diff --git a/internal/agent/loop_pipeline_callbacks.go b/internal/agent/loop_pipeline_callbacks.go
index e2789528..017ec498 100644
--- a/internal/agent/loop_pipeline_callbacks.go
+++ b/internal/agent/loop_pipeline_callbacks.go
@@ -28,6 +28,7 @@ func (l *Loop) pipelineCallbacks(req *RunRequest, bridgeRS *runState) pipelineCa
 		event.TeamID = req.TeamID
 		event.TeamTaskID = req.TeamTaskID
 		event.ParentAgentID = req.ParentAgentID
+		event.SenderID = req.SenderID
 		event.UserID = req.UserID
 		event.Channel = req.Channel
 		event.ChatID = req.ChatID
diff --git a/internal/agent/loop_pipeline_tool_callbacks.go b/internal/agent/loop_pipeline_tool_callbacks.go
index f0f85668..51d49638 100644
--- a/internal/agent/loop_pipeline_tool_callbacks.go
+++ b/internal/agent/loop_pipeline_tool_callbacks.go
@@ -222,6 +222,7 @@ func makeToolEmitRun(l *Loop, req *RunRequest) func(AgentEvent) {
 	return func(event AgentEvent) {
 		event.RunKind = req.RunKind
 		event.SessionKey = req.SessionKey
+		event.SenderID = req.SenderID
 		event.UserID = req.UserID
 		event.Channel = req.Channel
 		l.emit(event)
diff --git a/internal/agent/loop_pipeline_tool_callbacks_test.go b/internal/agent/loop_pipeline_tool_callbacks_test.go
index 866806c5..e1df4dd9 100644
--- a/internal/agent/loop_pipeline_tool_callbacks_test.go
+++ b/internal/agent/loop_pipeline_tool_callbacks_test.go
@@ -71,6 +71,7 @@ func TestMakeExecuteToolCall_EmitsToolCallEvent(t *testing.T) {
 		RunID:      "run-1",
 		SessionKey: "sess-A",
 		UserID:     "u-1",
+		SenderID:   "sender-1",
 		Channel:    "ws",
 		RunKind:    "",
 	}
@@ -102,6 +103,7 @@ func TestMakeExecuteToolRaw_EmitsToolCallEvent(t *testing.T) {
 		RunID:      "run-2",
 		SessionKey: "sess-B",
 		UserID:     "u-2",
+		SenderID:   "sender-2",
 		Channel:    "ws",
 		RunKind:    "",
 	}
@@ -133,7 +135,7 @@ func TestMakeExecuteToolRaw_ConcurrentCallsEmitAllEvents(t *testing.T) {
 	col := &eventCollector{}
 	l := newTestLoopForToolCallbacks(col.onEvent)
 
-	req := &RunRequest{RunID: "run-3", SessionKey: "sess-C", UserID: "u-3", Channel: "ws"}
+	req := &RunRequest{RunID: "run-3", SessionKey: "sess-C", UserID: "u-3", SenderID: "sender-3", Channel: "ws"}
 	exec := l.makeExecuteToolRaw(req)
 
 	const n = 5
@@ -175,6 +177,9 @@ func assertToolCallPayload(t *testing.T, ev AgentEvent, tc providers.ToolCall, r
 	if ev.UserID != req.UserID {
 		t.Errorf("UserID: got %q, want %q", ev.UserID, req.UserID)
 	}
+	if ev.SenderID != req.SenderID {
+		t.Errorf("SenderID: got %q, want %q", ev.SenderID, req.SenderID)
+	}
 	payload, ok := ev.Payload.(map[string]any)
 	if !ok {
 		t.Fatalf("Payload is not map[string]any: %T", ev.Payload)
diff --git a/internal/agent/loop_run.go b/internal/agent/loop_run.go
index 82be8488..6231a6dd 100644
--- a/internal/agent/loop_run.go
+++ b/internal/agent/loop_run.go
@@ -26,6 +26,7 @@ func (l *Loop) Run(ctx context.Context, req RunRequest) (*RunResult, error) {
 		event.TeamID = req.TeamID
 		event.TeamTaskID = req.TeamTaskID
 		event.ParentAgentID = req.ParentAgentID
+		event.SenderID = req.SenderID
 		event.UserID = req.UserID
 		event.Channel = req.Channel
 		event.ChatID = req.ChatID
diff --git a/internal/agent/loop_types.go b/internal/agent/loop_types.go
index 8dd106e8..a9e72e07 100644
--- a/internal/agent/loop_types.go
+++ b/internal/agent/loop_types.go
@@ -277,6 +277,7 @@ type AgentEvent struct {
 	ParentAgentID string `json:"parentAgentId,omitempty"`
 
 	// Routing context (helps WS clients filter by user/channel/session)
+	SenderID   string `json:"senderId,omitempty"` // original acting user; differs from UserID in group chats
 	UserID     string `json:"userId,omitempty"`
 	Channel    string `json:"channel,omitempty"`
 	ChatID     string `json:"chatId,omitempty"`