src/ZB.MOM.WW.OtOpcUa.Server/OpcUa/DriverEquipmentContentRegistry.cs

@@ -0,0 +1,47 @@
+using ZB.MOM.WW.OtOpcUa.Core.OpcUa;
+
+namespace ZB.MOM.WW.OtOpcUa.Server.OpcUa;
+
+/// <summary>
+///     Holds pre-loaded <see cref="EquipmentNamespaceContent"/> snapshots keyed by
+///     <c>DriverInstanceId</c>. Populated once during <see cref="OpcUaServerService"/> startup
+///     (after <see cref="NodeBootstrap"/> resolves the generation) so the synchronous lookup
+///     delegate on <see cref="OpcUaApplicationHost"/> can serve the walker from memory without
+///     blocking on async DB I/O mid-dispatch.
+/// </summary>
+/// <remarks>
+///     <para>The registry is intentionally a shared mutable singleton with set-once-per-bootstrap
+///     semantics rather than an immutable map passed by value — the composition in Program.cs
+///     builds <see cref="OpcUaApplicationHost"/> before <see cref="NodeBootstrap"/> runs, so the
+///     registry must exist at DI-compose time but be empty until the generation is known. A
+///     driver registered after the initial populate pass simply returns null from
+///     <see cref="Get"/> + the wire-in falls back to the "no UNS content, let DiscoverAsync own
+///     it" path that PR #155 established.</para>
+/// </remarks>
+public sealed class DriverEquipmentContentRegistry
+{
+    private readonly Dictionary<string, EquipmentNamespaceContent> _content =
+        new(StringComparer.OrdinalIgnoreCase);
+    private readonly Lock _lock = new();
+
+    public EquipmentNamespaceContent? Get(string driverInstanceId)
+    {
+        lock (_lock)
+        {
+            return _content.TryGetValue(driverInstanceId, out var c) ? c : null;
+        }
+    }
+
+    public void Set(string driverInstanceId, EquipmentNamespaceContent content)
+    {
+        lock (_lock)
+        {
+            _content[driverInstanceId] = content;
+        }
+    }
+
+    public int Count
+    {
+        get { lock (_lock) { return _content.Count; } }
+    }
+}

src/ZB.MOM.WW.OtOpcUa.Server/OpcUaServerService.cs

@@ -1,3 +1,4 @@
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using ZB.MOM.WW.OtOpcUa.Core.Hosting;
@@ -15,6 +16,8 @@ public sealed class OpcUaServerService(
     NodeBootstrap bootstrap,
     DriverHost driverHost,
     OpcUaApplicationHost applicationHost,
+    DriverEquipmentContentRegistry equipmentContentRegistry,
+    IServiceScopeFactory scopeFactory,
     ILogger<OpcUaServerService> logger) : BackgroundService
 {
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
@@ -24,6 +27,15 @@ public sealed class OpcUaServerService(
         var result = await bootstrap.LoadCurrentGenerationAsync(stoppingToken);
         logger.LogInformation("Bootstrap complete: source={Source} generation={Gen}", result.Source, result.GenerationId);
 
+        // ADR-001 Option A — populate per-driver Equipment namespace snapshots into the
+        // registry before StartAsync walks the address space. The walker on the OPC UA side
+        // reads synchronously from the registry; pre-loading here means the hot path stays
+        // non-blocking + each driver pays at most one Config-DB query at bootstrap time.
+        // Skipped when no generation is Published yet — the fleet boots into a UNS-less
+        // address space until the first publish, then the registry fills on next restart.
+        if (result.GenerationId is { } gen)
+            await PopulateEquipmentContentAsync(gen, stoppingToken);
+
         // PR 17: stand up the OPC UA server + drive discovery per registered driver. Driver
         // registration itself (RegisterAsync on DriverHost) happens during an earlier DI
         // extension once the central config DB query + per-driver factory land; for now the
@@ -48,4 +60,30 @@ public sealed class OpcUaServerService(
         await applicationHost.DisposeAsync();
         await driverHost.DisposeAsync();
     }
+
+    /// <summary>
+    ///     Pre-load an <c>EquipmentNamespaceContent</c> snapshot for each registered driver at
+    ///     the bootstrapped generation. Null results (driver has no Equipment rows —
+    ///     Modbus/AB CIP/TwinCAT/FOCAS today per decisions #116–#121) are skipped: the walker
+    ///     wire-in sees Get(driverId) return null + falls back to DiscoverAsync-owns-it.
+    ///     Opens one scope so the scoped <c>OtOpcUaConfigDbContext</c> is shared across all
+    ///     per-driver queries rather than paying scope-setup overhead per driver.
+    /// </summary>
+    private async Task PopulateEquipmentContentAsync(long generationId, CancellationToken ct)
+    {
+        using var scope = scopeFactory.CreateScope();
+        var loader = scope.ServiceProvider.GetRequiredService<EquipmentNamespaceContentLoader>();
+
+        var loaded = 0;
+        foreach (var driverId in driverHost.RegisteredDriverIds)
+        {
+            var content = await loader.LoadAsync(driverId, generationId, ct).ConfigureAwait(false);
+            if (content is null) continue;
+            equipmentContentRegistry.Set(driverId, content);
+            loaded++;
+        }
+        logger.LogInformation(
+            "Equipment namespace snapshots loaded for {Count}/{Total} driver(s) at generation {Gen}",
+            loaded, driverHost.RegisteredDriverIds.Count, generationId);
+    }
 }

