diff --git a/tests/analytical_visualization/app.py b/tests/analytical_visualization/app.py
index 86e379a..0e54dea 100644
--- a/tests/analytical_visualization/app.py
+++ b/tests/analytical_visualization/app.py
@@ -252,7 +252,19 @@ with st.sidebar.expander("Parallelism", expanded=True):
         st.session_state["tp"] = _snap(_sb_sug.tp, _TP_OPTS)
         st.session_state["pp"] = _snap(_sb_sug.pp, _PP_OPTS)
         st.session_state["dp"] = 1
+        st.session_state["ep"] = 1
         st.session_state["cp_placement"] = _sb_sug.cp_placement
+        # auto_suggest only explores (cp, tp, pp, cp_placement); reset
+        # every other TopologyConfig field to its dataclass default so
+        # the applied topology matches what memory-min actually scored
+        # (else stale tp_placement="cube" etc. explodes cubes_used).
+        st.session_state["tp_placement"] = "pe"
+        st.session_state["kv_mode"] = "split"
+        st.session_state["cp_ring_variant"] = "kv"
+        # ffn_scope_label is a dynamic string (embeds current tp/cp) —
+        # dropping the key lets the radio fall back to index=1 which is
+        # "TP+CP", the TopologyConfig default.
+        st.session_state.pop("ffn_scope_label", None)
         st.session_state["_pl_active_scope"] = _sb_scope
         st.rerun()
 
diff --git a/tests/analytical_visualization/test_auto_explore.py b/tests/analytical_visualization/test_auto_explore.py
index 06cf1cf..dd164c9 100644
--- a/tests/analytical_visualization/test_auto_explore.py
+++ b/tests/analytical_visualization/test_auto_explore.py
@@ -19,8 +19,9 @@ from tests.analytical_visualization.auto_explore import (
     run_auto_explore,
     score_config,
 )
+from tests.analytical_visualization.autosuggest import auto_suggest
 from tests.analytical_visualization.model_config import (
-    FullConfig, MachineParams,
+    FullConfig, MachineParams, TopologyConfig,
 )
 from tests.analytical_visualization.model_presets import PRESETS
 
@@ -208,6 +209,39 @@ def test_ffn_only_latency_less_than_full_and_different_from_attn():
     )
 
 
+def test_auto_suggest_cubes_match_default_topology():
+    """A TopologyConfig built from auto_suggest's returned (cp, tp, pp,
+    cp_placement) with all other fields left at their dataclass defaults
+    must produce the same cubes_used the Suggestion reports. Guards the
+    sidebar apply: any session_state key auto_suggest doesn't explore
+    (tp_placement, kv_shard_mode, cp_ring_variant, ep, ffn_shard_scope)
+    must be reset to the default before rerun, else the applied topology
+    won't match what the memory-min search actually scored.
+    """
+    machine = MachineParams()
+    matrix = [
+        ("Llama 3 70B", 8192),
+        ("Llama 3 70B", 32768),
+        ("Llama 3 8B",  131072),
+        ("Qwen 3 32B",  32768),
+    ]
+    for name, skv in matrix:
+        m = PRESETS[name].model
+        for ia, ff in [(True, False), (False, True), (True, True)]:
+            sug = auto_suggest(m, machine, s_kv=skv, mode="decode",
+                               include_attention=ia, include_ffn=ff)
+            topo = TopologyConfig(
+                cp=sug.cp, tp=sug.tp, pp=sug.pp,
+                s_kv=skv, mode="decode", b=1,
+                cp_placement=sug.cp_placement,
+            )
+            assert topo.cubes_used == sug.cubes_used, (
+                f"{name} skv={skv} scope=(ia={ia},ff={ff}): "
+                f"topo.cubes_used={topo.cubes_used} != "
+                f"sug.cubes_used={sug.cubes_used}"
+            )
+
+
 def test_parallelism_sensitivity_includes_baseline_value():
     """Each row's values contain the baseline_value."""
     from tests.analytical_visualization.auto_explore import (