docs(code-reviews): regenerate index after batch 4 High fixes; normalize re-triaged SF-002 severity field

code-reviews/README.md

@@ -40,10 +40,10 @@ module file and counted in **Total**.
 | Severity | Open findings |
 |----------|---------------|
 | Critical | 0 |
-| High | 12 |
+| High | 3 |
 | Medium | 100 |
-| Low | 89 |
+| Low | 90 |
-| **Total** | **201** |
+| **Total** | **193** |
 
 ## Module Status
 
@@ -65,9 +65,9 @@ module file and counted in **Total**.
 | [NotificationService](NotificationService/findings.md) | 2026-05-16 | `9c60592` | 0/0/5/3 | 8 | 12 |
 | [Security](Security/findings.md) | 2026-05-16 | `9c60592` | 0/0/4/4 | 8 | 11 |
 | [SiteEventLogging](SiteEventLogging/findings.md) | 2026-05-16 | `9c60592` | 0/0/4/3 | 7 | 11 |
-| [SiteRuntime](SiteRuntime/findings.md) | 2026-05-16 | `9c60592` | 0/3/8/5 | 16 | 16 |
+| [SiteRuntime](SiteRuntime/findings.md) | 2026-05-16 | `9c60592` | 0/0/8/5 | 13 | 16 |
-| [StoreAndForward](StoreAndForward/findings.md) | 2026-05-16 | `9c60592` | 0/2/4/6 | 12 | 14 |
+| [StoreAndForward](StoreAndForward/findings.md) | 2026-05-16 | `9c60592` | 0/0/4/7 | 11 | 14 |
-| [TemplateEngine](TemplateEngine/findings.md) | 2026-05-16 | `9c60592` | 0/5/5/4 | 14 | 14 |
+| [TemplateEngine](TemplateEngine/findings.md) | 2026-05-16 | `9c60592` | 0/1/5/4 | 10 | 14 |
 
 ## Pending Findings
 
@@ -80,22 +80,13 @@ description, location, recommendation — lives in the module's `findings.md`.
 
 _None open._
 
-### High (12)
+### High (3)
 
 | ID | Module | Title |
 |----|--------|-------|
 | ClusterInfrastructure-001 | [ClusterInfrastructure](ClusterInfrastructure/findings.md) | Module implements none of its documented responsibilities |
 | DeploymentManager-006 | [DeploymentManager](DeploymentManager/findings.md) | Query-the-site-before-redeploy idempotency requirement not implemented |
-| SiteRuntime-001 | [SiteRuntime](SiteRuntime/findings.md) | `Instance.SetAttribute` never writes to the Data Connection Layer |
-| SiteRuntime-002 | [SiteRuntime](SiteRuntime/findings.md) | `RouteInboundApiSetAttributes` always treats writes as static overrides |
-| SiteRuntime-003 | [SiteRuntime](SiteRuntime/findings.md) | Redeployment relies on a fixed 500 ms reschedule and can collide on the child actor name |
-| StoreAndForward-002 | [StoreAndForward](StoreAndForward/findings.md) | Messages enqueued with no registered handler are buffered but never deliverable |
-| StoreAndForward-003 | [StoreAndForward](StoreAndForward/findings.md) | Off-by-one in retry accounting: immediate failure pre-counts as retry 1 |
-| TemplateEngine-001 | [TemplateEngine](TemplateEngine/findings.md) | Deeply nested composed members are dropped during flattening |
 | TemplateEngine-002 | [TemplateEngine](TemplateEngine/findings.md) | Derived templates omit all base alarms; composed alarms cannot be overridden per slot |
-| TemplateEngine-003 | [TemplateEngine](TemplateEngine/findings.md) | `UpdateAttributeAsync` lets a non-locked attribute change its fixed DataType / DataSourceReference |
-| TemplateEngine-004 | [TemplateEngine](TemplateEngine/findings.md) | Alarm on-trigger script references are never resolved (empty placeholder) |
-| TemplateEngine-005 | [TemplateEngine](TemplateEngine/findings.md) | Collision validation is skipped when creating a child template |
 
 ### Medium (100)
 
@@ -202,7 +193,7 @@ _None open._
 | TemplateEngine-009 | [TemplateEngine](TemplateEngine/findings.md) | N+1 query in `TemplateDeletionService.CanDeleteTemplateAsync` |
 | TemplateEngine-010 | [TemplateEngine](TemplateEngine/findings.md) | `InstanceService` documents optimistic concurrency that is not implemented |
 
-### Low (89)
+### Low (90)
 
 | ID | Module | Title |
 |----|--------|-------|
@@ -285,6 +276,7 @@ _None open._
 | SiteRuntime-014 | [SiteRuntime](SiteRuntime/findings.md) | Trigger-expression evaluation blocks the coordinator actor thread |
 | SiteRuntime-015 | [SiteRuntime](SiteRuntime/findings.md) | `LoggerFactory` created per Instance Actor and never disposed |
 | SiteRuntime-016 | [SiteRuntime](SiteRuntime/findings.md) | Short-lived execution actors, replication actor, and repositories are untested |
+| StoreAndForward-002 | [StoreAndForward](StoreAndForward/findings.md) | Messages enqueued with no registered handler are buffered but never deliverable |
 | StoreAndForward-006 | [StoreAndForward](StoreAndForward/findings.md) | `GetParkedMessagesAsync` count and page run without a transaction |
 | StoreAndForward-007 | [StoreAndForward](StoreAndForward/findings.md) | Async work in `ParkedMessageHandlerActor` uses `ContinueWith` without scheduler/affinity guarantees |
 | StoreAndForward-008 | [StoreAndForward](StoreAndForward/findings.md) | A SQLite connection is opened and torn down on every storage call |

code-reviews/SiteRuntime/findings.md

@@ -8,7 +8,7 @@
 | Last reviewed | 2026-05-16 |
 | Reviewer | claude-agent |
 | Commit reviewed | `9c60592` |
-| Open findings | 16 |
+| Open findings | 13 |
 
 ## Summary
 
@@ -51,7 +51,7 @@ actor, and the repositories are untested.
 |--|--|
 | Severity | High |
 | Category | Design-document adherence |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.SiteRuntime/Scripts/ScriptRuntimeContext.cs:106`, `src/ScadaLink.SiteRuntime/Actors/InstanceActor.cs:204` |
 
 **Description**
@@ -84,7 +84,15 @@ or branching inside the handler.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (`<pending>`): `InstanceActor.HandleSetStaticAttribute` now resolves
+the target attribute's data binding from `_configuration`. Data-sourced attributes are
+routed via a new `HandleSetDataAttribute` that Asks the DCL with a `WriteTagRequest` and
+pipes the device-write outcome back to the caller as a `SetStaticAttributeResponse` —
+no override is persisted and `_attributes` is not optimistically mutated. Static
+attributes keep the override path and now also reply with a `SetStaticAttributeResponse`.
+`ScriptRuntimeContext.SetAttribute` is now `async Task` and Asks the Instance Actor,
+throwing `InvalidOperationException` on a failed device write so scripts get the failure
+synchronously.
 
 ### SiteRuntime-002 — `RouteInboundApiSetAttributes` always treats writes as static overrides
 
@@ -92,7 +100,7 @@ _Unresolved._
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.SiteRuntime/Actors/DeploymentManagerActor.cs:632` |
 
 **Description**
@@ -115,7 +123,13 @@ response path.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (`<pending>`): `RouteInboundApiSetAttributes` now Asks the Instance
+Actor per attribute (instead of fire-and-forget Tell) and aggregates the
+`SetStaticAttributeResponse` results. Because the Instance Actor handler is the
+SiteRuntime-001 corrected handler, data-sourced attributes now reach the DCL and the
+`RouteToSetAttributesResponse` reflects the real per-attribute outcome — a non-existent
+attribute or a failed device write is reported as failure rather than an unconditional
+optimistic `true`.
 
 ### SiteRuntime-003 — Redeployment relies on a fixed 500 ms reschedule and can collide on the child actor name
 
@@ -123,7 +137,7 @@ _Unresolved._
 |--|--|
 | Severity | High |
 | Category | Akka.NET conventions |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.SiteRuntime/Actors/DeploymentManagerActor.cs:222` |
 
 **Description**
@@ -148,7 +162,15 @@ instance) until termination completes.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (`<pending>`): `HandleDeploy` no longer uses a fixed 500 ms
+reschedule. When a redeployment targets a running instance, the existing Instance Actor
+is `Context.Watch`-ed and stopped, and the in-flight `DeployInstanceCommand` is buffered
+in a `_pendingRedeploys` map keyed by the terminating actor ref. A new `Terminated`
+handler recreates the Instance Actor only after the predecessor (and its whole subtree)
+has fully stopped, eliminating the `InvalidActorNameException` race and the
+unconditional redeploy-latency penalty. The shared `ApplyDeployment` helper also skips
+the `_totalDeployedCount` increment for redeployments, so the deployed-instance count no
+longer drifts (this additionally addresses the root cause behind SiteRuntime-004).
 
 ### SiteRuntime-004 — `_totalDeployedCount` is incremented on redeployment of an existing instance
 

code-reviews/StoreAndForward/findings.md

@@ -8,7 +8,7 @@
 | Last reviewed | 2026-05-16 |
 | Reviewer | claude-agent |
 | Commit reviewed | `9c60592` |
-| Open findings | 12 |
+| Open findings | 11 |
 
 ## Summary
 
@@ -94,7 +94,8 @@ commit whose message references `StoreAndForward-001`.
 
 | | |
 |--|--|
-| Severity | High |
+| Severity | Low |
+| Original severity | High (re-triaged down to Low on 2026-05-16 — see Re-triage note) |
 | Category | Error handling & resilience |
 | Status | Open |
 | Location | `src/ScadaLink.StoreAndForward/StoreAndForwardService.cs:162`, `:201` |
@@ -121,9 +122,39 @@ handler exists rather than silently buffering an undeliverable message, and wire
 registration is intended, the retry sweep should treat a still-missing handler as a
 transient condition with bounded logging rather than a permanent no-op.
 
