diff --git a/.claude/rules/drivers.md b/.claude/rules/drivers.md
index 1c2dfd3e1..8047bfd87 100644
--- a/.claude/rules/drivers.md
+++ b/.claude/rules/drivers.md
@@ -296,7 +296,7 @@ host logger factory (wired in `DriverFactoryBootstrap`; the FOCAS and TwinCAT fa
   `InvalidDataException` — before #804 the 400 was a transport fault and the `OUT_OF_RANGE` re-baseline never ran
   live. The restart (`instanceId`) test also runs on every re-baseline snapshot (on 2.x that is where a restart is
   first seen). 3 re-baselines with no `/sample` chunk ⇒ Degraded with `LastSuccessfulRead` still advancing (no
-  watchdog reconnect loop over a `SampleCount` ≥ `bufferSize`). Every parse prohibits DTDs; the streams walk is
+  watchdog reconnect loop over a `SampleCount` > `bufferSize` — live: `count == bufferSize` is accepted; Test Connect + init warn, #825). Every parse prohibits DTDs; the streams walk is
   depth-bounded (64 — an unbounded recursion is a process-killing `StackOverflowException`). Non-finite floats are
   never Good; integer-valued decimals serve integral tags losslessly. Matrix: `docs/drivers/MTConnect.md`.
 - **MTConnect CONDITION alarms (#626):** a CONDITION raw tag is a native Part 9 condition only when its `TagConfig`
diff --git a/docs/drivers/MTConnect.md b/docs/drivers/MTConnect.md
index 81641b708..90b4f4cbd 100644
--- a/docs/drivers/MTConnect.md
+++ b/docs/drivers/MTConnect.md
@@ -362,7 +362,7 @@ what the driver's cursor expects) is detected **two ways**, both triggering a
 **Re-baselines without progress are bounded *and visible* (#804).** The reconnect
 backoff already paced a stream that only ever re-baselines (`A_rebaseline_that_delivers_nothing…`),
 but every `/current` also marked the stream delivered, so the driver read **Healthy**
-for ever while no `/sample` chunk arrived — the live case is a `SampleCount` at or
+for ever while no `/sample` chunk arrived — the live case is a `SampleCount`
 above the Agent's `bufferSize`, refused `OUT_OF_RANGE` (`'count' must be less than N`)
 on every open. After **3** consecutive re-baselines with no chunk in between
 (`MaxRebaselinesWithoutProgress`, the Java driver's `MAX_REBASELINES_WITHOUT_PROGRESS`)
@@ -371,11 +371,12 @@ observations in between"` and one Warning naming the `bufferSize` cause; it stay
 Degraded across further re-baselines until a chunk is delivered. Values keep flowing
 off the re-baselines and `LastSuccessfulRead` keeps advancing — each `/current` is the
 Agent answering — so the comms-loss watchdog does not reconnect-loop a configuration
-problem. Size `SampleCount` below the Agent's `bufferSize` (in the `/probe` header).
+problem. Size `SampleCount` at most the Agent's `bufferSize` (in the `/probe` header).
 **It is caught before it happens (#825):** the `/probe` header's `bufferSize` is parsed
 (`MTConnectProbeModel.BufferSize`, advisory — missing/malformed is null, never a parse failure); **Test
 Connect** reads `sampleCount` (default 1000 when absent) and answers Ok **with a warning** (an amber
-"OK with warning" chip showing the text) when it is at or above the buffer, and the driver's **initialize**
+"OK with warning" chip showing the text) when it is **above** the buffer (live, cppagent 2.7: `count == bufferSize` is
+accepted, `bufferSize + 1` refused `'count' must be less than {bufferSize+1}`), and the driver's **initialize**
 (every deploy) logs the same Warning and puts `agentBufferSize` on the `/hosts` diagnostics bag.
 
