diff --git a/src/components/clinical-dashboard/recent-query-storage.ts b/src/components/clinical-dashboard/recent-query-storage.ts
index 10cf29bcd..f21f099f1 100644
--- a/src/components/clinical-dashboard/recent-query-storage.ts
+++ b/src/components/clinical-dashboard/recent-query-storage.ts
@@ -27,3 +27,21 @@ export function clearLegacyRecentQueries() {
     // Recent queries are a convenience only.
   }
 }
+
+// Sign-out / session-expiry boundary: on a shared workstation the next person
+// must not inherit anyone's recent clinical question text, so remove every
+// owner-scoped key too, not just the legacy unscoped residue.
+export function clearRecentQueries() {
+  if (typeof window === "undefined") return;
+  try {
+    clearLegacyRecentQueries();
+    for (let index = window.sessionStorage.length - 1; index >= 0; index -= 1) {
+      const key = window.sessionStorage.key(index);
+      if (key?.startsWith(`${recentQueryStorageKey}:`)) {
+        window.sessionStorage.removeItem(key);
+      }
+    }
+  } catch {
+    // Recent queries are a convenience only.
+  }
+}
diff --git a/src/lib/answer-thread-storage.ts b/src/lib/answer-thread-storage.ts
index 2a0ac1d0e..aef2334ee 100644
--- a/src/lib/answer-thread-storage.ts
+++ b/src/lib/answer-thread-storage.ts
@@ -2,6 +2,9 @@ import type { RagAnswer, SearchResult } from "@/lib/types";
 
 export const answerThreadStorageKey = "clinical-kb-answer-thread";
 export const maxStoredAnswerTurns = 12;
+// sessionStorage already dies with the tab, but long-lived clinical-workstation
+// tabs can idle for days; bound how long raw query/answer text stays restorable.
+export const answerThreadTtlMs = 12 * 60 * 60 * 1000;
 
 export type StoredAnswerTurn = {
   id: string;
@@ -17,6 +20,12 @@ export type PersistedAnswerThread = {
   collapsedTurnIds: string[];
 };
 
+// Stored envelope = the thread plus a write timestamp. savedAt stays internal to
+// this module: loads strip it after the TTL check so callers round-trip the
+// plain PersistedAnswerThread shape. Payloads written before the TTL existed
+// have no savedAt and are accepted once; the next save stamps them.
+type PersistedAnswerThreadEnvelope = PersistedAnswerThread & { savedAt?: number };
+
 const maxStorageBytes = 4_500_000;
 
 function isStoredAnswerTurn(value: unknown): value is StoredAnswerTurn {
@@ -35,8 +44,15 @@ function isStoredAnswerTurn(value: unknown): value is StoredAnswerTurn {
 
 function normalizePersistedAnswerThread(value: unknown): PersistedAnswerThread | null {
   if (!value || typeof value !== "object") return null;
-  const record = value as Partial<PersistedAnswerThread>;
+  const record = value as Partial<PersistedAnswerThreadEnvelope>;
   if (record.version !== 1) return null;
+  if (
+    typeof record.savedAt === "number" &&
+    Number.isFinite(record.savedAt) &&
+    Date.now() - record.savedAt > answerThreadTtlMs
+  ) {
+    return null;
+  }
   const priorTurns = Array.isArray(record.priorTurns)
     ? record.priorTurns.filter(isStoredAnswerTurn).slice(-maxStoredAnswerTurns)
     : [];
@@ -84,11 +100,12 @@ export function loadPersistedAnswerThread(ownerId: string): PersistedAnswerThrea
 export function savePersistedAnswerThread(ownerId: string, thread: PersistedAnswerThread): boolean {
   if (typeof window === "undefined" || !ownerId) return false;
   try {
-    const payload: PersistedAnswerThread = {
+    const payload: PersistedAnswerThreadEnvelope = {
       version: 1,
       priorTurns: thread.priorTurns.slice(-maxStoredAnswerTurns),
       latestTurn: thread.latestTurn,
       collapsedTurnIds: thread.collapsedTurnIds,
+      savedAt: Date.now(),
     };
     const serialized = JSON.stringify(payload);
     if (serialized.length > maxStorageBytes) return false;
diff --git a/src/lib/supabase/client.tsx b/src/lib/supabase/client.tsx
index 7dd9b67ab..8d8ff644b 100644
--- a/src/lib/supabase/client.tsx
+++ b/src/lib/supabase/client.tsx
@@ -4,6 +4,7 @@ import { createBrowserClient } from "@supabase/ssr";
 import { type Session, type SupabaseClient } from "@supabase/supabase-js";
 import { createContext, type ReactNode, useCallback, useContext, useEffect, useMemo, useRef, useState } from "react";
 import { clearPersistedAnswerThread } from "@/lib/answer-thread-storage";
+import { clearRecentQueries } from "@/components/clinical-dashboard/recent-query-storage";
 import { authSessionFingerprint, createAuthRequestLifecycle } from "@/lib/auth-request-lifecycle";
 import { checkSupabaseProjectConfig, formatSupabaseProjectCheck } from "@/lib/supabase/project";
 
