Resolve Client.Dotnet-004..008 code-review findings

Client.Dotnet-004: documented DefaultCallTimeout as both the per-attempt
deadline and the shared retry budget, and removed DeadlineExceeded from the
transient-retry set (a client-imposed deadline cannot be helped by retrying).

Client.Dotnet-005: RegisterAsync/AddItemAsync/AddItem2Async silently returned
0 when a successful reply lacked the typed payload. They now throw a
descriptive MxGatewayException.

Client.Dotnet-006: added XML docs to the previously undocumented public
members MaxGrpcMessageBytes, GatewayProtocolVersion, WorkerProtocolVersion.

Client.Dotnet-007: corrected the AcknowledgeAlarmAsync XML comment — the RPC
requires the admin scope, not a non-existent invoke:alarm-ack sub-scope.

Client.Dotnet-008: the CLI redactor missed env-var-sourced keys because the
caller passed only the --api-key option. Redaction now uses the same
resolver, stripping env-var keys too.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/dotnet/MxGateway.Client.Cli/MxGatewayClientCli.cs

@@ -122,7 +122,10 @@ public static class MxGatewayClientCli
         }
         catch (Exception exception) when (exception is not OperationCanceledException)
         {
-            string? apiKey = arguments.GetOptional("api-key");
+            // Redact the effective API key — whether it came from --api-key or from
+            // the (documented default) --api-key-env environment variable — so a
+            // transport error message that echoes the bearer token is never printed.
+            string? apiKey = TryResolveApiKey(arguments);
             string message = MxGatewayCliSecretRedactor.Redact(exception.Message, apiKey);
 
             if (arguments.HasFlag("json"))
@@ -167,6 +170,27 @@ public static class MxGatewayClientCli
     }
 
     private static string ResolveApiKey(CliArguments arguments)
+    {
+        string? apiKey = TryResolveApiKey(arguments);
+        if (!string.IsNullOrWhiteSpace(apiKey))
+        {
+            return apiKey;
+        }
+
+        string apiKeyEnvironmentName = arguments.GetOptional("api-key-env")
+            ?? "MXGATEWAY_API_KEY";
+
+        throw new ArgumentException(
+            $"Gateway API key is required. Pass --api-key or set {apiKeyEnvironmentName}.");
+    }
+
+    /// <summary>
+    /// Resolves the effective API key from <c>--api-key</c> or, failing that, the
+    /// environment variable named by <c>--api-key-env</c> (default
+    /// <c>MXGATEWAY_API_KEY</c>). Returns <see langword="null"/> when no key is
+    /// configured; used for redaction where a missing key must not throw.
+    /// </summary>
+    private static string? TryResolveApiKey(CliArguments arguments)
     {
         string? apiKey = arguments.GetOptional("api-key");
         if (!string.IsNullOrWhiteSpace(apiKey))
@@ -177,14 +201,7 @@ public static class MxGatewayClientCli
         string apiKeyEnvironmentName = arguments.GetOptional("api-key-env")
             ?? "MXGATEWAY_API_KEY";
 
-        apiKey = Environment.GetEnvironmentVariable(apiKeyEnvironmentName);
-        if (!string.IsNullOrWhiteSpace(apiKey))
-        {
-            return apiKey;
-        }
-
-        throw new ArgumentException(
-            $"Gateway API key is required. Pass --api-key or set {apiKeyEnvironmentName}.");
+        return Environment.GetEnvironmentVariable(apiKeyEnvironmentName);
     }
 
     private static CancellationTokenSource CreateCancellation(CliArguments arguments, string command)

clients/dotnet/MxGateway.Client.Tests/MxGatewayClientCliTests.cs

@@ -106,6 +106,43 @@ public sealed class MxGatewayClientCliTests
         Assert.Contains("[redacted]", error.ToString());
     }
 
