diff --git a/docs/requirements/Component-ManagementService.md b/docs/requirements/Component-ManagementService.md
index 92637b25..9483c525 100644
--- a/docs/requirements/Component-ManagementService.md
+++ b/docs/requirements/Component-ManagementService.md
@@ -210,7 +210,7 @@ The two-person authorization workflow for writes through the MxAccess Gateway. B
 - **BrowseNodeCommand**: Browse an OPC UA / MxGateway connection's address space one level at a time; supports a `BrowseNext` continuation token (paging) and returns per-node type-info for OPC UA Variables. Actor-dispatched — the handler requires the command's `SiteIdentifier`, enforces site-scope, then relays via `CommunicationService.BrowseNodeAsync` (arch-review C4, CLI/UI parity). (`Design` role.)
 - **SearchAddressSpaceCommand**: Bounded recursive address-space search (depth + result caps, case-insensitive substring) against an OPC UA connection. Actor-dispatched, same `SiteIdentifier`-required + site-scope pattern, relayed via `CommunicationService.SearchAddressSpaceAsync` (arch-review C4). (`Design` role.)
 - **VerifyEndpointCommand**: Ask a site to probe an OPC UA endpoint (temporary client, short timeout) and report success / typed failure / a captured-but-untrusted server cert. Read-only — never trusts. Actor-dispatched, `SiteIdentifier`-required + site-scope, relayed via `CommunicationService.VerifyEndpointAsync` (arch-review C4). (`Design` role — runs inside the Admin-gated connection editor.)
-- **TrustServerCertCommand** / **RemoveServerCertCommand** / **ListServerCertsCommand**: Manage the site's OPC UA trusted-peer PKI store; Trust/Remove broadcast to **both** site nodes (see Component-SiteRuntime.md). (`Admin` role.)
+- **TrustServerCertCommand** / **RemoveServerCertCommand** / **ListServerCertsCommand**: Manage the site's OPC UA trusted-peer PKI store; Trust/Remove broadcast to **both** site nodes (see Component-SiteRuntime.md). Actor-dispatched and `Admin`-gated at the actor (arch-review C4) — each handler requires the command's `SiteIdentifier`, enforces site-scope, then relays via `CommunicationService.TrustServerCertAsync` / `RemoveServerCertAsync` / `ListServerCertsAsync`; the site-side reconcile across both nodes is owned by the site `CertStoreActor`. (`Admin` role.)
 
 ## Authorization
 
diff --git a/src/ZB.MOM.WW.ScadaBridge.Communication/CommunicationService.cs b/src/ZB.MOM.WW.ScadaBridge.Communication/CommunicationService.cs
index 115754f3..8a5a40b5 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Communication/CommunicationService.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Communication/CommunicationService.cs
@@ -432,7 +432,7 @@ public class CommunicationService
     /// <param name="command">The trust-server-cert command (connection name + DER + thumbprint).</param>
     /// <param name="cancellationToken">Cancellation token.</param>
     /// <returns>The cert-trust result (per-node aggregate success + first error).</returns>
-    public Task<CertTrustResult> TrustServerCertAsync(
+    public virtual Task<CertTrustResult> TrustServerCertAsync(
         string siteId,
         TrustServerCertCommand command,
         CancellationToken cancellationToken = default)
@@ -453,7 +453,7 @@ public class CommunicationService
     /// <param name="command">The list-server-certs command.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
     /// <returns>The cert-trust result carrying the listed certificates on success.</returns>
-    public Task<CertTrustResult> ListServerCertsAsync(
+    public virtual Task<CertTrustResult> ListServerCertsAsync(
         string siteId,
         ListServerCertsCommand command,
         CancellationToken cancellationToken = default)
@@ -474,7 +474,7 @@ public class CommunicationService
     /// <param name="command">The remove-server-cert command (thumbprint).</param>
     /// <param name="cancellationToken">Cancellation token.</param>
     /// <returns>The cert-trust result (per-node aggregate success + first error).</returns>
-    public Task<CertTrustResult> RemoveServerCertAsync(
+    public virtual Task<CertTrustResult> RemoveServerCertAsync(
         string siteId,
         RemoveServerCertCommand command,
         CancellationToken cancellationToken = default)
diff --git a/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs b/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
index 79556338..dd1229cf 100644
--- a/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
@@ -212,7 +212,12 @@ public class ManagementActor : ReceiveActor
             // gate must match — otherwise a Designer blocked in the UI could still
             // rotate a production credential via the CLI/Management API.
             or UpdateSmtpConfigCommand
-            or UpdateSmsConfigCommand => AdminOnly,
+            or UpdateSmsConfigCommand
+            // Server-certificate trust (arch-review C4). These mutate the site's
+            // trusted-peer PKI store — Admin, matching the Admin-gated UI cert
+            // page. Site-side reconcile semantics are owned by the site
+            // CertStoreActor (plan 03); this handler only relays.
+            or TrustServerCertCommand or RemoveServerCertCommand or ListServerCertsCommand => AdminOnly,
 
