diff --git a/docs/requirements/Component-ClusterInfrastructure.md b/docs/requirements/Component-ClusterInfrastructure.md
index da57e3e4..7bbf201e 100644
--- a/docs/requirements/Component-ClusterInfrastructure.md
+++ b/docs/requirements/Component-ClusterInfrastructure.md
@@ -197,6 +197,8 @@ Differences from central failover, all deliberate:
 
 `akka.cluster.min-nr-of-members` must be set to **1**. After failover, only one node is running. If set to 2, the surviving node waits for a second member before allowing the Cluster Singleton (Site Runtime Deployment Manager) to start — blocking all data collection and script execution indefinitely.
 
+`ScadaBridge:Cluster:AllowSingleNodeCluster` is **validation-only**: it merely relaxes the seed-count check (one seed instead of two) in `ClusterOptionsValidator`. It changes no runtime behaviour — not `min-nr-of-members` (always 1), not downing, not the bootstrap guard; a lone node forms its cluster because every node lists itself first in its seed list. The name is retained to avoid breaking deployed configs.
+
 ## Failure Detection Timing
 
 Configurable defaults for heartbeat and failure detection:
diff --git a/docs/requirements/Component-Host.md b/docs/requirements/Component-Host.md
index 3768047b..4ad0a194 100644
--- a/docs/requirements/Component-Host.md
+++ b/docs/requirements/Component-Host.md
@@ -345,3 +345,10 @@ built)* section for where the shipped code deviates from the original design).
 - **CentralUI / InboundAPI**: The Host maps their web endpoints into the ASP.NET Core pipeline on central nodes.
 - **ManagementService**: The Host registers the ManagementActor on central nodes; the CLI reaches it over the HTTP `/management` endpoints (in-process via `ManagementActorHolder`), not via any cluster transport. No ClusterClientReceptionist is configured (removed in Phase 4).
 - **HealthMonitoring**: The Host's startup validation and logging configuration provide the foundation for health reporting.
+
+## Review 2026-10-21 notes (Host edge)
+
+- **Port options come from the bound `NodeOptions`.** `Program.cs` binds `ScadaBridge:Node` once and reads `GrpcPort` / `CentralGrpcPort` / `MetricsPort` from it; the 8083/8084 defaults live only in `NodeOptions`. Central's dedicated metrics listener remains an explicit *presence* check on the raw key (a defaulted read would bind a new port on every existing central node).
+- **Inbound method warm-up is a hosted service** (`InboundMethodWarmupService`, registered after `AkkaHostedService`), not a pre-`RunAsync` loop — see Component-InboundAPI.md.
+- **`SitePskProvider` distinguishes a secret-store fault from a missing secret.** A store fault logs a Warning with the exception and throws `SecretStoreUnavailableException` (not cached); only a genuinely absent/empty/tombstoned secret produces the "seed `SB-GRPC-PSK-{site}`" message.
+- Central registers `ExternalSystemGatewayOptions.DefinitionCacheTtl = 10 s` ahead of `AddExternalSystemGateway()` so an explicit config value wins; sites leave it off.
diff --git a/src/ZB.MOM.WW.ScadaBridge.ClusterInfrastructure/ClusterOptions.cs b/src/ZB.MOM.WW.ScadaBridge.ClusterInfrastructure/ClusterOptions.cs
index 8c47fcee..b104bed1 100644
--- a/src/ZB.MOM.WW.ScadaBridge.ClusterInfrastructure/ClusterOptions.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.ClusterInfrastructure/ClusterOptions.cs
@@ -112,6 +112,13 @@ public class ClusterOptions
     /// node (normally ≥2 are required so either node can start first). Without this
     /// flag a single-node install must list a phantom second seed, which the node
     /// dials forever — log noise and a defeated validation intent (review 01).
+    /// <para>
+    /// <b>Validation-only.</b> This flag changes nothing at runtime: it only relaxes
+    /// <c>ClusterOptionsValidator</c>'s seed-count check. It does not touch
+    /// <c>min-nr-of-members</c>, the downing strategy or the bootstrap guard — a lone node
+    /// forms its cluster because it lists ITSELF first (self-first seed ordering), not because
+    /// of this flag. The name is kept (renaming would break deployed configs) (review 2026-10-21 08/O4).
+    /// </para>
     /// </summary>
     public bool AllowSingleNodeCluster { get; set; }
 
diff --git a/src/ZB.MOM.WW.ScadaBridge.Host/Program.cs b/src/ZB.MOM.WW.ScadaBridge.Host/Program.cs
index 4bf0a7ba..bd73e44f 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Host/Program.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Host/Program.cs
@@ -131,6 +131,11 @@ await using (var secretsProvider = expanderServices.BuildServiceProvider())
 // Full startup validation — fail fast before any DI or actor system setup
 StartupValidator.Validate(configuration);
 
