diff --git a/tools/RioSerialMonitor/MashTest.cs b/tools/RioSerialMonitor/MashTest.cs
index 1f10739..7c66baa 100644
--- a/tools/RioSerialMonitor/MashTest.cs
+++ b/tools/RioSerialMonitor/MashTest.cs
@@ -281,9 +281,13 @@ internal static class MashTest
         // --- counters AFTER ------------------------------------------------------
         Dictionary<RioStatusType, int> after = await SnapshotStatusAsync();
 
+        // Dispose the transport BEFORE awaiting the link: on a wedged (silent)
+        // board the receive loop sits in a pending serial read that ignores
+        // cancellation — closing the port is what unblocks it. Awaiting first
+        // hangs forever and eats the summary (seen on the baseline chip run).
         cts.Cancel();
-        try { await run; } catch { /* shutdown */ }
         transport.Dispose();
+        try { await run; } catch { /* shutdown */ }
 
         // --- summary (fixed layout for diffing runs) ------------------------------
         double mins = Math.Max(sw.Elapsed.TotalMinutes, 0.001);
diff --git a/tools/RioSerialMonitor/Program.cs b/tools/RioSerialMonitor/Program.cs
index c3f8298..b72acd7 100644
--- a/tools/RioSerialMonitor/Program.cs
+++ b/tools/RioSerialMonitor/Program.cs
@@ -148,9 +148,11 @@ Log(">>> NOW: press the MFD buttons, press keypad keys, and move the axis <<<");
 Log(">>> a pressed button should light up <<<");
 
 await Task.Delay(TimeSpan.FromSeconds(seconds));
+// Transport first: a silent board leaves the receive loop in a pending read
+// that only the port close unblocks (net48 ReadAsync ignores cancellation).
 cts.Cancel();
-try { await run; } catch { /* shutdown */ }
 transport.Dispose();
+try { await run; } catch { /* shutdown */ }
 
 Console.WriteLine();
 Console.WriteLine("== summary ==");