docs/reverse-engineering/grpc-interface-versions.md

@@ -0,0 +1,44 @@
+# 2023 R2 gRPC Interface-Version Integers (C3a)
+
+**Captured:** 2026-06-25  
+**Transport:** 2023 R2 gRPC (h2c, unauthenticated `GetInterfaceVersion` RPCs — no credentials required)  
+**Status:** LIVE — integers captured from a real AVEVA Historian 2023 R2 server.
+
+## Captured Values
+
+| Service        | UiVersion / Version | UiError / Error | Notes                                              |
+|---------------|---------------------|-----------------|----------------------------------------------------|
+| History        | 12                  | 0               | Matches `HistoryInterfaceVersionGrpc2023R2 = 12`   |
+| Retrieval      | 4                   | 0               | Matches `RetrievalInterfaceVersion = 4` (unchanged from 2020) |
+| Transaction    | 2                   | 0               | Matches `TransactionInterfaceVersion = 2` (unchanged from 2020) |
+| Status         | 4                   | 0               | Reachability-only; version integer is not version-gated (see note) |
+
+> **Field-name note:** The History, Retrieval, and Status proto responses use `UiError`/`UiVersion` fields.
+> The Transaction response uses `Error`/`Version` (different naming convention in the proto). Both are
+> captured correctly; the table uses a unified column header for readability.
+
+> **Status note:** `StatusService.GetStatusInterfaceVersion` returned UiVersion=4, UiError=0 on the live
+> 2023 R2 server. Status is classified as reachability-only — its version integer carries no semantic
+> meaning for the SDK's byte serializers — so its UiVersion is not gated and not asserted in tests.
+
+## Evidence Test
+
+`tests/AVEVA.Historian.Client.Tests/GrpcInterfaceVersionEvidenceTests.cs` —
+`GrpcInterfaceVersions_LiveServer_MatchAcceptedSet` reads these four RPCs live and asserts:
+- `history.UiError == 0` and `history.UiVersion ∈ {11, 12}`
+- `retrieval.UiError == 0` and `retrieval.UiVersion == 4`
+- `transaction.Error == 0` and `transaction.Version == 2`
+- `status.UiError == 0` (version not asserted)
+
+The test skips silently when `HISTORIAN_GRPC_HOST` is absent.
+
+## Gap Closed
+
+This document closes the **C3a** gap: "2023 R2 gRPC server-version integers not yet captured."
+Prior to this capture, the `HistorianServerVersionGate` accepted History=12, Retrieval=4, and
+Transaction=2 on the basis that they were inferred/expected-to-be-unchanged. All four integers are
+now confirmed from a live 2023 R2 server over the gRPC transport; no widening of `AcceptedVersions`
+is required (all captured values were already accepted).
+
+The 2020 WCF baseline (History=11, Retrieval=4, Transaction=2) was captured earlier via the
+`wcf-probe` command and is documented in `wcf-probe-remote-latest.json` and `wcf-contract-evidence.md`.

src/AVEVA.Historian.Client/HistorianServerVersionGate.cs

@@ -48,8 +48,12 @@ internal static class HistorianServerVersionGate
     /// The 2023 R2 gRPC HistoryService reports interface version 12. It is buffer-compatible with
     /// the 2020 version 11 — the OpenConnection3 v6 / token / DataQueryRequest / row buffers are
     /// byte-identical — confirmed by a live end-to-end gRPC read against a real 2023 R2 server
-    /// (2026-06-21). So both 11 and 12 are accepted for History. (Retrieval reported 4, matching
+    /// (2026-06-21). So both 11 and 12 are accepted for History.
-    /// the 2020 value, so it needs no widening.)
+    ///
+    /// Retrieval=4, Transaction=2, and Status UiError=0 are now confirmed captured live over the
+    /// 2023 R2 gRPC transport (2026-06-25, unauthenticated GetInterfaceVersion RPCs); see
+    /// <c>docs/reverse-engineering/grpc-interface-versions.md</c>. All captured values were already
+    /// accepted — no widening of <see cref="AcceptedVersions"/> was required.
     /// </summary>
     public const uint HistoryInterfaceVersionGrpc2023R2 = 12;
 