+**Re-triage note (2026-05-16)**
+
+The finding's central factual claim — *"No caller in the codebase ever calls
+`RegisterDeliveryHandler`"* and therefore *"every buffered message lands in this dead
+state"* — is **no longer true at the reviewed code**. `ScadaLink.Host`
+(`AkkaHostedService.RegisterSiteActors`, `AkkaHostedService.cs:353-379`) registers all
+three delivery handlers (`ExternalSystem`, `CachedDbWrite`, `Notification`) at site
+startup, immediately after `StoreAndForwardService.StartAsync()`. The finding was
+written against commit `9c60592` before that wiring existed; the High-severity
+"engine cannot deliver anything" outcome no longer occurs.
+
+The remaining residual risk is narrow: a message enqueued for a category that genuinely
+has no handler (e.g. an enqueue racing ahead of `RegisterDeliveryHandler`, or a future
+category added without a handler) is still buffered and then skipped by the sweep
+forever. That is a real but minor robustness gap, hence the **downgrade to Low**.
+
+It is left **Open** rather than fixed in this pass because the finding's recommended
+fix — making `EnqueueAsync` reject when no handler is registered — is a behavioural
+contract change, not a localised bug fix: the "buffer with no handler yet" path is
+exercised by `StoreAndForwardReplicationTests` and by three NotificationService and
+ExternalSystemGateway tests (`Send_TransientError_WithStoreAndForward_BuffersMessage`,
+`Send_Smtp4xxCommandException_ClassifiedTransientAndBuffered`,
+`Send_SmtpProtocolException_ClassifiedTransient`) which construct a real
+`StoreAndForwardService` without registering a handler and assert `WasBuffered`.
+Changing the contract requires deciding whether late handler registration is supported
+and updating tests in modules outside this review's edit scope — a design decision that
+should be made deliberately rather than forced here.
+
 **Resolution**
 
-_Unresolved._
+_Open — re-triaged to Low. Premise (no handler registration anywhere) is stale: Host
+now wires all three handlers. Residual gap is minor and the prescribed fix is a
+cross-module contract change needing a design decision._
 
 ### StoreAndForward-003 — Off-by-one in retry accounting: immediate failure pre-counts as retry 1
 
@@ -131,7 +162,7 @@ _Unresolved._
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.StoreAndForward/StoreAndForwardService.cs:153`, `:229`, `:233` |
 
 **Description**
@@ -159,7 +190,21 @@ the comparison. Update the affected test to match the chosen semantics.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (commit `<pending>`). `RetryCount` now consistently means "number
+of background retry-sweep attempts so far"; the initial immediate (or caller-made)
+delivery attempt is attempt 0 and is not counted, and `MaxRetries` bounds retry-sweep
+attempts after that initial attempt. `EnqueueAsync` no longer seeds `RetryCount = 1` on
+either the transient-immediate-failure path or the `attemptImmediateDelivery: false`
+path — a freshly buffered message has `RetryCount = 0`. `RetryMessageAsync` already
+increments before the `>= MaxRetries` check, which is now correct, so a message with
+`MaxRetries = 1` gets exactly one real retry before parking (previously zero). The
+`StoreAndForwardMessage.RetryCount` XML doc was corrected to match. Regression test
+`RetryPendingMessagesAsync_MaxRetriesOne_PerformsExactlyOneRetryBeforeParking` asserts
+the immediate attempt plus exactly one retry occur before parking; the affected
+existing tests (`EnqueueAsync_TransientFailure_BuffersForRetry`,
+`EnqueueAsync_AttemptImmediateDeliveryFalse_BuffersWithoutInvokingHandler`,
+`RetryPendingMessagesAsync_MaxRetriesReached_ParksMessage`) were updated to the
+corrected semantics.
 
 ### StoreAndForward-004 — `RegisterDeliveryHandler` XML doc contradicts the implemented contract
 

code-reviews/TemplateEngine/findings.md

@@ -8,7 +8,7 @@
 | Last reviewed | 2026-05-16 |
 | Reviewer | claude-agent |
 | Commit reviewed | `9c60592` |
-| Open findings | 14 |
+| Open findings | 10 |
 
 ## Summary
 
@@ -52,7 +52,7 @@ of attributes vs. alarms vs. scripts throughout the resolve/flatten/derive paths
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.TemplateEngine/Flattening/FlatteningService.cs:211`, `src/ScadaLink.TemplateEngine/Flattening/FlatteningService.cs:535`, `src/ScadaLink.TemplateEngine/Flattening/FlatteningService.cs:609` |
 
 **Description**
@@ -77,7 +77,13 @@ the recursion already in `TemplateResolver.AddComposedMembers` and
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (commit `<pending>`): replaced the hand-unrolled
+one/two-level composition loops in `ResolveComposedAttributes`,
+`ResolveComposedAlarms`, and `ResolveComposedScripts` with single recursive
+walks (`*Recursive` helpers) carrying the accumulated path prefix and a
+`visited` set, so composed members at arbitrary nesting depth are resolved.
+Regression tests: `Flatten_ThreeLevelComposition_AttributesAlarmsScriptsAllResolved`,
+`Flatten_NestedComposedAlarm_TriggerAttributePrefixed`.
 
 ### TemplateEngine-002 — Derived templates omit all base alarms; composed alarms cannot be overridden per slot
 
@@ -110,7 +116,22 @@ already do.
 
 **Resolution**
 
-_Unresolved._
+_Unresolved (re-triaged 2026-05-16)._ Partially mis-stated and out of the
+current fix scope. Correction to the description: composed/inherited alarms
+are **not** dropped from the flattened deployment output — `FlatteningService`
+resolves alarms from the entire inheritance chain (`ResolveInheritedAlarms`
+walks `templateChain`, which includes the base of a derived template), so an
+instance of a derived template still receives the base template's alarms. The
+real, valid gap is narrower: there is no per-slot **alarm override**
+mechanism. The fix genuinely requires adding `IsInherited` / `LockedInDerived`
+fields to the `TemplateAlarm` entity, which lives in `ScadaLink.Commons`
+(a different module). Adding an alarm copy loop to `BuildDerivedTemplate`
+without those fields would be actively harmful: copied alarm rows on the
+derived template would shadow the live base alarm with stale data during
+flattening (`ResolveInheritedAlarms` has no `IsInherited` skip for alarms,
+unlike attributes/scripts). Resolving this safely is a cross-module change
+(`Commons` + `TemplateEngine`) and must be scheduled as a coordinated edit;
+left **Open** pending that.
 
 ### TemplateEngine-003 — `UpdateAttributeAsync` lets a non-locked attribute change its fixed DataType / DataSourceReference
 
@@ -118,7 +139,7 @@ _Unresolved._
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.TemplateEngine/TemplateService.cs:285` |
 
 **Description**
@@ -147,7 +168,12 @@ apply block.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (commit `<pending>`): removed the `&& existing.IsLocked`
+guard in `UpdateAttributeAsync` so the fixed-field granularity error is always
+honoured, and removed the unconditional `existing.DataType` /
+`existing.DataSourceReference` assignments from the apply block. Regression
+tests: `UpdateAttribute_UnlockedAttribute_DataTypeChangeRejected`,
+`UpdateAttribute_UnlockedAttribute_DataSourceReferenceChangeRejected`.
 
 ### TemplateEngine-004 — Alarm on-trigger script references are never resolved (empty placeholder)
 
@@ -155,7 +181,7 @@ _Unresolved._
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.TemplateEngine/Flattening/FlatteningService.cs:695` |
 
 **Description**
@@ -179,7 +205,15 @@ and implement that consistently.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (commit `<pending>`): implemented `ResolveAlarmScriptReferences`.
+Alarm resolution now records each resolved alarm's `OnTriggerScriptId` keyed by
+canonical name, and script resolution records each resolved `TemplateScript.Id`
+keyed by its canonical name (both honour composition path prefixes). Step 7
+joins the two maps to set `ResolvedAlarm.OnTriggerScriptCanonicalName`, so the
+revision hash, diff, and `SemanticValidator` on-trigger-script-exists check now
+all see the reference. Regression tests:
+`Flatten_AlarmOnTriggerScript_ResolvedToCanonicalName`,
+`Flatten_ComposedAlarmOnTriggerScript_ResolvedWithPrefix`.
 
 ### TemplateEngine-005 — Collision validation is skipped when creating a child template
 
@@ -187,7 +221,7 @@ _Unresolved._
 |--|--|
 | Severity | High |
 | Category | Correctness & logic bugs |
-| Status | Open |
+| Status | Resolved |
 | Location | `src/ScadaLink.TemplateEngine/TemplateService.cs:56` |
 
 **Description**
@@ -210,7 +244,15 @@ that explicitly instead of leaving a no-op.
 
 **Resolution**
 
-_Unresolved._
+Resolved 2026-05-16 (commit `<pending>`): deleted the dead `if
+(parentTemplateId.HasValue)` block and its unused `GetAllTemplatesAsync`
+read in `CreateTemplateAsync`. A create-time collision check on a child is a
+guaranteed no-op — a freshly created template has no members of its own, the
+parent's members were already collision-validated on every member-mutating
+call, and a new child cannot be an ancestor of its parent. Replaced the no-op
+with an explanatory comment documenting that collision detection is enforced
+on `AddAttribute`/`AddAlarm`/`AddScript`/`AddComposition` and on rename.
+Regression test: `CreateTemplate_WithParent_DoesNotRunDeadCollisionQuery`.
 
 ### TemplateEngine-006 — Forbidden-API enforcement is a naive substring scan (bypassable and false-positive prone)
 

src/ScadaLink.SiteRuntime/Actors/DeploymentManagerActor.cs

@@ -39,6 +39,12 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
     private readonly ISiteHealthCollector? _healthCollector;
     private readonly IServiceProvider? _serviceProvider;
     private readonly Dictionary<string, IActorRef> _instanceActors = new();
+    /// <summary>
+    /// Tracks Instance Actors that are terminating as part of a redeployment, keyed by
+    /// the terminating actor ref. The buffered command is applied once <see cref="Terminated"/>
+    /// confirms the child has fully stopped (SiteRuntime-003).
+    /// </summary>
+    private readonly Dictionary<IActorRef, PendingRedeploy> _pendingRedeploys = new();
     private int _totalDeployedCount;
 
     public ITimerScheduler Timers { get; set; } = null!;
@@ -94,6 +100,10 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
 
         // Internal deploy persistence result
         Receive<DeployPersistenceResult>(HandleDeployPersistenceResult);
+
+        // Terminated signal — drains a buffered redeployment once the previous
+        // Instance Actor has fully stopped (SiteRuntime-003).
+        Receive<Terminated>(HandleTerminated);
     }
 
     protected override void PreStart()
@@ -211,6 +221,13 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
     /// <summary>
     /// Handles a new deployment: stores config in SQLite, clears previous static overrides,
     /// and creates or replaces the Instance Actor.
+    ///
+    /// Redeployment of an already-running instance must wait for the previous Instance
+    /// Actor to fully terminate (including PostStop on its descendants) before the
+    /// replacement is created — otherwise <see cref="Context.ActorOf"/> can collide on
+    /// the still-registered child name. Instead of guessing with a fixed timer, the
+    /// terminating child is watched and the in-flight command is buffered until the
+    /// <see cref="Terminated"/> signal arrives.
     /// </summary>
     private void HandleDeploy(DeployInstanceCommand command)
     {
@@ -219,28 +236,54 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
             "Deploying instance {Instance}, deploymentId={DeploymentId}",
             instanceName, command.DeploymentId);
 
-        // Stop existing actor if present (redeployment replaces)
+        // Redeployment replaces a running instance. Watch + stop the existing actor
+        // and buffer this command until its Terminated signal confirms the child
+        // (and its whole subtree) has fully stopped and freed its actor name.
         if (_instanceActors.TryGetValue(instanceName, out var existing))
         {
-            Context.Stop(existing);
             _instanceActors.Remove(instanceName);
-            // Wait for the child to be removed from the children collection
+            _pendingRedeploys[existing] = new PendingRedeploy(command, Sender);
-            // by yielding and retrying — Context.Stop is processed before the next message
+            Context.Watch(existing);
-            Context.System.Scheduler.ScheduleTellOnce(
+            Context.Stop(existing);
-                TimeSpan.FromMilliseconds(500), Self, command, Sender);
+            UpdateInstanceCounts();
             return;
         }
 
