Stop the next account on a shared browser from seeing the previous person's drafts

src/hooks/use-session-storage-sync.ts

@@ -1,10 +1,19 @@
 import { useEffect } from 'react';
-import { useSessionStore } from '@/lib/stores/session-store';
+import { useSessionStore, type SessionState } from '@/lib/stores/session-store';
 
 const SESSION_STORAGE_KEY = 'debate-trainer-storage';
 
 interface PersistedSessionPayload {
-  state?: Partial<ReturnType<typeof useSessionStore.getState>>;
+  state?: Partial<SessionState>;
+}
+
+/** Another tab's snapshot, or null when it belongs to a different account. */
+export function persistedSessionFromStorage(newValue: string, currentOwner: string | null): Partial<SessionState> | null {
+  const payload = JSON.parse(newValue) as PersistedSessionPayload;
+  if (!payload.state) return null;
+  const incomingOwner = payload.state.ownerUserId ?? null;
+  if (currentOwner && incomingOwner && incomingOwner !== currentOwner) return null;
+  return payload.state;
 }
 
 export function useSessionStorageSync() {
@@ -13,9 +22,8 @@ export function useSessionStorageSync() {
       if (event.key !== SESSION_STORAGE_KEY || !event.newValue) return;
 
       try {
-        const payload = JSON.parse(event.newValue) as PersistedSessionPayload;
-        if (!payload.state) return;
-        useSessionStore.setState(payload.state);
+        const next = persistedSessionFromStorage(event.newValue, useSessionStore.getState().ownerUserId);
+        if (next) useSessionStore.setState(next);
       } catch (error) {
         console.warn('[SessionStore] Failed to sync persisted state from another tab:', error);
       }

src/lib/stores/debate-store.ts

@@ -57,6 +57,8 @@ interface DebateState {
   setOneOff: (oneOff: boolean) => void;
   openDialog: (dialog: DebateDialog, motion?: string) => void;
   resetLocalData: () => void;
+  /** Drops another account's debate list before the server copy loads. */
+  prepareForUser: (userId: string) => void;
 }
 
 export function normalizeMotion(motion: string): string {
@@ -244,11 +246,18 @@ export const useDebateStore = create<DebateState>()(
         hydrationEpoch += 1;
         set({ ownerUserId: null, debates: [], currentDebateId: null, oneOff: false, hydrated: false, dialog: null, dialogMotion: '' });
       },
+
+      prepareForUser: (userId) => {
+        if (get().ownerUserId === userId) return;
+        hydrationEpoch += 1;
+        set({ ownerUserId: userId, debates: [], currentDebateId: null, oneOff: false, hydrated: false, dialog: null, dialogMotion: '' });
+      },
     }),
     {
       name: 'debatelab-current-debate',
       storage: createJSONStorage(() => localStorage),
       version: 1,
+      merge: mergePersistedDebateState,
       partialize: (state) => ({
         ownerUserId: state.ownerUserId,
         debates: state.debates,
@@ -258,6 +267,18 @@ export const useDebateStore = create<DebateState>()(
   ),
 );
 
+/**
+ * A rehydrate that finishes after sign-in must not restore another account's
+ * debate list. Lists saved before an owner was recorded stay only until this
+ * account is bound.
+ */
+export function mergePersistedDebateState(persistedState: unknown, currentState: DebateState): DebateState {
+  const saved = persistedState && typeof persistedState === 'object' ? persistedState as Partial<DebateState> : {};
+  const savedOwner = typeof saved.ownerUserId === 'string' ? saved.ownerUserId : null;
+  if (currentState.ownerUserId && savedOwner !== currentState.ownerUserId) return currentState;
+  return { ...currentState, ...saved, ownerUserId: savedOwner ?? currentState.ownerUserId };
+}
+
 export function selectCurrentDebate(state: Pick<DebateState, 'debates' | 'currentDebateId'>): Debate | null {
   return state.debates.find((debate) => debate.id === state.currentDebateId) ?? null;
 }