+    /// <summary>
+    /// Verifies that error output redacts the API key even when it was sourced from
+    /// the <c>--api-key-env</c> environment variable rather than passed via
+    /// <c>--api-key</c> — the documented default credential path.
+    /// </summary>
+    [Fact]
+    public async Task RunAsync_ErrorOutput_RedactsApiKey_WhenSourcedFromEnvironmentVariable()
+    {
+        const string environmentVariableName = "MXGATEWAY_TEST_API_KEY_REDACT";
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+
+        Environment.SetEnvironmentVariable(environmentVariableName, "env-secret-api-key");
+        try
+        {
+            int exitCode = await MxGatewayClientCli.RunAsync(
+                [
+                    "open-session",
+                    "--endpoint",
+                    "http://localhost:5000",
+                    "--api-key-env",
+                    environmentVariableName,
+                ],
+                output,
+                error,
+                _ => throw new InvalidOperationException("boom env-secret-api-key"));
+
+            Assert.Equal(1, exitCode);
+            Assert.DoesNotContain("env-secret-api-key", error.ToString());
+            Assert.Contains("[redacted]", error.ToString());
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable(environmentVariableName, null);
+        }
+    }
+
     /// <summary>Verifies that stream-events with max-events limit stops output in non-JSON format.</summary>
     [Fact]
     public async Task RunAsync_StreamEvents_WithMaxEventsStopsNonJsonOutput()

clients/dotnet/MxGateway.Client.Tests/MxGatewayClientSessionTests.cs

@@ -378,6 +378,84 @@ public sealed class MxGatewayClientSessionTests
         Assert.Equal(cancellation.Token, Assert.Single(transport.InvokeCalls).CallOptions.CancellationToken);
     }
 
+    /// <summary>
+    /// Verifies that a client-imposed <see cref="StatusCode.DeadlineExceeded"/> is not
+    /// retried. The deadline budget is shared across the whole safe-unary operation, so
+    /// an immediate retry would only fail again — the call must surface the failure.
+    /// </summary>
+    [Fact]
+    public async Task InvokeAsync_DoesNotRetrySafeDiagnosticCommand_OnDeadlineExceeded()
+    {
+        FakeGatewayTransport transport = CreateTransport();
+        transport.InvokeExceptions.Enqueue(
+            new RpcException(new Status(StatusCode.DeadlineExceeded, "deadline exceeded")));
+        transport.AddInvokeReply(new MxCommandReply
+        {
+            SessionId = "session-fixture",
+            Kind = MxCommandKind.Ping,
+            ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+        });
+        await using MxGatewayClient client = CreateClient(transport);
+        MxGatewaySession session = await client.OpenSessionAsync();
+
+        await Assert.ThrowsAsync<RpcException>(async () => await session.InvokeAsync(
+            new MxCommandRequest
+            {
+                SessionId = session.SessionId,
+                Command = new MxCommand { Kind = MxCommandKind.Ping, Ping = new PingCommand() },
+            }));
+
+        Assert.Single(transport.InvokeCalls);
+    }
+
+    /// <summary>
+    /// Verifies that a successful register reply missing the typed <c>register</c>
+    /// payload throws a descriptive <see cref="MxGatewayException"/> rather than
+    /// silently returning a zero server handle.
+    /// </summary>
+    [Fact]
+    public async Task RegisterAsync_Throws_WhenSuccessfulReplyMissingPayload()
+    {
+        FakeGatewayTransport transport = CreateTransport();
+        transport.AddInvokeReply(new MxCommandReply
+        {
+            SessionId = "session-fixture",
+            Kind = MxCommandKind.Register,
+            ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+        });
+        await using MxGatewayClient client = CreateClient(transport);
+        MxGatewaySession session = await client.OpenSessionAsync();
+
+        MxGatewayException exception = await Assert.ThrowsAsync<MxGatewayException>(
+            async () => await session.RegisterAsync("client-name"));
+
+        Assert.Contains("register", exception.Message, StringComparison.Ordinal);
+    }
+
+    /// <summary>
+    /// Verifies that a successful add-item reply missing the typed <c>add_item</c>
+    /// payload throws a descriptive <see cref="MxGatewayException"/> rather than
+    /// silently returning a zero item handle.
+    /// </summary>
+    [Fact]
+    public async Task AddItemAsync_Throws_WhenSuccessfulReplyMissingPayload()
+    {
+        FakeGatewayTransport transport = CreateTransport();
+        transport.AddInvokeReply(new MxCommandReply
+        {
+            SessionId = "session-fixture",
+            Kind = MxCommandKind.AddItem,
+            ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+        });
+        await using MxGatewayClient client = CreateClient(transport);
+        MxGatewaySession session = await client.OpenSessionAsync();
+
+        MxGatewayException exception = await Assert.ThrowsAsync<MxGatewayException>(
+            async () => await session.AddItemAsync(1, "Area.Pump.Speed"));
+
+        Assert.Contains("add_item", exception.Message, StringComparison.Ordinal);
+    }
+
     private static MxGatewayClient CreateClient(FakeGatewayTransport transport)
     {
         return new MxGatewayClient(transport.Options, transport);

