fix(chat): keep stored rectification titles on open

Opening a saved birth-time session no longer restamps the title or updatedAt from the wall clock. Occupies BUG-699, recurrence of BUG-553.

frontend/src/hooks/use-rectification-surface.ts

@@ -3,6 +3,7 @@
 import type { Dispatch, MutableRefObject, SetStateAction } from "react";
 
 import { resolveSessionTitle } from "@/lib/agent-reply";
+import { rectificationOpenIdentity } from "@/lib/rectification-session-open";
 import { showChatNotice as setComposerNotice } from "@/lib/chat-notice";
 import { writeSessionUrl } from "@/lib/chat-session-url";
 import type { ConsultationEntrypoint } from "@/lib/consultation-entrypoint";
@@ -213,16 +214,20 @@ export function useRectificationSurface(params: RectificationSurfaceParams) {
       // Merge the server-created session into the local list. The browser
       // never generates a Case id; it only mirrors the returned binding.
       const existing = sessions.find((session) => session.id === opened.sessionId);
-      const merged: ChatSession = {
-        id: opened.sessionId,
+      const openIdentity = rectificationOpenIdentity(existing, {
         title: resolveSessionTitle("生时校正", undefined, {
           entrypoint: "birth_time_rectification",
           existingTitles: sessions.map((session) => session.title),
         }),
+        updatedAt: timestamp(),
+      });
+      const merged: ChatSession = {
+        id: opened.sessionId,
+        title: openIdentity.title,
         theme: "general",
         modelId: modelCatalog.defaultModelId ?? "",
         messages: [],
-        updatedAt: timestamp(),
+        updatedAt: openIdentity.updatedAt,
         sessionType: "birth_time_rectification",
         rectificationCaseId: opened.caseId,
         pinned: existing?.pinned ?? false,

frontend/src/lib/agent-reply.ts

@@ -57,6 +57,9 @@ export function parseAgentReply(value: string, metadata?: ConsultationReplyMetad
 export type SessionTitleOptions = {
   readonly entrypoint?: ConsultationEntrypoint | null;
   readonly theme?: ConsultationDomain;
+  /** Wall clock. Only for minting a brand-new session. Re-titling an existing
+   *  session must pass that session's created time; the default `new Date()`
+   *  would stamp today's date onto old chats (BUG-699). */
   readonly at?: Date;
   readonly existingTitles?: readonly string[];
 };
@@ -89,7 +92,7 @@ export function resolveSessionTitle(
   modelTitle?: string,
   options: SessionTitleOptions = {},
 ): string {
-  const at = options.at ?? new Date();
+  const at = options.at ?? new Date(); // new sessions only; see SessionTitleOptions.at
   const existingTitles = options.existingTitles ?? [];
   if (modelTitle && !isGenericSessionTitle(modelTitle)) {
     return uniquifySessionTitle(clipTitle(modelTitle), existingTitles, at);

frontend/src/lib/rectification-session-open.ts

@@ -0,0 +1,9 @@
+export function rectificationOpenIdentity(
+  existing: { title: string; updatedAt: number } | undefined,
+  minted: { title: string; updatedAt: number },
+): { title: string; updatedAt: number } {
+  if (existing) {
+    return { title: existing.title, updatedAt: existing.updatedAt };
+  }
+  return minted;
+}

frontend/src/lib/rectification-session-title-repair.ts

@@ -0,0 +1,43 @@
+/** Product UI dates are wall-clock in China. Repair uses this zone, never UTC. */
+export const RECTIFICATION_TITLE_TIMEZONE = "Asia/Shanghai";
+
+export const RECTIFICATION_DATED_TITLE =
+  /^(\d{1,2})月(\d{1,2})日\s*·\s*生时校正(?:\s+\d{2}:\d{2})?$/;
+
+export function datedRectificationTitle(
+  createdAt: Date,
+  timeZone = RECTIFICATION_TITLE_TIMEZONE,
+): string {
+  const parts = new Intl.DateTimeFormat("en-US", {
+    timeZone,
+    month: "numeric",
+    day: "numeric",
+  }).formatToParts(createdAt);
+  const month = Number(parts.find((part) => part.type === "month")?.value);
+  const day = Number(parts.find((part) => part.type === "day")?.value);
+  if (!Number.isInteger(month) || !Number.isInteger(day)) {
+    return "生时校正";
+  }
+  return `${month}月${day}日 · 生时校正`;
+}
+
+export function repairedRectificationTitle(row: {
+  title: string;
+  createdAt: Date | null;
+}): string | null {
+  const matched = row.title.match(RECTIFICATION_DATED_TITLE);
+  if (!matched) return null;
+  if (!row.createdAt || Number.isNaN(row.createdAt.getTime())) {
+    return "生时校正";
+  }
+  const next = datedRectificationTitle(row.createdAt);
+  const nextMatch = next.match(RECTIFICATION_DATED_TITLE);
+  if (
+    nextMatch
+    && Number(matched[1]) === Number(nextMatch[1])
+    && Number(matched[2]) === Number(nextMatch[2])
+  ) {
+    return null;
+  }
+  return next;
+}