 **An Agent `instanceId` change means the Agent restarted**, and is checked
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.SampleLag.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.SampleLag.cs
index 3d6594792..1d130fbd1 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.SampleLag.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.SampleLag.cs
@@ -61,7 +61,8 @@ public sealed partial class MTConnectDriver : IDriverDiagnostics
     /// <summary>
     ///     lmxopcua#825 — the configuration warning for a <see cref="MTConnectDriverOptions.SampleCount"/> the Agent
     ///     will refuse. An Agent answers <c>/sample?count=N</c> with <c>OUT_OF_RANGE</c> ("'count' must be less than
-    ///     bufferSize") when <c>N ≥ bufferSize</c>, so such a driver never streams: it re-baselines from
+    ///     bufferSize + 1") when <c>N &gt; bufferSize</c> — live-measured on cppagent 2.7 (bufferSize 16384: 16384 is
+    ///     accepted, 16385 refused) — so such a driver never streams: it re-baselines from
     ///     <c>/current</c> and reports Degraded after three of them. Shared by <see cref="MTConnectDriverProbe"/>
     ///     (Test Connect) and the driver's initialize (deploy), so both say the same thing.
     /// </summary>
@@ -69,10 +70,10 @@ public sealed partial class MTConnectDriver : IDriverDiagnostics
     /// <param name="bufferSize">The Agent's buffer size, or null when its header did not say.</param>
     /// <returns>The warning text, or <see langword="null"/> when the count fits (or the buffer size is unknown).</returns>
     internal static string? SampleCountBufferWarning(int sampleCount, long? bufferSize) =>
-        bufferSize is { } size && sampleCount >= size
-            ? $"SampleCount {sampleCount.ToString(CultureInfo.InvariantCulture)} is at or above the Agent's bufferSize "
+        bufferSize is { } size && sampleCount > size
+            ? $"SampleCount {sampleCount.ToString(CultureInfo.InvariantCulture)} is above the Agent's bufferSize "
               + $"{size.ToString(CultureInfo.InvariantCulture)}: the Agent refuses every /sample stream (OUT_OF_RANGE), so "
-              + "values will only re-baseline from /current and the driver reports Degraded. Set SampleCount below "
+              + "values will only re-baseline from /current and the driver reports Degraded. Set SampleCount to at most "
               + $"{size.ToString(CultureInfo.InvariantCulture)}."
             : null;
 
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.cs
index 352220eb5..8cc6566a1 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriver.cs
@@ -2350,7 +2350,7 @@ public sealed partial class MTConnectDriver
 
                         // #804 — the backoff above PACES a stream that only ever re-baselines, but each /current
                         // also marked the stream delivered, so it read Healthy for ever while no /sample chunk
-                        // arrived (a SampleCount at or above the Agent's bufferSize is refused OUT_OF_RANGE on
+                        // arrived (a SampleCount above the Agent's bufferSize is refused OUT_OF_RANGE on
                         // EVERY open). After MaxRebaselinesWithoutProgress in a row it is reported Degraded, and
                         // stays so (holdStalled) until a chunk is delivered.
                         if (!outcome.DeliveredAny &&
@@ -2363,7 +2363,7 @@ public sealed partial class MTConnectDriver
 
                             _logger.LogWarning(
                                 outcome.Error,
-                                "MTConnect driver {DriverInstanceId}: {Count} consecutive /current re-baselines of {AgentUri} without a single /sample chunk in between; reporting the stream Degraded until one is delivered. Values are re-baselined, not streamed. An Agent answering every /sample with OUT_OF_RANGE usually means SampleCount is at or above its bufferSize.",
+                                "MTConnect driver {DriverInstanceId}: {Count} consecutive /current re-baselines of {AgentUri} without a single /sample chunk in between; reporting the stream Degraded until one is delivered. Values are re-baselined, not streamed. An Agent answering every /sample with OUT_OF_RANGE usually means SampleCount is above its bufferSize.",
                                 _driverInstanceId, rebaselinesWithoutProgress, AgentDisplay(options));
                         }
 
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriverProbe.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriverProbe.cs
index cc402eb07..62cd96dc0 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriverProbe.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDriverProbe.cs
@@ -135,7 +135,7 @@ public sealed class MTConnectDriverProbe : IDriverProbe
 
