fix(home): stop silent rectification open after login (BUG-599)

Bare `/` was treating the latest history session as active, so a returning account could auto-open a failed rectification Case and left-align the starter home.

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

frontend/src/app/globals.css

@@ -1903,11 +1903,13 @@ input:not([type="radio"]):not([type="checkbox"]):not([class^="ant-"]):not([class
 /* Starter workbench */
 .welcome {
   width: min(1040px, 100%);
+  margin-inline: auto;
   padding: var(--space-8) 0 var(--space-12);
 }
 
 .starter-list {
   width: min(1040px, 100%);
+  margin-inline: auto;
   display: grid;
   grid-template-columns: minmax(0, 1fr);
   gap: var(--space-6);
@@ -2229,6 +2231,7 @@ input:not([type="radio"]):not([type="checkbox"]):not([class^="ant-"]):not([class
 .composer-wrap-starter .composer,
 .composer-wrap-starter .composer-footer {
   width: min(1040px, 100%);
+  margin-inline: auto;
 }
 
 @media (min-width: 768px) and (max-width: 900px) {

frontend/src/app/page.tsx

@@ -231,7 +231,10 @@ import {
   bootstrapLoadingCopy,
   bootstrapPrepareSettled,
   bootstrapRevealDelayMs,
+  resolveStarterHomeLandingSessionId,
   sessionIdsToPrefetch,
+  shouldAutoOpenRectificationSession,
+  starterHomeLandingNeedsConsultation,
   type BootstrapPhase,
 } from "@/lib/home-bootstrap";
 
@@ -520,16 +523,19 @@ export default function Home() {
     return () => window.removeEventListener("popstate", onPopState);
   }, [hydrated]);
 
-  // A rectification session selected at bootstrap (deep link, refresh, the
-  // most recent session) is opened and hydrated during the prepare phase, so
-  // the reveal shows the surface itself rather than a plain transcript that is
-  // swapped out a moment later. After the reveal the same effect serves
-  // history navigation.
+  // A rectification session named in `?c=` (refresh, deep link, login return)
+  // is opened during prepare so the reveal shows the surface. Bare `/` after
+  // login must not open the latest history item in the background.
   useEffect(() => {
     if ((!hydrated && bootstrapPhase === "account")
       || !account
       || !modelCatalog
-      || activeSession?.sessionType !== "birth_time_rectification"
+      || !activeSession
+      || !shouldAutoOpenRectificationSession({
+        sessionType: activeSession.sessionType,
+        sessionId: activeSession.id,
+        search: window.location.search,
+      })
       || activeSession.id === rectificationSessionId
       || rectificationLoading
       || rectificationMutationPending
@@ -671,7 +677,11 @@ export default function Home() {
     dailyStarlanguageApplicable: Boolean(accountId) && profileComplete && natalMinuteAvailable,
     dailyStarlanguageSettled: dailyStarlanguage.kind !== "pending",
     entrySummarySettled: rectificationEntrySummarySettled,
-    rectificationApplicable: activeSession?.sessionType === "birth_time_rectification",
+    rectificationApplicable: shouldAutoOpenRectificationSession({
+      sessionType: activeSession?.sessionType,
+      sessionId: activeSession?.id,
+      search: typeof window === "undefined" ? "" : window.location.search,
+    }),
     rectificationSettled: activeSession?.id === rectificationSessionId
       || rectificationError !== ""
       || !profileComplete,
@@ -1013,7 +1023,35 @@ export default function Home() {
           search: window.location.search,
           storedReturnId: readLoginSessionReturn(),
         });
-        const activeListed = nextSessions.find((session) => session.id === bootstrapSelection.sessionId)
+        let landingSessionId = resolveStarterHomeLandingSessionId(
+          nextSessions,
+          bootstrapSelection.sessionId,
+          bootstrapSelection.urlAction,
+        );
+        if (starterHomeLandingNeedsConsultation(nextSessions, landingSessionId, bootstrapSelection.urlAction)) {
+          if (controller.signal.aborted) return;
+          const homeSession = createSession(
+            nextModelCatalog?.defaultModelId ?? "",
+            "consultation",
+            chartSnapshotForSession("self", [], nextProfile),
+          );
+          if (nextModelCatalog) {
+            await writeChatSession(homeSession.id, {
+              title: homeSession.title,
+              theme: homeSession.theme,
+              model_id: homeSession.modelId,
+              messages: [],
+              session_type: homeSession.sessionType,
+              rectification_case_id: homeSession.rectificationCaseId,
+              chart_profile_id: homeSession.chartProfileId,
+              chart_profile_name: homeSession.chartProfileName,
+              chart_profile_role: homeSession.chartProfileRole,
+            }, "create");
+          }
+          nextSessions = [homeSession, ...nextSessions];
+          landingSessionId = homeSession.id;
+        }
+        const activeListed = nextSessions.find((session) => session.id === landingSessionId)
           ?? nextSessions[0];
         if (activeListed && !activeListed.messagesHydrated && activeListed.sessionType === "consultation") {
           try {
@@ -1035,7 +1073,7 @@ export default function Home() {
         setStartGreeting(nextProfile.name.trim() ? createStartGreeting(nextProfile.name) : "");
         setOnboardingStep(missingProfileStep(nextProfile) ?? "name");
         setSessions(nextSessions);
-        setActiveSessionId(bootstrapSelection.sessionId);
+        setActiveSessionId(landingSessionId);
         if (bootstrapSelection.clearStoredReturn) clearLoginSessionReturn();
         if (bootstrapSelection.urlAction === "replace-clear") writeSessionUrl(null, "replace");
         if (bootstrapSelection.urlAction === "replace-selected") writeSessionUrl(bootstrapSelection.sessionId, "replace");
@@ -1744,7 +1782,7 @@ export default function Home() {
           </header>
 
