling.vue b/apps/stage-tamagotchi/src/renderer/pages/devtools/widgets-calling.vue
index 1b4198d9d..13e045d7d 100644
--- a/apps/stage-tamagotchi/src/renderer/pages/devtools/widgets-calling.vue
+++ b/apps/stage-tamagotchi/src/renderer/pages/devtools/widgets-calling.vue
@@ -243,6 +243,16 @@ function applyMapPreset() {
   form.ttlSeconds = ''
   resetFeedback()
 }
+
+function applyExtensionUiPreset() {
+  form.componentName = 'extension-ui'
+  form.sizePreset = 'custom'
+  form.customCols = '4'
+  form.customRows = '3'
+  form.componentProps = JSON.stringify({}, null, 2)
+  form.ttlSeconds = ''
+  resetFeedback()
+}
 </script>
 
 <template>
@@ -271,6 +281,13 @@ function applyMapPreset() {
         >
           Map Preset
         </Button>
+        <Button
+          variant="secondary"
+          :disabled="busy"
+          @click="applyExtensionUiPreset"
+        >
+          Extension UI Preset
+        </Button>
       </div>
     </div>
 
diff --git a/apps/stage-tamagotchi/src/renderer/pages/widgets.vue b/apps/stage-tamagotchi/src/renderer/pages/widgets.vue
index 3fc466bc2..52d7468e3 100644
--- a/apps/stage-tamagotchi/src/renderer/pages/widgets.vue
+++ b/apps/stage-tamagotchi/src/renderer/pages/widgets.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import type { WidgetSnapshot } from '../../shared/eventa'
+import type { WidgetSnapshot, WidgetWindowSize } from '../../shared/eventa'
 
 import { useElectronEventaContext, useElectronEventaInvoke } from '@proj-airi/electron-vueuse'
 import { computed, defineAsyncComponent, defineComponent, h, onBeforeUnmount, onMounted, ref, watch } from 'vue'
@@ -14,6 +14,7 @@ interface WidgetItem {
   componentName: string
   componentProps: Record<string, any>
   size: SizePreset
+  windowSize?: WidgetWindowSize
   ttlMs: number
 }
 
@@ -61,6 +62,7 @@ function applySnapshot(snapshot: WidgetSnapshot) {
     componentName: snapshot.componentName,
     componentProps: snapshot.componentProps ?? {},
     size: snapshot.size ?? 'm',
+    windowSize: snapshot.windowSize,
     ttlMs: snapshot.ttlMs ?? 0,
   }
 
@@ -120,10 +122,13 @@ onMounted(() => {
         return
       }
 
-      widget.value = {
+      applySnapshot({
         ...widget.value,
         componentProps: body.componentProps ?? widget.value.componentProps,
-      }
+        size: body.size ?? widget.value.size,
+        windowSize: body.windowSize ?? widget.value.windowSize,
+        ttlMs: body.ttlMs ?? widget.value.ttlMs,
+      })
     })
   }
   catch {}
@@ -155,15 +160,16 @@ onBeforeUnmount(() => {
 })
 
 const Registry: Record<string, ReturnType<typeof defineAsyncComponent>> = {
-  map: defineAsyncComponent(async () => (await import('../widgets/map')).Map),
-  weather: defineAsyncComponent(async () => (await import('../widgets/weather')).Weather),
+  'extension-ui': defineAsyncComponent(async () => (await import('../widgets/extension-ui')).ExtensionUi),
+  'map': defineAsyncComponent(async () => (await import('../widgets/map')).Map),
+  'weather': defineAsyncComponent(async () => (await import('../widgets/weather')).Weather),
 }
 
 const GenericWidget = defineComponent({
   name: 'GenericWidget',
   props: { title: { type: String, required: true }, modelValue: { type: Object, default: () => ({}) } },
   setup(props) {
-    return () => h('div', { class: 'h-full w-full flex flex-col gap-2 rounded-xl border border-neutral-200/30 bg-[rgba(28,28,28,0.72)] p-3 text-neutral-100 shadow-[0_8px_20px_rgba(0,0,0,0.35)] backdrop-blur-md dark:border-neutral-700/30' }, [
+    return () => h('div', { class: 'h-full w-full flex flex-col gap-2 rounded-xl bg-[rgba(28,28,28,0.72)] p-3 text-neutral-100 shadow-[0_8px_20px_rgba(0,0,0,0.35)] backdrop-blur-md' }, [
       h('div', { class: 'flex items-center justify-between' }, [
         h('div', { class: 'text-sm font-medium opacity-90' }, props.title),
       ]),
@@ -208,7 +214,7 @@ function handleClose() {
       ✕
     </button>
     <div v-if="!widgetId" class="h-full flex items-center justify-center">
-      <div class="border border-neutral-200/20 rounded-xl bg-neutral-900/40 px-4 py-3 text-sm text-neutral-200/80 backdrop-blur">
+      <div class="rounded-xl bg-neutral-900/40 px-4 py-3 text-sm text-neutral-200/80 backdrop-blur">
         Missing widget id. Launch the window via a component call to populate this view.
       </div>
     </div>
@@ -223,7 +229,7 @@ function handleClose() {
       />
     </div>
     <div v-else class="h-full flex items-center justify-center">
-      <div class="border border-neutral-200/20 rounded-xl bg-neutral-900/40 px-4 py-3 text-sm text-neutral-200/80 backdrop-blur">
+      <div class="rounded-xl bg-neutral-900/40 px-4 py-3 text-sm text-neutral-200/80 backdrop-blur">
         {{ loading ? 'Loading widget...' : `Waiting for widget data for "${widgetId}"` }}
       </div>
     </div>
diff --git a/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.test.ts b/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.test.ts
index 3b2d83eb5..b095a90ac 100644
--- a/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.test.ts
+++ b/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.test.ts
@@ -2,6 +2,7 @@ import type { WidgetInvokers } from './widgets'
 
 import { describe, expect, it, vi } from 'vitest'
 
+import { canRenderExtensionUi, sanitizeExtensionUiRenderProps } from '../../../widgets/extension-ui/host'
 import { executeWidgetAction, normalizeComponentProps } from './widgets'
 
 describe('widgets tool helpers', () => {
@@ -60,6 +61,127 @@ describe('widgets tool helpers', () => {
       })
     })
 