         /// <summary>
         ///     The <c>/sample</c> <c>count</c> (lmxopcua#825). Not needed to reach the Agent, but read so Test Connect
-        ///     can warn when it is at or above the Agent's <c>bufferSize</c> — a config the Agent will refuse on every
+        ///     can warn when it is above the Agent's <c>bufferSize</c> — a config the Agent will refuse on every
         ///     stream. Absent ⇒ the driver's own default.
         /// </summary>
         public int? SampleCount { get; set; }
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDtos.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDtos.cs
index a7b6ef792..3a1b48c4c 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDtos.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectDtos.cs
@@ -11,7 +11,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.MTConnect;
 /// <param name="BufferSize">
 ///     The Agent's observation ring-buffer size (the <c>/probe</c> <c>Header</c>'s <c>bufferSize</c>), or
 ///     <see langword="null"/> when the header omits it or it is not a positive integer. A <c>/sample</c>
-///     <c>count</c> at or above it is refused <c>OUT_OF_RANGE</c> by the Agent (lmxopcua#825).
+///     <c>count</c> above it is refused <c>OUT_OF_RANGE</c> by the Agent (lmxopcua#825; live: <c>count == bufferSize</c> is accepted).
 /// </param>
 public sealed record MTConnectProbeModel(IReadOnlyList<MTConnectDevice> Devices, long? BufferSize = null);
 
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectXml.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectXml.cs
index c9237a7fd..8285b25dd 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectXml.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectXml.cs
@@ -76,7 +76,7 @@ internal static class MTConnectXml
     /// <remarks>
     ///     <b>Why this exists (#804).</b> A modern Agent (cppagent 2.x, the fixture's
     ///     <c>mtconnect/agent:2.7</c>) does not serve its error documents under HTTP 200 the way older
-    ///     ones did: it answers an out-of-range <c>/sample?from=</c> — and a <c>count</c> at or above its
+    ///     ones did: it answers an out-of-range <c>/sample?from=</c> — and a <c>count</c> above its
     ///     buffer — with <b>HTTP 400</b>, and an unknown device with <b>404</b>, each carrying a
     ///     well-formed <c>MTConnectError</c> body. A status check alone turns those into an
     ///     <see cref="HttpRequestException"/>, which the pump treats as a transient transport loss and
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverTestConnectButton.razor b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverTestConnectButton.razor
index f133dae8f..356b8ef7f 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverTestConnectButton.razor
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/DriverTestConnectButton.razor
@@ -14,7 +14,7 @@
     {
         @if (_result.Ok && WarningOf(_result.Message) is { } warning)
         {
-            @* Reachable but misconfigured (e.g. MTConnect SampleCount >= the Agent's bufferSize, #825): a probe
+            @* Reachable but misconfigured (e.g. MTConnect SampleCount > the Agent's bufferSize, #825): a probe
                that answers Ok with a "WARNING:" message is shown amber with the warning, never a plain green OK. *@
             <span class="chip chip-warn" title="@warning">
                 OK with warning &middot; @_result.LatencyMs?.ToString("F0") ms
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.IntegrationTests/MTConnectAgentIntegrationTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.IntegrationTests/MTConnectAgentIntegrationTests.cs
index 85639ebcd..b77ade7cd 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.IntegrationTests/MTConnectAgentIntegrationTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.IntegrationTests/MTConnectAgentIntegrationTests.cs
@@ -868,7 +868,7 @@ public sealed class MTConnectAgentIntegrationTests(MTConnectAgentFixture agent)
     }
 
     /// <summary>
-    ///     #804 — a <c>SampleCount</c> at or above the Agent's <c>bufferSize</c> is refused <c>OUT_OF_RANGE</c> on
+    ///     #804 — a <c>SampleCount</c> above the Agent's <c>bufferSize</c> is refused <c>OUT_OF_RANGE</c> on
     ///     EVERY <c>/sample</c> open (live: <c>'count' must be less than N</c>). The driver keeps serving values off
     ///     <c>/current</c> re-baselines, and — after three in a row with no <c>/sample</c> chunk — reports the stream
     ///     Degraded with <c>LastSuccessfulRead</c> still advancing, rather than Healthy for ever (before #804 the
@@ -949,7 +949,8 @@ public sealed class MTConnectAgentIntegrationTests(MTConnectAgentFixture agent)
 
