diff --git a/static/messages.js b/static/messages.js
index 05dd8d2a..085f402c 100644
--- a/static/messages.js
+++ b/static/messages.js
@@ -1673,7 +1673,15 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
         tc={name:d.name||'tool', preview:d.preview||'', args:d.args||{}, snippet:'', done:true};
         inflight.toolCalls.push(tc);
       }
-      tc.preview=d.preview||tc.preview||'';
+      // Route result to .snippet (detail) instead of overwriting .preview
+      // (header).  During streaming .preview already holds the last progress
+      // text — replacing it with the same content caused header/detail
+      // duplication.  Fallback: if no progress events were sent, use the
+      // result as preview so the header is not blank.
+      if(d.preview){
+        tc.snippet=tc.snippet||d.preview;
+        if(!tc.preview) tc.preview=d.preview;
+      }
       tc.args=d.args||tc.args||{};
       tc.done=true;
       tc.is_error=!!d.is_error;
diff --git a/static/sessions.js b/static/sessions.js
index fc90f1f5..4a89c0d6 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -142,6 +142,9 @@ function _setSessionViewedCount(sid, messageCount = 0) {
   const next = Number.isFinite(messageCount) ? Number(messageCount) : 0;
   counts[sid] = next;
   _saveSessionViewedCounts();
+  // If the viewed count is now current, any prior completion-unread marker is
+  // stale — clear it so _hasUnreadForSession doesn't short-circuit (#3020).
+  _clearSessionCompletionUnread(sid);
 }
 
 function _getSessionCompletionUnread() {
@@ -407,8 +410,13 @@ function _markPollingCompletionUnreadTransitions(sessions) {
       )
     );
     const completedPersistedObservedStream = Boolean(observedStreaming && !isStreaming);
-    if ((completedObservedStream || completedPersistedObservedStream || completedWithNewMessages) && !_isSessionActivelyViewedForList(sid)) {
-      _markSessionCompletionUnread(sid, s.message_count);
+    if (completedObservedStream || completedPersistedObservedStream || completedWithNewMessages) {
+      if (!_isSessionActivelyViewedForList(sid)) {
+        _markSessionCompletionUnread(sid, s.message_count);
+      } else {
+        // Sync viewed count so we don't flag stale unread on tab switch (#3020)
+        _setSessionViewedCount(sid, messageCount);
+      }
     }
     _sessionStreamingById.set(sid, isStreaming);
     if (isStreaming) {
diff --git a/static/ui.js b/static/ui.js
index d209e151..2afe41ab 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -5682,6 +5682,19 @@ function appendLiveCompressionCard(state){
     node.setAttribute('data-compression-started-at',String(started));
     node.setAttribute('data-compression-message',String(state.message||'Auto-compressing context...'));
     _startCompressionElapsedTimer();
+  } else {
+    // Completion or error: clear the elapsed-timer attributes so the
+    // interval reader (_compressionLiveCardState) doesn't keep treating
+    // the replaced card as a running compression (#2973).
+    node.removeAttribute('data-compression-started-at');
+    node.removeAttribute('data-compression-message');
+    // Only clear the global timer when the *active* session has no running
+    // compression.  An SSE completion for a background session must not
+    // kill the timer that's driving the current session's display.
+    const _activeCompState = _compressionStateForCurrentSession();
+    if (!_activeCompState || !_activeCompState.automatic || _activeCompState.phase !== 'running') {
+      _clearCompressionElapsedTimer();
+    }
   }
   const existing=inner.querySelector('[data-live-compression-card="1"]');
   if(existing) existing.replaceWith(node);