diff --git a/src/app/dashboard/chat/chat-view.tsx b/src/app/dashboard/chat/chat-view.tsx
index 37734f5..fb49b88 100644
--- a/src/app/dashboard/chat/chat-view.tsx
+++ b/src/app/dashboard/chat/chat-view.tsx
@@ -64,6 +64,10 @@ interface UiMemory {
 }
 
 const ACTOR_STORAGE_KEY = "mega-ask-user";
+/** Per-actor: the thread they were last in, so leaving the page (e.g. via
+    the sidebar nav) and coming back resumes it instead of starting blank.
+    "New thread" clears this; picking a thread or sending a message sets it. */
+const ACTIVE_THREAD_STORAGE_PREFIX = "mega-ask-active-thread:";
 
 function loadStoredActor(): Actor | null {
   if (typeof window === "undefined") return null;
@@ -78,6 +82,25 @@ function loadStoredActor(): Actor | null {
   return null;
 }
 
+function loadStoredThreadId(actorId: string): string | null {
+  if (typeof window === "undefined") return null;
+  try {
+    return window.localStorage.getItem(ACTIVE_THREAD_STORAGE_PREFIX + actorId);
+  } catch {
+    return null;
+  }
+}
+
+function saveStoredThreadId(actorId: string, threadId: string | null) {
+  if (typeof window === "undefined") return;
+  try {
+    if (threadId) window.localStorage.setItem(ACTIVE_THREAD_STORAGE_PREFIX + actorId, threadId);
+    else window.localStorage.removeItem(ACTIVE_THREAD_STORAGE_PREFIX + actorId);
+  } catch {
+    /* ignore */
+  }
+}
+
 /** Relative time for the thread list ("2h ago", "Just now"). */
 function relativeTime(iso?: string): string {
   if (!iso) return "";
@@ -317,6 +340,7 @@ function ChatViewInner() {
   const loadThread = React.useCallback(
     async (threadId: string, forActor: Actor) => {
       setActiveThreadId(threadId);
+      saveStoredThreadId(forActor.id, threadId);
       setTurns([]);
       setError(null);
       try {
@@ -361,20 +385,6 @@ function ChatViewInner() {
     [],
   );
 
-  // React to the URL's ?thread= — covers first load and back/forward.
-  React.useEffect(() => {
-    if (!actor) return;
-    const fromUrl = searchParams.get("thread");
-    if (fromUrl && fromUrl !== activeThreadIdRef.current) {
-      loadThread(fromUrl, actor);
-    } else if (!fromUrl && activeThreadIdRef.current) {
-      setActiveThreadId(null);
-      setTurns([]);
-    }
-    // Only re-run when the actor first resolves or the URL changes.
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [actor, searchParams]);
-
   const goToThread = React.useCallback(
     (threadId: string | null, mode: "push" | "replace" = "push") => {
       const url = threadId ? `${pathname}?thread=${threadId}` : pathname;
@@ -384,13 +394,35 @@ function ChatViewInner() {
     [pathname, router],
   );
 
+  // React to the URL's ?thread= — covers first load and back/forward.
+  React.useEffect(() => {
+    if (!actor) return;
+    const fromUrl = searchParams.get("thread");
+    if (fromUrl && fromUrl !== activeThreadIdRef.current) {
+      loadThread(fromUrl, actor);
+    } else if (!fromUrl && activeThreadIdRef.current) {
+      setActiveThreadId(null);
+      setTurns([]);
+    } else if (!fromUrl && !activeThreadIdRef.current) {
+      // No thread in the URL and nothing loaded yet — resume the last
+      // thread this actor was in (e.g. after leaving via the sidebar nav
+      // and coming back), rather than silently starting a blank one.
+      // "New thread" clears the stored id, so that still lands here empty.
+      const stored = loadStoredThreadId(actor.id);
+      if (stored) goToThread(stored, "replace");
+    }
+    // Only re-run when the actor first resolves or the URL changes.
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [actor, searchParams]);
+
   const startNewThread = React.useCallback(() => {
+    if (actor) saveStoredThreadId(actor.id, null);
     setActiveThreadId(null);
     setTurns([]);
     setError(null);
     setSidebarOpen(false);
     goToThread(null, "push");
-  }, [goToThread]);
+  }, [actor, goToThread]);
 
   const selectThread = React.useCallback(
     (t: ThreadSummary) => {
@@ -614,6 +646,7 @@ function ChatViewInner() {
               // reflect it in the URL and sidebar.
               activeThreadIdRef.current = data.id;
               setActiveThreadId(data.id);
+              saveStoredThreadId(actor.id, data.id);
               setThreads((prev) => [
                 { id: data.id, title: data.title, last_message_at: new Date().toISOString() },
                 ...prev.filter((t) => t.id !== data.id),
@@ -761,6 +794,7 @@ function ChatViewInner() {
         if (!activeThreadIdRef.current && data.threadId) {
           activeThreadIdRef.current = data.threadId;
           setActiveThreadId(data.threadId);
+          saveStoredThreadId(actor.id, data.threadId);
           setThreads((prev) => [
             { id: data.threadId, title: data.threadTitle ?? file.name, last_message_at: new Date().toISOString() },
             ...prev.filter((t) => t.id !== data.threadId),