         // Area management — any-of [Designer, Deployer] (arch-review C6).
         // Exposed both in the Designer tooling and inside the Central UI
@@ -443,6 +448,9 @@ public class ManagementActor : ReceiveActor
             BrowseNodeCommand cmd => await HandleBrowseNode(sp, cmd, user),
             SearchAddressSpaceCommand cmd => await HandleSearchAddressSpace(sp, cmd, user),
             VerifyEndpointCommand cmd => await HandleVerifyEndpoint(sp, cmd, user),
+            TrustServerCertCommand cmd => await HandleTrustServerCert(sp, cmd, user),
+            RemoveServerCertCommand cmd => await HandleRemoveServerCert(sp, cmd, user),
+            ListServerCertsCommand cmd => await HandleListServerCerts(sp, cmd, user),
             QueryParkedMessagesCommand cmd => await HandleQueryParkedMessages(sp, cmd, user),
             RetryParkedMessageCommand cmd => await HandleRetryParkedMessage(sp, cmd, user),
             DiscardParkedMessageCommand cmd => await HandleDiscardParkedMessage(sp, cmd, user),
@@ -2955,6 +2963,39 @@ public class ManagementActor : ReceiveActor
         return await commService.VerifyEndpointAsync(site, cmd);
     }
 
+    // Server-certificate trust (arch-review C4). Admin-gated at the role check
+    // above. These mutate the site's trusted-peer PKI store — the handler only
+    // relays; the site-side broadcast/reconcile across both nodes is owned by
+    // the site CertStoreActor (plan 03). SiteIdentifier is REQUIRED so the actor
+    // knows which site to route to.
+
+    private static async Task<object?> HandleTrustServerCert(IServiceProvider sp, TrustServerCertCommand cmd, AuthenticatedUser user)
+    {
+        var site = cmd.SiteIdentifier
+            ?? throw new ManagementCommandException("SiteIdentifier is required when trusting a server certificate via the management API.");
+        await EnforceSiteScopeForIdentifier(sp, user, site);
+        var commService = sp.GetRequiredService<CommunicationService>();
+        return await commService.TrustServerCertAsync(site, cmd);
+    }
+
+    private static async Task<object?> HandleRemoveServerCert(IServiceProvider sp, RemoveServerCertCommand cmd, AuthenticatedUser user)
+    {
+        var site = cmd.SiteIdentifier
+            ?? throw new ManagementCommandException("SiteIdentifier is required when removing a server certificate via the management API.");
+        await EnforceSiteScopeForIdentifier(sp, user, site);
+        var commService = sp.GetRequiredService<CommunicationService>();
+        return await commService.RemoveServerCertAsync(site, cmd);
+    }
+
+    private static async Task<object?> HandleListServerCerts(IServiceProvider sp, ListServerCertsCommand cmd, AuthenticatedUser user)
+    {
+        var site = cmd.SiteIdentifier
+            ?? throw new ManagementCommandException("SiteIdentifier is required when listing server certificates via the management API.");
+        await EnforceSiteScopeForIdentifier(sp, user, site);
+        var commService = sp.GetRequiredService<CommunicationService>();
+        return await commService.ListServerCertsAsync(site, cmd);
+    }
+
     private static async Task<object?> HandleQueryParkedMessages(IServiceProvider sp, QueryParkedMessagesCommand cmd, AuthenticatedUser user)
     {
         await EnforceSiteScopeForIdentifier(sp, user, cmd.SiteIdentifier);
diff --git a/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs b/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
index 888c80bc..7c29dd2e 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
@@ -3250,6 +3250,84 @@ public class ManagementActorTests : TestKit, IDisposable
         ExpectMsg<ManagementUnauthorized>(TimeSpan.FromSeconds(5));
     }
 