+    it('forwards custom window sizing when spawning a widget', async () => {
+      const invokers = makeInvokers()
+      vi.mocked(invokers.addWidget).mockResolvedValue('sized-widget')
+
+      await executeWidgetAction({
+        action: 'spawn',
+        id: ' sized-widget ',
+        componentName: 'weather',
+        componentProps: '{"city":"Taipei"}',
+        size: 'l',
+        ttlSeconds: 0,
+        windowSize: {
+          width: 620,
+          height: 760,
+          minWidth: 480,
+          minHeight: 320,
+        },
+      } as any, { invokers })
+
+      expect(invokers.addWidget).toHaveBeenCalledWith({
+        id: 'sized-widget',
+        componentName: 'weather',
+        componentProps: { city: 'Taipei' },
+        size: 'l',
+        ttlMs: 0,
+        windowSize: {
+          width: 620,
+          height: 760,
+          minWidth: 480,
+          minHeight: 320,
+        },
+      })
+    })
+
+    it('preserves extension-ui payloads when spawning dynamic modules', async () => {
+      const invokers = makeInvokers()
+      vi.mocked(invokers.addWidget).mockResolvedValue('chess-main')
+
+      await executeWidgetAction({
+        action: 'spawn',
+        id: ' chess-main ',
+        componentName: 'extension-ui',
+        componentProps: JSON.stringify({
+          moduleId: 'chess-main',
+          title: 'Extension UI',
+          windowSize: {
+            width: 720,
+            height: 540,
+            minWidth: 480,
+          },
+          payload: {
+            side: 'white',
+          },
+        }),
+        size: 'm',
+        ttlSeconds: 0,
+      }, { invokers })
+
+      expect(invokers.addWidget).toHaveBeenCalledWith(expect.objectContaining({
+        id: 'chess-main',
+        componentName: 'extension-ui',
+        componentProps: expect.objectContaining({
+          moduleId: 'chess-main',
+          title: 'Extension UI',
+          windowSize: {
+            width: 720,
+            height: 540,
+            minWidth: 480,
+          },
+          payload: {
+            side: 'white',
+          },
+        }),
+        windowSize: {
+          width: 720,
+          height: 540,
+          minWidth: 480,
+        },
+      }))
+    })
+
+    it('sanitizes reserved extension-ui host props before dispatch', async () => {
+      const invokers = makeInvokers()
+      vi.mocked(invokers.addWidget).mockResolvedValue('guarded-main')
+
+      await executeWidgetAction({
+        action: 'spawn',
+        id: ' guarded-main ',
+        componentName: 'extension-ui',
+        componentProps: JSON.stringify({
+          'moduleId': 'guarded-main',
+          'title': 'Guarded Module',
+          'modelValue': { injected: true },
+          'module': { injected: true },
+          'moduleConfig': { injected: true },
+          'model-value': { injected: true },
+          'module-config': { injected: true },
+          'payload': {
+            safe: true,
+          },
+        }),
+        size: 'm',
+        ttlSeconds: 0,
+      }, { invokers })
+
+      const dispatched = vi.mocked(invokers.addWidget).mock.calls[0]?.[0]
+      expect(dispatched).toBeDefined()
+      expect(dispatched?.componentProps).toMatchObject({
+        moduleId: 'guarded-main',
+        title: 'Guarded Module',
+        payload: {
+          safe: true,
+        },
+      })
+      expect(dispatched?.componentProps).not.toHaveProperty('modelValue')
+      expect(dispatched?.componentProps).not.toHaveProperty('module')
+      expect(dispatched?.componentProps).not.toHaveProperty('moduleConfig')
+      expect(dispatched?.componentProps).not.toHaveProperty('model-value')
+      expect(dispatched?.componentProps).not.toHaveProperty('module-config')
+    })
+
     it('updates props and trims id', async () => {
       const invokers = makeInvokers()
       await executeWidgetAction({
@@ -118,4 +240,46 @@ describe('widgets tool helpers', () => {
       expect(invokers.clearWidgets).toHaveBeenCalledTimes(1)
     })
   })
+
+  describe('extension-ui host helpers', () => {
+    it('removes host-controlled render props from payload props', () => {
+      expect(sanitizeExtensionUiRenderProps({
+        'title': 'Override',
+        'modelValue': { injected: true },
+        'module': { injected: true },
+        'moduleConfig': { injected: true },
+        'model-value': { injected: true },
+        'module-config': { injected: true },
+        'safe': true,
+      })).toEqual({
+        safe: true,
+      })
+    })
+
+    it('requires a registered module before rendering a resolved widget', () => {
+      expect(canRenderExtensionUi({
+        loading: false,
+        moduleSnapshot: undefined,
+        iframeSrc: 'https://example.com',
+      })).toBe(false)
+
+      expect(canRenderExtensionUi({
+        loading: false,
+        error: 'module missing',
+        moduleSnapshot: {
+          moduleId: 'module-1',
+          ownerSessionId: 'session-1',
+          ownerPluginId: 'plugin-1',
+          kitId: 'kit.widget',
+          kitModuleType: 'window',
+          state: 'active',
+          runtime: 'electron',
+          revision: 1,
+          updatedAt: Date.now(),
+          config: {},
+        },
+        iframeSrc: 'https://example.com',
+      })).toBe(false)
+    })
+  })
 })
diff --git a/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.ts b/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.ts
index 898224df5..3b4b7e944 100644
--- a/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.ts
+++ b/apps/stage-tamagotchi/src/renderer/stores/tools/builtin/widgets.ts
@@ -1,11 +1,15 @@
 import type { Tool } from '@xsai/shared-chat'
 
+import type { WidgetWindowSize } from '../../../../shared/eventa'
+
 import { defineInvoke } from '@moeru/eventa'
 import { createContext } from '@moeru/eventa/adapters/electron/renderer'
 import { tool } from '@xsai/tool'
 import { z } from 'zod'
 
 import { widgetsAdd, widgetsClear, widgetsOpenWindow, widgetsPrepareWindow, widgetsRemove, widgetsUpdate } from '../../../../shared/eventa'
+import { normalizeWidgetWindowSize } from '../../../../shared/utils/electron/windows/window-size'
+import { sanitizeExtensionUiDispatchProps } from '../../../widgets/extension-ui/host'
 
 type SizePreset = 's' | 'm' | 'l'
 
@@ -16,6 +20,7 @@ type WidgetActionInput
     componentName: string
     componentProps: string | Record<string, any>
     size: SizePreset
+    windowSize?: WidgetWindowSize
     ttlSeconds: number
   }
   | {
@@ -24,6 +29,7 @@ type WidgetActionInput
     componentProps: string | Record<string, any>
     componentName?: string
     size?: SizePreset
+    windowSize?: WidgetWindowSize
     ttlSeconds?: number
   }
   | {
@@ -32,6 +38,7 @@ type WidgetActionInput
     componentName?: string
     componentProps?: string | Record<string, any>
     size?: SizePreset
+    windowSize?: WidgetWindowSize
     ttlSeconds?: number
   }
   | {
@@ -40,6 +47,7 @@ type WidgetActionInput
     componentName?: string
     componentProps?: string | Record<string, any>
     size?: SizePreset
+    windowSize?: WidgetWindowSize
     ttlSeconds?: number
   }
   | {
@@ -48,6 +56,7 @@ type WidgetActionInput
     componentName?: string
     componentProps?: string | Record<string, any>
     size?: SizePreset
+    windowSize?: WidgetWindowSize
     ttlSeconds?: number
   }
 
@@ -76,12 +85,22 @@ function resolveInvokers(override?: WidgetInvokers): WidgetInvokers {
   return cachedInvokers
 }
 
+const widgetWindowSizeParams = z.object({
+  width: z.number().positive(),
+  height: z.number().positive(),
+  minWidth: z.number().positive().optional(),
+  minHeight: z.number().positive().optional(),
+  maxWidth: z.number().positive().optional(),
+  maxHeight: z.number().positive().optional(),
+}).strict()
+
 const widgetParams = z.object({
   action: z.enum(['spawn', 'update', 'remove', 'clear', 'open']).describe('Choose one: spawn, update, remove, clear, open'),
   id: z.string().describe('Widget id; required for update/remove, optional for spawn/open'),
   componentName: z.string().describe('Widget component to render, e.g. weather (required for spawn)'),
   componentProps: z.string().describe('Widget props as JSON string (e.g. {"city":"Tokyo"})'),
   size: z.enum(['s', 'm', 'l']),
+  windowSize: widgetWindowSizeParams.optional().describe('Optional pixel window size and constraints, e.g. {"width":620,"height":760,"minWidth":480}'),
   ttlSeconds: z.number().int().nonnegative().describe('Auto-close timer in seconds (spawn only)'),
 }).strict()
 
@@ -108,6 +127,28 @@ export function normalizeComponentProps(raw?: string | Record<string, any>) {
   return {}
 }
 
+function resolveWindowSize(
+  componentName: string | undefined,
+  componentProps: Record<string, any>,
+  windowSize?: WidgetWindowSize,
+) {
+  const explicitWindowSize = normalizeWidgetWindowSize(windowSize)
+  if (explicitWindowSize)
+    return explicitWindowSize
+
+  if (componentName?.trim().toLowerCase() !== 'extension-ui')
+    return undefined
+
+  return normalizeWidgetWindowSize(componentProps.windowSize)
+}
+
+function sanitizeComponentPropsForDispatch(componentName: string | undefined, componentProps: Record<string, any>) {
+  if (componentName?.trim().toLowerCase() !== 'extension-ui')
+    return componentProps
+
+  return sanitizeExtensionUiDispatchProps(componentProps)
+}
+
 export async function executeWidgetAction(input: WidgetActionInput, deps?: { invokers?: WidgetInvokers }) {
   const invokers = resolveInvokers(deps?.invokers)
   const normalizedId = input.id?.trim() || undefined
@@ -118,12 +159,15 @@ export async function executeWidgetAction(input: WidgetActionInput, deps?: { inv
         throw new Error('componentName is required to spawn a widget.')
 