tests/AVEVA.Historian.Client.Tests/GrpcInterfaceVersionEvidenceTests.cs

@@ -0,0 +1,102 @@
+using AVEVA.Historian.Client.Grpc;
+using GrpcHistory = ArchestrA.Grpc.Contract.History;
+using GrpcRetrieval = ArchestrA.Grpc.Contract.Retrieval;
+using GrpcStatus = ArchestrA.Grpc.Contract.Status;
+using GrpcTransaction = ArchestrA.Grpc.Contract.Transaction;
+using Xunit.Abstractions;
+
+namespace AVEVA.Historian.Client.Tests;
+
+/// <summary>
+/// Live evidence test (C3a): reads the four unauthenticated <c>GetInterfaceVersion</c> RPCs from a
+/// real 2023 R2 Historian over gRPC and asserts the accepted version set. These RPCs run before any
+/// credential exchange, so no HISTORIAN_USER / HISTORIAN_PASSWORD is required — only a reachable host.
+///
+/// Skips silently when <c>HISTORIAN_GRPC_HOST</c> is absent (offline / CI). The captured integers
+/// are recorded in <c>docs/reverse-engineering/grpc-interface-versions.md</c> and close the C3a
+/// "2023 R2 gRPC server-version integers not yet captured" gap.
+/// </summary>
+public sealed class GrpcInterfaceVersionEvidenceTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public GrpcInterfaceVersionEvidenceTests(ITestOutputHelper output) => _output = output;
+
+    [Fact]
+    public void GrpcInterfaceVersions_LiveServer_MatchAcceptedSet()
+    {
+        string host = Environment.GetEnvironmentVariable("HISTORIAN_GRPC_HOST") ?? "";
+        if (string.IsNullOrWhiteSpace(host))
+        {
+            _output.WriteLine("SKIP: HISTORIAN_GRPC_HOST is not set — no live historian available.");
+            return;
+        }
+
+        HistorianClientOptions options = BuildOptions(host);
+
+        using HistorianGrpcConnection connection = HistorianGrpcChannelFactory.Create(options);
+        DateTime deadline = DateTime.UtcNow.Add(TimeSpan.FromSeconds(10));
+
+        GrpcHistory.GetInterfaceVersionResponse history =
+            new GrpcHistory.HistoryService.HistoryServiceClient(connection.Channel)
+                .GetInterfaceVersion(new GrpcHistory.GetInterfaceVersionRequest(), connection.Metadata, deadline, default);
+
+        GrpcRetrieval.GetRetrievalInterfaceVersionResponse retrieval =
+            new GrpcRetrieval.RetrievalService.RetrievalServiceClient(connection.Channel)
+                .GetRetrievalInterfaceVersion(new GrpcRetrieval.GetRetrievalInterfaceVersionRequest(), connection.Metadata, deadline, default);
+
+        GrpcStatus.GetStatusInterfaceVersionResponse status =
+            new GrpcStatus.StatusService.StatusServiceClient(connection.Channel)
+                .GetStatusInterfaceVersion(new GrpcStatus.GetStatusInterfaceVersionRequest(), connection.Metadata, deadline, default);
+
+        GrpcTransaction.GetTransactionInterfaceVersionResponse transaction =
+            new GrpcTransaction.TransactionService.TransactionServiceClient(connection.Channel)
+                .GetTransactionInterfaceVersion(new GrpcTransaction.GetTransactionInterfaceVersionRequest(), connection.Metadata, deadline, default);
+
+        _output.WriteLine($"History    UiVersion={history.UiVersion}    UiError={history.UiError}");
+        _output.WriteLine($"Retrieval  UiVersion={retrieval.UiVersion}  UiError={retrieval.UiError}");
+        _output.WriteLine($"Status     UiVersion={status.UiVersion}     UiError={status.UiError}");
+        // Note: Transaction response fields are named Error/Version (not UiError/UiVersion) per the proto.
+        _output.WriteLine($"Transaction Version={transaction.Version}   Error={transaction.Error}");
+
+        // History: accepted set is {11 (2020 WCF), 12 (2023 R2 gRPC)}.
+        Assert.Equal(0u, history.UiError);
+        Assert.Contains(history.UiVersion, new uint[] { 11u, 12u });
+
+        // Retrieval: 4 on both 2020 WCF and 2023 R2 gRPC.
+        Assert.Equal(0u, retrieval.UiError);
+        Assert.Equal(4u, retrieval.UiVersion);
+
+        // Transaction: 2 (confirmed by live gRPC capture — see grpc-interface-versions.md).
+        // NOTE: the Transaction response proto uses Error/Version (not UiError/UiVersion).
+        Assert.Equal(0u, transaction.Error);
+        Assert.Equal(2u, transaction.Version);
+
+        // Status: reachability-only — UiError must be 0; UiVersion is intentionally 0 by design.
+        Assert.Equal(0u, status.UiError);
+    }
+
+    private static HistorianClientOptions BuildOptions(string host)
+    {
+        string? user = Environment.GetEnvironmentVariable("HISTORIAN_USER");
+        string? password = Environment.GetEnvironmentVariable("HISTORIAN_PASSWORD");
+        bool explicitCreds = !string.IsNullOrEmpty(user);
+        int port = int.TryParse(Environment.GetEnvironmentVariable("HISTORIAN_GRPC_PORT"), out int parsed)
+            ? parsed
+            : HistorianClientOptions.DefaultGrpcPort;
+        bool tls = string.Equals(Environment.GetEnvironmentVariable("HISTORIAN_GRPC_TLS"), "true", StringComparison.OrdinalIgnoreCase);
+
+        return new HistorianClientOptions
+        {
+            Host = host,
+            Port = port,
+            Transport = HistorianTransport.RemoteGrpc,
+            GrpcUseTls = tls,
+            AllowUntrustedServerCertificate = tls,
+            ServerDnsIdentity = Environment.GetEnvironmentVariable("HISTORIAN_GRPC_DNSID"),
+            IntegratedSecurity = !explicitCreds,
+            UserName = user ?? string.Empty,
+            Password = password ?? string.Empty,
+        };
+    }
+}

tests/AVEVA.Historian.Client.Tests/HistorianServerVersionGateTests.cs

@@ -71,8 +71,9 @@ public sealed class HistorianServerVersionGateTests
     [Fact]
     public void Validate_VerificationDisabled_NeverThrows()
     {
-        // A wildly wrong version is tolerated when the operator opts out (e.g. bringing up a
+        // A wildly wrong version is tolerated when the operator opts out. The 2023 R2 gRPC
-        // 2023 R2 gRPC server whose reported integers have not yet been captured).
+        // integers are now captured live (see docs/reverse-engineering/grpc-interface-versions.md)
+        // and all accepted; this opt-out is a safety valve for some future, not-yet-captured value.
         HistorianServerVersionGate.Validate(HistorianServiceInterface.History, 999u, Options(verify: false));
         HistorianServerVersionGate.Validate(HistorianServiceInterface.Retrieval, 0u, Options(verify: false));
     }