+    // ========================================================================
+    // Admin-gated actor dispatch for the site cert-trust commands
+    // (arch-review C4): TrustServerCert / RemoveServerCert / ListServerCerts.
+    // These mutate the site's trusted-peer PKI store, so they are gated
+    // Administrator — matching the Admin-gated cert-management UI. SiteIdentifier
+    // is REQUIRED; the handler only relays (site-side reconcile is CertStoreActor).
+    // ========================================================================
+
+    [Fact]
+    public void TrustServerCert_DesignerOnly_Unauthorized()
+    {
+        var actor = CreateActor();
+        actor.Tell(Envelope(new TrustServerCertCommand("conn", "ZGVy", "AB12", "SITE1"), "Designer"));
+        ExpectMsg<ManagementUnauthorized>(TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void TrustServerCert_WithoutSiteIdentifier_ReturnsError()
+    {
+        var actor = CreateActor();
+        actor.Tell(Envelope(new TrustServerCertCommand("conn", "ZGVy", "AB12"), "Administrator"));
+        var resp = ExpectMsg<ManagementError>(TimeSpan.FromSeconds(5));
+        Assert.Contains("SiteIdentifier", resp.Error);
+    }
+
+    [Fact]
+    public void TrustServerCert_Admin_RelaysToSite()
+    {
+        var stub = new StubCommunicationService();
+        _services.AddSingleton<CommunicationService>(stub);
+        var actor = CreateActor();
+        actor.Tell(Envelope(new TrustServerCertCommand("conn", "ZGVy", "AB12", "SITE1"), "Administrator"));
+        ExpectMsg<ManagementSuccess>(TimeSpan.FromSeconds(5));
+        Assert.Equal(1, stub.TrustCount);
+        Assert.Equal("SITE1", stub.LastTrustSite);
+    }
+
+    [Fact]
+    public void RemoveServerCert_Admin_RelaysToSite()
+    {
+        var stub = new StubCommunicationService();
+        _services.AddSingleton<CommunicationService>(stub);
+        var actor = CreateActor();
+        actor.Tell(Envelope(new RemoveServerCertCommand("AB12", "SITE1"), "Administrator"));
+        ExpectMsg<ManagementSuccess>(TimeSpan.FromSeconds(5));
+        Assert.Equal(1, stub.RemoveCount);
+        Assert.Equal("SITE1", stub.LastRemoveSite);
+    }
+
+    [Fact]
+    public void RemoveServerCert_WithoutSiteIdentifier_ReturnsError()
+    {
+        var actor = CreateActor();
+        actor.Tell(Envelope(new RemoveServerCertCommand("AB12"), "Administrator"));
+        var resp = ExpectMsg<ManagementError>(TimeSpan.FromSeconds(5));
+        Assert.Contains("SiteIdentifier", resp.Error);
+    }
+
+    [Fact]
+    public void ListServerCerts_Admin_RelaysToSite()
+    {
+        var stub = new StubCommunicationService();
+        _services.AddSingleton<CommunicationService>(stub);
+        var actor = CreateActor();
+        actor.Tell(Envelope(new ListServerCertsCommand("SITE1"), "Administrator"));
+        ExpectMsg<ManagementSuccess>(TimeSpan.FromSeconds(5));
+        Assert.Equal(1, stub.ListCertsCount);
+        Assert.Equal("SITE1", stub.LastListCertsSite);
+    }
+
+    [Fact]
+    public void ListServerCerts_DesignerOnly_Unauthorized()
+    {
+        var actor = CreateActor();
+        actor.Tell(Envelope(new ListServerCertsCommand("SITE1"), "Designer"));
+        ExpectMsg<ManagementUnauthorized>(TimeSpan.FromSeconds(5));
+    }
+
     /// <summary>
     /// Records remote-query relays for the actor-dispatch tests. The browse /
     /// search / verify / cert-trust methods on <see cref="CommunicationService"/>
@@ -3268,6 +3346,36 @@ public class ManagementActorTests : TestKit, IDisposable
         public string? LastSearchSite { get; private set; }
         public int VerifyCount { get; private set; }
         public string? LastVerifySite { get; private set; }
+        public int TrustCount { get; private set; }
+        public string? LastTrustSite { get; private set; }
+        public int RemoveCount { get; private set; }
+        public string? LastRemoveSite { get; private set; }
+        public int ListCertsCount { get; private set; }
+        public string? LastListCertsSite { get; private set; }
+
+        public override Task<CertTrustResult> TrustServerCertAsync(
+            string siteId, TrustServerCertCommand command, CancellationToken ct = default)
+        {
+            TrustCount++;
+            LastTrustSite = siteId;
+            return Task.FromResult(new CertTrustResult(true, null, null));
+        }
+
+        public override Task<CertTrustResult> RemoveServerCertAsync(
+            string siteId, RemoveServerCertCommand command, CancellationToken ct = default)
+        {
+            RemoveCount++;
+            LastRemoveSite = siteId;
+            return Task.FromResult(new CertTrustResult(true, null, null));
+        }
+
+        public override Task<CertTrustResult> ListServerCertsAsync(
+            string siteId, ListServerCertsCommand command, CancellationToken ct = default)
+        {
+            ListCertsCount++;
+            LastListCertsSite = siteId;
+            return Task.FromResult(new CertTrustResult(true, null, null));
+        }
 
         public override Task<BrowseNodeResult> BrowseNodeAsync(
             string siteId, BrowseNodeCommand command, CancellationToken ct = default)