     /// <summary>
     ///     #825 — Test Connect reads the live Agent's <c>/probe</c> <c>bufferSize</c> and warns (still Ok) when the
-    ///     configured <c>SampleCount</c> would be refused; one below the buffer is the falsifiability control.
+    ///     configured <c>SampleCount</c> would be refused. The live Agent accepts <c>count == bufferSize</c> and refuses
+    ///     <c>bufferSize + 1</c>, so both sides of that edge are checked against the Agent itself as well as the probe.
     /// </summary>
     [Fact(Timeout = TestTimeoutMs)]
     public async Task Test_Connect_warns_when_SampleCount_reaches_the_live_agents_buffer_size()
@@ -963,14 +964,22 @@ public sealed class MTConnectAgentIntegrationTests(MTConnectAgentFixture agent)
             Assert.Skip($"The Agent at {agent.AgentUri} declares no usable bufferSize in its /probe header.");
         }
 
+        // The Agent's own edge, so the warning threshold is pinned to what the Agent actually does.
+        using (var http = new HttpClient { Timeout = TimeSpan.FromSeconds(15) })
+        {
+            (await http.GetStringAsync($"{agent.AgentUri}/sample?count={bufferSize.Value}", Ct)).ShouldNotContain("OUT_OF_RANGE");
+            var over = await http.GetAsync($"{agent.AgentUri}/sample?count={bufferSize.Value + 1}", Ct);
+            (await over.Content.ReadAsStringAsync(Ct)).ShouldContain("OUT_OF_RANGE");
+        }
+
         var refused = await new MTConnectDriverProbe().ProbeAsync(
-            JsonSerializer.Serialize(new { agentUri = agent.AgentUri, sampleCount = bufferSize.Value }),
+            JsonSerializer.Serialize(new { agentUri = agent.AgentUri, sampleCount = bufferSize.Value + 1 }),
             TimeSpan.FromSeconds(15), Ct);
         refused.Ok.ShouldBeTrue(refused.Message);
-        refused.Message!.ShouldContain($"WARNING: SampleCount {bufferSize.Value} is at or above the Agent's bufferSize {bufferSize.Value}");
+        refused.Message!.ShouldContain($"WARNING: SampleCount {bufferSize.Value + 1} is above the Agent's bufferSize {bufferSize.Value}");
 
         var fits = await new MTConnectDriverProbe().ProbeAsync(
-            JsonSerializer.Serialize(new { agentUri = agent.AgentUri, sampleCount = bufferSize.Value - 1 }),
+            JsonSerializer.Serialize(new { agentUri = agent.AgentUri, sampleCount = bufferSize.Value }),
             TimeSpan.FromSeconds(15), Ct);
         fits.Ok.ShouldBeTrue(fits.Message);
         fits.Message!.ShouldNotContain("WARNING");
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectBufferSizeWarningTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectBufferSizeWarningTests.cs
index 1f6c72e67..dbe00e969 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectBufferSizeWarningTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectBufferSizeWarningTests.cs
@@ -7,7 +7,7 @@ using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 namespace ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests;
 
 /// <summary>
-///     lmxopcua#825 — a <c>SampleCount</c> at or above the Agent's <c>bufferSize</c> is refused <c>OUT_OF_RANGE</c> on
+///     lmxopcua#825 — a <c>SampleCount</c> above the Agent's <c>bufferSize</c> is refused <c>OUT_OF_RANGE</c> on
 ///     every <c>/sample</c> stream. The <c>/probe</c> header carries <c>bufferSize</c>, so Test Connect and the
 ///     driver's initialize (deploy) both warn instead of leaving it to surface as a Degraded stream.
 /// </summary>
@@ -37,15 +37,15 @@ public sealed class MTConnectBufferSizeWarningTests
         MTConnectProbeParser.Parse(ProbeXml(attribute)).BufferSize.ShouldBe(expected);
 
