diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Deployment/FlowDebugger.razor b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Deployment/FlowDebugger.razor
index 309a3ceb..d5ab097f 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Deployment/FlowDebugger.razor
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Deployment/FlowDebugger.razor
@@ -59,14 +59,18 @@
                         }
                     </select>
                 </div>
-                <div class="col-md-2">
+                @* Wider than the site select beside it: the field carries a whole instance
+                   name, not a short site name. The script-entry branch still sums to 8 of 12
+                   (site 2 + instance 3 + script 3) alongside the auto-width toolbar columns. *@
+                <div class="col-md-3">
                     <label class="form-label form-label-sm">Instance</label>
                     @* A site can hold hundreds of instances, so this is the shared area-tree
                        combobox, not a flat list (design 2026-09-08). _areas/_instances are
                        loaded once per site — the picker treats a new list as a site change. *@
                     <InstancePicker Areas="_areas" Instances="_instances"
                                     SelectedInstanceId="_selectedInstanceId" SelectedInstanceIdChanged="OnInstancePickedAsync"
-                                    Disabled="@(_running || _selectedSiteId == 0)" DataTestPrefix="flow-instance" />
+                                    Disabled="@(_running || _selectedSiteId == 0)"
+                                    Placeholder="Search instances…" DataTestPrefix="flow-instance" />
                 </div>
                 <div class="col-md-3">
                     <label class="form-label form-label-sm">Script</label>
diff --git a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Deployment/FlowDebuggerPageTests.cs b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Deployment/FlowDebuggerPageTests.cs
index 0a368c08..ed738665 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Deployment/FlowDebuggerPageTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Deployment/FlowDebuggerPageTests.cs
@@ -815,4 +815,31 @@ public class FlowDebuggerPageTests : BunitContext
         cut.WaitForAssertion(() =>
             Assert.Equal("Sim01", cut.Find("[data-test='flow-instance-input']").GetAttribute("value")));
     }
+
+    [Fact]
+    public void ScriptEntry_SiteChange_ClearsThePickedInstance()
+    {
+        RegisterServices();
+        WireInstance();
+        // A second site the operator can switch to, with no instances of its own.
+        _sites.GetAllSitesAsync(Arg.Any<CancellationToken>()).Returns(Task.FromResult<IReadOnlyList<Site>>(
+            [new Site("Plant A", "site-a") { Id = 1 }, new Site("Plant B", "site-b") { Id = 2 }]));
+        _templates.GetInstancesBySiteIdAsync(2, Arg.Any<CancellationToken>())
+            .Returns(Task.FromResult<IReadOnlyList<Instance>>([]));
+        _templates.GetAreasBySiteIdAsync(2, Arg.Any<CancellationToken>())
+            .Returns(Task.FromResult<IReadOnlyList<Area>>([]));
+
+        var cut = Render<FlowDebuggerPage>();
+        cut.Find("button[data-test='flow-entry-script']").Click();
+        cut.Find("select[data-test='flow-site-select']").Change("1");
+        PickInstance(cut, 7);
+        Assert.Equal("Sim01", cut.Find("[data-test='flow-instance-input']").GetAttribute("value"));
+
+        cut.Find("select[data-test='flow-site-select']").Change("2");
+
+        // The pick is dropped on both sides: the page's id and the picker's field text, which
+        // it re-derives because the new site handed it a different instance list.
+        Assert.Equal(string.Empty, cut.Find("[data-test='flow-instance-input']").GetAttribute("value"));
+        Assert.Equal(["— choose —"], cut.FindAll("select[data-test='flow-script-select'] option").Select(o => o.TextContent.Trim()).ToList());
+    }
 }