+        // Fresh deployment — no existing actor to replace.
+        ApplyDeployment(command, Sender, isRedeploy: false);
+    }
+
+    /// <summary>
+    /// Recreates an Instance Actor once its predecessor has fully terminated during a
+    /// redeployment, draining the buffered <see cref="DeployInstanceCommand"/>.
+    /// </summary>
+    private void HandleTerminated(Terminated terminated)
+    {
+        if (!_pendingRedeploys.Remove(terminated.ActorRef, out var pending))
+            return;
+
+        ApplyDeployment(pending.Command, pending.OriginalSender, isRedeploy: true);
+    }
+
+    /// <summary>
+    /// Creates the Instance Actor, persists the config, and replies to the deployer.
+    /// A redeployment is an update of an existing instance, so the deployed-instance
+    /// counter is only incremented for genuinely new deployments.
+    /// </summary>
+    private void ApplyDeployment(DeployInstanceCommand command, IActorRef sender, bool isRedeploy)
+    {
+        var instanceName = command.InstanceUniqueName;
+
         // Ensure DCL connections exist for any data-sourced attributes
         EnsureDclConnections(command.FlattenedConfigurationJson);
 
-        // Create the Instance Actor immediately (no existing actor to replace)
+        // Create the Instance Actor immediately
         CreateInstanceActor(instanceName, command.FlattenedConfigurationJson);
-        _totalDeployedCount++;
+        if (!isRedeploy)
+            _totalDeployedCount++;
         UpdateInstanceCounts();
 
         // Persist to SQLite and clear static overrides asynchronously
-        var sender = Sender;
         Task.Run(async () =>
         {
             await _storage.StoreDeployedConfigAsync(
@@ -614,9 +657,11 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
 
     /// <summary>
     /// Writes attribute values on a deployed instance for a Route.To().SetAttribute(s)
-    /// call (or a central Test Run bound to the instance). Writes are Tell'd to the
+    /// call (or a central Test Run bound to the instance). Each write is Ask'd to the
-    /// Instance Actor — serialized through its mailbox — and acknowledged optimistically,
+    /// Instance Actor, which routes data-sourced attributes through the DCL and static
-    /// matching the fire-and-forget semantics of Instance.SetAttribute.
+    /// attributes to a persisted override. The response reflects the real per-attribute
+    /// outcome (a non-existent attribute or a failed device write reports failure),
+    /// rather than an unconditional optimistic ack.
     /// </summary>
     private void RouteInboundApiSetAttributes(RouteToSetAttributesRequest request)
     {
@@ -629,14 +674,33 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
             return;
         }
 
-        foreach (var (name, value) in request.AttributeValues)
+        var sender = Sender;
-        {
+        var correlationId = request.CorrelationId;
-            instanceActor.Tell(new SetStaticAttributeCommand(
+        var asks = request.AttributeValues
-                request.CorrelationId, request.InstanceUniqueName, name, value, DateTimeOffset.UtcNow));
+            .Select(kvp => instanceActor.Ask<SetStaticAttributeResponse>(
-        }
+                new SetStaticAttributeCommand(
+                    correlationId, request.InstanceUniqueName, kvp.Key, kvp.Value, DateTimeOffset.UtcNow),
+                TimeSpan.FromSeconds(30)))
+            .ToArray();
 
-        Sender.Tell(new RouteToSetAttributesResponse(
+        Task.WhenAll(asks).ContinueWith(t =>
-            request.CorrelationId, true, null, DateTimeOffset.UtcNow));
+        {
+            if (!t.IsCompletedSuccessfully)
+                return new RouteToSetAttributesResponse(
+                    correlationId, false,
+                    t.Exception?.GetBaseException().Message ?? "Attribute write timed out",
+                    DateTimeOffset.UtcNow);
+
+            var failures = t.Result
+                .Where(r => !r.Success)
+                .Select(r => $"{r.AttributeName}: {r.ErrorMessage}")
+                .ToArray();
+
+            return failures.Length == 0
+                ? new RouteToSetAttributesResponse(correlationId, true, null, DateTimeOffset.UtcNow)
+                : new RouteToSetAttributesResponse(
+                    correlationId, false, string.Join("; ", failures), DateTimeOffset.UtcNow);
+        }).PipeTo(sender);
     }
 
     /// <summary>
@@ -789,4 +853,9 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
         EnableInstanceCommand Command, DeployedInstance? Config, string? Error, IActorRef OriginalSender);
     internal record DeployPersistenceResult(
         string DeploymentId, string InstanceName, bool Success, string? Error, IActorRef OriginalSender);
+
+    /// <summary>
+    /// A redeployment command buffered until the previous Instance Actor terminates.
+    /// </summary>
+    internal record PendingRedeploy(DeployInstanceCommand Command, IActorRef OriginalSender);
 }

src/ScadaLink.SiteRuntime/Actors/InstanceActor.cs

@@ -198,10 +198,44 @@ public class InstanceActor : ReceiveActor
     }
 
     /// <summary>
-    /// Updates a static attribute in memory and persists the override to SQLite.
+    /// Handles an attribute write (<c>Instance.SetAttribute</c> / Inbound API).
     /// WP-24: State mutation serialized through this actor's mailbox.
+    ///
+    /// The write is routed by the attribute's data binding:
+    ///   * Data-sourced attribute  → forwards a <see cref="WriteTagRequest"/> to the
+    ///     DCL, which writes the physical device. The in-memory value is NOT
+    ///     optimistically updated and NO static override is persisted — the
+    ///     confirmed device value arrives later via the subscription. Success or
+    ///     failure of the device write is returned to the caller.
+    ///   * Static attribute → updates the in-memory value and persists the override
+    ///     to SQLite.
+    ///
+    /// Either way the caller receives a <see cref="SetStaticAttributeResponse"/>.
     /// </summary>
     private void HandleSetStaticAttribute(SetStaticAttributeCommand command)
+    {
+        // Resolve the target attribute's data binding from the flattened config.
+        var resolved = _configuration?.Attributes
+            .FirstOrDefault(a => a.CanonicalName == command.AttributeName);
+
+        var isDataSourced = resolved != null
+            && !string.IsNullOrEmpty(resolved.DataSourceReference)
+            && !string.IsNullOrEmpty(resolved.BoundDataConnectionName);
+
+        if (isDataSourced)
+        {
+            HandleSetDataAttribute(command, resolved!);
+            return;
+        }
+
+        HandleSetStaticAttributeCore(command);
+    }
+
+    /// <summary>
+    /// Static attribute write: updates in-memory state, publishes the change,
+    /// persists the override to SQLite, and replies with success.
+    /// </summary>
+    private void HandleSetStaticAttributeCore(SetStaticAttributeCommand command)
     {
         _attributes[command.AttributeName] = command.Value;
 
@@ -216,8 +250,7 @@ public class InstanceActor : ReceiveActor
 
         PublishAndNotifyChildren(changed);
 
-        // Persist asynchronously -- fire and forget since the actor is the source of truth
+        // Persist asynchronously -- fire and forget since the actor is the source of truth.
-        // and SetAttribute is called from scripts via Tell (no response consumer).
         var instanceName = _instanceUniqueName;
         var attributeName = command.AttributeName;
         var logger = _logger;
@@ -230,6 +263,58 @@ public class InstanceActor : ReceiveActor
                     instanceName,
                     attributeName);
             }, TaskContinuationOptions.OnlyOnFaulted);
+
+        Sender.Tell(new SetStaticAttributeResponse(
+            command.CorrelationId, _instanceUniqueName, command.AttributeName,
+            true, null, DateTimeOffset.UtcNow));
+    }
+
+    /// <summary>
+    /// Data-sourced attribute write: forwards a write request to the DCL and pipes
+    /// the device write result back to the caller. The in-memory value is left
+    /// untouched (it is refreshed by the subscription when the device confirms);
+    /// no static override is persisted for a data-sourced attribute.
+    /// </summary>
+    private void HandleSetDataAttribute(SetStaticAttributeCommand command, ResolvedAttribute resolved)
+    {
+        var caller = Sender;
+        var correlationId = command.CorrelationId;
+        var attributeName = command.AttributeName;
+        var instanceName = _instanceUniqueName;
+
+        if (_dclManager == null)
+        {
+            _logger.LogWarning(
+                "SetAttribute on data-sourced attribute {Instance}.{Attribute} cannot be routed — no DCL manager configured",
+                instanceName, attributeName);
+            caller.Tell(new SetStaticAttributeResponse(
+                correlationId, instanceName, attributeName, false,
+                "Data Connection Layer not available for write.", DateTimeOffset.UtcNow));
+            return;
+        }
+
+        var writeRequest = new WriteTagRequest(
+            correlationId,
+            resolved.BoundDataConnectionName!,
+            resolved.DataSourceReference!,
+            command.Value,
+            DateTimeOffset.UtcNow);
+
+        // Ask the DCL and pipe the result back to the original caller. The DCL
+        // returns the failure synchronously so the script can handle it.
+        _dclManager.Ask<WriteTagResponse>(writeRequest, TimeSpan.FromSeconds(30))
+            .ContinueWith(t =>
+            {
+                if (t.IsCompletedSuccessfully)
+                    return new SetStaticAttributeResponse(
+                        correlationId, instanceName, attributeName,
+                        t.Result.Success, t.Result.ErrorMessage, DateTimeOffset.UtcNow);
+
+                return new SetStaticAttributeResponse(
+                    correlationId, instanceName, attributeName, false,
+                    t.Exception?.GetBaseException().Message ?? "DCL write timed out",
+                    DateTimeOffset.UtcNow);
+            }).PipeTo(caller);
     }
 
     /// <summary>

src/ScadaLink.SiteRuntime/Scripts/ScopeAccessors.cs

@@ -25,17 +25,17 @@ public class AttributeAccessor
 
     public object? this[string key]
     {
+        // Both reads and writes block on the actor Ask; the write also blocks
+        // on the DCL round-trip for data-connected attributes. The async
+        // variants (GetAsync/SetAsync) are preferred where awaiting is possible.
         get => _ctx.GetAttribute(Resolve(key)).GetAwaiter().GetResult();
-        set => _ctx.SetAttribute(Resolve(key), value?.ToString() ?? string.Empty);
+        set => _ctx.SetAttribute(Resolve(key), value?.ToString() ?? string.Empty).GetAwaiter().GetResult();
     }
 
     public Task<object?> GetAsync(string key) => _ctx.GetAttribute(Resolve(key));
 
     public Task SetAsync(string key, object? value)
-    {
+        => _ctx.SetAttribute(Resolve(key), value?.ToString() ?? string.Empty);
-        _ctx.SetAttribute(Resolve(key), value?.ToString() ?? string.Empty);
-        return Task.CompletedTask;
-    }
 }
 
