diff --git a/docs/pr-media/1715/activity-focus-reload.png b/docs/pr-media/1715/activity-focus-reload.png
new file mode 100644
index 00000000..5ca8f736
Binary files /dev/null and b/docs/pr-media/1715/activity-focus-reload.png differ
diff --git a/static/sessions.js b/static/sessions.js
index 713098c1..f40290d5 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -430,6 +430,10 @@ async function loadSession(sid){
     S.messages=INFLIGHT[sid].messages;
     S.toolCalls=(INFLIGHT[sid].toolCalls||[]);
     S.busy=true;
+    // appendLiveToolCard() is guarded by S.activeStreamId; restore it before
+    // replaying persisted live tools so the compact Activity count survives
+    // switching away from and back to an active chat (#1715).
+    S.activeStreamId=activeStreamId;
     syncTopbar();renderMessages();appendThinking();loadDir('.');
     clearLiveToolCards();
     if(typeof placeLiveToolCardsHost==='function') placeLiveToolCardsHost();
@@ -440,7 +444,6 @@ async function loadSession(sid){
     startApprovalPolling(sid);
     if(typeof startClarifyPolling==='function') startClarifyPolling(sid);
     if(typeof _fetchYoloState==='function') _fetchYoloState(sid);
-    S.activeStreamId=activeStreamId;
     if(INFLIGHT[sid].reattach&&activeStreamId&&typeof attachLiveStream==='function'){
       INFLIGHT[sid].reattach=false;
       if (_loadingSessionId !== sid) return;
diff --git a/tests/test_regressions.py b/tests/test_regressions.py
index e2a6ff12..444ec66e 100644
--- a/tests/test_regressions.py
+++ b/tests/test_regressions.py
@@ -415,7 +415,7 @@ def test_loadSession_inflight_restores_live_tool_cards(cleanup_test_sessions):
     # INFLIGHT branch must call appendLiveToolCard
     inflight_idx = src.find("if(INFLIGHT[sid]){")
     assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
-    inflight_block = src[inflight_idx:inflight_idx+500]
+    inflight_block = src[inflight_idx:inflight_idx+900]
     assert "appendLiveToolCard" in inflight_block,         "loadSession INFLIGHT branch must restore live tool cards via appendLiveToolCard"
     assert "clearLiveToolCards" in inflight_block,         "loadSession INFLIGHT branch must clear old live cards before restoring"
 
@@ -601,6 +601,29 @@ def test_loadSession_inflight_sets_busy_before_renderMessages(cleanup_test_sessi
         "loadSession must set S.busy=true before renderMessages() to avoid duplicate tool cards"
 
 
+def test_loadSession_inflight_sets_active_stream_before_replaying_live_tool_cards(cleanup_test_sessions):
+    """#1715: returning to an active chat must replay persisted tool cards.
+
+    appendLiveToolCard() intentionally no-ops unless S.activeStreamId is already
+    set for the viewed streaming session. If loadSession() restores S.toolCalls
+    and replays them before assigning S.activeStreamId, the compact Activity
+    counter drops the previously-seen tools after a focus change.
+    """
+    src = (REPO_ROOT / "static/sessions.js").read_text()
+    inflight_idx = src.find("if(INFLIGHT[sid]){")
+    assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
+    inflight_block = src[inflight_idx:inflight_idx+1000]
+    active_pos = inflight_block.find("S.activeStreamId=activeStreamId;")
+    replay_pos = inflight_block.find("appendLiveToolCard(tc);")
+    attach_pos = inflight_block.find("attachLiveStream(sid, activeStreamId")
+    assert active_pos >= 0, "loadSession INFLIGHT branch must restore S.activeStreamId"
+    assert replay_pos >= 0, "loadSession INFLIGHT branch must replay persisted live tool cards"
+    assert active_pos < replay_pos, \
+        "S.activeStreamId must be restored before appendLiveToolCard() replays persisted tools"
+    assert attach_pos < 0 or active_pos < attach_pos, \
+        "S.activeStreamId should also be restored before SSE reattach can deliver more tool events"
+
+
 def test_streaming_bridge_accepts_current_tool_progress_callback_signature(cleanup_test_sessions):
     """R17: api/streaming.py must accept the current Hermes agent callback contract.
     The agent now calls tool_progress_callback(event_type, name, preview, args, **kwargs).