     [Theory]
-    [InlineData(16383, 16384L, false)]
-    [InlineData(16384, 16384L, true)]
+    [InlineData(16384, 16384L, false)] // live, cppagent 2.7: count == bufferSize is accepted
+    [InlineData(16385, 16384L, true)]  // ... and bufferSize + 1 refused OUT_OF_RANGE
     [InlineData(20000, 16384L, true)]
     [InlineData(1_000_000, null, false)]
-    public void The_warning_fires_exactly_at_and_above_the_buffer_size(int sampleCount, long? bufferSize, bool warns)
+    public void The_warning_fires_only_above_the_buffer_size(int sampleCount, long? bufferSize, bool warns)
     {
         var warning = MTConnectDriver.SampleCountBufferWarning(sampleCount, bufferSize);
         (warning is not null).ShouldBe(warns);
-        if (warns) warning!.ShouldContain($"below {bufferSize}");
+        if (warns) warning!.ShouldContain($"at most {bufferSize}");
     }
 
     [Fact]
@@ -53,7 +53,7 @@ public sealed class MTConnectBufferSizeWarningTests
     {
         var probe = new MTConnectDriverProbe(new StubHandler(ProbeXml("16384")));
         var r = await probe.ProbeAsync(
-            "{\"agentUri\":\"http://stub-agent:5000\",\"sampleCount\":16384}", TimeSpan.FromSeconds(3),
+            "{\"agentUri\":\"http://stub-agent:5000\",\"sampleCount\":16385}", TimeSpan.FromSeconds(3),
             TestContext.Current.CancellationToken);
 
         r.Ok.ShouldBeTrue("the Agent answered — reachability is not the problem");
@@ -70,7 +70,7 @@ public sealed class MTConnectBufferSizeWarningTests
             "{\"agentUri\":\"http://stub-agent:5000\"}", TimeSpan.FromSeconds(3), TestContext.Current.CancellationToken);
 
         r.Ok.ShouldBeTrue();
-        r.Message!.ShouldContain("SampleCount 1000 is at or above the Agent's bufferSize 512");
+        r.Message!.ShouldContain("SampleCount 1000 is above the Agent's bufferSize 512");
     }
 
     [Fact]
@@ -78,7 +78,7 @@ public sealed class MTConnectBufferSizeWarningTests
     {
         var probe = new MTConnectDriverProbe(new StubHandler(ProbeXml("16384")));
         var r = await probe.ProbeAsync(
-            "{\"agentUri\":\"http://stub-agent:5000\",\"sampleCount\":1000}", TimeSpan.FromSeconds(3),
+            "{\"agentUri\":\"http://stub-agent:5000\",\"sampleCount\":16384}", TimeSpan.FromSeconds(3),
             TestContext.Current.CancellationToken);
 
         r.Ok.ShouldBeTrue();
@@ -86,7 +86,8 @@ public sealed class MTConnectBufferSizeWarningTests
     }
 
     [Theory]
-    [InlineData(131072, true)]
+    [InlineData(131073, true)]
+    [InlineData(131072, false)]
     [InlineData(1000, false)]
     public async Task Initialize_warns_and_surfaces_the_buffer_size_on_the_diagnostics_bag(int sampleCount, bool warns)
     {
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectSubscribeTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectSubscribeTests.cs
index ccaccf26a..b60d1683e 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectSubscribeTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectSubscribeTests.cs
@@ -1168,7 +1168,7 @@ public sealed class MTConnectSubscribeTests
 
     /// <summary>
     ///     <b>#804 (Java-driver parity: <c>MAX_REBASELINES_WITHOUT_PROGRESS</c>).</b> An Agent that answers EVERY
-    ///     <c>/sample</c> open with <c>OUT_OF_RANGE</c> (live: a <c>count</c> at or above its <c>bufferSize</c>) is
+    ///     <c>/sample</c> open with <c>OUT_OF_RANGE</c> (live: a <c>count</c> above its <c>bufferSize</c>) is
     ///     re-baselined from <c>/current</c> each time, and the backoff paces that — but every re-baseline also marked
     ///     the stream delivered, so the driver read <b>Healthy</b> for ever while not one <c>/sample</c> chunk arrived.
     ///     After <see cref="MTConnectDriver.MaxRebaselinesWithoutProgress"/> in a row it is Degraded and stays so