diff --git a/docs/AlarmClientDiscovery.md b/docs/AlarmClientDiscovery.md
index 537856f..24045cd 100644
--- a/docs/AlarmClientDiscovery.md
+++ b/docs/AlarmClientDiscovery.md
@@ -196,6 +196,46 @@ absence.
    gateway-worker installation runs under a service account
    that may have access where `dotnet test` doesn't.
 
+## InitializeConsumer required — fourth probe run, 2026-05-01
+
+Adding `InitializeConsumer("AlarmProbe.Tests")` before
+`RegisterConsumer` made `\Galaxy!` appear in `GetProviders`
+(count=1, status 0 → 100 within 500ms). So #2 and #3 above are
+NOT the cause — the consumer can see the alarm provider once it
+calls Initialize. That's a missing API-call ordering, not a
+permission or service issue.
+
+```
+InitializeConsumer -> 0
+RegisterConsumer -> 0
+GetProviders [after Register] -> rc=0 count=0 list=[]
+Subscribe('\Galaxy!') -> 0
+GetProviders [after Subscribe] -> rc=0 count=1 list=[  0 \Galaxy!]
+GetProviders [poll #1] -> rc=0 count=1 list=[100 \Galaxy!]
+```
+
+Despite the provider being visible at "100% query complete" for
+the entire 60s window, `GetStatistics` continued to report
+`total=0 active=0 codes=[7]` — no alarm transitions reached the
+consumer even with a System Platform script flipping the test
+boolean every 10s during the run.
+
+That isolates the remaining unknown to whether the test bool's
+alarm extension is actually generating MxAccess alarm-provider
+events when its value flips. The probe has confirmed every link
+in the consumer chain works (Initialize → Register → Subscribe →
+provider visible at 100%) — what's missing is alarm traffic from
+the producer side. ObjectViewer or another live consumer running
+alongside the script is the next discriminator: does it visibly
+see the alarm fire?
+
+API-ordering finding: `InitializeConsumer` MUST precede
+`RegisterConsumer` (or at least, must be called before
+`GetProviders` returns anything). PR A.5's `AlarmClientConsumer`
+omits `InitializeConsumer` entirely — that's a bug fix to apply
+even before A.2 lands, since without it the provider chain never
+becomes visible.
+
 ### Implications for A.2 implementation
 
 The A.2 PR's value is unmeasurable until at least one alarm
diff --git a/src/MxGateway.Worker.Tests/AlarmClientWmProbeTests.cs b/src/MxGateway.Worker.Tests/AlarmClientWmProbeTests.cs
index 303b220..39f1b04 100644
--- a/src/MxGateway.Worker.Tests/AlarmClientWmProbeTests.cs
+++ b/src/MxGateway.Worker.Tests/AlarmClientWmProbeTests.cs
@@ -231,6 +231,22 @@ public sealed class AlarmClientWmProbeTests : IDisposable
         try
         {
             client = new AlarmClient();
+
+            // Try InitializeConsumer first — separate from RegisterConsumer
+            // per the discovered API surface; previous probe runs skipped
+            // it. Some AVEVA managed-client patterns require Initialize
+            // before Register; others reverse the order. Try Initialize
+            // first; on failure proceed to Register.
+            try
+            {
+                int init = client.InitializeConsumer("AlarmProbe.Tests");
+                Log($"InitializeConsumer -> {init}");
+            }
+            catch (Exception ex)
+            {
+                Log($"InitializeConsumer threw: {ex.GetType().Name}: {ex.Message}");
+            }
+
             int register = client.RegisterConsumer(
                 hWnd: probeWindow.ToInt32(),
                 szProductName: "AlarmProbe",
@@ -239,18 +255,7 @@ public sealed class AlarmClientWmProbeTests : IDisposable
                 bRetainHiddenAlarms: false);
             Log($"RegisterConsumer -> {register}");
 
-            // Discover what providers AVEVA sees before subscribing, so we
-            // can spot a wrong subscription expression up front.
-            try
-            {
-                var providers = new System.Collections.Generic.List<string>();
-                int gp = client.GetProviders(providers);
-                Log($"GetProviders -> rc={gp} count={providers.Count} list=[{string.Join(", ", providers)}]");
-            }
-            catch (Exception ex)
-            {
-                Log($"GetProviders threw: {ex.GetType().Name}: {ex.Message}");
-            }
+            LogProviders(client, "after Register");
 
             int subscribe = client.Subscribe(
                 szSubscription: SubscriptionExpression,
@@ -261,6 +266,8 @@ public sealed class AlarmClientWmProbeTests : IDisposable
                 FilterSpecification: eAlarmFilterState.asNone);
             Log($"Subscribe('{SubscriptionExpression}') -> {subscribe}");
 
+            LogProviders(client, "after Subscribe");
+
             // 3c. Pump for the configured duration. Log every message we see
             //    (filtered light to avoid noise from WM_PAINT / WM_TIMER /
             //    WM_GETICON spam from typical pumps). Poll GetStatistics on
@@ -290,6 +297,7 @@ public sealed class AlarmClientWmProbeTests : IDisposable
                 if (DateTime.UtcNow >= nextPoll)
                 {
                     PollGetStatistics(client, ++pollCount);
+                    LogProviders(client, $"poll #{pollCount}");
                     nextPoll = DateTime.UtcNow + PollInterval;
                 }
                 Thread.Sleep(10);
@@ -316,6 +324,26 @@ public sealed class AlarmClientWmProbeTests : IDisposable
     }
 
     private string lastStatsSummary = string.Empty;
+    private string lastProvidersSummary = string.Empty;
+
+    private void LogProviders(AlarmClient client, string when)
+    {
+        try
+        {
+            var providers = new System.Collections.Generic.List<string>();
+            int rc = client.GetProviders(providers);
+            string summary = $"count={providers.Count} list=[{string.Join(", ", providers)}]";
+            if (summary != lastProvidersSummary)
+            {
+                Log($"GetProviders [{when}] -> rc={rc} {summary} (changed)");
+                lastProvidersSummary = summary;
+            }
+        }
+        catch (Exception ex)
+        {
+            Log($"GetProviders [{when}] threw: {ex.GetType().Name}: {ex.Message}");
+        }
+    }
 
     /// <summary>
     ///     Drive an MxAccess write to <see cref="TriggerTagReference"/> with the