+// Bound node options: the single home of port defaults (NodeOptions), so the Kestrel setup below
+// never repeats literal 8083/8084 defaults at the call sites (review 2026-10-21 08/O5).
+var nodeOptions = configuration.GetSection("ScadaBridge:Node").Get<ZB.MOM.WW.ScadaBridge.Host.NodeOptions>()
+    ?? new ZB.MOM.WW.ScadaBridge.Host.NodeOptions();
+
 // Read node options for Serilog enrichment
 var nodeRole = configuration["ScadaBridge:Node:Role"]!;
 var nodeHostname = configuration["ScadaBridge:Node:NodeHostname"] ?? "unknown";
@@ -188,7 +193,7 @@ try
         // The site branch has the same ConfigureKestrel shape but no ASPNETCORE_URLS surface
         // to lose (it binds every port it needs — gRPC + metrics — explicitly). Central must
         // therefore RE-BIND its HTTP port(s) here alongside the gRPC port.
-        var centralGrpcPort = configuration.GetValue<int>("ScadaBridge:Node:CentralGrpcPort", 8083);
+        var centralGrpcPort = nodeOptions.CentralGrpcPort;
         // "urls" is WebHostDefaults.ServerUrlsKey — the host setting ASPNETCORE_URLS/--urls
         // populate. Read it as a literal so this needs no extra Hosting using.
         var httpUrls = configuration["ASPNETCORE_URLS"]
@@ -296,6 +301,12 @@ try
 
         builder.Services.AddHealthMonitoring();
         builder.Services.AddCentralHealthAggregation();
+        // Central resolves definitions from SQL Server on every call; cache them briefly
+        // (review 2026-10-21 05/P2). Registered BEFORE AddExternalSystemGateway so an explicit
+        // ScadaBridge:ExternalSystemGateway:DefinitionCacheTtl binding still wins. Sites keep it
+        // off — their repository is already a deploy-invalidated snapshot.
+        builder.Services.Configure<ZB.MOM.WW.ScadaBridge.ExternalSystemGateway.ExternalSystemGatewayOptions>(
+            o => o.DefinitionCacheTtl = TimeSpan.FromSeconds(10));
         builder.Services.AddExternalSystemGateway();
         builder.Services.AddNotificationService();
 
@@ -593,6 +604,12 @@ try
         // routes against agree on which node is active.
         builder.Services.AddSingleton<ZB.MOM.WW.ScadaBridge.InboundAPI.IActiveNodeGate, ActiveNodeGate>();
 
+        // Warm the inbound method compile cache in the BACKGROUND once the host is running and
+        // this node is the active one (review 2026-10-21 05/U3). Registered after
+        // AkkaHostedService so it never sits in front of the cluster join; the eager compile that
+        // used to block here before app.RunAsync() is gone.
+        builder.Services.AddHostedService<ZB.MOM.WW.ScadaBridge.InboundAPI.InboundMethodWarmupService>();
+
         // Admin-triggered manual failover of the central pair (Health page control,
         // decision 2026-07-22). Central-only: the seam is declared in CentralUI so that
         // project stays Akka-free, and only this branch has a cluster to act on.
@@ -745,17 +762,8 @@ try
         app.MapDeploymentConfigAPI();
         app.MapHub<ZB.MOM.WW.ScadaBridge.ManagementService.DebugStreamHub>("/hubs/debug-stream");
 
-        // Compile and register all Inbound API method scripts at startup
-        using (var scope = app.Services.CreateScope())
-        {
-            var apiRepo = scope.ServiceProvider.GetRequiredService<ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories.IInboundApiRepository>();
-            var executor = app.Services.GetRequiredService<ZB.MOM.WW.ScadaBridge.InboundAPI.InboundScriptExecutor>();
-            var methods = await apiRepo.GetAllApiMethodsAsync();
-            // Parallel: CompileAndRegister is safe for concurrent callers (ConcurrentDictionary
-            // caches, no shared mutable compile state); serial Roslyn compiles stretch the
-            // failover-recovery window at hundreds of methods.
-            Parallel.ForEach(methods, method => executor.CompileAndRegister(method));
-        }
+        // Inbound API method scripts are pre-compiled by InboundMethodWarmupService after startup
+        // (background, active node only); the per-request lazy compile guarantees correctness.
 
         await app.RunAsync();
     }
@@ -778,15 +786,15 @@ try
         // Windows Service support (no-op when not running as a Windows Service)
         builder.Host.UseWindowsService();
 
-        // Read GrpcPort from config (NodeOptions already has default 8083)
-        var grpcPort = configuration.GetValue<int>("ScadaBridge:Node:GrpcPort", 8083);
+        // GrpcPort from the bound NodeOptions (default 8083)
+        var grpcPort = nodeOptions.GrpcPort;
 
-        // Read MetricsPort from config (NodeOptions already has default 8084).
+        // MetricsPort from the bound NodeOptions (default 8084).
         // Separate HTTP/1.1 listener so a standard HTTP/1.1 Prometheus scraper can
         // reach /metrics; the gRPC port stays HTTP/2-only below. The default is
         // 8084 — distinct from RemotingPort (8082, Akka) and GrpcPort (8083) so the
         // metrics listener never collides with the Akka remoting port on site nodes.
-        var metricsPort = configuration.GetValue<int>("ScadaBridge:Node:MetricsPort", 8084);
+        var metricsPort = nodeOptions.MetricsPort;
 
         // Configure Kestrel for HTTP/2 only on the gRPC port (plus the h2 keepalive that
         // makes a half-open inbound stream detectable) — see SiteKestrelSetup.