@@ -137,9 +138,13 @@ export function AuthProvider({ children }: { children: ReactNode }) {
         if (data.session) {
           setError(null);
           setNotice(null);
-        } else if (callbackError) {
-          setError(decodeURIComponent(callbackError));
-          setNotice(null);
+        } else {
+          clearPersistedAnswerThread();
+          clearRecentQueries();
+          if (callbackError) {
+            setError(decodeURIComponent(callbackError));
+            setNotice(null);
+          }
         }
       } catch {
         if (!active) return;
@@ -158,6 +163,9 @@ export function AuthProvider({ children }: { children: ReactNode }) {
       if (nextSession) {
         setError(null);
         setNotice(null);
+      } else {
+        clearPersistedAnswerThread();
+        clearRecentQueries();
       }
     });
 
@@ -265,6 +273,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     invalidateAuthRequests();
     await client.auth.signOut();
     clearPersistedAnswerThread();
+    clearRecentQueries();
     setSession(null);
     setStatus("signed_out");
     setError(null);
@@ -274,6 +283,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   const markSessionExpired = useCallback(() => {
     invalidateAuthRequests();
     clearPersistedAnswerThread();
+    clearRecentQueries();
     setSession(null);
     setStatus("expired");
     setNotice(null);
diff --git a/tests/answer-thread-storage.test.ts b/tests/answer-thread-storage.test.ts
index e9e1fbad3..21d2a3b8f 100644
--- a/tests/answer-thread-storage.test.ts
+++ b/tests/answer-thread-storage.test.ts
@@ -3,6 +3,7 @@ import { describe, expect, it, vi, beforeEach, afterEach } from "vitest";
 import type { RagAnswer } from "@/lib/types";
 import {
   answerThreadStorageKey,
+  answerThreadTtlMs,
   clearPersistedAnswerThread,
   loadPersistedAnswerThread,
   savePersistedAnswerThread,
@@ -93,4 +94,25 @@ describe("answer thread storage", () => {
     storage.set(`${answerThreadStorageKey}:user-a`, JSON.stringify({ version: 2 }));
     expect(loadPersistedAnswerThread("user-a")).toBeNull();
   });
+
+  it("expires persisted threads once the TTL has elapsed", () => {
+    storage.set(
+      `${answerThreadStorageKey}:user-a`,
+      JSON.stringify({ ...sampleThread, savedAt: Date.now() - answerThreadTtlMs - 1 }),
+    );
+    expect(loadPersistedAnswerThread("user-a")).toBeNull();
+  });
+
+  it("keeps fresh threads and stamps savedAt on save", () => {
+    savePersistedAnswerThread("user-a", sampleThread);
+    const raw = JSON.parse(storage.get(`${answerThreadStorageKey}:user-a`) ?? "{}");
+    expect(typeof raw.savedAt).toBe("number");
+    expect(Date.now() - raw.savedAt).toBeLessThan(answerThreadTtlMs);
+    expect(loadPersistedAnswerThread("user-a")).toEqual(sampleThread);
+  });
+
+  it("accepts legacy payloads without a savedAt stamp", () => {
+    storage.set(`${answerThreadStorageKey}:user-a`, JSON.stringify(sampleThread));
+    expect(loadPersistedAnswerThread("user-a")).toEqual(sampleThread);
+  });
 });
diff --git a/tests/recent-query-storage.test.ts b/tests/recent-query-storage.test.ts
index 22d30eabe..571f73f40 100644
--- a/tests/recent-query-storage.test.ts
+++ b/tests/recent-query-storage.test.ts
@@ -3,6 +3,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { recentQueryStorageKey } from "@/components/clinical-dashboard/dashboard-contracts";
 import {
   clearLegacyRecentQueries,
+  clearRecentQueries,
   demoRecentQueryOwnerId,
   loadRecentQueries,
 } from "@/components/clinical-dashboard/recent-query-storage";
@@ -15,6 +16,12 @@ describe("recent query storage", () => {
     localStore = new Map<string, string>();
     sessionStore = new Map<string, string>();
     const storageFor = (store: Map<string, string>) => ({
+      get length() {
+        return store.size;
+      },
+      key(index: number) {
+        return [...store.keys()][index] ?? null;
+      },
       getItem(key: string) {
         return store.get(key) ?? null;
       },
@@ -75,4 +82,20 @@ describe("recent query storage", () => {
     expect(sessionStore.has(recentQueryStorageKey)).toBe(false);
     expect(loadRecentQueries("user-a")).toEqual(["scoped query"]);
   });
+
+  it("clearRecentQueries removes the legacy keys and every owner-scoped key", () => {
+    // Sign-out / expiry boundary: the next person on a shared workstation must
+    // not inherit anyone's recent clinical question text.
+    localStore.set(recentQueryStorageKey, JSON.stringify(["legacy"]));
+    sessionStore.set(recentQueryStorageKey, JSON.stringify(["legacy"]));
+    sessionStore.set(`${recentQueryStorageKey}:user-a`, JSON.stringify(["a"]));
+    sessionStore.set(`${recentQueryStorageKey}:user-b`, JSON.stringify(["b"]));
+    sessionStore.set("unrelated-key", "untouched");
+
+    clearRecentQueries();
+
+    expect(localStore.has(recentQueryStorageKey)).toBe(false);
+    expect([...sessionStore.keys()].some((key) => key.startsWith(recentQueryStorageKey))).toBe(false);
+    expect(sessionStore.get("unrelated-key")).toBe("untouched");
+  });
 });