       const componentProps = normalizeComponentProps(input.componentProps)
+      const sanitizedComponentProps = sanitizeComponentPropsForDispatch(input.componentName, componentProps)
+      const windowSize = resolveWindowSize(input.componentName, sanitizedComponentProps, input.windowSize)
       const ttlMs = input.ttlSeconds ? Math.floor(input.ttlSeconds * 1000) : 0
       const id = await invokers.addWidget({
         id: normalizedId,
         componentName: input.componentName,
-        componentProps,
+        componentProps: sanitizedComponentProps,
         size: input.size ?? 'm',
+        windowSize,
         ttlMs,
       })
 
@@ -134,9 +178,12 @@ export async function executeWidgetAction(input: WidgetActionInput, deps?: { inv
         throw new Error('id is required to update a widget.')
 
       const componentProps = normalizeComponentProps(input.componentProps)
+      const sanitizedComponentProps = sanitizeComponentPropsForDispatch(input.componentName, componentProps)
+      const windowSize = resolveWindowSize(input.componentName, sanitizedComponentProps, input.windowSize)
       await invokers.updateWidget({
         id: normalizedId,
-        componentProps,
+        componentProps: sanitizedComponentProps,
+        windowSize,
       })
 
       return `Updated widget (${normalizedId}).`
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/components/extension-ui-host.vue b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/components/extension-ui-host.vue
new file mode 100644
index 000000000..cc3408d59
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/components/extension-ui-host.vue
@@ -0,0 +1,207 @@
+<script setup lang="ts">
+import type { ComponentPublicInstance } from 'vue'
+
+import type { PluginHostModuleSummary, PluginModuleWidgetPayload } from '../../../../shared/eventa'
+
+import { useElectronEventaInvoke } from '@proj-airi/electron-vueuse'
+import { isPlainObject } from 'es-toolkit'
+import { computed, shallowRef } from 'vue'
+
+import { electronPluginGetAssetBaseUrl, electronPluginInspect } from '../../../../shared/eventa'
+import { useExtensionUIForModule } from '../composables/use-extension-ui-for-module'
+import { useIframeMessagePort } from '../composables/use-iframe-message-port'
+import { canRenderExtensionUi, sanitizeExtensionUiRenderProps } from '../host'
+
+const props = withDefaults(defineProps<{
+  title?: string
+  modelValue?: Record<string, any>
+  moduleId?: string
+  componentProps?: Record<string, any>
+  payload?: Record<string, any>
+}>(), {
+  title: 'Extension UI',
+  modelValue: () => ({}),
+  moduleId: undefined,
+  componentProps: undefined,
+  payload: undefined,
+})
+
+function firstString(...values: unknown[]) {
+  for (const value of values) {
+    if (typeof value !== 'string') {
+      continue
+    }
+
+    const normalized = value.trim()
+    if (normalized) {
+      return normalized
+    }
+  }
+
+  return undefined
+}
+
+function omitControlFields(record: Record<string, any>) {
+  const {
+    componentProps: _componentProps,
+    moduleId: _moduleId,
+    payload: _payload,
+    title: _title,
+    windowSize: _windowSize,
+    ...rest
+  } = record
+
+  return rest
+}
+
+const inspectPluginHost = useElectronEventaInvoke(electronPluginInspect)
+const getPluginAssetBaseUrl = useElectronEventaInvoke(electronPluginGetAssetBaseUrl)
+
+const model = computed<PluginModuleWidgetPayload & Record<string, unknown>>(() => (
+  isPlainObject(props.modelValue) ? props.modelValue as PluginModuleWidgetPayload & Record<string, unknown> : {} as PluginModuleWidgetPayload & Record<string, unknown>
+))
+const moduleId = computed(() => firstString(props.moduleId, model.value.moduleId))
+const resolvedTitle = computed(() => firstString(props.title, model.value.title, moduleId.value) ?? 'Extension UI')
+const resolvedWidgetProps = computed(() => sanitizeExtensionUiRenderProps({
+  ...omitControlFields(model.value),
+  ...(isPlainObject(model.value.componentProps) ? model.value.componentProps as Record<string, unknown> : {}),
+  ...(isPlainObject(props.componentProps) ? props.componentProps as Record<string, unknown> : {}),
+  ...(isPlainObject(props.payload) ? props.payload as Record<string, unknown> : {}),
+  ...(isPlainObject(model.value.payload) ? model.value.payload as Record<string, unknown> : {}),
+}))
+
+const {
+  loading,
+  error,
+  moduleSnapshot,
+  moduleConfig,
+  iframeConfig,
+  iframeSrc,
+  iframeSrcdoc,
+  resolvedIframeSrc,
+  iframeMountError,
+} = useExtensionUIForModule({ moduleId, inspectPluginHost: () => inspectPluginHost(), getPluginAssetBaseUrl: () => getPluginAssetBaseUrl() })
+
+const iframeSandbox = computed(() => firstString(
+  iframeConfig.value.sandbox,
+  model.value.iframeSandbox,
+  'allow-scripts allow-same-origin allow-forms allow-popups',
+))
+
+const iframeElement = shallowRef<HTMLIFrameElement | null>(null)
+
+const { iframeLoadError, onIframeError, onIframeLoad } = useIframeMessagePort(
+  iframeElement,
+  {
+    moduleId,
+    moduleSnapshot: computed(() => moduleSnapshot.value as PluginHostModuleSummary | undefined),
+    moduleConfig,
+    propsPayload: resolvedWidgetProps,
+  },
+)
+
+function setIframeElement(element: Element | ComponentPublicInstance | null) {
+  iframeElement.value = element instanceof HTMLIFrameElement ? element : null
+}
+
+const canRenderIframe = computed(() => canRenderExtensionUi({
+  loading: loading.value,
+  error: error.value,
+  iframeLoadError: iframeLoadError.value,
+  iframeMountError: iframeMountError.value,
+  moduleSnapshot: moduleSnapshot.value,
+  iframeSrc: resolvedIframeSrc.value,
+  iframeSrcdoc: iframeSrcdoc.value,
+}))
+</script>
+
+<template>
+  <div :class="['h-full', 'w-full']">
+    <iframe
+      v-if="canRenderIframe"
+      :ref="setIframeElement"
+      :src="resolvedIframeSrc"
+      :srcdoc="iframeSrcdoc"
+      :sandbox="iframeSandbox"
+      :class="['h-full', 'w-full', 'rounded-xl', 'bg-transparent']"
+      allowtransparency="true"
+      :style="{ colorScheme: 'auto' }"
+      @load="onIframeLoad"
+      @error="onIframeError"
+    />
+
+    <div
+      v-else
+      :class="[
+        'h-full',
+        'w-full',
+        'flex',
+        'flex-col',
+        'gap-3',
+        'rounded-xl',
+        'bg-[rgba(28,28,28,0.72)]',
+        'p-4',
+        'text-neutral-100',
+        'shadow-[0_8px_20px_rgba(0,0,0,0.35)]',
+        'backdrop-blur-md',
+      ]"
+    >
+      <div :class="['flex', 'items-center', 'justify-between', 'gap-3']">
+        <div>
+          <div :class="['text-sm', 'font-semibold']">
+            {{ resolvedTitle }}
+          </div>
+          <div :class="['text-xs', 'opacity-70']">
+            {{ moduleId ?? 'No module id provided' }}
+          </div>
+        </div>
+        <div
+          v-if="moduleSnapshot"
+          :class="['rounded-full', 'bg-white/10', 'px-2', 'py-1', 'text-[11px]', 'uppercase', 'tracking-[0.08em]']"
+        >
+          {{ moduleSnapshot.state }}
+        </div>
+      </div>
+
+      <div v-if="loading" :class="['text-sm', 'opacity-80']">
+        Loading extension UI...
+      </div>
+
+      <div v-else-if="error" :class="['rounded-lg', 'bg-amber-500/12', 'p-3', 'text-sm', 'text-amber-100']">
+        {{ error }}
+      </div>
+
+      <div v-else-if="iframeLoadError" :class="['rounded-lg', 'bg-amber-500/12', 'p-3', 'text-sm', 'text-amber-100']">
+        {{ iframeLoadError }}
+      </div>
+
+      <div v-else-if="iframeMountError" :class="['rounded-lg', 'bg-amber-500/12', 'p-3', 'text-sm', 'text-amber-100']">
+        {{ iframeMountError }}
+      </div>
+
+      <div v-else-if="!iframeSrc && !iframeSrcdoc" :class="['text-sm', 'opacity-80']">
+        This module is registered, but it did not declare an iframe source to mount yet.
+      </div>
+
+      <dl v-if="moduleSnapshot" :class="['grid', 'grid-cols-[auto_1fr]', 'gap-x-3', 'gap-y-2', 'text-xs', 'opacity-80']">
+        <dt>Kit</dt>
+        <dd>{{ moduleSnapshot.kitId }}</dd>
+        <dt>Type</dt>
+        <dd>{{ moduleSnapshot.kitModuleType }}</dd>
+        <dt>Runtime</dt>
+        <dd>{{ moduleSnapshot.runtime }}</dd>
+        <dt>Revision</dt>
+        <dd>{{ moduleSnapshot.revision }}</dd>
+        <dt>Iframe</dt>
+        <dd>{{ iframeSrc ? 'src configured' : (iframeSrcdoc ? 'srcdoc configured' : 'unresolved') }}</dd>
+      </dl>
+
+      <div :class="['min-h-0', 'flex-1', 'overflow-auto', 'rounded-lg', 'bg-black/15', 'p-3']">
+        <pre :class="['whitespace-pre-wrap', 'break-words', 'text-[11px]', 'opacity-80']">{{ JSON.stringify({
+          config: moduleConfig,
+          props: resolvedWidgetProps,
+        }, null, 2) }}</pre>
+      </div>
+    </div>
+  </div>
+</template>
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/components/index.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/components/index.ts
new file mode 100644
index 000000000..db05f0bf3
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/components/index.ts
@@ -0,0 +1 @@
+export { default as ExtensionUiHost } from './extension-ui-host.vue'
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/composables/use-extension-ui-for-module.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/composables/use-extension-ui-for-module.ts
new file mode 100644
index 000000000..0fcb27ff9
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/composables/use-extension-ui-for-module.ts
@@ -0,0 +1,165 @@
+import type { ComputedRef } from 'vue'
+
+import type { PluginHostModuleSummary } from '../../../../shared/eventa'
+
+import { errorMessageFrom } from '@moeru/std'
+import { isPlainObject } from 'es-toolkit'
+import { computed, shallowRef, watch } from 'vue'
+
+function firstString(...values: unknown[]) {
+  for (const value of values) {
+    if (typeof value !== 'string') {
+      continue
+    }
+
+    const normalized = value.trim()
+    if (normalized) {
+      return normalized
+    }
+  }
+
+  return undefined
+}
+
+const trailingSlashesPattern = /\/+$/
+
+/**
+ * Resolves the inspected extension UI module snapshot and derives iframe-facing config for the host.