 /// <summary>

src/ScadaLink.SiteRuntime/Scripts/ScriptRuntimeContext.cs

@@ -99,18 +99,31 @@ public class ScriptRuntimeContext
     }
 
     /// <summary>
-    /// Sets an attribute value. For data-connected attributes, forwards to DCL via Instance Actor.
+    /// Sets an attribute value. For data-connected attributes the Instance Actor
-    /// For static attributes, updates in-memory and persists to SQLite via Instance Actor.
+    /// forwards the write to the DCL, which writes the physical device; the
-    /// All mutations serialized through the Instance Actor mailbox.
+    /// in-memory value is not optimistically updated. For static attributes the
+    /// Instance Actor updates the in-memory value and persists the override to
+    /// SQLite. All mutations are serialized through the Instance Actor mailbox.
+    ///
+    /// The write is awaited so that a device-write failure on a data-connected
+    /// attribute is surfaced synchronously to the calling script as an
+    /// <see cref="InvalidOperationException"/>.
     /// </summary>
-    public void SetAttribute(string attributeName, string value)
+    public async Task SetAttribute(string attributeName, string value)
     {
         var correlationId = Guid.NewGuid().ToString();
         var command = new SetStaticAttributeCommand(
             correlationId, _instanceName, attributeName, value, DateTimeOffset.UtcNow);
 
-        // Tell (fire-and-forget) — mutation serialized through Instance Actor
+        // Ask — mutation serialized through the Instance Actor mailbox; the reply
-        _instanceActor.Tell(command);
+        // carries the device-write outcome for data-connected attributes.
+        var response = await _instanceActor.Ask<SetStaticAttributeResponse>(command, _askTimeout);
+
+        if (!response.Success)
+        {
+            throw new InvalidOperationException(
+                $"SetAttribute('{attributeName}') failed: {response.ErrorMessage}");
+        }
     }
 
     /// <summary>

src/ScadaLink.StoreAndForward/StoreAndForwardMessage.cs

@@ -20,10 +20,14 @@ public class StoreAndForwardMessage
     /// <summary>JSON-serialized payload containing the call details.</summary>
     public string PayloadJson { get; set; } = string.Empty;
 
-    /// <summary>Number of delivery attempts so far.</summary>
+    /// <summary>
+    /// Number of retry-sweep attempts performed so far. The initial (immediate or
+    /// caller-made) delivery attempt is attempt 0 and is not counted here; this
+    /// field counts only background retry attempts (StoreAndForward-003).
+    /// </summary>
     public int RetryCount { get; set; }
 
-    /// <summary>Maximum retry attempts before parking (0 = no limit).</summary>
+    /// <summary>Maximum retry-sweep attempts before parking (0 = no limit).</summary>
     public int MaxRetries { get; set; }
 
     /// <summary>Retry interval in milliseconds.</summary>

src/ScadaLink.StoreAndForward/StoreAndForwardService.cs

@@ -148,13 +148,14 @@ public class StoreAndForwardService
             }
             catch (Exception ex)
             {
-                // Transient failure — buffer for retry
+                // Transient failure — buffer for retry. The immediate attempt is
+                // attempt 0; RetryCount tracks only sweep retries, so it stays 0
+                // here (StoreAndForward-003).
                 _logger.LogWarning(ex,
                     "Immediate delivery to {Target} failed (transient), buffering for retry",
                     target);
 
                 message.LastAttemptAt = DateTimeOffset.UtcNow;
-                message.RetryCount = 1;
                 message.LastError = ex.Message;
                 await BufferAsync(message);
 
@@ -165,11 +166,11 @@ public class StoreAndForwardService
 
         // Either no handler is registered yet, or the caller already attempted
         // delivery itself — buffer for the background retry sweep to deliver.
+        // The initial attempt (caller-made, or skipped because no handler is
+        // registered) is attempt 0; RetryCount tracks only sweep retries and
+        // therefore stays 0 here (StoreAndForward-003).
         if (!attemptImmediateDelivery)
         {
-            // The caller made (and failed) one attempt before handing the
-            // message over, so it counts as the first retry.
-            message.RetryCount = 1;
             message.LastAttemptAt = DateTimeOffset.UtcNow;
         }
         await BufferAsync(message);

src/ScadaLink.TemplateEngine/Flattening/FlatteningService.cs

@@ -78,17 +78,23 @@ public class FlatteningService
             // Step 4: Apply connection bindings
             ApplyConnectionBindings(instance.ConnectionBindings, attributes, dataConnections);
 
-            // Step 5: Resolve alarms from inheritance chain
+            // Step 5: Resolve alarms from inheritance chain.
-            var alarms = ResolveInheritedAlarms(templateChain);
+            // alarmScriptIds maps a resolved alarm's canonical name to the
-            ResolveComposedAlarms(templateChain, compositionMap, composedTemplateChains, alarms);
+            // TemplateScript.Id of its on-trigger script (if any).
+            var alarmScriptIds = new Dictionary<string, int>(StringComparer.Ordinal);
+            var alarms = ResolveInheritedAlarms(templateChain, prefix: null, alarmScriptIds);
+            ResolveComposedAlarms(templateChain, compositionMap, composedTemplateChains, alarms, alarmScriptIds);
             ApplyInstanceAlarmOverrides(instance.AlarmOverrides, alarms);
 
-            // Step 6: Resolve scripts from inheritance chain
+            // Step 6: Resolve scripts from inheritance chain.
-            var scripts = ResolveInheritedScripts(templateChain);
+            // scriptCanonicalById maps a TemplateScript.Id to its resolved
-            ResolveComposedScripts(templateChain, compositionMap, composedTemplateChains, scripts);
+            // canonical name, used to wire up alarm on-trigger script refs.
+            var scriptCanonicalById = new Dictionary<int, string>();
+            var scripts = ResolveInheritedScripts(templateChain, prefix: null, scriptCanonicalById);
+            ResolveComposedScripts(templateChain, compositionMap, composedTemplateChains, scripts, scriptCanonicalById);
 
             // Step 7: Resolve alarm on-trigger script references to canonical names
-            ResolveAlarmScriptReferences(alarms, scripts);
+            ResolveAlarmScriptReferences(alarms, alarmScriptIds, scriptCanonicalById);
 
             // Step 8: Collect connection configurations for deployment packaging
             var connections = new Dictionary<string, ConnectionConfig>();
@@ -221,57 +227,56 @@ public class FlatteningService
                 continue;
 
             foreach (var composition in compositions)
+                ResolveComposedAttributesRecursive(
+                    composition, composition.InstanceName,
+                    compositionMap, composedTemplateChains, attributes, new HashSet<int>());
+        }
+    }
+
+    /// <summary>
+    /// Recursively resolves the attributes of a composed module and every
+    /// module nested inside it (to arbitrary depth), path-qualifying each
+    /// canonical name with the accumulated <paramref name="prefix"/>.
+    /// </summary>
+    private static void ResolveComposedAttributesRecursive(
+        TemplateComposition composition,
+        string prefix,
+        IReadOnlyDictionary<int, IReadOnlyList<TemplateComposition>> compositionMap,
+        IReadOnlyDictionary<int, IReadOnlyList<Template>> composedTemplateChains,
+        Dictionary<string, ResolvedAttribute> attributes,
+        HashSet<int> visited)
+    {
+        if (!composedTemplateChains.TryGetValue(composition.ComposedTemplateId, out var composedChain))
+            return;
+
+        var composedAttrs = ResolveInheritedAttributes(composedChain);
+        foreach (var (name, attr) in composedAttrs)
+        {
+            var canonicalName = $"{prefix}.{name}";
+            // Don't overwrite if already defined (most-derived wins)
+            if (!attributes.ContainsKey(canonicalName))
             {
-                if (!composedTemplateChains.TryGetValue(composition.ComposedTemplateId, out var composedChain))
+                attributes[canonicalName] = attr with
-                    continue;
-
-                var prefix = composition.InstanceName;
-                var composedAttrs = ResolveInheritedAttributes(composedChain);
-
-                foreach (var (name, attr) in composedAttrs)
                 {
-                    var canonicalName = $"{prefix}.{name}";
+                    CanonicalName = canonicalName,
-                    // Don't overwrite if already defined (most-derived wins)
+                    Source = "Composed"
-                    if (!attributes.ContainsKey(canonicalName))
+                };
-                    {
-                        attributes[canonicalName] = attr with
-                        {
-                            CanonicalName = canonicalName,
-                            Source = "Composed"
-                        };
-                    }
-                }
-
-                // Recurse into nested compositions
-                foreach (var composedTemplate in composedChain)
-                {
-                    if (!compositionMap.TryGetValue(composedTemplate.Id, out var nestedCompositions))
-                        continue;
-
-                    foreach (var nested in nestedCompositions)
-                    {
-                        if (!composedTemplateChains.TryGetValue(nested.ComposedTemplateId, out var nestedChain))
-                            continue;
-
-                        var nestedPrefix = $"{prefix}.{nested.InstanceName}";
-                        var nestedAttrs = ResolveInheritedAttributes(nestedChain);
-
-                        foreach (var (name, attr) in nestedAttrs)
-                        {
-                            var canonicalName = $"{nestedPrefix}.{name}";
-                            if (!attributes.ContainsKey(canonicalName))
-                            {
-                                attributes[canonicalName] = attr with
-                                {
-                                    CanonicalName = canonicalName,
-                                    Source = "Composed"
-                                };
-                            }
-                        }
-                    }
-                }
             }
         }
+
+        // Descend into nested compositions of every template in the chain.
+        foreach (var composedTemplate in composedChain)
+        {
+            if (!visited.Add(composedTemplate.Id))
+                continue;
+            if (!compositionMap.TryGetValue(composedTemplate.Id, out var nestedCompositions))
+                continue;
+
+            foreach (var nested in nestedCompositions)
+                ResolveComposedAttributesRecursive(
+                    nested, $"{prefix}.{nested.InstanceName}",
+                    compositionMap, composedTemplateChains, attributes, visited);
+        }
     }
 
     private static void ApplyInstanceOverrides(
@@ -356,10 +361,22 @@ public class FlatteningService
         }
     }
 
+    /// <summary>
+    /// Resolves alarms from an inheritance chain. When <paramref name="prefix"/>
+    /// is non-null the alarm names are returned bare (caller path-qualifies);
+    /// the keys of the returned dictionary are always bare alarm names.
+    /// <paramref name="alarmScriptIds"/> is populated with the on-trigger
+    /// script id of each resolved alarm keyed by the canonical name the alarm
+    /// will ultimately carry (bare name when <paramref name="prefix"/> is null,
+    /// otherwise <c>prefix.name</c>).
+    /// </summary>
     private static Dictionary<string, ResolvedAlarm> ResolveInheritedAlarms(
-        IReadOnlyList<Template> templateChain)
+        IReadOnlyList<Template> templateChain,
+        string? prefix,
+        Dictionary<string, int> alarmScriptIds)
     {
         var result = new Dictionary<string, ResolvedAlarm>(StringComparer.Ordinal);
+        var scriptIdByName = new Dictionary<string, int>(StringComparer.Ordinal);
 
         for (int i = templateChain.Count - 1; i >= 0; i--)
         {
@@ -394,9 +411,20 @@ public class FlatteningService
                     OnTriggerScriptCanonicalName = null, // Resolved later
                     Source = source
                 };
+
+                if (alarm.OnTriggerScriptId.HasValue)
+                    scriptIdByName[alarm.Name] = alarm.OnTriggerScriptId.Value;
+                else
+                    scriptIdByName.Remove(alarm.Name);
             }
         }
 
+        foreach (var (name, scriptId) in scriptIdByName)
+        {
+            var canonical = prefix == null ? name : $"{prefix}.{name}";
+            alarmScriptIds[canonical] = scriptId;
+        }
+
         return result;
     }
 
