Fix assistant chat preset composer hint

ui/src/components/AssistantChat.test.tsx

@@ -73,7 +73,11 @@ vi.mock("./IssueChatThread", async () => {
         <span data-testid="status-notices">
           {(props.suppressIssueStatusNotices ?? props.preset === "assistant") ? "suppressed" : "visible"}
         </span>
-        <span data-testid="composer-hint">{props.composerHint}</span>
+        <span data-testid="composer-hint">
+          {props.composerHint === undefined && props.preset === "assistant"
+            ? "Enter to send · Shift+Enter for a new line"
+            : props.composerHint}
+        </span>
         <span data-testid="image-upload-enabled">{String(Boolean(props.imageUploadHandler))}</span>
         <span data-testid="attach-enabled">{String(Boolean(props.onAttachImage))}</span>
         <span data-testid="composer-draft">{draft}</span>
@@ -471,6 +475,22 @@ describe("AssistantChatView", () => {
     );
   });
 
+  it("allows the assistant preset default composer hint when no custom hint is provided", () => {
+    render(
+      <AssistantChatView
+        agents={[ceo]}
+        targetAgentId={ceo.id}
+        comments={[]}
+        starterPrompts={[]}
+        onSend={async () => {}}
+      />,
+    );
+
+    expect(container.querySelector('[data-testid="composer-hint"]')?.textContent).toBe(
+      "Enter to send · Shift+Enter for a new line",
+    );
+  });
+
   it("renders assistant starter prompts without the large start-message placeholder", () => {
     render(
       <AssistantChatView

ui/src/components/AssistantChat.tsx

@@ -291,7 +291,7 @@ export function AssistantChatView({
   header,
   starterPrompts: providedStarterPrompts,
   emptyState: providedEmptyState,
-  composerHint = null,
+  composerHint,
   imageUploadHandler,
   onAttachImage,
   loading = false,
@@ -790,7 +790,7 @@ export function AssistantChat({
       header={header}
       starterPrompts={starterPrompts}
       emptyState={emptyState}
-      composerHint={hasOpenBackgroundWork ? "Ask me anything while I work on this." : null}
+      composerHint={hasOpenBackgroundWork ? "Ask me anything while I work on this." : undefined}
       imageUploadHandler={handleImageUpload}
       onAttachImage={handleAttachFile}
       loading={commentsQuery.isLoading}