src/lib/stores/session-store.ts

@@ -121,6 +121,8 @@ export interface FlowchartData {
 }
 
 export interface SessionState {
+  /** Account these persisted drafts belong to. Null until sign-in binds them. */
+  ownerUserId: string | null;
   generateResult: GenerateOutput | null;
   generateLoading: boolean;
   /** The Generate section being regenerated; kept here so it survives leaving the page. */
@@ -235,6 +237,12 @@ export interface SessionState {
   serverHydration: 'pending' | 'partial' | 'complete';
   clearAllData: () => Promise<void>;
   resetLocalData: () => void;
+  /**
+   * Binds persisted drafts to the signed-in account. A different account, or
+   * drafts saved before accounts were recorded, is cleared first so one
+   * browser cannot show the previous person's work.
+   */
+  prepareForUser: (userId: string) => void;
   clearSession: () => void;
 
   pendingFlowchartData: FlowchartData | null;
@@ -285,6 +293,54 @@ function normalizeFolder(folder?: string | null) {
   return trimmed || 'General';
 }
 
+/** Device-only work that must not cross accounts. Server lists reload after this. */
+function sessionWorkForAccount(ownerUserId: string | null): Partial<SessionState> {
+  return {
+    ownerUserId,
+    serverHydration: 'pending',
+    savedCases: [],
+    savedAttacks: [],
+    savedBrainstorms: [],
+    savedFactoids: [],
+    savedChats: [],
+    savedFlowcharts: [],
+    savedCrossfires: [],
+    autosavedCases: [],
+    autosavedAttacks: [],
+    autosavedBrainstorms: [],
+    autosavedFactoids: [],
+    askChatId: null,
+    askChatDebateId: null,
+    askPersistedCount: 0,
+    sourceFolders: ['General'],
+    sourceLibrary: [],
+    generateResult: null,
+    attackResult: null,
+    brainstormResult: null,
+    factoidsResult: null,
+    askMessages: [],
+    askStreamingAssistant: null,
+    pendingFlowchartData: null,
+    generateForm: {},
+    generateResultDebateId: undefined,
+    attackForm: {},
+    brainstormForm: {},
+    factoidsForm: {},
+  };
+}
+
+/**
+ * Keeps a rehydrate that finishes after sign-in from putting another account's
+ * snapshot back. Drafts with no owner are kept only while nobody is bound yet;
+ * binding then clears them.
+ */
+export function mergePersistedSessionState(persistedState: unknown, currentState: SessionState): SessionState {
+  const saved = persistedState && typeof persistedState === 'object' ? persistedState as Partial<SessionState> : {};
+  const savedOwner = typeof saved.ownerUserId === 'string' ? saved.ownerUserId : null;
+  if (currentState.ownerUserId && savedOwner !== currentState.ownerUserId) return currentState;
+  return { ...currentState, ...saved, ownerUserId: savedOwner ?? currentState.ownerUserId };
+}
+
 function mergeSourceFolders(currentFolders: string[], sources: Source[] = []) {
   return Array.from(new Set([
     'General',
@@ -460,6 +516,7 @@ export function parseSourceProvenance(value: unknown): SourceProvenance | undefi
 export const useSessionStore = create<SessionState>()(
   persist(
     (set, get) => ({
+      ownerUserId: null as string | null,
       generateResult: null as GenerateOutput | null,
       generateLoading: false,
       generateRegeneratingSection: null as string | null,
@@ -1265,39 +1322,11 @@ export const useSessionStore = create<SessionState>()(
           askPersistedCount: 0,
         });
       },
-      resetLocalData: () => set({
-        serverHydration: 'pending',
-        savedCases: [],
-        savedAttacks: [],
-        savedBrainstorms: [],
-        savedFactoids: [],
-        savedChats: [],
-        savedFlowcharts: [],
-        savedCrossfires: [],
-        autosavedCases: [],
-        autosavedAttacks: [],
-        autosavedBrainstorms: [],
-        autosavedFactoids: [],
-        askChatId: null,
-        askChatDebateId: null,
-        askPersistedCount: 0,
-        sourceFolders: ['General'],
-        sourceLibrary: [],
-        generateResult: null,
-        attackResult: null,
-        brainstormResult: null,
-        factoidsResult: null,
-        askMessages: [],
-        askStreamingAssistant: null,
-        // Drafts belong to the signed-in user too; the next person on this
-        // browser must not see them prefilled.
-        pendingFlowchartData: null,
-        generateForm: {},
-        generateResultDebateId: undefined,
-        attackForm: {},
-        brainstormForm: {},
-        factoidsForm: {},
-      }),
+      resetLocalData: () => set(sessionWorkForAccount(null)),
+      prepareForUser: (userId) => {
+        if (get().ownerUserId === userId) return;
+        set(sessionWorkForAccount(userId));
+      },
 
