feat(agent-ui): maybe auto-derive untitled session title (A6.196)

packages/agent-ui/README.md

@@ -311,6 +311,7 @@ consumption of shared panel shells:
 | A6.193 | Rename session title in list |
 | A6.194 | Apply session workspace target |
 | A6.195 | Remove session + next active id |
+| A6.196 | Maybe auto-derive untitled session title |
 
 ### A5 complete enough
 

packages/agent-ui/src/__tests__/maybeDeriveSessionTitle.test.ts

@@ -0,0 +1,23 @@
+import { describe, expect, it } from "vitest";
+import { DEFAULT_SESSION_TITLE } from "../lib/backendSessionTitle.js";
+import { maybeDeriveSessionTitleList } from "../lib/maybeDeriveSessionTitle.js";
+
+describe("maybeDeriveSessionTitleList", () => {
+  it("renames untitled only when changed", () => {
+    const sessions = [
+      { id: "a", title: DEFAULT_SESSION_TITLE, updatedAt: 1 },
+    ];
+    expect(maybeDeriveSessionTitleList(sessions, "a", "Hello", 2)?.[0]).toMatchObject({
+      title: "Hello",
+      updatedAt: 2,
+    });
+    expect(maybeDeriveSessionTitleList(sessions, "a", DEFAULT_SESSION_TITLE)).toBeNull();
+    expect(
+      maybeDeriveSessionTitleList(
+        [{ id: "a", title: "Fixed", updatedAt: 1 }],
+        "a",
+        "Hello",
+      ),
+    ).toBeNull();
+  });
+});

packages/agent-ui/src/index.ts

@@ -900,6 +900,8 @@ export {
   removeSessionFromList,
   nextActiveIdAfterDelete,
 } from "./lib/removeSessionFromList.js";
+export { maybeDeriveSessionTitleList } from "./lib/maybeDeriveSessionTitle.js";
+export type { DerivableSession } from "./lib/maybeDeriveSessionTitle.js";
 export type {
   SessionWorkspaceTarget,
   SessionWorkspaceFields,

packages/agent-ui/src/lib/maybeDeriveSessionTitle.ts

@@ -0,0 +1,25 @@
+/**
+ * Pure auto-title update decision for untitled sessions (A6.196).
+ */
+
+import { isUntitledSessionTitle } from "./isUntitledSessionTitle.js";
+import { renameSessionInList } from "./renameSessionInList.js";
+
+export type DerivableSession = { id: string; title: string; updatedAt: number };
+
+/**
+ * When a session is still untitled and `nextTitle` differs, return a renamed
+ * list; otherwise `null` so the host can skip store writes.
+ */
+export function maybeDeriveSessionTitleList<T extends DerivableSession>(
+  sessions: readonly T[],
+  id: string,
+  nextTitle: string,
+  now: number = Date.now(),
+): T[] | null {
+  const meta = sessions.find((s) => s.id === id);
+  if (!meta) return null;
+  if (!isUntitledSessionTitle(meta.title)) return null;
+  if (nextTitle === meta.title) return null;
+  return renameSessionInList(sessions, id, nextTitle, now);
+}

src/modules/ai/store/chatStore.ts

@@ -1,6 +1,5 @@
 import {
   DEFAULT_SESSION_TITLE,
-  isUntitledSessionTitle,
   appendDeletedSessionId,
   resolveActiveSessionOnHydrate,
   createUntitledSessionMeta,
@@ -9,6 +8,7 @@ import {
   applySessionWorkspaceTarget,
   removeSessionFromList,
   nextActiveIdAfterDelete,
+  maybeDeriveSessionTitleList,
 } from "@altai/agent-ui";
 import type { UIMessage } from "ai";
 import { native } from "../lib/native";
@@ -410,15 +410,9 @@ function persistNativeMessages(id: string, messages: UIMessage[]): void {
   // otherwise we'd rewrite the sessions array (and trigger re-renders + a
   // store write) on every streamed event.
   const state = useChatStore.getState();
-  const meta = state.sessions.find((s) => s.id === id);
-  if (!meta) return;
-  const isUntitled = isUntitledSessionTitle(meta.title);
-  if (!isUntitled) return;
   const nextTitle = deriveTitle(messages);
-  if (nextTitle === meta.title) return;
-  const next = state.sessions.map((s) =>
-    s.id === id ? { ...s, title: nextTitle, updatedAt: Date.now() } : s,
-  );
+  const next = maybeDeriveSessionTitleList(state.sessions, id, nextTitle);
+  if (!next) return;
   useChatStore.setState({ sessions: next });
   void saveSessionsList(next);
 }