fix: suppress noisy hook lifecycle events

Stop forwarding hook lifecycle events when a project has no configured
.github/hooks/*.json commands so the UI only receives meaningful hook
activity. Also expose the configured-hook state on the bundle, cover the
suppression wiring with tests, and document the updated event semantics.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ARCHITECTURE.md

@@ -206,7 +206,7 @@ The protocol also carries **turn-scoped lifecycle events** alongside output delt
 
 - **Sub-agent events**: started, completed, failed, selected, deselected — surfaced when custom agents are defined
 - **Skill invocation events**: emitted when an agent-side skill is triggered
-- **Hook lifecycle events**: start and end of registered hooks, including Aryx-managed SDK hooks and project hook files discovered from `.github/hooks/*.json`
+- **Hook lifecycle events**: start and end of configured project hook commands discovered from `.github/hooks/*.json`; Aryx suppresses the SDK's built-in no-op hook chatter so the UI only sees meaningful hook activity
 - **Session compaction events**: start and complete, with token-reduction metrics when infinite sessions trigger context trimming
 - **Session usage events**: current token count and context-window limit for usage-bar rendering
 - **Pending-messages-modified events**: emitted when mid-turn steering changes the pending message queue

sidecar/src/Aryx.AgentHost/Services/CopilotAgentBundle.cs

@@ -13,13 +13,16 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
 {
     private readonly List<IAsyncDisposable> _disposables = [];
 
-    private CopilotAgentBundle(IReadOnlyList<AIAgent> agents)
+    internal CopilotAgentBundle(IReadOnlyList<AIAgent> agents, bool hasConfiguredHooks)
     {
         Agents = agents;
+        HasConfiguredHooks = hasConfiguredHooks;
     }
 
     public IReadOnlyList<AIAgent> Agents { get; }
 
+    public bool HasConfiguredHooks { get; }
+
     public static async Task<CopilotAgentBundle> CreateAsync(
         RunTurnCommandDto command,
         Func<PatternAgentDefinitionDto, PermissionRequest, PermissionInvocation, Task<PermissionRequestResult>> onPermissionRequest,
@@ -72,7 +75,7 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
             disposables.Add(agent);
         }
 
-        CopilotAgentBundle bundle = new(agents);
+        CopilotAgentBundle bundle = new(agents, hasConfiguredHooks: !configuredHooks.IsEmpty);
         bundle._disposables.AddRange(disposables);
         return bundle;
     }

sidecar/src/Aryx.AgentHost/Services/CopilotTurnExecutionState.cs

@@ -28,6 +28,8 @@ internal sealed class CopilotTurnExecutionState
 
     public bool HasPendingExitPlanModeRequest { get; private set; }
 
+    public bool SuppressHookLifecycleEvents { get; set; }
+
     public async Task EmitThinkingIfNeeded(
         AgentIdentity agent,
         Func<SidecarEventDto, Task> onEvent)
@@ -113,11 +115,17 @@ internal sealed class CopilotTurnExecutionState
                 break;
             case HookStartEvent hookStart:
                 ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateHookLifecycleEvent(agent, "start", hookStart.Data));
+                if (!SuppressHookLifecycleEvents)
+                {
+                    _pendingEvents.Enqueue(CreateHookLifecycleEvent(agent, "start", hookStart.Data));
+                }
                 break;
             case HookEndEvent hookEnd:
                 ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateHookLifecycleEvent(agent, "end", hookEnd.Data));
+                if (!SuppressHookLifecycleEvents)
+                {
+                    _pendingEvents.Enqueue(CreateHookLifecycleEvent(agent, "end", hookEnd.Data));
+                }
                 break;
             case SessionUsageInfoEvent usageInfo:
                 ActiveAgent = agent;

sidecar/src/Aryx.AgentHost/Services/CopilotWorkflowRunner.cs

@@ -75,6 +75,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
                     }
                 },
                 runCancellation.Token);
+            ConfigureHookLifecycleEventSuppression(state, bundle);
             Workflow workflow = bundle.BuildWorkflow(command.Pattern);
             List<ChatMessage> inputMessages = command.Messages.Select(WorkflowTranscriptProjector.ToChatMessage).ToList();
             WorkflowTranscriptProjector.AttachMessageMode(inputMessages, command.MessageMode);
@@ -118,6 +119,16 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
         }
     }
 
+    internal static void ConfigureHookLifecycleEventSuppression(
+        CopilotTurnExecutionState state,
+        CopilotAgentBundle bundle)
+    {
+        ArgumentNullException.ThrowIfNull(state);
+        ArgumentNullException.ThrowIfNull(bundle);
+
+        state.SuppressHookLifecycleEvents = !bundle.HasConfiguredHooks;
+    }
+
     private static async Task EmitPendingEventsAsync(
         CopilotTurnExecutionState state,
         Func<SidecarEventDto, Task> onEvent)

sidecar/tests/Aryx.AgentHost.Tests/CopilotAgentBundleTests.cs

@@ -53,6 +53,15 @@ public sealed class CopilotAgentBundleTests
         Assert.Equal(["glob", "view"], sessionConfig.AvailableTools);
     }
 