       clearSession: () => set({
         generateResult: null,
@@ -1324,6 +1353,7 @@ export const useSessionStore = create<SessionState>()(
       // older clients: the server replaces them on hydrate, and keeping them
       // would resurrect purged legacy rows and debate-less sources.
       version: 1,
+      merge: mergePersistedSessionState,
       migrate: (persistedState) => {
         const state = { ...(persistedState as Record<string, unknown>) };
         for (const key of [

src/lib/stores/settings-store.ts

@@ -20,6 +20,8 @@ type CoreFeatureTab = Exclude<FeatureTab, 'sparring'>;
 type FeatureConfigs = Record<CoreFeatureTab, ProviderConfig> & Partial<Record<'sparring', ProviderConfig>>;
 
 interface SettingsState {
+  /** Account these device settings belong to. Null until sign-in binds them. */
+  ownerUserId: string | null;
   language: AppLanguage;
   outputLanguage: AppLanguage;
   theme: 'light' | 'dark' | 'system';
@@ -36,6 +38,8 @@ interface SettingsState {
   setWikiResearchEnabled: (enabled: boolean) => void;
   hydrateFromServer: () => Promise<void>;
   resetLocalData: (preserveLanguage?: boolean) => void;
+  /** Drops another account's prompt and model choices before the server copy loads. */
+  prepareForUser: (userId: string) => void;
 }
 
 const DEFAULT_PROVIDER = 'openrouter';
@@ -205,9 +209,22 @@ async function persistMigratedFeatureConfigs(
   }
 }
 
+/**
+ * A rehydrate that finishes after sign-in must not restore another account's
+ * prompt or model choices. Settings saved before an owner was recorded stay
+ * only until this account is bound.
+ */
+export function mergePersistedSettingsState(persistedState: unknown, currentState: SettingsState): SettingsState {
+  const saved = persistedState && typeof persistedState === 'object' ? persistedState as Partial<SettingsState> : {};
+  const savedOwner = typeof saved.ownerUserId === 'string' ? saved.ownerUserId : null;
+  if (currentState.ownerUserId && savedOwner !== currentState.ownerUserId) return currentState;
+  return { ...currentState, ...saved, ownerUserId: savedOwner ?? currentState.ownerUserId };
+}
+
 export const useSettingsStore = create<SettingsState>()(
   persist(
     (set, get) => ({
+      ownerUserId: null as string | null,
       language: 'en',
       outputLanguage: 'en',
       theme: 'system',
@@ -338,6 +355,7 @@ export const useSettingsStore = create<SettingsState>()(
       resetLocalData: (preserveLanguage = false) => {
         const language = preserveLanguage ? get().language : 'en';
         set({
+          ownerUserId: null,
           language,
           outputLanguage: 'en',
           theme: 'system',
@@ -347,10 +365,20 @@ export const useSettingsStore = create<SettingsState>()(
         });
         void applyAppLanguage(language);
       },
+      prepareForUser: (userId) => {
+        if (get().ownerUserId === userId) return;
+        set({
+          ownerUserId: userId,
+          customSystemPrompt: undefined,
+          featureConfigs: getDefaultFeatureConfigs(),
+          wikiResearchEnabled: false,
+        });
+      },
     }),
     {
       name: 'debate-trainer-settings',
       version: 2,
+      merge: mergePersistedSettingsState,
       migrate: (persistedState: unknown, version) => {
         const saved = asRecord(persistedState);
         if (!saved) return persistedState;