@@ -536,7 +564,8 @@ public class FlatteningService
         IReadOnlyList<Template> templateChain,
         IReadOnlyDictionary<int, IReadOnlyList<TemplateComposition>> compositionMap,
         IReadOnlyDictionary<int, IReadOnlyList<Template>> composedTemplateChains,
-        Dictionary<string, ResolvedAlarm> alarms)
+        Dictionary<string, ResolvedAlarm> alarms,
+        Dictionary<string, int> alarmScriptIds)
     {
         foreach (var template in templateChain)
         {
@@ -544,34 +573,74 @@ public class FlatteningService
                 continue;
 
             foreach (var composition in compositions)
-            {
+                ResolveComposedAlarmsRecursive(
-                if (!composedTemplateChains.TryGetValue(composition.ComposedTemplateId, out var composedChain))
+                    composition, composition.InstanceName,
-                    continue;
+                    compositionMap, composedTemplateChains, alarms, alarmScriptIds,
-
+                    new HashSet<int>());
-                var prefix = composition.InstanceName;
-                var composedAlarms = ResolveInheritedAlarms(composedChain);
-
-                foreach (var (name, alarm) in composedAlarms)
-                {
-                    var canonicalName = $"{prefix}.{name}";
-                    if (!alarms.ContainsKey(canonicalName))
-                    {
-                        alarms[canonicalName] = alarm with
-                        {
-                            CanonicalName = canonicalName,
-                            TriggerConfiguration = PrefixTriggerAttribute(alarm.TriggerConfiguration, prefix),
-                            Source = "Composed"
-                        };
-                    }
-                }
-            }
         }
     }
 
+    /// <summary>
+    /// Recursively resolves the alarms of a composed module and every module
+    /// nested inside it, path-qualifying each canonical name with the
+    /// accumulated <paramref name="prefix"/>.
+    /// </summary>
+    private static void ResolveComposedAlarmsRecursive(
+        TemplateComposition composition,
+        string prefix,
+        IReadOnlyDictionary<int, IReadOnlyList<TemplateComposition>> compositionMap,
+        IReadOnlyDictionary<int, IReadOnlyList<Template>> composedTemplateChains,
+        Dictionary<string, ResolvedAlarm> alarms,
+        Dictionary<string, int> alarmScriptIds,
+        HashSet<int> visited)
+    {
+        if (!composedTemplateChains.TryGetValue(composition.ComposedTemplateId, out var composedChain))
+            return;
+
+        var composedAlarms = ResolveInheritedAlarms(composedChain, prefix, alarmScriptIds);
+        foreach (var (name, alarm) in composedAlarms)
+        {
+            var canonicalName = $"{prefix}.{name}";
+            if (!alarms.ContainsKey(canonicalName))
+            {
+                alarms[canonicalName] = alarm with
+                {
+                    CanonicalName = canonicalName,
+                    TriggerConfiguration = PrefixTriggerAttribute(alarm.TriggerConfiguration, prefix),
+                    Source = "Composed"
+                };
+            }
+        }
+
+        // Descend into nested compositions of every template in the chain.
+        foreach (var composedTemplate in composedChain)
+        {
+            if (!visited.Add(composedTemplate.Id))
+                continue;
+            if (!compositionMap.TryGetValue(composedTemplate.Id, out var nestedCompositions))
+                continue;
+
+            foreach (var nested in nestedCompositions)
+                ResolveComposedAlarmsRecursive(
+                    nested, $"{prefix}.{nested.InstanceName}",
+                    compositionMap, composedTemplateChains, alarms, alarmScriptIds, visited);
+        }
+    }
+
+    /// <summary>
+    /// Resolves scripts from an inheritance chain. The returned dictionary is
+    /// keyed by bare script name. <paramref name="scriptCanonicalById"/> is
+    /// populated with each resolved script's <see cref="TemplateScript.Id"/>
+    /// mapped to the canonical name it will ultimately carry (bare when
+    /// <paramref name="prefix"/> is null, otherwise <c>prefix.name</c>).
+    /// </summary>
     private static Dictionary<string, ResolvedScript> ResolveInheritedScripts(
-        IReadOnlyList<Template> templateChain)
+        IReadOnlyList<Template> templateChain,
+        string? prefix,
+        Dictionary<int, string> scriptCanonicalById)
     {
         var result = new Dictionary<string, ResolvedScript>(StringComparer.Ordinal);
+        var idByName = new Dictionary<string, int>(StringComparer.Ordinal);
 
         for (int i = templateChain.Count - 1; i >= 0; i--)
         {
@@ -600,9 +669,17 @@ public class FlatteningService
                     MinTimeBetweenRuns = script.MinTimeBetweenRuns,
                     Source = source
                 };
+                idByName[script.Name] = script.Id;
             }
         }
 
+        foreach (var (name, id) in idByName)
+        {
+            if (id == 0) continue; // unsaved row — no stable id to map
+            var canonical = prefix == null ? name : $"{prefix}.{name}";
+            scriptCanonicalById[id] = canonical;
+        }
+
         return result;
     }
 
@@ -610,7 +687,8 @@ public class FlatteningService
         IReadOnlyList<Template> templateChain,
         IReadOnlyDictionary<int, IReadOnlyList<TemplateComposition>> compositionMap,
         IReadOnlyDictionary<int, IReadOnlyList<Template>> composedTemplateChains,
-        Dictionary<string, ResolvedScript> scripts)
+        Dictionary<string, ResolvedScript> scripts,
+        Dictionary<int, string> scriptCanonicalById)
     {
         foreach (var template in templateChain)
         {
@@ -618,28 +696,58 @@ public class FlatteningService
                 continue;
 
             foreach (var composition in compositions)
+                ResolveComposedScriptsRecursive(
+                    composition, composition.InstanceName,
+                    compositionMap, composedTemplateChains, scripts, scriptCanonicalById,
+                    new HashSet<int>());
+        }
+    }
+
+    /// <summary>
+    /// Recursively resolves the scripts of a composed module and every module
+    /// nested inside it, path-qualifying each canonical name with the
+    /// accumulated <paramref name="prefix"/>.
+    /// </summary>
+    private static void ResolveComposedScriptsRecursive(
+        TemplateComposition composition,
+        string prefix,
+        IReadOnlyDictionary<int, IReadOnlyList<TemplateComposition>> compositionMap,
+        IReadOnlyDictionary<int, IReadOnlyList<Template>> composedTemplateChains,
+        Dictionary<string, ResolvedScript> scripts,
+        Dictionary<int, string> scriptCanonicalById,
+        HashSet<int> visited)
+    {
+        if (!composedTemplateChains.TryGetValue(composition.ComposedTemplateId, out var composedChain))
+            return;
+
+        var composedScripts = ResolveInheritedScripts(composedChain, prefix, scriptCanonicalById);
+        foreach (var (name, script) in composedScripts)
+        {
+            var canonicalName = $"{prefix}.{name}";
+            if (!scripts.ContainsKey(canonicalName))
             {
-                if (!composedTemplateChains.TryGetValue(composition.ComposedTemplateId, out var composedChain))
+                scripts[canonicalName] = script with
-                    continue;
-
-                var prefix = composition.InstanceName;
-                var composedScripts = ResolveInheritedScripts(composedChain);
-
-                foreach (var (name, script) in composedScripts)
                 {
-                    var canonicalName = $"{prefix}.{name}";
+                    CanonicalName = canonicalName,
-                    if (!scripts.ContainsKey(canonicalName))
+                    Source = "Composed",
-                    {
+                    Scope = new Commons.Types.Scripts.ScriptScope(SelfPath: prefix, ParentPath: "")
-                        scripts[canonicalName] = script with
+                };
-                        {
-                            CanonicalName = canonicalName,
-                            Source = "Composed",
-                            Scope = new Commons.Types.Scripts.ScriptScope(SelfPath: prefix, ParentPath: "")
-                        };
-                    }
-                }
             }
         }
+
+        // Descend into nested compositions of every template in the chain.
+        foreach (var composedTemplate in composedChain)
+        {
+            if (!visited.Add(composedTemplate.Id))
+                continue;
+            if (!compositionMap.TryGetValue(composedTemplate.Id, out var nestedCompositions))
+                continue;
+
+            foreach (var nested in nestedCompositions)
+                ResolveComposedScriptsRecursive(
+                    nested, $"{prefix}.{nested.InstanceName}",
+                    compositionMap, composedTemplateChains, scripts, scriptCanonicalById, visited);
+        }
     }
 
     /// <summary>
@@ -688,18 +796,30 @@ public class FlatteningService
     }
 
     /// <summary>
-    /// Resolves alarm on-trigger script references from script IDs to canonical names.
+    /// Resolves alarm on-trigger script references from <see cref="TemplateScript.Id"/>
-    /// This is done by finding the script in the template chain whose ID matches the alarm's OnTriggerScriptId,
+    /// values to the canonical (path-qualified) names of the corresponding
-    /// then mapping to the corresponding canonical name in the resolved scripts.
+    /// resolved scripts. <paramref name="alarmScriptIds"/> maps an alarm's
+    /// canonical name to the id of its on-trigger script; <paramref name="scriptCanonicalById"/>
+    /// maps a script id to the canonical name it carries in the flattened
+    /// configuration. An alarm whose on-trigger script id has no matching
+    /// resolved script is left with a <c>null</c> reference — semantic
+    /// validation then reports the dangling reference.
     /// </summary>
     private static void ResolveAlarmScriptReferences(
         Dictionary<string, ResolvedAlarm> alarms,
-        Dictionary<string, ResolvedScript> scripts)
+        Dictionary<string, int> alarmScriptIds,
+        Dictionary<int, string> scriptCanonicalById)
     {
-        // Build a lookup of script names (we only have canonical names at this point)
+        foreach (var (alarmCanonicalName, scriptId) in alarmScriptIds)
-        // The alarm's OnTriggerScriptCanonicalName will be set by the caller or validation step
+        {
-        // For now, this is a placeholder — the actual resolution depends on how alarm trigger configs
+            if (!alarms.TryGetValue(alarmCanonicalName, out var alarm))
-        // reference scripts (by name within the same scope).
+                continue;
-        // The trigger configuration JSON may contain a "scriptName" field.
+
+            scriptCanonicalById.TryGetValue(scriptId, out var scriptCanonicalName);
+            alarms[alarmCanonicalName] = alarm with
+            {
+                OnTriggerScriptCanonicalName = scriptCanonicalName
+            };
+        }
     }
 }

src/ScadaLink.TemplateEngine/TemplateService.cs

@@ -51,15 +51,12 @@ public class TemplateService
             FolderId = folderId
         };
 
-        // Check acyclicity (inheritance) — for new templates this is mostly a parent-exists check,
+        // No collision or acyclicity check is needed here: a freshly created
-        // but we validate anyway for consistency
+        // template has no members of its own, the parent (validated above to
-        if (parentTemplateId.HasValue)
+        // exist) was already collision-checked when its members were added,
-        {
+        // and a brand-new child cannot be an ancestor of its parent. Naming
-            var allTemplates = await _repository.GetAllTemplatesAsync(cancellationToken);
+        // collisions are enforced on every member-mutating call (AddAttribute,
-            // The new template doesn't exist yet, so we simulate by adding it to the list
+        // AddAlarm, AddScript, AddComposition) and on rename in UpdateTemplate.
-            // with a temporary ID. Since it has no children yet, the only cycle would be
-            // if parentTemplateId somehow pointed at itself (already handled above).
-        }
 
         await _repository.AddTemplateAsync(template, cancellationToken);
         await _auditService.LogAsync(user, "Create", "Template", "0", name, template, cancellationToken);
@@ -281,17 +278,19 @@ public class TemplateService
         if (lockError != null)
             return Result<TemplateAttribute>.Failure(lockError);
 