         {!rectificationSurfaceOpen && (
-          <div ref={conversation} className={`conversation${!activeSession?.messages.length && Boolean(activeSession?.messagesHydrated) && !onboardingFormActive ? " is-empty" : ""}${!profileComplete ? " is-onboarding" : ""}${onboardingFormActive ? " is-onboarding-form" : ""}`}>
+          <div ref={conversation} className={`conversation${!onboardingFormActive && !activeSession?.messages.length && (Boolean(activeSession?.messagesHydrated) || activeSession?.sessionType !== "consultation") ? " is-empty" : ""}${!profileComplete ? " is-onboarding" : ""}${onboardingFormActive ? " is-onboarding-form" : ""}`}>
             {!activeSession?.messages.length ? (
             <div className="welcome">
               {!profileComplete ? (

frontend/src/lib/home-bootstrap.ts

@@ -8,8 +8,62 @@
  * settled, or when the prepare budget runs out — never with a spinner inside.
  */
 
+import { parseSessionUrlQuery } from "./chat-session-url.ts";
+
 export type BootstrapPhase = "account" | "prepare";
 
+export type LandingSession = Readonly<{
+  id: string;
+  sessionType: string;
+  messages: readonly unknown[];
+}>;
+
+export type LandingUrlAction = "keep" | "replace-selected" | "replace-clear" | "none";
+
+/**
+ * A rectification Case is opened only when the address bar names that session
+ * (`?c=`), including refresh and a login return that restored the URL. Bare `/`
+ * after login must not open the latest history item in the background.
+ */
+export function shouldAutoOpenRectificationSession(input: {
+  readonly sessionType: string | undefined;
+  readonly sessionId: string | undefined;
+  readonly search: string;
+}): boolean {
+  if (input.sessionType !== "birth_time_rectification" || !input.sessionId) return false;
+  return parseSessionUrlQuery(input.search).sessionId === input.sessionId;
+}
+
+/**
+ * Default `/` landing prefers an empty consultation so the starter home can
+ * center. Deep links and login-return URLs keep the requested session.
+ */
+export function resolveStarterHomeLandingSessionId(
+  sessions: readonly LandingSession[],
+  selectedId: string,
+  urlAction: LandingUrlAction,
+): string {
+  if (urlAction === "keep" || urlAction === "replace-selected") return selectedId;
+  const selected = sessions.find((session) => session.id === selectedId);
+  if (selected?.sessionType !== "birth_time_rectification") return selectedId;
+  const emptyConsultation = sessions.find(
+    (session) => session.sessionType === "consultation" && session.messages.length === 0,
+  );
+  if (emptyConsultation) return emptyConsultation.id;
+  const anyConsultation = sessions.find((session) => session.sessionType === "consultation");
+  return anyConsultation?.id ?? selectedId;
+}
+
+export function starterHomeLandingNeedsConsultation(
+  sessions: readonly LandingSession[],
+  landingId: string,
+  urlAction: LandingUrlAction,
+): boolean {
+  if (urlAction === "keep" || urlAction === "replace-selected") return false;
+  const landing = sessions.find((session) => session.id === landingId);
+  return !landing || landing.sessionType === "birth_time_rectification";
+}
+
 export const BOOTSTRAP_PREPARE_TIMEOUT_MS = 4000;
 export const SESSION_PREFETCH_COUNT = 5;
 
@@ -19,7 +73,7 @@ export type BootstrapPrepareState = Readonly<{
   dailyStarlanguageApplicable: boolean;
   dailyStarlanguageSettled: boolean;
   entrySummarySettled: boolean;
-  /** The selected session is a rectification session: its Case must be open and hydrated before the reveal. */
+  /** A URL-named rectification session must be opened and hydrated before reveal. */
   rectificationApplicable?: boolean;
   rectificationSettled?: boolean;
 }>;