+ *
+ * Use when:
+ * - A widget host needs to inspect one plugin module by id before mounting its iframe
+ * - Host code needs normalized `src` / `srcdoc` values and loopback asset URL resolution
+ *
+ * Expects:
+ * - `moduleId` is the current extension module identifier when one is selected
+ * - `inspectPluginHost` returns the latest module snapshot list from the Electron bridge
+ * - `getPluginAssetBaseUrl` returns the loopback asset base URL when the asset server is available
+ *
+ * Returns:
+ * - Reactive loading and error state for module inspection
+ * - The resolved module snapshot and normalized iframe configuration values
+ */
+export function useExtensionUIForModule(options: {
+  moduleId: ComputedRef<string | undefined>
+  inspectPluginHost: () => Promise<{ modules: PluginHostModuleSummary[] }>
+  getPluginAssetBaseUrl: () => Promise<string>
+}) {
+  const loading = shallowRef(false)
+  const error = shallowRef<string>()
+  const moduleSnapshot = shallowRef<PluginHostModuleSummary>()
+  const pluginAssetBaseUrl = shallowRef<string>()
+  let requestVersion = 0
+
+  async function refreshPluginAssetBaseUrl() {
+    try {
+      pluginAssetBaseUrl.value = await options.getPluginAssetBaseUrl()
+    }
+    catch {
+      pluginAssetBaseUrl.value = undefined
+    }
+  }
+
+  watch(options.moduleId, async (nextModuleId) => {
+    const currentRequestVersion = ++requestVersion
+
+    loading.value = true
+    error.value = undefined
+    moduleSnapshot.value = undefined
+
+    await refreshPluginAssetBaseUrl()
+
+    if (!nextModuleId) {
+      if (currentRequestVersion === requestVersion) {
+        loading.value = false
+        error.value = 'Missing extension UI module id.'
+      }
+      return
+    }
+
+    try {
+      const snapshot = await options.inspectPluginHost()
+      if (currentRequestVersion !== requestVersion) {
+        return
+      }
+
+      moduleSnapshot.value = snapshot.modules.find(module => module.moduleId === nextModuleId)
+      if (!moduleSnapshot.value) {
+        error.value = `Extension UI module "${nextModuleId}" is not registered.`
+      }
+    }
+    catch (cause) {
+      if (currentRequestVersion !== requestVersion) {
+        return
+      }
+
+      error.value = errorMessageFrom(cause) || 'Failed to inspect extension UI modules.'
+    }
+    finally {
+      if (currentRequestVersion === requestVersion) {
+        loading.value = false
+      }
+    }
+  }, { immediate: true })
+
+  const moduleConfig = computed(() => isPlainObject(moduleSnapshot.value?.config) ? moduleSnapshot.value.config as Record<string, unknown> : {})
+  const widgetConfig = computed(() => isPlainObject(moduleConfig.value.widget) ? moduleConfig.value.widget as Record<string, unknown> : {})
+  const iframeConfig = computed(() => isPlainObject(widgetConfig.value.iframe) ? widgetConfig.value.iframe as Record<string, unknown> : {})
+
+  const iframeSrc = computed(() => firstString(
+    iframeConfig.value.src,
+    widgetConfig.value.iframeSrc,
+    moduleConfig.value.iframeSrc,
+  ))
+
+  const iframeSrcdoc = computed(() => firstString(
+    iframeConfig.value.srcdoc,
+    widgetConfig.value.iframeSrcdoc,
+    moduleConfig.value.iframeSrcdoc,
+  ))
+
+  const resolvedIframeSrc = computed(() => {
+    const src = iframeSrc.value
+    if (!src) {
+      return undefined
+    }
+
+    if (src.startsWith('/_airi/plugins/')) {
+      const baseUrl = pluginAssetBaseUrl.value
+      if (!baseUrl) {
+        return undefined
+      }
+
+      return new URL(src, `${baseUrl.replace(trailingSlashesPattern, '')}/`).toString()
+    }
+
+    return src
+  })
+
+  const iframeMountError = computed(() => {
+    if (!iframeSrc.value?.startsWith('/_airi/plugins/')) {
+      return undefined
+    }
+
+    if (resolvedIframeSrc.value) {
+      return undefined
+    }
+
+    return 'Plugin asset loopback server is unavailable.'
+  })
+
+  return {
+    loading,
+    error,
+    moduleSnapshot,
+    moduleConfig,
+    widgetConfig,
+    iframeConfig,
+    iframeSrc,
+    iframeSrcdoc,
+    resolvedIframeSrc,
+    iframeMountError,
+    pluginAssetBaseUrl,
+
+    refreshPluginAssetBaseUrl,
+  }
+}
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/composables/use-iframe-message-port.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/composables/use-iframe-message-port.ts
new file mode 100644
index 000000000..1e7df3574
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/composables/use-iframe-message-port.ts
@@ -0,0 +1,105 @@
+import type { MaybeElementRef } from '@vueuse/core'
+import type { ComputedRef } from 'vue'
+
+import type { PluginHostModuleSummary } from '../../../../shared/eventa'
+
+import { unrefElement } from '@vueuse/core'
+import { onBeforeUnmount, shallowRef, watch } from 'vue'
+
+import {
+  extensionUiBridgeEventaChannel,
+  extensionUiBridgeInitEvent,
+  extensionUiBridgeReadyEvent,
+} from '../shared/eventa'
+import { createWindowMessageEventaContext } from '../shared/eventa-runtime'
+
+/**
+ * Manages typed parent-to-iframe messaging for one extension UI iframe.
+ *
+ * Use when:
+ * - A renderer widget mounts an extension iframe and needs to keep it synchronized with host state
+ * - A module iframe needs a typed postMessage transport for init and ready handshakes
+ *
+ * Expects:
+ * - `target` resolves to the mounted iframe element when available
+ * - `moduleId` changes when the mounted extension module changes
+ * - `moduleSnapshot`, `moduleConfig`, and `propsPayload` stay structured-clone-safe for postMessage transport
+ *
+ * Returns:
+ * - Eventa iframe context for optional host-side message handling
+ * - Reactive iframe load error state
+ * - iframe load/error handlers for the host component template
+ */
+export function useIframeMessagePort(
+  target: MaybeElementRef,
+  options: {
+    moduleId: ComputedRef<string | undefined>
+    moduleSnapshot: ComputedRef<PluginHostModuleSummary | undefined>
+    moduleConfig: ComputedRef<Record<string, unknown>>
+    propsPayload: ComputedRef<Record<string, unknown>>
+  },
+) {
+  const iframeLoadError = shallowRef<string>()
+
+  const iframeRuntime = createWindowMessageEventaContext({
+    channel: extensionUiBridgeEventaChannel,
+    currentWindow: window,
+    expectedSource: () => {
+      const iframeElement = unrefElement(target)
+      return iframeElement instanceof HTMLIFrameElement ? iframeElement.contentWindow : null
+    },
+    targetWindow: () => {
+      const iframeElement = unrefElement(target)
+      return iframeElement instanceof HTMLIFrameElement ? iframeElement.contentWindow : null
+    },
+  })
+
+  function createInitPayload() {
+    return {
+      moduleId: options.moduleSnapshot.value?.moduleId,
+      module: options.moduleSnapshot.value,
+      config: options.moduleConfig.value,
+      props: options.propsPayload.value,
+    }
+  }
+
+  function emitInitPayload() {
+    iframeRuntime.context.emit(extensionUiBridgeInitEvent, createInitPayload())
+  }
+
+  function onIframeLoad() {
+    iframeLoadError.value = undefined
+    emitInitPayload()
+  }
+
+  function onIframeError() {
+    iframeLoadError.value = 'Failed to load extension UI iframe source.'
+  }
+
+  iframeRuntime.context.on(extensionUiBridgeReadyEvent, () => {
+    emitInitPayload()
+  })
+
+  watch(options.moduleId, () => {
+    emitInitPayload()
+  }, { immediate: true })
+
+  watch(options.propsPayload, () => {
+    emitInitPayload()
+  })
+
+  watch(options.moduleConfig, () => {
+    emitInitPayload()
+  })
+
+  onBeforeUnmount(() => {
+    iframeRuntime.dispose()
+  })
+
+  return {
+    context: iframeRuntime.context,
+    iframeLoadError,
+    onIframeLoad,
+    onIframeError,
+  }
+}
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/host.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/host.ts
new file mode 100644
index 000000000..df0d3de97
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/host.ts
@@ -0,0 +1,47 @@
+import type { PluginHostModuleSummary } from '../../../shared/eventa'
+
+const extensionUiDispatchReservedPropKeys = new Set([
+  'modelValue',
+  'module',
+  'moduleConfig',
+  'model-value',
+  'module-config',
+])
+
+const extensionUiRenderReservedPropKeys = new Set([
+  'title',
+  ...extensionUiDispatchReservedPropKeys,
+])
+
+function sanitizeExtensionUiProps(record: Record<string, any>, reservedKeys: Set<string>) {
+  return Object.fromEntries(
+    Object.entries(record).filter(([key]) => !reservedKeys.has(key)),
+  )
+}
+
+export function sanitizeExtensionUiDispatchProps(record: Record<string, any>) {
+  return sanitizeExtensionUiProps(record, extensionUiDispatchReservedPropKeys)
+}
+
+export function sanitizeExtensionUiRenderProps(record: Record<string, any>) {
+  return sanitizeExtensionUiProps(record, extensionUiRenderReservedPropKeys)
+}
+
+export function canRenderExtensionUi(options: {
+  loading: boolean
+  error?: string
+  iframeLoadError?: string
+  iframeMountError?: string
+  moduleSnapshot?: PluginHostModuleSummary
+  iframeSrc?: string
+  iframeSrcdoc?: string
+}) {
+  return Boolean(
+    options.moduleSnapshot
+    && (options.iframeSrc || options.iframeSrcdoc)
+    && !options.loading
+    && !options.error
+    && !options.iframeLoadError
+    && !options.iframeMountError,
+  )
+}
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/index.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/index.ts
new file mode 100644
index 000000000..c8251ca00
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/index.ts
@@ -0,0 +1 @@
+export { ExtensionUiHost as ExtensionUi } from './components'
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa-runtime.test.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa-runtime.test.ts
new file mode 100644
index 000000000..0d4a4b00f
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa-runtime.test.ts
@@ -0,0 +1,134 @@
+import { describe, expect, it } from 'vitest'
+
+import {
+  extensionUiBridgeInitEvent,
+  extensionUiBridgePublishEvent,
+} from './eventa'
+import { createWindowMessageEventaContext } from './eventa-runtime'
