diff --git a/src/PlanViewer.App/Controls/QuerySessionControl.axaml.cs b/src/PlanViewer.App/Controls/QuerySessionControl.axaml.cs
index 0c331f0..78ab33a 100644
--- a/src/PlanViewer.App/Controls/QuerySessionControl.axaml.cs
+++ b/src/PlanViewer.App/Controls/QuerySessionControl.axaml.cs
@@ -78,11 +78,15 @@ public QuerySessionControl(ICredentialService credentialService, ConnectionStore
             QueryEditor.TextArea.Focus();
         };
 
-        // Dispose TextMate when detached (e.g. tab switch) to release renderers/transformers
+        // Dispose TextMate when detached (e.g. tab switch) to release renderers/transformers.
+        // Also cancel any in-flight status-clear dispatch so it doesn't fire on a dead control.
         DetachedFromVisualTree += (_, _) =>
         {
             _textMateInstallation?.Dispose();
             _textMateInstallation = null;
+            _statusClearCts?.Cancel();
+            _statusClearCts?.Dispose();
+            _statusClearCts = null;
         };
 
         // Focus the editor when the Editor tab is selected; toggle plan-dependent buttons
diff --git a/src/PlanViewer.App/Dialogs/QueryStoreHistoryWindow.axaml.cs b/src/PlanViewer.App/Dialogs/QueryStoreHistoryWindow.axaml.cs
index ca5d9b1..b39825a 100644
--- a/src/PlanViewer.App/Dialogs/QueryStoreHistoryWindow.axaml.cs
+++ b/src/PlanViewer.App/Dialogs/QueryStoreHistoryWindow.axaml.cs
@@ -169,6 +169,16 @@ public static string MapOrderByToMetricTag(string orderBy)
             : "AvgCpuMs";
     }
 
+    protected override void OnClosed(EventArgs e)
+    {
+        // Cancel any in-flight history fetch so the SqlConnection doesn't sit open on the
+        // server after the dialog is dismissed.
+        _fetchCts?.Cancel();
+        _fetchCts?.Dispose();
+        _fetchCts = null;
+        base.OnClosed(e);
+    }
+
     private async System.Threading.Tasks.Task LoadHistoryAsync()
     {
         _fetchCts?.Cancel();
diff --git a/src/PlanViewer.Core/Services/KeychainCredentialService.cs b/src/PlanViewer.Core/Services/KeychainCredentialService.cs
index 4e1f9cb..772eceb 100644
--- a/src/PlanViewer.Core/Services/KeychainCredentialService.cs
+++ b/src/PlanViewer.Core/Services/KeychainCredentialService.cs
@@ -103,11 +103,14 @@ private static (int ExitCode, string Output) RunSecurity(params string[] args)
         using var process = Process.Start(psi);
         if (process == null) return (-1, string.Empty);
 
+        // Read both streams concurrently. Doing stderr synchronously while stdout is
+        // async can deadlock if stderr fills its pipe buffer before the process exits
+        // (reproduces on `security dump-keychain` with large keychains).
         var stdoutTask = process.StandardOutput.ReadToEndAsync();
-        var stderr = process.StandardError.ReadToEnd();
+        var stderrTask = process.StandardError.ReadToEndAsync();
         process.WaitForExit();
-        var stdout = stdoutTask.Result;
+        Task.WaitAll(stdoutTask, stderrTask);
 
-        return (process.ExitCode, stdout + stderr);
+        return (process.ExitCode, stdoutTask.Result + stderrTask.Result);
     }
 }
diff --git a/src/PlanViewer.Core/Services/ReproScriptBuilder.cs b/src/PlanViewer.Core/Services/ReproScriptBuilder.cs
index aa1136b..8b94f09 100644
--- a/src/PlanViewer.Core/Services/ReproScriptBuilder.cs
+++ b/src/PlanViewer.Core/Services/ReproScriptBuilder.cs
@@ -20,6 +20,20 @@ namespace PlanViewer.Core.Services;
 /// </summary>
 public static class ReproScriptBuilder
 {
+    /// <summary>
+    /// Valid T-SQL isolation level names (uppercase) that may appear in a SET TRANSACTION
+    /// ISOLATION LEVEL statement. Used to gate interpolation so arbitrary upstream strings
+    /// can't land in the generated script.
+    /// </summary>
+    private static readonly HashSet<string> IsolationLevels = new(StringComparer.Ordinal)
+    {
+        "READ UNCOMMITTED",
+        "READ COMMITTED",
+        "REPEATABLE READ",
+        "SNAPSHOT",
+        "SERIALIZABLE",
+    };
+
     /// <summary>
     /// Builds a complete reproduction script from available query data.
     /// </summary>
@@ -94,10 +108,11 @@ public static string BuildReproScript(
         sb.AppendLine("*/");
         sb.AppendLine();
 
-        /* USE database (skip for Azure SQL DB — USE is invalid there) */
+        /* USE database (skip for Azure SQL DB — USE is invalid there).
+           Double any ']' in the identifier so names like 'cool]stuff' still parse. */
         if (!string.IsNullOrEmpty(databaseName) && !isAzureSqlDb)
         {
-            sb.AppendLine($"USE [{databaseName}];");
+            sb.AppendLine($"USE [{databaseName.Replace("]", "]]")}];");
             sb.AppendLine();
         }
 
@@ -116,7 +131,9 @@ public static string BuildReproScript(
 
         if (!string.IsNullOrEmpty(isolationLevel))
         {
-            sb.AppendLine($"SET TRANSACTION ISOLATION LEVEL {isolationLevel.ToUpperInvariant()};");
+            var upper = isolationLevel.ToUpperInvariant();
+            if (IsolationLevels.Contains(upper))
+                sb.AppendLine($"SET TRANSACTION ISOLATION LEVEL {upper};");
         }
         sb.AppendLine("SET NOCOUNT ON;");
         sb.AppendLine();
diff --git a/src/PlanViewer.Core/Services/ShowPlanParser.cs b/src/PlanViewer.Core/Services/ShowPlanParser.cs
index 31c93d6..db1a374 100644
--- a/src/PlanViewer.Core/Services/ShowPlanParser.cs
+++ b/src/PlanViewer.Core/Services/ShowPlanParser.cs
@@ -1832,6 +1832,7 @@ private static double ParseDouble(string? value)
     private static long ParseLong(string? value)
     {
         if (string.IsNullOrEmpty(value)) return 0;
-        return long.TryParse(value, out var result) ? result : 0;
+        return long.TryParse(value, System.Globalization.NumberStyles.Integer,
+            System.Globalization.CultureInfo.InvariantCulture, out var result) ? result : 0;
     }
 }