diff --git a/tests/test_undo_redo_sim.py b/tests/test_undo_redo_sim.py
index ceacfeac..b497a0e0 100644
--- a/tests/test_undo_redo_sim.py
+++ b/tests/test_undo_redo_sim.py
@@ -7,7 +7,7 @@ def test_undo_redo_lifecycle(live_gui):
  client = ApiHookClient()
  client.click("btn_reset")
  time.sleep(2)
- 
+
  assert client.wait_for_server(timeout=15), "Hook server did not start"
 
  # 1. Set initial state
@@ -15,16 +15,22 @@ def test_undo_redo_lifecycle(live_gui):
  client.set_value('temperature', 0.5)
  client.set_value('ai_input', "Initial Input")
 
- # Wait for settle and first push (S_init -> S0)
- time.sleep(3.0)
+ # Wait for settle and first push (S_init -> S0).
+ # The render loop's snapshot debounce is 1.5s, but in a shared
+ # live_gui subprocess the render loop runs much slower due to other
+ # tests' API calls contending for the main thread. The 8s wait below
+ # is generous enough to handle batch contention (was 3s; bumped
+ # after batch run showed undo applied the wrong snapshot, indicating
+ # the push hadn't fired yet when undo was clicked).
+ time.sleep(8.0)
 
  # 2. Change state
  print("Modifying state...")
  client.set_value('temperature', 1.5)
  client.set_value('ai_input', "Modified Input")
 
- # Wait for settle and second push (S0 -> S1)
- time.sleep(3.0)
+ # Wait for settle and second push (S0 -> S1). Same rationale as above.
+ time.sleep(8.0)
 
  # Verify current state
  temp = client.get_value('temperature')
@@ -36,16 +42,16 @@ def test_undo_redo_lifecycle(live_gui):
  # 3. Undo (S1 -> S0)
  print("Sending Undo...")
  client.click('btn_undo')
- time.sleep(2.0)
- 
+ time.sleep(4.0)
+
  assert client.get_value('ai_input') == "Initial Input"
  assert client.get_value('temperature') == 0.5
 
  # 4. Redo (S0 -> S1)
  print("Sending Redo...")
  client.click('btn_redo')
- time.sleep(2.0)
- 
+ time.sleep(4.0)
+
  assert client.get_value('ai_input') == "Modified Input"
  assert client.get_value('temperature') == 1.5