+    [Fact]
+    public void Constructor_StoresWhetherHooksAreConfigured()
+    {
+        CopilotAgentBundle bundle = new([], hasConfiguredHooks: true);
+
+        Assert.True(bundle.HasConfiguredHooks);
+        Assert.Empty(bundle.Agents);
+    }
+
     [Fact]
     public async Task CreateConfiguredSessionConfig_MergesInstructionsAndConvertsHandoffDeclarations()
     {

sidecar/tests/Aryx.AgentHost.Tests/CopilotTurnExecutionStateTests.cs

@@ -212,23 +212,7 @@ public sealed class CopilotTurnExecutionStateTests
         RunTurnCommandDto command = CreateCommand();
         CopilotTurnExecutionState state = new(command);
 
-        state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
-            SessionEvent.FromJson(
-                """
-                {
-                  "type": "hook.start",
-                  "data": {
-                    "hookInvocationId": "hook-1",
-                    "hookType": "postToolUse",
-                    "input": {
-                      "toolName": "view"
-                    }
-                  },
-                  "id": "66666666-6666-6666-6666-666666666666",
-                  "timestamp": "2026-03-27T00:00:00Z"
-                }
-                """));
+        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookStartEvent());
 
         HookLifecycleEventDto evt = Assert.Single(state.DrainPendingEvents().OfType<HookLifecycleEventDto>());
         Assert.Equal("start", evt.Phase);
@@ -237,6 +221,36 @@ public sealed class CopilotTurnExecutionStateTests
         Assert.NotNull(evt.Input);
     }
 
+    [Fact]
+    public void ObserveSessionEvent_HookEnd_QueuesHookLifecycleEvent()
+    {
+        RunTurnCommandDto command = CreateCommand();
+        CopilotTurnExecutionState state = new(command);
+
+        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookEndEvent());
+
+        HookLifecycleEventDto evt = Assert.Single(state.DrainPendingEvents().OfType<HookLifecycleEventDto>());
+        Assert.Equal("end", evt.Phase);
+        Assert.Equal("postToolUse", evt.HookType);
+        Assert.Equal("hook-1", evt.HookInvocationId);
+        Assert.True(evt.Success);
+    }
+
+    [Fact]
+    public void ObserveSessionEvent_HookLifecycleEvents_AreSuppressedWhenConfigured()
+    {
+        RunTurnCommandDto command = CreateCommand();
+        CopilotTurnExecutionState state = new(command)
+        {
+            SuppressHookLifecycleEvents = true,
+        };
+
+        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookStartEvent());
+        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookEndEvent());
+
+        Assert.Empty(state.DrainPendingEvents());
+    }
+
     [Fact]
     public void ObserveSessionEvent_SessionCompactionComplete_QueuesCompactionEvent()
     {
@@ -295,6 +309,45 @@ public sealed class CopilotTurnExecutionStateTests
         Assert.Equal("agent-1", evt.AgentId);
     }
 
+    private static SessionEvent CreateHookStartEvent()
+    {
+        return SessionEvent.FromJson(
+            """
+            {
+              "type": "hook.start",
+              "data": {
+                "hookInvocationId": "hook-1",
+                "hookType": "postToolUse",
+                "input": {
+                  "toolName": "view"
+                }
+              },
+              "id": "66666666-6666-6666-6666-666666666666",
+              "timestamp": "2026-03-27T00:00:00Z"
+            }
+            """);
+    }
+
+    private static SessionEvent CreateHookEndEvent()
+    {
+        return SessionEvent.FromJson(
+            """
+            {
+              "type": "hook.end",
+              "data": {
+                "hookInvocationId": "hook-1",
+                "hookType": "postToolUse",
+                "success": true,
+                "output": {
+                  "status": "ok"
+                }
+              },
+              "id": "99999999-9999-9999-9999-999999999999",
+              "timestamp": "2026-03-27T00:00:00Z"
+            }
+            """);
+    }
+
     private static RunTurnCommandDto CreateCommand()
     {
         return new RunTurnCommandDto

sidecar/tests/Aryx.AgentHost.Tests/CopilotWorkflowRunnerTests.cs

@@ -11,6 +11,18 @@ namespace Aryx.AgentHost.Tests;
 
 public sealed class CopilotWorkflowRunnerTests
 {
+    [Fact]
+    public void ConfigureHookLifecycleEventSuppression_SetsStateFromBundle()
+    {
+        RunTurnCommandDto command = CreateApprovalCommand();
+        CopilotTurnExecutionState state = new(command);
+        CopilotAgentBundle bundle = new(Array.Empty<AIAgent>(), hasConfiguredHooks: false);
+
+        CopilotWorkflowRunner.ConfigureHookLifecycleEventSuppression(state, bundle);
+
+        Assert.True(state.SuppressHookLifecycleEvents);
+    }
+
     [Fact]
     public void SelectNewOutputMessages_SkipsFullTranscriptPrefix()
     {