src/ZB.MOM.WW.OtOpcUa.Server/Program.cs

@@ -86,7 +86,25 @@ builder.Services.AddSingleton<IUserAuthenticator>(sp => ldapOptions.Enabled
 builder.Services.AddSingleton<ILocalConfigCache>(_ => new LiteDbConfigCache(options.LocalCachePath));
 builder.Services.AddSingleton<DriverHost>();
 builder.Services.AddSingleton<NodeBootstrap>();
-builder.Services.AddSingleton<OpcUaApplicationHost>();
+
+// ADR-001 Option A wiring — the registry is the handoff between OpcUaServerService's
+// bootstrap-time population pass + OpcUaApplicationHost's StartAsync walker invocation.
+// DriverEquipmentContentRegistry.Get is the equipmentContentLookup delegate that PR #155
+// added to OpcUaApplicationHost's ctor seam.
+builder.Services.AddSingleton<DriverEquipmentContentRegistry>();
+builder.Services.AddScoped<EquipmentNamespaceContentLoader>();
+
+builder.Services.AddSingleton<OpcUaApplicationHost>(sp =>
+{
+    var registry = sp.GetRequiredService<DriverEquipmentContentRegistry>();
+    return new OpcUaApplicationHost(
+        sp.GetRequiredService<OpcUaServerOptions>(),
+        sp.GetRequiredService<DriverHost>(),
+        sp.GetRequiredService<IUserAuthenticator>(),
+        sp.GetRequiredService<ILoggerFactory>(),
+        sp.GetRequiredService<ILogger<OpcUaApplicationHost>>(),
+        equipmentContentLookup: registry.Get);
+});
 builder.Services.AddHostedService<OpcUaServerService>();
 
 // Central-config DB access for the host-status publisher (LMX follow-up #7). Scoped context

tests/ZB.MOM.WW.OtOpcUa.Server.Tests/DriverEquipmentContentRegistryTests.cs

@@ -0,0 +1,57 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.OpcUa;
+using ZB.MOM.WW.OtOpcUa.Server.OpcUa;
+
+namespace ZB.MOM.WW.OtOpcUa.Server.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class DriverEquipmentContentRegistryTests
+{
+    private static readonly EquipmentNamespaceContent EmptyContent =
+        new(Areas: [], Lines: [], Equipment: [], Tags: []);
+
+    [Fact]
+    public void Get_Returns_Null_For_Unknown_Driver()
+    {
+        var registry = new DriverEquipmentContentRegistry();
+        registry.Get("galaxy-prod").ShouldBeNull();
+        registry.Count.ShouldBe(0);
+    }
+
+    [Fact]
+    public void Set_Then_Get_Returns_Stored_Content()
+    {
+        var registry = new DriverEquipmentContentRegistry();
+        registry.Set("galaxy-prod", EmptyContent);
+
+        registry.Get("galaxy-prod").ShouldBeSameAs(EmptyContent);
+        registry.Count.ShouldBe(1);
+    }
+
+    [Fact]
+    public void Get_Is_Case_Insensitive_For_Driver_Id()
+    {
+        // DriverInstanceId keys are OrdinalIgnoreCase across the codebase (Equipment /
+        // Tag rows, walker grouping). Registry matches that contract so callers don't have
+        // to canonicalize driver ids before lookup.
+        var registry = new DriverEquipmentContentRegistry();
+        registry.Set("Galaxy-Prod", EmptyContent);
+        registry.Get("galaxy-prod").ShouldBeSameAs(EmptyContent);
+        registry.Get("GALAXY-PROD").ShouldBeSameAs(EmptyContent);
+    }
+
+    [Fact]
+    public void Set_Overwrites_Existing_Content_For_Same_Driver()
+    {
+        var registry = new DriverEquipmentContentRegistry();
+        var first = EmptyContent;
+        var second = new EquipmentNamespaceContent([], [], [], []);
+
+        registry.Set("galaxy-prod", first);
+        registry.Set("galaxy-prod", second);
+
+        registry.Get("galaxy-prod").ShouldBeSameAs(second);
+        registry.Count.ShouldBe(1);
+    }
+}