feat(ai): auto-title conversations from the first message

__tests__/lib/ai-conversations.test.ts

@@ -8,6 +8,8 @@ import {
   getConversation,
   deleteConversation,
   addMessage,
+  renameConversation,
+  deriveConversationTitle,
 } from "~/lib/ai-conversations";
 
 const mockApiFetch = apiFetch as jest.Mock;
@@ -111,4 +113,34 @@ describe("conversation CRUD", () => {
       expect.objectContaining({ method: "DELETE" }),
     );
   });
+
+  it("renames a conversation via PATCH", async () => {
+    mockApiFetch.mockResolvedValue(res({ status: 200 }));
+    await renameConversation("c1", "Renamed");
+    expect(mockApiFetch).toHaveBeenCalledWith(
+      "/api/v1/ai/conversations/c1",
+      expect.objectContaining({ method: "PATCH", body: JSON.stringify({ title: "Renamed" }) }),
+    );
+  });
+});
+
+describe("deriveConversationTitle", () => {
+  it("uses a short first message verbatim, collapsing whitespace", () => {
+    expect(deriveConversationTitle("  How many   orders? ")).toBe("How many orders?");
+  });
+
+  it("truncates long messages at a word boundary with an ellipsis", () => {
+    const msg = "Show me everything that happened across all of the projects this past quarter please";
+    const title = deriveConversationTitle(msg);
+    expect(title.length).toBeLessThanOrEqual(49);
+    expect(title.endsWith("…")).toBe(true);
+    const stem = title.slice(0, -1); // drop the ellipsis
+    expect(msg.startsWith(stem)).toBe(true); // a real prefix of the message
+    // the very next char in the message is whitespace → we cut on a word boundary
+    expect(/\s/.test(msg[stem.length])).toBe(true);
+  });
+
+  it("falls back for empty input", () => {
+    expect(deriveConversationTitle("   ")).toBe("New conversation");
+  });
 });

__tests__/stores/ai-chat-store.test.ts

@@ -1,5 +1,7 @@
 jest.mock("~/lib/ai-chat", () => ({ streamAiChat: jest.fn() }));
 jest.mock("~/lib/ai-conversations", () => ({
+  // Keep the pure helpers (deriveConversationTitle) real; stub the network ones.
+  ...jest.requireActual("~/lib/ai-conversations"),
   conversationsAvailable: jest.fn(),
   listConversations: jest.fn(),
   createConversation: jest.fn(),
@@ -146,6 +148,8 @@ describe("ai-chat-store", () => {
       await get().send("a question");
 
       expect(conv.createConversation).toHaveBeenCalledTimes(1);
+      // titled from the first message
+      expect(conv.createConversation).toHaveBeenCalledWith("a question");
       expect(get().conversationId).toBe("c1");
       // user + assistant persisted to the server
       expect(conv.addMessage).toHaveBeenCalledWith("c1", { role: "user", content: "a question" });

lib/ai-conversations.ts

@@ -134,3 +134,25 @@ export async function addMessage(id: string, message: ConversationMessage): Prom
     body: JSON.stringify(message),
   });
 }
+
+export async function renameConversation(id: string, title: string): Promise<void> {
+  await apiFetch(`${BASE}/${encodeURIComponent(id)}`, {
+    method: "PATCH",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ title }),
+  }).catch(() => {});
+}
+
+/**
+ * A human title for a conversation derived from its first user message — the
+ * same first-message fallback the web (`objectui`) uses for display. The
+ * server's LLM auto-titling only fires on its own chat-persist path (which the
+ * mobile client bypasses), so we set this at creation instead.
+ */
+export function deriveConversationTitle(firstMessage: string): string {
+  const oneLine = firstMessage.replace(/\s+/g, " ").trim();
+  if (oneLine === "") return "New conversation";
+  if (oneLine.length <= 48) return oneLine;
+  // Trim to a word boundary under the cap.
+  return oneLine.slice(0, 48).replace(/\s+\S*$/, "").trimEnd() + "…";
+}

stores/ai-chat-store.ts

@@ -8,6 +8,7 @@ import {
   getConversation,
   deleteConversation,
   addMessage,
+  deriveConversationTitle,
   type ConversationSummary,
 } from "~/lib/ai-conversations";
 
@@ -183,7 +184,9 @@ export const useAIChatStore = create<AIChatState>((set, get) => ({
     let conversationId = get().conversationId;
     if (serverBacked && !conversationId) {
       try {
-        const conv = await createConversation();
+        // Title the conversation from its first message (the server's LLM
+        // auto-titling only runs on its own persist path, which we bypass).
+        const conv = await createConversation(deriveConversationTitle(trimmed));
         conversationId = conv.id;
         set({ conversationId });
         rememberActiveId(conversationId);