fix(web): persist generated session titles against the post-RPC title (BUG-557)

The first-round title guard compared the pre-RPC snapshot, so append_consultation_question had already rewritten the title and the model name never landed.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/app/api/consult/route.ts

@@ -83,6 +83,7 @@ import {
   checkpointSessionContextSummary,
   generateSessionContextSummaryText,
 } from "@/lib/session-context-summary";
+import { persistGuardedSessionTitle } from "@/lib/session-title-guard";
 import { generateSessionTitle, shouldGenerateSessionTitle } from "@/lib/session-title-agent";
 import { z } from "zod";
 
@@ -565,6 +566,14 @@ export async function POST(request: Request) {
     );
   }
 
+  const expectedTitle = typeof chatSession.title === "string" ? chatSession.title : "";
+  const { data: titleRow } = await supabase
+    .from("chat_sessions")
+    .select("title")
+    .eq("id", sessionId)
+    .eq("user_id", userId)
+    .maybeSingle();
+
   const usageStartedAt = Date.now();
   async function checkpointConsultationContext() {
     try {
@@ -690,7 +699,7 @@ export async function POST(request: Request) {
   // its settle-and-log entry point here so the request-level catch below can
   // still emit it.
   const agenticFailure: { report?: (error: unknown) => Promise<void> } = {};
-  const expectedTitle = typeof chatSession.title === "string" ? chatSession.title : "";
+  const titleAfterRpc = typeof titleRow?.title === "string" ? titleRow.title : expectedTitle;
   const titleSideEvent = shouldGenerateSessionTitle({
     title: expectedTitle,
     sessionType: chatSession.session_type,
@@ -703,15 +712,13 @@ export async function POST(request: Request) {
       signal: request.signal,
     }).then(async (title) => {
       if (!title) return null;
-      try {
-        const { error } = await supabase.from("chat_sessions").update({ title })
-          .eq("id", sessionId)
-          .eq("user_id", userId)
-          .eq("title", expectedTitle);
-        if (error) console.warn("session title persist failed", error);
-      } catch (error) {
-        console.warn("session title persist failed", error);
-      }
+      await persistGuardedSessionTitle({
+        client: supabase,
+        sessionId,
+        userId,
+        expectedTitle: titleAfterRpc,
+        title,
+      });
       return { type: "session.title" as const, title };
     }).catch((error) => {
       console.warn("session title failed", error);

frontend/src/lib/session-title-guard.ts

@@ -0,0 +1,40 @@
+type GuardedTitleUpdate = {
+  eq: (column: string, value: string) => GuardedTitleUpdate;
+  select: (columns: "id") => PromiseLike<{ data: Array<{ id?: string }> | null; error: unknown }>;
+};
+
+export type GuardedTitleClient = {
+  from: (table: "chat_sessions") => {
+    update: (values: { title: string }) => GuardedTitleUpdate;
+  };
+};
+
+export async function persistGuardedSessionTitle(input: {
+  client: GuardedTitleClient;
+  sessionId: string;
+  userId: string;
+  expectedTitle: string;
+  title: string;
+  warn?: (message: string, extra?: unknown) => void;
+}): Promise<"updated" | "missed" | "failed"> {
+  const warn = input.warn ?? ((message: string, extra?: unknown) => console.warn(message, extra));
+  try {
+    const { data, error } = await input.client.from("chat_sessions").update({ title: input.title })
+      .eq("id", input.sessionId)
+      .eq("user_id", input.userId)
+      .eq("title", input.expectedTitle)
+      .select("id");
+    if (error) {
+      warn("session title persist failed", error);
+      return "failed";
+    }
+    if (!data?.length) {
+      warn("session title guard missed");
+      return "missed";
+    }
+    return "updated";
+  } catch (error) {
+    warn("session title persist failed", error);
+    return "failed";
+  }
+}