+
+class MockWindow {
+  peer?: MockWindow
+
+  private readonly listeners = new Map<string, Map<EventListenerOrEventListenerObject, (event: Event) => void>>()
+
+  addEventListener(type: string, listener: EventListenerOrEventListenerObject | null) {
+    if (!listener) {
+      return
+    }
+
+    if (!this.listeners.has(type)) {
+      this.listeners.set(type, new Map())
+    }
+
+    const handler = typeof listener === 'function'
+      ? listener
+      : (event: Event) => listener.handleEvent(event)
+
+    this.listeners.get(type)?.set(listener, handler)
+  }
+
+  removeEventListener(type: string, listener: EventListenerOrEventListenerObject | null) {
+    if (!listener) {
+      return
+    }
+
+    this.listeners.get(type)?.delete(listener)
+  }
+
+  postMessage(data: unknown) {
+    const messageEvent = {
+      data,
+      source: this.peer ?? null,
+    } as MessageEvent
+
+    for (const listener of this.listeners.get('message')?.values() ?? []) {
+      listener(messageEvent as unknown as Event)
+    }
+  }
+}
+
+/**
+ * @example
+ * describe('createWindowMessageEventaContext', () => {
+ *   it('relays typed events between parent and iframe windows', async () => {
+ *     expect(true).toBe(true)
+ *   })
+ * })
+ */
+describe('createWindowMessageEventaContext', () => {
+  /**
+   * @example
+   * it('relays typed events between parent and iframe windows', async () => {
+   *   expect(payload.moduleId).toBe('module-chess')
+   * })
+   */
+  it('relays typed events between parent and iframe windows', async () => {
+    const parentWindow = new MockWindow()
+    const iframeWindow = new MockWindow()
+    parentWindow.peer = iframeWindow
+    iframeWindow.peer = parentWindow
+
+    const host = createWindowMessageEventaContext({
+      channel: 'test:extension-ui',
+      currentWindow: parentWindow as unknown as Window,
+      expectedSource: () => iframeWindow as unknown as Window,
+      targetWindow: () => iframeWindow as unknown as Window,
+    })
+    const iframe = createWindowMessageEventaContext({
+      channel: 'test:extension-ui',
+      currentWindow: iframeWindow as unknown as Window,
+      expectedSource: () => parentWindow as unknown as Window,
+      targetWindow: () => parentWindow as unknown as Window,
+    })
+
+    const initPayload = new Promise<{ moduleId: string }>((resolve) => {
+      iframe.context.on(extensionUiBridgeInitEvent, (event) => {
+        if (!event.body?.moduleId) {
+          return
+        }
+
+        resolve({ moduleId: event.body.moduleId })
+      })
+    })
+
+    host.context.emit(extensionUiBridgeInitEvent, {
+      moduleId: 'module-chess',
+      config: {},
+      module: undefined,
+      props: {},
+    })
+
+    await expect(initPayload).resolves.toEqual(expect.objectContaining({
+      moduleId: 'module-chess',
+    }))
+
+    const publishedPayload = new Promise<Record<string, unknown>>((resolve) => {
+      host.context.on(extensionUiBridgePublishEvent, (event) => {
+        if (!event.body) {
+          return
+        }
+
+        resolve(event.body)
+      })
+    })
+
+    iframe.context.emit(extensionUiBridgePublishEvent, {
+      topic: {
+        namespace: 'plugin.chess',
+        name: 'request',
+      },
+      payload: {
+        requestId: 'req-1',
+      },
+    })
+
+    await expect(publishedPayload).resolves.toEqual(expect.objectContaining({
+      payload: expect.objectContaining({
+        requestId: 'req-1',
+      }),
+    }))
+
+    host.dispose()
+    iframe.dispose()
+  })
+})
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa-runtime.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa-runtime.ts
new file mode 100644
index 000000000..c3502efd3
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa-runtime.ts
@@ -0,0 +1,141 @@
+import { createContext } from '@moeru/eventa/adapters/event-target'
+import { isPlainObject } from 'es-toolkit'
+
+const EVENTA_MESSAGE_EVENT = 'eventa:message'
+
+interface WindowMessageEventaEnvelope {
+  __eventa: true
+  channel: string
+  sourceId: string
+  detail?: unknown
+}
+
+type RuntimeEventListener = (event: Event) => void
+
+class WindowMessageEventTarget implements EventTarget {
+  private readonly listeners = new Map<string, Map<EventListenerOrEventListenerObject, RuntimeEventListener>>()
+
+  constructor(private readonly send: (message: WindowMessageEventaEnvelope) => void) {}
+
+  addEventListener(type: string, listener: EventListenerOrEventListenerObject | null) {
+    if (!listener) {
+      return
+    }
+
+    if (!this.listeners.has(type)) {
+      this.listeners.set(type, new Map())
+    }
+
+    const handler: RuntimeEventListener = typeof listener === 'function'
+      ? listener
+      : event => listener.handleEvent(event)
+
+    this.listeners.get(type)?.set(listener, handler)
+  }
+
+  removeEventListener(type: string, listener: EventListenerOrEventListenerObject | null) {
+    if (!listener) {
+      return
+    }
+
+    this.listeners.get(type)?.delete(listener)
+  }
+
+  dispatchEvent(event: Event) {
+    const detail = 'detail' in event ? (event as CustomEvent).detail : undefined
+    this.send({
+      __eventa: true,
+      channel: '',
+      sourceId: '',
+      detail,
+    })
+
+    return true
+  }
+
+  emit(type: string, detail?: unknown) {
+    const event = { type, detail } as CustomEvent
+    for (const listener of this.listeners.get(type)?.values() ?? []) {
+      listener(event)
+    }
+  }
+}
+
+function isWindowMessageEventaEnvelope(value: unknown, channel: string): value is WindowMessageEventaEnvelope {
+  if (!isPlainObject(value)) {
+    return false
+  }
+
+  return value.__eventa === true
+    && value.channel === channel
+    && typeof value.sourceId === 'string'
+}
+
+/**
+ * Creates an Eventa context backed by `window.postMessage`.
+ *
+ * Use when:
+ * - A host window needs typed messaging with an iframe
+ * - An iframe wants Eventa ergonomics without a bespoke adapter package
+ *
+ * Expects:
+ * - `currentWindow` is the window receiving `message` events
+ * - `targetWindow` resolves to the peer window when outbound events are emitted
+ * - `channel` uniquely scopes one logical bridge on the page
+ *
+ * Returns:
+ * - An Eventa context plus a disposer that removes window listeners
+ */
+export function createWindowMessageEventaContext(options: {
+  channel: string
+  currentWindow: Window
+  targetWindow: () => Window | null | undefined
+  expectedSource?: () => MessageEventSource | null | undefined
+  targetOrigin?: string
+}) {
+  const sourceId = Math.random().toString(36).slice(2, 10)
+  const eventTarget = new WindowMessageEventTarget((message) => {
+    const targetWindow = options.targetWindow()
+    if (!targetWindow) {
+      return
+    }
+
+    targetWindow.postMessage({
+      ...message,
+      channel: options.channel,
+      sourceId,
+    }, options.targetOrigin ?? '*')
+  })
+
+  const { context, dispose } = createContext(eventTarget, {
+    messageEventName: EVENTA_MESSAGE_EVENT,
+    errorEventName: false,
+  })
+
+  const onWindowMessage = (event: MessageEvent) => {
+    if (!isWindowMessageEventaEnvelope(event.data, options.channel)) {
+      return
+    }
+
+    const expectedSource = options.expectedSource?.()
+    if (expectedSource && event.source !== expectedSource) {
+      return
+    }
+
+    if (event.data.sourceId === sourceId) {
+      return
+    }
+
+    eventTarget.emit(EVENTA_MESSAGE_EVENT, event.data.detail)
+  }
+
+  options.currentWindow.addEventListener('message', onWindowMessage)
+
+  return {
+    context,
+    dispose: () => {
+      options.currentWindow.removeEventListener('message', onWindowMessage)
+      dispose()
+    },
+  }
+}
diff --git a/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa.ts b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa.ts
new file mode 100644
index 000000000..62edb1bab
--- /dev/null
+++ b/apps/stage-tamagotchi/src/renderer/widgets/extension-ui/shared/eventa.ts
@@ -0,0 +1,46 @@
+import type { PluginHostModuleSummary } from '../../../../shared/eventa'
+
+import { defineEventa } from '@moeru/eventa'
+
+export const extensionUiBridgeEventaChannel = 'airi:extension-ui:bridge'
+
+/**
+ * Initializes an extension UI iframe with the latest host-side snapshot.
+ *
+ * Use when:
+ * - A module iframe finishes loading and needs its initial model
+ * - Host-side props or config changed and the iframe should resync
+ *
+ * Expects:
+ * - `config` and `props` are structured-clone-safe records
+ * - `module` is the currently inspected module snapshot when available
+ *
+ * Returns:
+ * - The payload forwarded from host to iframe over the Eventa bridge
+ */
+export interface ExtensionUiBridgeInitPayload {
+  moduleId?: string
+  module?: PluginHostModuleSummary
+  config: Record<string, unknown>
+  props: Record<string, unknown>
+}
+
+/**
+ * Structured-clone-safe module bridge payload.
+ *
+ * Use when:
+ * - An iframe publishes a channel envelope to the host
+ * - The host forwards a channel envelope back into the iframe
+ *
+ * Expects:
+ * - Consumers validate envelope fields at the boundary
+ *
+ * Returns:
+ * - A generic message envelope that stays transport-agnostic
+ */
+export type ExtensionUiBridgeEnvelope = Record<string, unknown>
+
+export const extensionUiBridgeInitEvent = defineEventa<ExtensionUiBridgeInitPayload>('eventa:event:extension-ui:bridge:init')
+export const extensionUiBridgeReadyEvent = defineEventa<void>('eventa:event:extension-ui:bridge:ready')
+export const extensionUiBridgePublishEvent = defineEventa<ExtensionUiBridgeEnvelope>('eventa:event:extension-ui:bridge:publish')
+export const extensionUiBridgeBroadcastEvent = defineEventa<ExtensionUiBridgeEnvelope>('eventa:event:extension-ui:bridge:broadcast')
diff --git a/apps/stage-tamagotchi/src/shared/eventa.ts b/apps/stage-tamagotchi/src/shared/eventa.ts
index f3ab02fb7..03dca5fa4 100644
--- a/apps/stage-tamagotchi/src/shared/eventa.ts
+++ b/apps/stage-tamagotchi/src/shared/eventa.ts
@@ -53,10 +53,12 @@ export const electronSetUpdaterPreferences = defineInvokeEventa<ElectronUpdaterP
 