clients/dotnet/MxGateway.Client/MxGatewayClient.cs

@@ -184,9 +184,10 @@ public sealed class MxGatewayClient : IAsyncDisposable
 
     /// <summary>
     /// Acknowledges an active MXAccess alarm condition through the gateway. The
-    /// gateway authenticates the request against the API key's <c>invoke:alarm-ack</c>
-    /// scope and forwards the acknowledge to the worker's MXAccess session;
-    /// the resulting <see cref="MxStatusProxy"/> is returned in the reply.
+    /// gateway authorizes <see cref="AcknowledgeAlarmRequest"/> against the API
+    /// key's <c>admin</c> scope (there is no finer-grained alarm-ack sub-scope)
+    /// and forwards the acknowledge to the worker's MXAccess session; the
+    /// resulting <see cref="MxStatusProxy"/> is returned in the reply.
     /// </summary>
     /// <param name="request">The acknowledge request — alarm reference, comment, operator user.</param>
     /// <param name="cancellationToken">Cancellation token for the operation.</param>

clients/dotnet/MxGateway.Client/MxGatewayClientContractInfo.cs

@@ -7,9 +7,19 @@ namespace MxGateway.Client;
 /// </summary>
 public static class MxGatewayClientContractInfo
 {
+    /// <summary>
+    /// Gets the gateway gRPC protocol version compiled into this client package.
+    /// A client and gateway are wire-compatible only when this value matches the
+    /// gateway's advertised gateway protocol version.
+    /// </summary>
     public const uint GatewayProtocolVersion =
         GatewayContractInfo.GatewayProtocolVersion;
 
+    /// <summary>
+    /// Gets the worker frame protocol version compiled into this client package.
+    /// Exposed for diagnostics so callers can report the worker protocol the
+    /// shared contracts were generated against.
+    /// </summary>
     public const uint WorkerProtocolVersion =
         GatewayContractInfo.WorkerProtocolVersion;
 }

clients/dotnet/MxGateway.Client/MxGatewayClientOptions.cs

@@ -38,7 +38,12 @@ public sealed class MxGatewayClientOptions
     public TimeSpan ConnectTimeout { get; init; } = TimeSpan.FromSeconds(10);
 
     /// <summary>
-    /// Gets the default timeout for unary gRPC calls.
+    /// Gets the timeout budget for a unary gRPC operation. This is both the gRPC
+    /// deadline stamped on each individual attempt and the overall budget for the
+    /// whole safe-unary operation: for retryable calls the initial attempt, every
+    /// retry, and the backoff delays between them all share this single budget.
+    /// It is therefore an upper bound on the total wall-clock time a safe-unary
+    /// call can take, not a fresh per-retry allowance.
     /// </summary>
     public TimeSpan DefaultCallTimeout { get; init; } = TimeSpan.FromSeconds(30);
 
@@ -47,6 +52,11 @@ public sealed class MxGatewayClientOptions
     /// </summary>
     public TimeSpan? StreamTimeout { get; init; }
 
+    /// <summary>
+    /// Gets the maximum size, in bytes, of a single gRPC message the client will
+    /// send or receive. Applied to both the send and receive limits of the
+    /// underlying channel. Defaults to 16 MiB.
+    /// </summary>
     public int MaxGrpcMessageBytes { get; init; } = 16 * 1024 * 1024;
 
