fix: avoid repeated daily starlanguage refresh

frontend/src/app/page.tsx

@@ -102,6 +102,7 @@ import {
   requestOnboardingWithRecovery,
 } from "@/lib/onboarding-client";
 import { protectOnboardingPhrases } from "@/lib/onboarding-copy";
+import { preserveShallowEqual } from "@/lib/preserve-shallow-equal";
 import {
   SessionModelPersistenceQueue,
   persistSessionModelSelection,
@@ -1797,7 +1798,7 @@ export default function Home() {
       const latest = await fetchAccount();
       if (!accountRefreshGuard.current.isCurrent(requestIdentity)) return;
       const nextProfile = readProfile(latest.profile);
-      setProfile(nextProfile);
+      setProfile((current) => preserveShallowEqual(current, nextProfile));
       setAccount(latest);
       setAccountError("");
     } catch (caught) {

frontend/src/lib/preserve-shallow-equal.ts

@@ -0,0 +1,18 @@
+export function preserveShallowEqual<T extends object>(current: T, next: T): T {
+  if (Object.is(current, next)) return current;
+
+  const currentRecord = current as Record<string, unknown>;
+  const nextRecord = next as Record<string, unknown>;
+  const currentKeys = Object.keys(currentRecord);
+  const nextKeys = Object.keys(nextRecord);
+
+  if (currentKeys.length !== nextKeys.length) return next;
+
+  for (const key of currentKeys) {
+    if (!Object.hasOwn(nextRecord, key) || !Object.is(currentRecord[key], nextRecord[key])) {
+      return next;
+    }
+  }
+
+  return current;
+}

frontend/tests/profile-state.test.ts

@@ -0,0 +1,52 @@
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import test from "node:test";
+import { preserveShallowEqual } from "../src/lib/preserve-shallow-equal.ts";
+
+const pageSource = readFileSync(new URL("../src/app/page.tsx", import.meta.url), "utf8");
+
+test("preserves the current profile reference when refreshed values are unchanged", () => {
+  const current = {
+    name: "测试用户",
+    date: "2000-01-01",
+    time: "",
+    birthTimeSource: "period_only",
+    birthTimePeriod: "evening",
+    timezoneId: "Asia/Shanghai",
+    latitude: 31.23,
+    longitude: 121.47,
+    timezoneOffset: null,
+  };
+  const refreshed = { ...current };
+
+  assert.notEqual(refreshed, current);
+  assert.equal(preserveShallowEqual(current, refreshed), current);
+});
+
+test("uses the refreshed profile reference when a value changed", () => {
+  const current = {
+    name: "测试用户",
+    birthTimePeriod: "evening",
+    timezoneId: "Asia/Shanghai",
+  };
+  const refreshed = {
+    ...current,
+    birthTimePeriod: "morning",
+  };
+
+  assert.equal(preserveShallowEqual(current, refreshed), refreshed);
+});
+
+test("account refresh preserves an equivalent normalized profile instead of replacing it", () => {
+  const refreshAccountStart = pageSource.indexOf("async function refreshAccount()");
+  const refreshAccountSource = pageSource.slice(
+    refreshAccountStart,
+    pageSource.indexOf("function updateSession", refreshAccountStart),
+  );
+
+  assert.match(
+    refreshAccountSource,
+    /setProfile\(\(current\) => preserveShallowEqual\(current, nextProfile\)\)/,
+  );
+  assert.doesNotMatch(refreshAccountSource, /setProfile\(nextProfile\)/);
+});