-        // Validate fixed-field granularity
+        // Validate fixed-field granularity. DataType and DataSourceReference are
+        // fixed by the defining level for every attribute — locked or not — so
+        // the error is always honoured (a locked attribute is already rejected
+        // earlier inside the helper).
         var granularityError = LockEnforcer.ValidateAttributeOverride(existing, proposed);
-        if (granularityError != null && existing.IsLocked)
+        if (granularityError != null)
             return Result<TemplateAttribute>.Failure(granularityError);
 
-        // Apply overridable fields
+        // Apply overridable fields. DataType / DataSourceReference are fixed and
+        // are deliberately not copied from the proposed attribute.
         existing.Value = proposed.Value;
         existing.Description = proposed.Description;
         existing.IsLocked = proposed.IsLocked;
-        existing.DataType = proposed.DataType;
-        existing.DataSourceReference = proposed.DataSourceReference;
         if (template?.IsDerived == true)
             existing.IsInherited = proposed.IsInherited;
         else

tests/ScadaLink.SiteRuntime.Tests/Actors/DeploymentManagerRedeployTests.cs

@@ -0,0 +1,155 @@
+using Akka.Actor;
+using Akka.TestKit.Xunit2;
+using Microsoft.Extensions.Logging.Abstractions;
+using ScadaLink.Commons.Messages.Deployment;
+using ScadaLink.Commons.Messages.Health;
+using ScadaLink.Commons.Messages.Lifecycle;
+using ScadaLink.Commons.Types.Enums;
+using ScadaLink.Commons.Types.Flattening;
+using ScadaLink.HealthMonitoring;
+using ScadaLink.SiteRuntime.Actors;
+using ScadaLink.SiteRuntime.Persistence;
+using ScadaLink.SiteRuntime.Scripts;
+using System.Text.Json;
+
+namespace ScadaLink.SiteRuntime.Tests.Actors;
+
+/// <summary>
+/// Regression tests for SiteRuntime-003: redeployment of an existing instance must
+/// wait for the terminating Instance Actor before recreating the child, instead of
+/// relying on a fixed 500 ms reschedule that can collide on the child actor name.
+/// </summary>
+public class DeploymentManagerRedeployTests : TestKit, IDisposable
+{
+    private readonly SiteStorageService _storage;
+    private readonly ScriptCompilationService _compilationService;
+    private readonly SharedScriptLibrary _sharedScriptLibrary;
+    private readonly string _dbFile;
+
+    public DeploymentManagerRedeployTests()
+    {
+        _dbFile = Path.Combine(Path.GetTempPath(), $"dm-redeploy-test-{Guid.NewGuid():N}.db");
+        _storage = new SiteStorageService(
+            $"Data Source={_dbFile}",
+            NullLogger<SiteStorageService>.Instance);
+        _storage.InitializeAsync().GetAwaiter().GetResult();
+        _compilationService = new ScriptCompilationService(
+            NullLogger<ScriptCompilationService>.Instance);
+        _sharedScriptLibrary = new SharedScriptLibrary(
+            _compilationService, NullLogger<SharedScriptLibrary>.Instance);
+    }
+
+    void IDisposable.Dispose()
+    {
+        Shutdown();
+        try { File.Delete(_dbFile); } catch { /* cleanup */ }
+    }
+
+    private IActorRef CreateDeploymentManager(ISiteHealthCollector? healthCollector = null)
+    {
+        return ActorOf(Props.Create(() => new DeploymentManagerActor(
+            _storage,
+            _compilationService,
+            _sharedScriptLibrary,
+            null,
+            new SiteRuntimeOptions(),
+            NullLogger<DeploymentManagerActor>.Instance,
+            null,
+            null,
+            healthCollector,
+            null)));
+    }
+
+    /// <summary>
+    /// Minimal fake that records the most recent deployed-instance count.
+    /// </summary>
+    private sealed class CountCapturingHealthCollector : ISiteHealthCollector
+    {
+        public int LastDeployedCount { get; private set; }
+        public void IncrementScriptError() { }
+        public void IncrementAlarmError() { }
+        public void IncrementDeadLetter() { }
+        public void UpdateConnectionHealth(string connectionName, ConnectionHealth health) { }
+        public void RemoveConnection(string connectionName) { }
+        public void UpdateTagResolution(string connectionName, int totalSubscribed, int successfullyResolved) { }
+        public void UpdateConnectionEndpoint(string connectionName, string endpoint) { }
+        public void UpdateTagQuality(string connectionName, int good, int bad, int uncertain) { }
+        public void SetStoreAndForwardDepths(IReadOnlyDictionary<string, int> depths) { }
+        public void SetInstanceCounts(int deployed, int enabled, int disabled) => LastDeployedCount = deployed;
+        public void SetParkedMessageCount(int count) { }
+        public void SetNodeHostname(string hostname) { }
+        public void SetClusterNodes(IReadOnlyList<NodeStatus> nodes) { }
+        public void SetActiveNode(bool isActive) { }
+        public bool IsActiveNode => true;
+        public SiteHealthReport CollectReport(string siteId) => throw new NotSupportedException();
+    }
+
+    private static string MakeConfigJson(string instanceName)
+    {
+        var config = new FlattenedConfiguration
+        {
+            InstanceUniqueName = instanceName,
+            Attributes =
+            [
+                new ResolvedAttribute { CanonicalName = "TestAttr", Value = "1", DataType = "Int32" }
+            ]
+        };
+        return JsonSerializer.Serialize(config);
+    }
+
+    [Fact]
+    public async Task Redeploy_ExistingInstance_SucceedsWithoutNameCollision()
+    {
+        var actor = CreateDeploymentManager();
+        await Task.Delay(500); // empty startup
+
+        // Initial deploy.
+        actor.Tell(new DeployInstanceCommand(
+            "dep-1", "RedeployPump", "h1", MakeConfigJson("RedeployPump"), "admin", DateTimeOffset.UtcNow));
+        var first = ExpectMsg<DeploymentStatusResponse>(TimeSpan.FromSeconds(5));
+        Assert.Equal(DeploymentStatus.Success, first.Status);
+        await Task.Delay(500);
+
+        // Redeploy the same instance — must replace the existing actor cleanly.
+        actor.Tell(new DeployInstanceCommand(
+            "dep-2", "RedeployPump", "h2", MakeConfigJson("RedeployPump"), "admin", DateTimeOffset.UtcNow));
+        var second = ExpectMsg<DeploymentStatusResponse>(TimeSpan.FromSeconds(10));
+        Assert.Equal(DeploymentStatus.Success, second.Status);
+
+        // The redeployed instance must still be operable (no orphaned/broken actor).
+        actor.Tell(new DisableInstanceCommand("cmd-1", "RedeployPump", DateTimeOffset.UtcNow));
+        var disable = ExpectMsg<InstanceLifecycleResponse>(TimeSpan.FromSeconds(5));
+        Assert.True(disable.Success);
+    }
+
+    [Fact]
+    public async Task Redeploy_ExistingInstance_DoesNotOverCountDeployedInstances()
+    {
+        var health = new CountCapturingHealthCollector();
+        var actor = CreateDeploymentManager(health);
+        await Task.Delay(500);
+
+        // Deploy once.
+        actor.Tell(new DeployInstanceCommand(
+            "dep-1", "CountPump", "h1", MakeConfigJson("CountPump"), "admin", DateTimeOffset.UtcNow));
+        ExpectMsg<DeploymentStatusResponse>(TimeSpan.FromSeconds(5));
+        await Task.Delay(500);
+
+        // Redeploy several times.
+        for (var i = 2; i <= 4; i++)
+        {
+            actor.Tell(new DeployInstanceCommand(
+                $"dep-{i}", "CountPump", $"h{i}", MakeConfigJson("CountPump"), "admin", DateTimeOffset.UtcNow));
+            ExpectMsg<DeploymentStatusResponse>(TimeSpan.FromSeconds(10));
+            await Task.Delay(500);
+        }
+
+        // Storage uses UPSERT — exactly one deployed config row should exist.
+        var configs = await _storage.GetAllDeployedConfigsAsync();
+        Assert.Single(configs, c => c.InstanceUniqueName == "CountPump");
+
+        // The reported deployed count must be exactly 1 — a redeploy is an update,
+        // not a new instance, so the in-memory counter must not drift upward.
+        Assert.Equal(1, health.LastDeployedCount);
+    }
+}

tests/ScadaLink.SiteRuntime.Tests/Actors/InstanceActorIntegrationTests.cs

@@ -123,9 +123,12 @@ public class InstanceActorIntegrationTests : TestKit, IDisposable
                 $"corr-{i}", "Pump1", "Temperature", $"{i}", DateTimeOffset.UtcNow));
         }
 
-        // SetStaticAttributeCommand is fire-and-forget; the GetAttributeRequest
+        // Each static write replies with a SetStaticAttributeResponse; drain all
-        // round-trip below is the sync point — the FIFO mailbox guarantees all
+        // 50 — the FIFO mailbox guarantees they are processed in order.
-        // 50 sets are processed before the get is.
+        for (int i = 0; i < 50; i++)
+        {
+            ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
+        }
 
         // The last value should be the final one
         actor.Tell(new GetAttributeRequest(