     /// <summary>

clients/dotnet/MxGateway.Client/MxGatewayClientRetryPolicy.cs

@@ -61,8 +61,13 @@ internal static class MxGatewayClientRetryPolicy
 
     private static bool IsTransientStatus(StatusCode statusCode)
     {
+        // DeadlineExceeded is intentionally NOT treated as transient. The deadline
+        // on every unary call is client-imposed (CreateCallOptions stamps the
+        // DefaultCallTimeout budget), and that same budget is shared across the
+        // initial attempt plus all retries plus backoff. A DeadlineExceeded means
+        // the shared budget is exhausted, so an immediate retry would only fail
+        // again — burning the remaining budget on a call that cannot succeed.
         return statusCode is StatusCode.Unavailable
-            or StatusCode.DeadlineExceeded
             or StatusCode.ResourceExhausted;
     }
 }

clients/dotnet/MxGateway.Client/MxGatewaySession.cs

@@ -101,7 +101,8 @@ public sealed class MxGatewaySession : IAsyncDisposable
         MxCommandReply reply = await RegisterRawAsync(clientName, cancellationToken)
             .ConfigureAwait(false);
         reply.EnsureProtocolSuccess().EnsureMxAccessSuccess();
-        return reply.Register?.ServerHandle ?? reply.ReturnValue.Int32Value;
+        return reply.Register?.ServerHandle
+            ?? throw CreateMissingPayloadException(reply, "register");
     }
 
     /// <summary>
@@ -143,7 +144,8 @@ public sealed class MxGatewaySession : IAsyncDisposable
                 cancellationToken)
             .ConfigureAwait(false);
         reply.EnsureProtocolSuccess().EnsureMxAccessSuccess();
-        return reply.AddItem?.ItemHandle ?? reply.ReturnValue.Int32Value;
+        return reply.AddItem?.ItemHandle
+            ?? throw CreateMissingPayloadException(reply, "add_item");
     }
 
     /// <summary>
@@ -194,7 +196,8 @@ public sealed class MxGatewaySession : IAsyncDisposable
                 cancellationToken)
             .ConfigureAwait(false);
         reply.EnsureProtocolSuccess().EnsureMxAccessSuccess();
-        return reply.AddItem2?.ItemHandle ?? reply.ReturnValue.Int32Value;
+        return reply.AddItem2?.ItemHandle
+            ?? throw CreateMissingPayloadException(reply, "add_item2");
     }
 
     /// <summary>
@@ -723,4 +726,21 @@ public sealed class MxGatewaySession : IAsyncDisposable
             cancellationToken);
     }
 
+    /// <summary>
+    /// Builds the exception thrown when a command reply passed protocol and
+    /// MXAccess success checks but is missing the typed handle-bearing payload
+    /// the command contract requires. Surfacing this as a clear error avoids
+    /// silently handing a zero handle to the caller (it would otherwise fall
+    /// through to <see cref="MxCommandReply.ReturnValue"/>, which is 0 when the
+    /// reply carries no return value).
+    /// </summary>
+    private static MxGatewayException CreateMissingPayloadException(
+        MxCommandReply reply,
+        string expectedPayload)
+    {
+        return new MxGatewayException(
+            $"Gateway reply for command kind={reply.Kind} reported success but is missing "
+            + $"the required '{expectedPayload}' payload; cannot resolve a handle. "
+            + $"session={reply.SessionId}; correlation={reply.CorrelationId}");
+    }
 }

clients/dotnet/README.md

@@ -142,7 +142,8 @@ dotnet run --project clients/dotnet/MxGateway.Client.Cli -- smoke --endpoint htt
 `smoke` opens a session, registers a client, adds one item, advises it,
 optionally writes a value when `--type` and `--value` are supplied, reads a
 bounded event stream, and closes the session in a `finally` block. CLI error
-output redacts API keys supplied through `--api-key`.
+output redacts the effective API key, whether it was supplied through
+`--api-key` or resolved from the `--api-key-env` environment variable.
 
 ## Galaxy Repository Browse