 export const electronPluginList = defineInvokeEventa<PluginRegistrySnapshot>('eventa:invoke:electron:plugins:list')
 export const electronPluginSetEnabled = defineInvokeEventa<PluginRegistrySnapshot, { name: string, enabled: boolean, path?: string }>('eventa:invoke:electron:plugins:set-enabled')
+export const electronPluginSetAutoReload = defineInvokeEventa<PluginRegistrySnapshot, { name: string, enabled: boolean }>('eventa:invoke:electron:plugins:set-auto-reload')
 export const electronPluginLoadEnabled = defineInvokeEventa<PluginRegistrySnapshot>('eventa:invoke:electron:plugins:load-enabled')
 export const electronPluginLoad = defineInvokeEventa<PluginRegistrySnapshot, { name: string }>('eventa:invoke:electron:plugins:load')
 export const electronPluginUnload = defineInvokeEventa<PluginRegistrySnapshot, { name: string }>('eventa:invoke:electron:plugins:unload')
 export const electronPluginInspect = defineInvokeEventa<PluginHostDebugSnapshot>('eventa:invoke:electron:plugins:inspect')
+export const electronPluginGetAssetBaseUrl = defineInvokeEventa<string>('eventa:invoke:electron:plugins:asset-base-url')
 export const electronPluginUpdateCapability = defineInvokeEventa<PluginCapabilityState, PluginCapabilityPayload>('eventa:invoke:electron:plugins:capability:update')
 
