diff --git a/packages/editor/src/index.tsx b/packages/editor/src/index.tsx
index d8888cdb66..2722c069d9 100644
--- a/packages/editor/src/index.tsx
+++ b/packages/editor/src/index.tsx
@@ -253,6 +253,7 @@ export { TerrainSculptPanel } from './components/ui/controls/terrain-sculpt-pane
 export { ToggleControl } from './components/ui/controls/toggle-control'
 export { ToolOptionsPanel } from './components/ui/controls/tool-options-panel'
 export { FloatingLevelSelector } from './components/ui/floating-level-selector'
+export { IconRefGlyph, IconRefImage } from './components/ui/icon-ref'
 export { CATALOG_ITEMS } from './components/ui/item-catalog/catalog-items'
 // A base plate's panel (one connected footprint's floor and foundation); the
 // slab kind's panel hands base plates to it.
@@ -725,6 +726,7 @@ export {
   resolvePlanarCursorPosition,
 } from './lib/planar-cursor-placement'
 export type {
+  ChatStartProps,
   ChatToolCardProps,
   ChatToolOutput,
   PluginChatExtension,
diff --git a/packages/editor/src/lib/plugin-chat.ts b/packages/editor/src/lib/plugin-chat.ts
index d7edfe821c..9833c2a612 100644
--- a/packages/editor/src/lib/plugin-chat.ts
+++ b/packages/editor/src/lib/plugin-chat.ts
@@ -28,6 +28,19 @@ export type ChatToolCardProps = {
   }
 }
 
+/**
+ * What a plugin's start screen does through the host's chat, before anything is said. `send` sends
+ * a message now, its pictures by reference (a host-stored image), and `attach` puts files on the
+ * next message, in the composer: both at the level that runs the plugin's tools. `requirePro` only
+ * asks whether the person's plan includes that level ("Pro" is the hosted product's name for it):
+ * it answers false after offering the upgrade, and changes nothing in the chat.
+ */
+export type ChatStartProps = {
+  send(text: string, images?: readonly { url: string; name: string }[]): void
+  attach(files: readonly File[]): void
+  requirePro(): boolean
+}
+
 /**
  * A plugin's contribution to a host's chat, exported from its browser entry beside its panels and
  * views; its tool contracts are its `./agent-tools` export. Which tools a turn offers, and to whom,
@@ -47,4 +60,6 @@ export type PluginChatExtension = {
   actions?: readonly { id: string; label: string; hint: string; prompt: string }[]
   /** File extensions or MIME types the plugin's tools read, which the composer then accepts. */
   accepts?: readonly string[]
+  /** What the chat shows while its thread is empty, loaded lazily. */
+  start?: () => Promise<{ default: ComponentType<ChatStartProps> }>
 }
diff --git a/wiki/architecture/plugin-authoring.md b/wiki/architecture/plugin-authoring.md
index 1579bc093c..0b45be1d67 100644
--- a/wiki/architecture/plugin-authoring.md
+++ b/wiki/architecture/plugin-authoring.md
@@ -358,6 +358,7 @@ export const signageChat: PluginChatExtension = {
   cards: { signage_schedule: () => import('./schedule-card') },
   actions: [{ id: 'exit-signs', label: 'Exit signs', hint: 'Sign every exit', prompt: 'Place exit signs on every level.' }],
   accepts: ['.csv'],
+  start: () => import('./chat-start'),
 }
 ```
 
@@ -368,6 +369,7 @@ export const signageChat: PluginChatExtension = {
 - **The host decides.** Which tools a turn offers, to whom and at what cost, whether a `chatOnly` request is honoured, and how far `timeoutMs` may go are host policy, like a panel's `access`. Being in `installedPlugins` is necessary, not sufficient. These packages define the shapes; a host keeps its own catalog of the plugins it serves.
 - **Trusted code.** These exports run with the application's privileges: a zod schema is code, and an executor or a card runs in the page. Hosts load reviewed, pinned plugins. The purity rule keeps contracts loadable in a sandboxed workflow; it does not isolate them.
 - **Cards and outputs.** A card renders from the persisted call alone (`toolName`, `input`, `output`, `state`), so a reloaded chat shows the same card; its `actions` open a view, select nodes or send a prompt. A `ChatToolOutput` carries images by reference (`ref`), never bytes. `actions` add entries to the composer's `/` menu; `accepts` lists the file types the plugin's tools read.
+- **A start screen.** `start` is what the host's chat shows while its thread is empty. It acts only through its `ChatStartProps`: `send` a message (pictures by reference) or `attach` files to the composer, both at the level the plugin's tools run at, and `requirePro()` before a step that needs that level: it answers false after the host offered the upgrade, and changes nothing in the chat. Render registry icons with `IconRefGlyph`, as the editor does.
 
 The rules both surfaces follow for these tools are in [agent surfaces](agent-surfaces.md#plugin-tools).