feat(common): expose plugin chat surface

plugins/example-plugin/web/AGENTS.md

@@ -74,7 +74,7 @@ instance Studio renders — same behavior, same styles, no second copy in the
 bundle. See `src/SharedUiPage.tsx`.
 
 ```ts
-import { StudioDataView, useStudioDataViewState } from '@nemo/common';
+import { AssistantChat, StudioDataView, useStudioDataViewState } from '@nemo/common';
 ```
 
 - **Bare specifier only.** A deep `@nemo/common/src/...` import is not
@@ -92,6 +92,11 @@ import { StudioDataView, useStudioDataViewState } from '@nemo/common';
   fine (they erase). A shared component that needs data takes it as a prop or
   callback and the caller supplies it from `host.sdk`; `CreateSecretModal`'s
   `onCreate` and `fetchAllPages`' page fetcher are the pattern.
+- **`AssistantChat` is shared.** A plugin can point it at an authenticated,
+  OpenAI-compatible `baseURL`; Studio supplies its current access token and
+  chat runtime. Use `messageContentProps.markdownLinkComponent` when a plugin
+  owns trusted, in-app citation targets. The plugin should still own the panel,
+  prompts, endpoint, and citation behavior specific to its feature.
 - **Types come from source**, via `paths` in `tsconfig.json`; `@nemo/common` is
   unpublished, so there is nothing to install. `src/env.d.ts` declares the `*.css`
   side-effect imports those sources carry.

web/packages/common/src/components/AssistantChat/index.test.tsx

@@ -195,6 +195,29 @@ describe('AssistantChat', () => {
     interactionTimeoutMs
   );
 
+  it('allows a caller to render trusted Markdown links in messages', async () => {
+    mocks.createChatCompletion.mockResolvedValueOnce(
+      createCompletion('[Trace source](#zoomer-node=summary-1)')
+    );
+    renderAssistantChat(
+      <AssistantChat
+        model="test-model"
+        workspace="default"
+        messageContentProps={{
+          markdownLinkComponent: ({ href, children }) => <a href={href}>{children}</a>,
+        }}
+      />
+    );
+
+    await userEvent.type(screen.getByRole('textbox', { name: /Task prompt/i }), 'Show evidence');
+    await userEvent.click(screen.getByRole('button', { name: /Submit/i }));
+
+    expect(await screen.findByRole('link', { name: 'Trace source' })).toHaveAttribute(
+      'href',
+      '#zoomer-node=summary-1'
+    );
+  });
+
   it('renders base64 images returned by an image model stream', async () => {
     const imageUrl = 'data:image/png;base64,iVBORw0KGgo=';
     const stream = {

web/packages/common/src/components/AssistantChat/index.tsx

@@ -35,6 +35,7 @@ export const AssistantChat: FC<AssistantChatProps> = ({
   stopCount,
   slotComposerStart,
   emptyState,
+  messageContentProps,
   composerOverride,
   enableImageAttachments = true,
 }) => {
@@ -76,6 +77,7 @@ export const AssistantChat: FC<AssistantChatProps> = ({
           composerMode={composerMode}
           slotComposerStart={slotComposerStart}
           emptyState={emptyState}
+          messageContentProps={messageContentProps}
           composerOverride={composerOverride}
           enableImageAttachments={imageAttachmentsEnabled}
         />

web/packages/common/src/components/AssistantChat/types.ts

@@ -132,6 +132,8 @@ export interface AssistantChatProps {
     slotHeading?: string;
     slotSubheading?: string;
   };
+  /** Overrides used when rendering Markdown inside chat messages. */
+  messageContentProps?: AssistantChatMessageContentProps;
   composerOverride?: ReactNode;
   /**
    * @default true

web/packages/common/src/plugin.ts

@@ -5,6 +5,11 @@
 // Removals are breaking. Explicit exports, not `export *`.
 
 export { AccessibleTitle } from '@nemo/common/src/components/AccessibleTitle';
+export { AssistantChat } from '@nemo/common/src/components/AssistantChat';
+export type {
+  AssistantChatMessageContentProps,
+  AssistantChatProps,
+} from '@nemo/common/src/components/AssistantChat/types';
 export { AccordionSection } from '@nemo/common/src/components/AccordionSection';
 // CancelJobButton is deliberately NOT exported
 export { ConfirmationModal } from '@nemo/common/src/components/ConfirmationModal';