src/lib/supabase/AuthProvider.tsx

@@ -98,9 +98,12 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
   const [session, setSession] = useState<Session | null>(null);
   const [loading, setLoading] = useState(true);
   const hydrateSessionStore = useSessionStore((state) => state.hydrateFromServer);
+  const prepareSessionStore = useSessionStore((state) => state.prepareForUser);
   const hydrateSettingsStore = useSettingsStore((state) => state.hydrateFromServer);
+  const prepareSettingsStore = useSettingsStore((state) => state.prepareForUser);
   const hydrateSparringStore = useSparringStore((state) => state.hydrateSavedSessions);
   const prepareSparringStore = useSparringStore((state) => state.prepareForUser);
+  const prepareDebateStore = useDebateStore((state) => state.prepareForUser);
   const resetSessionData = useSessionStore((state) => state.resetLocalData);
   // A tool still writing for the previous account stops with its data.
   const resetSessionStore = useCallback(() => {
@@ -120,7 +123,13 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
     const hydrateStores = (userId?: string) => {
       if (!userId || hydratedUserId === userId) return;
       hydratedUserId = userId;
+      // Bind before any paint of protected pages. A full-page sign-in (magic
+      // link, Google) never sees the previous account's in-tab sign-out, so
+      // the persisted snapshot has to be checked against this user here.
+      prepareSessionStore(userId);
+      prepareSettingsStore(userId);
       prepareSparringStore(userId);
+      prepareDebateStore(userId);
       Promise.resolve(hydrateSessionStore()).catch((err) => console.warn('[Auth] hydrateSessionStore failed:', err));
       Promise.resolve(hydrateSettingsStore()).catch((err) => console.warn('[Auth] hydrateSettingsStore failed:', err));
       Promise.resolve(hydrateSparringStore()).catch((err) => console.warn('[Auth] hydrateSparringStore failed:', err));
@@ -176,7 +185,6 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
           setSession(oauthSession);
           currentUserIdRef.current = oauthSession.user?.id;
           setJamUserId(oauthSession.user?.id);
-          setLoading(false);
           hydrateStores(oauthSession.user?.id);
           return;
         }
@@ -224,7 +232,6 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
       setJamUserId(nextUserId);
       setActiveAccessToken(newSession?.access_token ?? null, newSession?.user.id ?? null);
       setSession(newSession);
-      setLoading(false);
 
       // Provider access tokens are short-lived. Keep them only for this browser
       // session; a later export must reauthorize if no fresh token is available.
@@ -241,6 +248,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
         resetDebateStore();
         useDebateContextStore.getState().resetLocalData();
         clearGoogleTokens();
+        setLoading(false);
         return;
       }
 
@@ -254,13 +262,14 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
       }
 
       hydrateStores(nextUserId);
+      setLoading(false);
     });
 
     return () => {
       mounted = false;
       authListener.subscription.unsubscribe();
     };
-  }, [hydrateDebateStore, hydrateSessionStore, hydrateSettingsStore, hydrateSparringStore, prepareSparringStore, resetDebateStore, resetSessionStore, resetSettingsStore, resetSparringStore]);
+  }, [hydrateDebateStore, hydrateSessionStore, hydrateSettingsStore, hydrateSparringStore, prepareDebateStore, prepareSessionStore, prepareSettingsStore, prepareSparringStore, resetDebateStore, resetSessionStore, resetSettingsStore, resetSparringStore]);
 
   // sessionStorage holds this tab's Google token and sparring state.
   const discardTabState = useCallback(() => {