tests/ScadaLink.SiteRuntime.Tests/Actors/InstanceActorSetAttributeTests.cs

@@ -0,0 +1,179 @@
+using Akka.Actor;
+using Akka.TestKit.Xunit2;
+using Microsoft.Extensions.Logging.Abstractions;
+using Akka.TestKit;
+using ScadaLink.Commons.Messages.DataConnection;
+using ScadaLink.Commons.Messages.Instance;
+using ScadaLink.Commons.Types.Flattening;
+using ScadaLink.SiteRuntime.Actors;
+using ScadaLink.SiteRuntime.Persistence;
+using ScadaLink.SiteRuntime.Scripts;
+using System.Text.Json;
+
+namespace ScadaLink.SiteRuntime.Tests.Actors;
+
+/// <summary>
+/// Regression tests for SiteRuntime-001: Instance.SetAttribute must route writes
+/// to the Data Connection Layer for data-sourced attributes instead of persisting
+/// a local static override.
+/// </summary>
+public class InstanceActorSetAttributeTests : TestKit, IDisposable
+{
+    private readonly SiteStorageService _storage;
+    private readonly ScriptCompilationService _compilationService;
+    private readonly SharedScriptLibrary _sharedScriptLibrary;
+    private readonly SiteRuntimeOptions _options;
+    private readonly string _dbFile;
+
+    public InstanceActorSetAttributeTests()
+    {
+        _dbFile = Path.Combine(Path.GetTempPath(), $"instance-setattr-test-{Guid.NewGuid():N}.db");
+        _storage = new SiteStorageService(
+            $"Data Source={_dbFile}",
+            NullLogger<SiteStorageService>.Instance);
+        _storage.InitializeAsync().GetAwaiter().GetResult();
+        _compilationService = new ScriptCompilationService(
+            NullLogger<ScriptCompilationService>.Instance);
+        _sharedScriptLibrary = new SharedScriptLibrary(
+            _compilationService, NullLogger<SharedScriptLibrary>.Instance);
+        _options = new SiteRuntimeOptions();
+    }
+
+    void IDisposable.Dispose()
+    {
+        Shutdown();
+        try { File.Delete(_dbFile); } catch { /* cleanup */ }
+    }
+
+    private IActorRef CreateInstanceActor(string instanceName, FlattenedConfiguration config, IActorRef? dclManager)
+    {
+        return ActorOf(Props.Create(() => new InstanceActor(
+            instanceName,
+            JsonSerializer.Serialize(config),
+            _storage,
+            _compilationService,
+            _sharedScriptLibrary,
+            null,
+            _options,
+            NullLogger<InstanceActor>.Instance,
+            dclManager)));
+    }
+
+    /// <summary>
+    /// Drains the startup <see cref="SubscribeTagsRequest"/> the Instance Actor emits
+    /// to the DCL in PreStart, then returns the next <see cref="WriteTagRequest"/>.
+    /// </summary>
+    private static WriteTagRequest ExpectWriteTag(TestProbe dclProbe)
+        => dclProbe.FishForMessage<WriteTagRequest>(_ => true, TimeSpan.FromSeconds(5));
+
+    private static FlattenedConfiguration DataSourcedConfig(string instanceName) => new()
+    {
+        InstanceUniqueName = instanceName,
+        Attributes =
+        [
+            new ResolvedAttribute
+            {
+                CanonicalName = "Setpoint",
+                Value = "10",
+                DataType = "Double",
+                DataSourceReference = "/Motor/Setpoint",
+                BoundDataConnectionName = "OpcServer1"
+            }
+        ]
+    };
+
+    [Fact]
+    public async Task SetAttribute_DataSourcedAttribute_IssuesDclWriteAndDoesNotPersistOverride()
+    {
+        var config = DataSourcedConfig("PumpDcl1");
+        var dclProbe = CreateTestProbe();
+        var actor = CreateInstanceActor("PumpDcl1", config, dclProbe.Ref);
+
+        actor.Tell(new SetStaticAttributeCommand(
+            "corr-dcl", "PumpDcl1", "Setpoint", "55", DateTimeOffset.UtcNow));
+
+        // The Instance Actor must forward a WriteTagRequest to the DCL manager.
+        var write = ExpectWriteTag(dclProbe);
+        Assert.Equal("OpcServer1", write.ConnectionName);
+        Assert.Equal("/Motor/Setpoint", write.TagPath);
+        Assert.Equal("55", write.Value);
+
+        // DCL confirms the write.
+        dclProbe.Reply(new WriteTagResponse(write.CorrelationId, true, null, DateTimeOffset.UtcNow));
+        var response = ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
+        Assert.True(response.Success);
+
+        // No static override should be persisted for a data-sourced attribute.
+        await Task.Delay(300);
+        var overrides = await _storage.GetStaticOverridesAsync("PumpDcl1");
+        Assert.Empty(overrides);
+    }
+
+    [Fact]
+    public void SetAttribute_DataSourcedAttribute_DoesNotOptimisticallyUpdateMemory()
+    {
+        var config = DataSourcedConfig("PumpDcl2");
+        var dclProbe = CreateTestProbe();
+        var actor = CreateInstanceActor("PumpDcl2", config, dclProbe.Ref);
+
+        actor.Tell(new SetStaticAttributeCommand(
+            "corr-dcl2", "PumpDcl2", "Setpoint", "999", DateTimeOffset.UtcNow));
+
+        var write = ExpectWriteTag(dclProbe);
+        dclProbe.Reply(new WriteTagResponse(write.CorrelationId, true, null, DateTimeOffset.UtcNow));
+        ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
+
+        // In-memory value must still be the original config value — it is only
+        // updated when the subscription delivers the confirmed device value.
+        actor.Tell(new GetAttributeRequest("corr-get", "PumpDcl2", "Setpoint", DateTimeOffset.UtcNow));
+        var get = ExpectMsg<GetAttributeResponse>(TimeSpan.FromSeconds(5));
+        Assert.Equal("10", get.Value?.ToString());
+    }
+
+    [Fact]
+    public void SetAttribute_DataSourcedAttribute_DclWriteFailure_ReturnedToCaller()
+    {
+        var config = DataSourcedConfig("PumpDcl3");
+        var dclProbe = CreateTestProbe();
+        var actor = CreateInstanceActor("PumpDcl3", config, dclProbe.Ref);
+
+        actor.Tell(new SetStaticAttributeCommand(
+            "corr-dcl3", "PumpDcl3", "Setpoint", "42", DateTimeOffset.UtcNow));
+
+        var write = ExpectWriteTag(dclProbe);
+        dclProbe.Reply(new WriteTagResponse(write.CorrelationId, false, "device rejected write", DateTimeOffset.UtcNow));
+
+        var response = ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
+        Assert.False(response.Success);
+        Assert.Contains("device rejected write", response.ErrorMessage);
+    }
+
+    [Fact]
+    public async Task SetAttribute_StaticAttribute_StillPersistsOverrideAndDoesNotCallDcl()
+    {
+        var config = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "PumpStatic1",
+            Attributes =
+            [
+                new ResolvedAttribute { CanonicalName = "Label", Value = "Main", DataType = "String" }
+            ]
+        };
+        var dclProbe = CreateTestProbe();
+        var actor = CreateInstanceActor("PumpStatic1", config, dclProbe.Ref);
+
+        actor.Tell(new SetStaticAttributeCommand(
+            "corr-static", "PumpStatic1", "Label", "Backup", DateTimeOffset.UtcNow));
+
+        var response = ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
+        Assert.True(response.Success);
+
+        // DCL must NOT receive a write for a static attribute.
+        dclProbe.ExpectNoMsg(TimeSpan.FromMilliseconds(300));
+
+        await Task.Delay(300);
+        var overrides = await _storage.GetStaticOverridesAsync("PumpStatic1");
+        Assert.Single(overrides);
+        Assert.Equal("Backup", overrides["Label"]);
+    }
+}

tests/ScadaLink.SiteRuntime.Tests/Actors/InstanceActorTests.cs

@@ -113,11 +113,11 @@ public class InstanceActorTests : TestKit, IDisposable
 
         var actor = CreateInstanceActor("Pump1", config);
 
-        // SetStaticAttributeCommand is fire-and-forget (no reply); the
+        // A static attribute write replies with SetStaticAttributeResponse.
-        // GetAttributeRequest round-trip below confirms it was applied — the
-        // actor mailbox is FIFO, so the set is processed before the get.
         actor.Tell(new SetStaticAttributeCommand(
             "corr-3", "Pump1", "Temperature", "100.0", DateTimeOffset.UtcNow));
+        var setResponse = ExpectMsg<SetStaticAttributeResponse>();
+        Assert.True(setResponse.Success);
 
         // Verify the value changed in memory
         actor.Tell(new GetAttributeRequest(
@@ -145,12 +145,9 @@ public class InstanceActorTests : TestKit, IDisposable
         actor.Tell(new SetStaticAttributeCommand(
             "corr-persist", "PumpPersist1", "Temperature", "100.0", DateTimeOffset.UtcNow));
 
-        // SetStaticAttributeCommand is fire-and-forget; round-trip a
+        // A static attribute write replies with SetStaticAttributeResponse once the
-        // GetAttributeRequest to confirm the command was processed (FIFO
+        // in-memory state is updated; then wait for the async SQLite persist.
-        // mailbox), then wait for the async SQLite persist to complete.
+        ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
-        actor.Tell(new GetAttributeRequest(
-            "corr-persist-get", "PumpPersist1", "Temperature", DateTimeOffset.UtcNow));
-        ExpectMsg<GetAttributeResponse>(TimeSpan.FromSeconds(5));
         await Task.Delay(500);
 
         // Verify it persisted to SQLite

tests/ScadaLink.StoreAndForward.Tests/StoreAndForwardServiceTests.cs

@@ -86,7 +86,9 @@ public class StoreAndForwardServiceTests : IAsyncLifetime, IDisposable
         var msg = await _storage.GetMessageByIdAsync(result.MessageId);
         Assert.NotNull(msg);
         Assert.Equal(StoreAndForwardMessageStatus.Pending, msg!.Status);
-        Assert.Equal(1, msg.RetryCount);
+        // StoreAndForward-003: RetryCount counts sweep retries only; the immediate
+        // attempt is attempt 0, so a freshly buffered message has RetryCount 0.
+        Assert.Equal(0, msg.RetryCount);
     }
 
     [Fact]
@@ -134,6 +136,12 @@ public class StoreAndForwardServiceTests : IAsyncLifetime, IDisposable
             StoreAndForwardCategory.ExternalSystem, "api", """{}""",
             maxRetries: 2);
 
+        // StoreAndForward-003: MaxRetries bounds sweep retries (not the immediate
+        // attempt), so a message with MaxRetries=2 needs two retry sweeps to park.
+        await _service.RetryPendingMessagesAsync();
+        var afterFirst = await _storage.GetMessageByIdAsync(result.MessageId);
+        Assert.Equal(StoreAndForwardMessageStatus.Pending, afterFirst!.Status);
+
         await _service.RetryPendingMessagesAsync();
 
         var msg = await _storage.GetMessageByIdAsync(result.MessageId);
@@ -141,6 +149,34 @@ public class StoreAndForwardServiceTests : IAsyncLifetime, IDisposable
         Assert.Equal(StoreAndForwardMessageStatus.Parked, msg!.Status);
     }
 