 export const pluginProtocolListProvidersEventName = 'proj-airi:plugin-sdk:apis:protocol:resources:providers:list-providers'
@@ -95,12 +97,31 @@ export function createRequestWindowEventa(namespace: string) {
 export const noticeWindowEventa = createRequestWindowEventa('notice')
 
 // Widgets / Adhoc window events
+export interface WidgetWindowSize {
+  width: number
+  height: number
+  minWidth?: number
+  minHeight?: number
+  maxWidth?: number
+  maxHeight?: number
+}
+
+export interface PluginModuleWidgetPayload {
+  moduleId: string
+  title?: string
+  widgetComponent?: string
+  componentProps?: Record<string, any>
+  payload?: Record<string, any>
+  windowSize?: WidgetWindowSize
+}
+
 export interface WidgetsAddPayload {
   id?: string
   componentName: string
   componentProps?: Record<string, any>
   // size presets or explicit spans; renderer decides mapping
   size?: 's' | 'm' | 'l' | { cols?: number, rows?: number }
+  windowSize?: WidgetWindowSize
   // auto-dismiss in ms; if omitted, persistent until closed by user
   ttlMs?: number
 }
@@ -110,14 +131,24 @@ export interface WidgetSnapshot {
   componentName: string
   componentProps: Record<string, any>
   size: 's' | 'm' | 'l' | { cols?: number, rows?: number }
+  windowSize?: WidgetWindowSize
   ttlMs: number
 }
 
+export interface WidgetsUpdatePayload {
+  id: string
+  componentProps?: Record<string, any>
+  size?: 's' | 'm' | 'l' | { cols?: number, rows?: number }
+  windowSize?: WidgetWindowSize
+  ttlMs?: number
+}
+
 export interface PluginManifestSummary {
   name: string
   entrypoints: Record<string, string | undefined>
   path: string
   enabled: boolean
+  autoReload: boolean
   loaded: boolean
   isNew: boolean
 }
@@ -151,13 +182,57 @@ export interface PluginHostSessionSummary {
   moduleId: string
 }
 
+export interface PluginHostKitCapabilitySummary {
+  key: string
+  actions: string[]
+}
+
+export interface PluginHostKitSummary {
+  kitId: string
+  version: string
+  capabilities: PluginHostKitCapabilitySummary[]
+  runtimes: Array<'electron' | 'node' | 'web'>
+}
+
+export interface PluginHostModuleSummary {
+  moduleId: string
+  ownerSessionId: string
+  ownerPluginId: string
+  kitId: string
+  kitModuleType: string
+  state: 'announced' | 'active' | 'degraded' | 'withdrawn'
+  runtime: 'electron' | 'node' | 'web'
+  revision: number
+  updatedAt: number
+  config: Record<string, unknown>
+}
+
 export interface PluginHostDebugSnapshot {
   registry: PluginRegistrySnapshot
   sessions: PluginHostSessionSummary[]
+  kits: PluginHostKitSummary[]
+  modules: PluginHostModuleSummary[]
   capabilities: PluginCapabilityState[]
   refreshedAt: number
 }
 
+export interface ElectronPluginToolDescriptor {
+  id: string
+  title: string
+  description: string
+  activation: {
+    keywords: string[]
+    patterns: string[]
+  }
+}
+
+export interface ElectronPluginXsaiToolDefinition {
+  ownerPluginId: string
+  name: string
+  description: string
+  parameters: Record<string, unknown>
+}
+
 export interface ElectronMcpStdioServerConfig {
   command: string
   args?: string[]
@@ -217,12 +292,19 @@ export const electronMcpApplyAndRestart = defineInvokeEventa<ElectronMcpStdioApp
 export const electronMcpGetRuntimeStatus = defineInvokeEventa<ElectronMcpStdioRuntimeStatus>('eventa:invoke:electron:mcp:get-runtime-status')
 export const electronMcpListTools = defineInvokeEventa<ElectronMcpToolDescriptor[]>('eventa:invoke:electron:mcp:list-tools')
 export const electronMcpCallTool = defineInvokeEventa<ElectronMcpCallToolResult, ElectronMcpCallToolPayload>('eventa:invoke:electron:mcp:call-tool')
+export const electronPluginListAgentTools = defineInvokeEventa<ElectronPluginToolDescriptor[]>('eventa:invoke:electron:plugins:tools:list')
+export const electronPluginListXsaiTools = defineInvokeEventa<ElectronPluginXsaiToolDefinition[]>('eventa:invoke:electron:plugins:tools:list-xsai')
+export const electronPluginInvokeTool = defineInvokeEventa<unknown, {
+  ownerPluginId: string
+  name: string
+  input: unknown
+}>('eventa:invoke:electron:plugins:tools:invoke')
 
 export const widgetsOpenWindow = defineInvokeEventa<void, { id?: string }>('eventa:invoke:electron:windows:widgets:open')
 export const widgetsAdd = defineInvokeEventa<string | undefined, WidgetsAddPayload>('eventa:invoke:electron:windows:widgets:add')
 export const widgetsRemove = defineInvokeEventa<void, { id: string }>('eventa:invoke:electron:windows:widgets:remove')
 export const widgetsClear = defineInvokeEventa('eventa:invoke:electron:windows:widgets:clear')
-export const widgetsUpdate = defineInvokeEventa<void, { id: string, componentProps?: Record<string, any> }>('eventa:invoke:electron:windows:widgets:update')
+export const widgetsUpdate = defineInvokeEventa<void, WidgetsUpdatePayload>('eventa:invoke:electron:windows:widgets:update')
 export const widgetsFetch = defineInvokeEventa<WidgetSnapshot | void, { id: string }>('eventa:invoke:electron:windows:widgets:fetch')
 export const widgetsPrepareWindow = defineInvokeEventa<string | undefined, { id?: string }>('eventa:invoke:electron:windows:widgets:prepare')
 
