fix: scope onboarding fallback greeting

frontend/src/app/page.tsx

@@ -46,6 +46,7 @@ import { chatMessageViews, type ChatMessage } from "@/lib/chat-message-view";
 import {
   OnboardingAuthenticationError,
   type OnboardingContent,
+  createOnboardingFallbackGreeting,
   createStartGreeting,
   isCurrentOnboardingRequest,
   onboardingProfileFingerprint,
@@ -2320,7 +2321,7 @@ export default function Home() {
                 <OnboardingChatMessage role="assistant" text={onboarding?.greeting
                   || (onboardingPending
                     ? `${profile.name.trim()}，稍等一下，我正在准备几个适合开始的问题。`
-                    : startGreeting || `${profile.name.trim()}，从你此刻最关心的问题开始吧。`)} />
+                    : createOnboardingFallbackGreeting(profile.name))} />
               )}
 
               {!profileComplete && onboardingStep === "birth" && onboardingCardReady && (

frontend/src/lib/onboarding-client.ts

@@ -104,6 +104,10 @@ export function createStartGreeting(
   return variants[Math.floor(variantSelection * variants.length)](displayName);
 }
 
+export function createOnboardingFallbackGreeting(name: string): string {
+  return `${name.trim()}，从你此刻最关心的问题开始吧。`;
+}
+
 export function onboardingProfileFingerprint(profile: OnboardingProfileFingerprintInput): string {
   return JSON.stringify([
     profile.name,

frontend/tests/onboarding-client.test.ts

@@ -3,10 +3,6 @@ import test from "node:test";
 import {
   OnboardingAuthenticationError,
   OnboardingRequestError,
-  createStartGreeting,
-  isCurrentOnboardingRequest,
-  onboardingProfileFingerprint,
-  onboardingRequestIdentity,
   requestOnboardingWithRecovery,
 } from "../src/lib/onboarding-client.ts";
 
@@ -20,28 +16,6 @@ const personalizedOnboarding = {
   source: "cache",
 } as const;
 
-const completeProfile = {
-  name: "林遥", date: "1990-06-15", time: "12:30", reportedTime: "12:30",
-  birthTimeSource: "hospital_record", birthTimePeriod: "", birthTimeClue: "出生证明", birthTimeStatus: "confirmed",
-  uncertaintyBeforeMinutes: 0, uncertaintyAfterMinutes: 0, rectificationCaseId: "", countryCode: "CN", provinceCode: "110000", cityCode: "110000-city", districtCode: "110101",
-} as const;
-
-test("rejects a stale completion after a complete profile changes", () => {
-  // Given: one account starts onboarding for a complete persisted profile.
-  const firstIdentity = onboardingRequestIdentity("account-1", onboardingProfileFingerprint(completeProfile));
-
-  // When: a presentation-affecting profile field changes before that request completes.
-  const changedFingerprint = onboardingProfileFingerprint({ ...completeProfile, name: "周宁" });
-  const currentIdentity = onboardingRequestIdentity("account-1", changedFingerprint);
-  const committedGreeting = createStartGreeting("周宁", new Date("2026-07-19T08:00:00+08:00"), 0);
-
-  // Then: the new profile has a distinct identity and its greeting cannot retain the old name.
-  assert.notEqual(currentIdentity, firstIdentity);
-  assert.equal(isCurrentOnboardingRequest(currentIdentity, firstIdentity), false);
-  assert.match(committedGreeting, /周宁/);
-  assert.doesNotMatch(committedGreeting, /林遥/);
-});
-
 test("returns personalized cache content after a timeout and pending response", async () => {
   // Given: the first request times out, the second is provisional, and the third is terminal.
   const originalFetch = globalThis.fetch;

frontend/tests/onboarding-presentation.test.ts

@@ -0,0 +1,35 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import {
+  createOnboardingFallbackGreeting,
+  createStartGreeting,
+  isCurrentOnboardingRequest,
+  onboardingProfileFingerprint,
+  onboardingRequestIdentity,
+} from "../src/lib/onboarding-client.ts";
+
+const completeProfile = {
+  name: "林遥", date: "1990-06-15", time: "12:30", reportedTime: "12:30",
+  birthTimeSource: "hospital_record", birthTimePeriod: "", birthTimeClue: "出生证明", birthTimeStatus: "confirmed",
+  uncertaintyBeforeMinutes: 0, uncertaintyAfterMinutes: 0, rectificationCaseId: "", countryCode: "CN", provinceCode: "110000", cityCode: "110000-city", districtCode: "110101",
+} as const;
+
+test("rejects stale A presentation and derives terminal and fallback greetings from profile B", () => {
+  // Given: one account starts onboarding for a complete persisted profile A.
+  const firstIdentity = onboardingRequestIdentity("account-1", onboardingProfileFingerprint(completeProfile));
+
+  // When: the name changes before that request completes and profile B is presented.
+  const changedProfile = { ...completeProfile, name: "周宁" };
+  const currentIdentity = onboardingRequestIdentity("account-1", onboardingProfileFingerprint(changedProfile));
+  const terminalGreeting = createStartGreeting(changedProfile.name, new Date("2026-07-19T08:00:00+08:00"), 0);
+  const fallbackGreeting = createOnboardingFallbackGreeting(changedProfile.name);
+
+  // Then: stale work is rejected and neither presentation path can retain A's name.
+  assert.notEqual(currentIdentity, firstIdentity);
+  assert.equal(isCurrentOnboardingRequest(currentIdentity, firstIdentity), false);
+  for (const greeting of [terminalGreeting, fallbackGreeting]) {
+    assert.match(greeting, /周宁/);
+    assert.doesNotMatch(greeting, /林遥/);
+  }
+  assert.equal(fallbackGreeting, "周宁，从你此刻最关心的问题开始吧。");
+});