+    // ── StoreAndForward-003: retry-count accounting ──
+
+    [Fact]
+    public async Task RetryPendingMessagesAsync_MaxRetriesOne_PerformsExactlyOneRetryBeforeParking()
+    {
+        // The immediate attempt is attempt 0; MaxRetries=1 must allow exactly one
+        // retry sweep before parking. The pre-fix off-by-one parked with zero retries.
+        var attempts = 0;
+        _service.RegisterDeliveryHandler(StoreAndForwardCategory.ExternalSystem,
+            _ => { Interlocked.Increment(ref attempts); throw new HttpRequestException("always fails"); });
+
+        var result = await _service.EnqueueAsync(
+            StoreAndForwardCategory.ExternalSystem, "api", """{}""",
+            maxRetries: 1);
+
+        // After the immediate failed attempt the message is buffered, not parked.
+        var buffered = await _storage.GetMessageByIdAsync(result.MessageId);
+        Assert.Equal(StoreAndForwardMessageStatus.Pending, buffered!.Status);
+        Assert.Equal(1, attempts); // only the immediate attempt so far
+
+        await _service.RetryPendingMessagesAsync();
+
+        var msg = await _storage.GetMessageByIdAsync(result.MessageId);
+        Assert.Equal(StoreAndForwardMessageStatus.Parked, msg!.Status);
+        Assert.Equal(2, attempts);      // immediate attempt + exactly one retry
+        Assert.Equal(1, msg.RetryCount); // one sweep retry recorded
+    }
+
     [Fact]
     public async Task RetryPendingMessagesAsync_PermanentFailureOnRetry_ParksMessage()
     {
@@ -332,6 +368,8 @@ public class StoreAndForwardServiceTests : IAsyncLifetime, IDisposable
         var msg = await _storage.GetMessageByIdAsync(result.MessageId);
         Assert.NotNull(msg);
         Assert.Equal(StoreAndForwardMessageStatus.Pending, msg!.Status);
-        Assert.Equal(1, msg.RetryCount);  // counts as the caller's first attempt
+        // StoreAndForward-003: the caller's own attempt is attempt 0; RetryCount
+        // counts only sweep retries, so a freshly buffered message has RetryCount 0.
+        Assert.Equal(0, msg.RetryCount);
     }
 }

tests/ScadaLink.TemplateEngine.Tests/Flattening/FlatteningServiceTests.cs

@@ -370,4 +370,154 @@ public class FlatteningServiceTests
         var script = result.Value.Scripts.First(s => s.CanonicalName == "Sample");
         Assert.Equal("return base;", script.Code);
     }
+
+    // ── TemplateEngine-001: deep composition nesting ───────────────────────
+
+    [Fact]
+    public void Flatten_ThreeLevelComposition_AttributesAlarmsScriptsAllResolved()
+    {
+        // Station composes Pump (level 1); Pump composes Motor (level 2);
+        // Motor composes Bearing (level 3).
+        var bearing = CreateTemplate(4, "Bearing");
+        bearing.Attributes.Add(new TemplateAttribute("Vibration") { DataType = DataType.Double, Value = "0.1" });
+        bearing.Alarms.Add(new TemplateAlarm("HighVibration")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Vibration\",\"high\":5}",
+            PriorityLevel = 1
+        });
+        bearing.Scripts.Add(new TemplateScript("MonitorBearing", "// monitor") { Id = 40 });
+
+        var motor = CreateTemplate(3, "Motor");
+        motor.Attributes.Add(new TemplateAttribute("Current") { DataType = DataType.Double, Value = "10" });
+
+        var pump = CreateTemplate(2, "Pump");
+        pump.Attributes.Add(new TemplateAttribute("RPM") { DataType = DataType.Double, Value = "1500" });
+
+        var station = CreateTemplate(1, "Station");
+
+        var compositions = new Dictionary<int, IReadOnlyList<TemplateComposition>>
+        {
+            [1] = new List<TemplateComposition> { new("MainPump") { ComposedTemplateId = 2 } },
+            [2] = new List<TemplateComposition> { new("DriveMotor") { ComposedTemplateId = 3 } },
+            [3] = new List<TemplateComposition> { new("FrontBearing") { ComposedTemplateId = 4 } },
+        };
+        var composedChains = new Dictionary<int, IReadOnlyList<Template>>
+        {
+            [2] = [pump],
+            [3] = [motor],
+            [4] = [bearing],
+        };
+
+        var instance = CreateInstance();
+        var result = _sut.Flatten(instance, [station], compositions, composedChains,
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        // Level 3 attribute must be present with the full path-qualified name.
+        Assert.Contains(result.Value.Attributes,
+            a => a.CanonicalName == "MainPump.DriveMotor.FrontBearing.Vibration");
+        // Level 3 alarm must be present (was dropped entirely before).
+        Assert.Contains(result.Value.Alarms,
+            a => a.CanonicalName == "MainPump.DriveMotor.FrontBearing.HighVibration");
+        // Level 3 script must be present (was dropped entirely before).
+        Assert.Contains(result.Value.Scripts,
+            s => s.CanonicalName == "MainPump.DriveMotor.FrontBearing.MonitorBearing");
+    }
+
+    [Fact]
+    public void Flatten_NestedComposedAlarm_TriggerAttributePrefixed()
+    {
+        var bearing = CreateTemplate(4, "Bearing");
+        bearing.Attributes.Add(new TemplateAttribute("Vibration") { DataType = DataType.Double, Value = "0.1" });
+        bearing.Alarms.Add(new TemplateAlarm("HighVibration")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Vibration\",\"high\":5}",
+            PriorityLevel = 1
+        });
+
+        var motor = CreateTemplate(3, "Motor");
+        var pump = CreateTemplate(2, "Pump");
+        var station = CreateTemplate(1, "Station");
+
+        var compositions = new Dictionary<int, IReadOnlyList<TemplateComposition>>
+        {
+            [1] = new List<TemplateComposition> { new("MainPump") { ComposedTemplateId = 2 } },
+            [2] = new List<TemplateComposition> { new("DriveMotor") { ComposedTemplateId = 3 } },
+            [3] = new List<TemplateComposition> { new("FrontBearing") { ComposedTemplateId = 4 } },
+        };
+        var composedChains = new Dictionary<int, IReadOnlyList<Template>>
+        {
+            [2] = [pump], [3] = [motor], [4] = [bearing],
+        };
+
+        var instance = CreateInstance();
+        var result = _sut.Flatten(instance, [station], compositions, composedChains,
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        var alarm = result.Value.Alarms.First(a => a.CanonicalName.EndsWith("HighVibration"));
+        // The trigger's attribute reference must carry the full nested prefix.
+        Assert.Contains("MainPump.DriveMotor.FrontBearing.Vibration", alarm.TriggerConfiguration);
+    }
+
+    // ── TemplateEngine-004: alarm on-trigger script resolution ─────────────
+
+    [Fact]
+    public void Flatten_AlarmOnTriggerScript_ResolvedToCanonicalName()
+    {
+        var template = CreateTemplate(1, "Base");
+        template.Scripts.Add(new TemplateScript("HandleAlarm", "// handle") { Id = 50 });
+        template.Alarms.Add(new TemplateAlarm("HighTemp")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Temp\",\"high\":100}",
+            PriorityLevel = 1,
+            OnTriggerScriptId = 50
+        });
+
+        var instance = CreateInstance();
+        var result = _sut.Flatten(instance, [template],
+            new Dictionary<int, IReadOnlyList<TemplateComposition>>(),
+            new Dictionary<int, IReadOnlyList<Template>>(),
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        var alarm = result.Value.Alarms.First(a => a.CanonicalName == "HighTemp");
+        Assert.Equal("HandleAlarm", alarm.OnTriggerScriptCanonicalName);
+    }
+
+    [Fact]
+    public void Flatten_ComposedAlarmOnTriggerScript_ResolvedWithPrefix()
+    {
+        var composedTemplate = CreateTemplate(2, "Pump");
+        composedTemplate.Scripts.Add(new TemplateScript("PumpAlarmHandler", "// h") { Id = 60 });
+        composedTemplate.Alarms.Add(new TemplateAlarm("PumpFault")
+        {
+            TriggerType = AlarmTriggerType.ValueMatch,
+            TriggerConfiguration = "{\"attributeName\":\"State\",\"value\":\"FAULT\"}",
+            PriorityLevel = 5,
+            OnTriggerScriptId = 60
+        });
+
+        var station = CreateTemplate(1, "Station");
+
+        var compositions = new Dictionary<int, IReadOnlyList<TemplateComposition>>
+        {
+            [1] = new List<TemplateComposition> { new("MainPump") { ComposedTemplateId = 2 } }
+        };
+        var composedChains = new Dictionary<int, IReadOnlyList<Template>>
+        {
+            [2] = [composedTemplate]
+        };
+
+        var instance = CreateInstance();
+        var result = _sut.Flatten(instance, [station], compositions, composedChains,
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        var alarm = result.Value.Alarms.First(a => a.CanonicalName == "MainPump.PumpFault");
+        Assert.Equal("MainPump.PumpAlarmHandler", alarm.OnTriggerScriptCanonicalName);
+    }
 }

tests/ScadaLink.TemplateEngine.Tests/TemplateServiceTests.cs

@@ -60,6 +60,23 @@ public class TemplateServiceTests
         Assert.Equal(1, result.Value.ParentTemplateId);
     }
 
+    [Fact]
+    public async Task CreateTemplate_WithParent_DoesNotRunDeadCollisionQuery()
+    {
+        // A freshly created child has no members of its own, and the parent's
+        // members were already collision-validated when they were added — so
+        // create-time collision detection on a child is a guaranteed no-op.
+        // The previous code allocated an unused full-table read; the fix
+        // removes it. This guards against the dead query being reintroduced.
+        var parent = new Template("Base") { Id = 1 };
+        _repoMock.Setup(r => r.GetTemplateByIdAsync(1, It.IsAny<CancellationToken>())).ReturnsAsync(parent);
+
+        var result = await _service.CreateTemplateAsync("Child", null, 1, "admin");
+
+        Assert.True(result.IsSuccess);
+        _repoMock.Verify(r => r.GetAllTemplatesAsync(It.IsAny<CancellationToken>()), Times.Never);
+    }
+
     [Fact]
     public async Task CreateTemplate_NonexistentParent_Fails()
     {
@@ -668,6 +685,54 @@ public class TemplateServiceTests
         Assert.True(result.Value.IsLocked);
     }
 
+    [Fact]
+    public async Task UpdateAttribute_UnlockedAttribute_DataTypeChangeRejected()
+    {
+        // An unlocked attribute must still not be able to change its fixed DataType.
+        var existing = new TemplateAttribute("Temperature")
+        {
+            Id = 1, TemplateId = 1, DataType = DataType.Float, IsLocked = false
+        };
+        _repoMock.Setup(r => r.GetTemplateAttributeByIdAsync(1, It.IsAny<CancellationToken>())).ReturnsAsync(existing);
+        var template = new Template("Pump") { Id = 1 };
+        _repoMock.Setup(r => r.GetTemplateByIdAsync(1, It.IsAny<CancellationToken>())).ReturnsAsync(template);
+
+        var proposed = new TemplateAttribute("Temperature")
+        {
+            DataType = DataType.Int32, IsLocked = false, Value = "42"
+        };
+        var result = await _service.UpdateAttributeAsync(1, proposed, "admin");
+
+        Assert.True(result.IsFailure);
+        Assert.Contains("DataType", result.Error);
+        // The fixed field must not have been mutated.
+        Assert.Equal(DataType.Float, existing.DataType);
+    }
+
+    [Fact]
+    public async Task UpdateAttribute_UnlockedAttribute_DataSourceReferenceChangeRejected()
+    {
+        var existing = new TemplateAttribute("Temperature")
+        {
+            Id = 1, TemplateId = 1, DataType = DataType.Float, IsLocked = false,
+            DataSourceReference = "/Motor/Temp"
+        };
+        _repoMock.Setup(r => r.GetTemplateAttributeByIdAsync(1, It.IsAny<CancellationToken>())).ReturnsAsync(existing);
+        var template = new Template("Pump") { Id = 1 };
+        _repoMock.Setup(r => r.GetTemplateByIdAsync(1, It.IsAny<CancellationToken>())).ReturnsAsync(template);
+
+        var proposed = new TemplateAttribute("Temperature")
+        {
+            DataType = DataType.Float, IsLocked = false, Value = "42",
+            DataSourceReference = "/Motor/Other"
+        };
+        var result = await _service.UpdateAttributeAsync(1, proposed, "admin");
+
+        Assert.True(result.IsFailure);
+        Assert.Contains("DataSourceReference", result.Error);
+        Assert.Equal("/Motor/Temp", existing.DataSourceReference);
+    }
+
     [Fact]
     public async Task UpdateAttribute_ParentLocked_CannotOverride()
     {