@@ -278,7 +360,7 @@ export const stageThreeRuntimeTraceRemoteDisableEvent = defineEventa<StageThreeR
 export const widgetsRenderEvent = defineEventa<WidgetSnapshot>('eventa:event:electron:windows:widgets:render')
 export const widgetsRemoveEvent = defineEventa<{ id: string }>('eventa:event:electron:windows:widgets:remove')
 export const widgetsClearEvent = defineEventa('eventa:event:electron:windows:widgets:clear')
-export const widgetsUpdateEvent = defineEventa<{ id: string, componentProps?: Record<string, any> }>('eventa:event:electron:windows:widgets:update')
+export const widgetsUpdateEvent = defineEventa<WidgetsUpdatePayload>('eventa:event:electron:windows:widgets:update')
 
 // Onboarding window events
 export const electronOnboardingClose = defineInvokeEventa('eventa:invoke:electron:windows:onboarding:close')
diff --git a/apps/stage-tamagotchi/src/shared/utils/electron/windows/window-size.ts b/apps/stage-tamagotchi/src/shared/utils/electron/windows/window-size.ts
new file mode 100644
index 000000000..452665f92
--- /dev/null
+++ b/apps/stage-tamagotchi/src/shared/utils/electron/windows/window-size.ts
@@ -0,0 +1,52 @@
+import type { WidgetWindowSize } from '../../../eventa'
+
+/**
+ * Normalizes widget window size input before it is applied to an Electron window.
+ *
+ * Use when:
+ * - Widget payloads provide optional window size overrides
+ * - Main and renderer callers need one shared sanitization path before display clamping
+ *
+ * Expects:
+ * - `width` and `height` are finite positive numbers when present
+ *
+ * Returns:
+ * - A floored size object with invalid constraints removed, or `undefined` when the payload is unusable
+ *
+ * Before:
+ * - `{ width: 620.9, height: 480.2, minWidth: -10, maxHeight: 720.8 }`
+ * - `{ width: 0, height: 480 }`
+ *
+ * After:
+ * - `{ width: 620, height: 480, maxHeight: 720 }`
+ * - `undefined`
+ */
+export function normalizeWidgetWindowSize(
+  windowSize?: WidgetWindowSize | Record<string, unknown>,
+): WidgetWindowSize | undefined {
+  if (!windowSize || typeof windowSize !== 'object' || Array.isArray(windowSize))
+    return undefined
+
+  const width = Number(windowSize.width)
+  const height = Number(windowSize.height)
+
+  if (!Number.isFinite(width) || width <= 0 || !Number.isFinite(height) || height <= 0)
+    return undefined
+
+  const normalized: WidgetWindowSize = {
+    width: Math.floor(width),
+    height: Math.floor(height),
+  }
+
+  for (const key of ['minWidth', 'minHeight', 'maxWidth', 'maxHeight'] as const) {
+    const value = windowSize[key]
+    if (value === undefined)
+      continue
+
+    const numericValue = Number(value)
+    if (Number.isFinite(numericValue) && numericValue > 0)
+      normalized[key] = Math.floor(numericValue)
+  }
+
+  return normalized
+}
diff --git a/services/twitter-services/src/adapters/mcp-adapter.ts b/services/twitter-services/src/adapters/mcp-adapter.ts
index 2fce28493..06dfa2c94 100644
--- a/services/twitter-services/src/adapters/mcp-adapter.ts
+++ b/services/twitter-services/src/adapters/mcp-adapter.ts
@@ -3,11 +3,12 @@ import type { Tweet } from '../core/services/tweet'
 import type { TwitterServices } from '../types/services'
 
 import { Buffer } from 'node:buffer'
-import { createServer } from 'node:http'
+import { createServer, ServerResponse } from 'node:http'
 
 import { McpServer, ResourceTemplate } from '@modelcontextprotocol/sdk/server/mcp.js'
 import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js'
-import { createApp, createRouter, defineEventHandler, toNodeListener } from 'h3'
+import { createRouter, defineEventHandler, H3 } from 'h3'
+import { toNodeHandler } from 'h3/node'
 import { z } from 'zod'
 
 import { useTwitterTimelineServices } from '../core/services/timeline'
@@ -23,7 +24,7 @@ import { logger } from '../utils/logger'
  */
 export class MCPAdapter {
   private mcpServer: McpServer
-  private app: ReturnType<typeof createApp>
+  private app: H3
   private server: ReturnType<typeof createServer> | null = null
   private port: number
   private activeTransports: SSEServerTransport[] = []
@@ -49,7 +50,7 @@ export class MCPAdapter {
     })
 
     // Create H3 app
-    this.app = createApp()
+    this.app = new H3()
 
     // Configure resources and tools
     this.configureServer()
@@ -425,19 +426,31 @@ export class MCPAdapter {
 
     // Set up CORS
     router.use('*', defineEventHandler((event) => {
-      event.node.res.setHeader('Access-Control-Allow-Origin', '*')
-      event.node.res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS')
-      event.node.res.setHeader('Access-Control-Allow-Headers', 'Content-Type')
+      const node = event.node
+      if (!node?.res || !node.req) {
+        return
+      }
 
-      if (event.node.req.method === 'OPTIONS') {
-        event.node.res.statusCode = 204
-        event.node.res.end()
+      node.res.setHeader('Access-Control-Allow-Origin', '*')
+      node.res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS')
+      node.res.setHeader('Access-Control-Allow-Headers', 'Content-Type')
+
+      if (node.req.method === 'OPTIONS') {
+        node.res.statusCode = 204
+        node.res.end()
       }
     }))
 
     // SSE endpoint
     router.get('/sse', defineEventHandler(async (event) => {
-      const { req, res } = event.node
+      const node = event.node
+      if (!node?.res || !node.req) {
+        return { error: 'Node response is unavailable' }
+      }
+      const { req, res } = node
+      if (!(res instanceof ServerResponse)) {
+        return { error: 'HTTP ServerResponse is required for SSE transport' }
+      }
 
       res.setHeader('Content-Type', 'text/event-stream')
       res.setHeader('Cache-Control', 'no-cache')
@@ -461,9 +474,14 @@ export class MCPAdapter {
 
     // Messages endpoint - receive client requests
     router.post('/messages', defineEventHandler(async (event) => {
+      const node = event.node
+      if (!node?.res) {
+        return { error: 'Node response is unavailable' }
+      }
+
       if (this.activeTransports.length === 0) {
         logger.mcp.warn('Received message request but no active SSE connections')
-        event.node.res.statusCode = 503
+        node.res.statusCode = 503
         return { error: 'No active SSE connections' }
       }
 
@@ -475,6 +493,10 @@ export class MCPAdapter {
         // Simple handling - send to most recent transport
         // Note: In production, should use session ID to route to correct transport
         const transport = this.activeTransports.at(-1)
+        if (!transport) {
+          node.res.statusCode = 503
+          return { error: 'No active transport' }
+        }
 
         // Manually handle POST message, as H3 is not Express-compatible
         const response = await transport.handleMessage(body)
@@ -486,7 +508,7 @@ export class MCPAdapter {
       }
       catch (error) {
         logger.mcp.errorWithError('Error handling MCP message:', error)
-        event.node.res.statusCode = 500
+        node.res.statusCode = 500
         return { error: errorToMessage(error) }
       }
     }))
@@ -520,7 +542,7 @@ export class MCPAdapter {
 
       try {
         // Create Node.js HTTP server
-        this.server = createServer(toNodeListener(this.app))
+        this.server = createServer(toNodeHandler(this.app))
 
         // Add error event handlers
         this.server.on('error', (error) => {