diff --git a/src/microsoft/opentelemetry/a365/hosting/scope_helpers/utils.py b/src/microsoft/opentelemetry/a365/hosting/scope_helpers/utils.py
index a02da39d..9476f5ed 100644
--- a/src/microsoft/opentelemetry/a365/hosting/scope_helpers/utils.py
+++ b/src/microsoft/opentelemetry/a365/hosting/scope_helpers/utils.py
@@ -37,7 +37,7 @@ def get_caller_pairs(activity: Activity) -> Iterator[tuple[str, Any]]:
     frm = activity.from_property
     if not frm:
         return
-    yield USER_ID_KEY, frm.aad_object_id
+    yield USER_ID_KEY, frm.aad_object_id or frm.agentic_user_id or frm.id
     yield USER_NAME_KEY, frm.name
     yield USER_EMAIL_KEY, frm.agentic_user_id
 
diff --git a/tests/a365/hosting/scope_helpers/test_scope_helper_utils.py b/tests/a365/hosting/scope_helpers/test_scope_helper_utils.py
index 8d0ee845..07f5a63f 100644
--- a/tests/a365/hosting/scope_helpers/test_scope_helper_utils.py
+++ b/tests/a365/hosting/scope_helpers/test_scope_helper_utils.py
@@ -83,6 +83,64 @@ def test_get_channel_pairs():
     assert (CHANNEL_LINK_KEY, None) in result
 
 
+def test_get_caller_pairs_fallback_to_frm_id():
+    """Test get_caller_pairs falls back to frm.id when aad_object_id is None (non-Teams channel)."""
+    from_account = ChannelAccount(
+        id="slack-user-123",
+        name="Slack User",
+        agentic_user_id=None,
+        aad_object_id=None,
+    )
+    activity = Activity(type="message", from_property=from_account)
+
+    result = list(get_caller_pairs(activity))
+
+    assert (USER_ID_KEY, "slack-user-123") in result
+
+
+def test_get_caller_pairs_fallback_to_agentic_user_id():
+    """Test get_caller_pairs falls back to agentic_user_id for A2A when aad_object_id is None."""
+    from_account = ChannelAccount(
+        id="raw-id",
+        name="Agent Caller",
+        agentic_user_id="agent-auid-456",
+        aad_object_id=None,
+    )
+    activity = Activity(type="message", from_property=from_account)
+
+    result = list(get_caller_pairs(activity))
+
+    assert (USER_ID_KEY, "agent-auid-456") in result
+
+
+def test_get_caller_pairs_aad_object_id_takes_precedence():
+    """Test get_caller_pairs uses aad_object_id when all identifiers are set."""
+    from_account = ChannelAccount(
+        id="raw-id",
+        name="Teams User",
+        agentic_user_id="agent-auid",
+        aad_object_id="aad-wins",
+    )
+    activity = Activity(type="message", from_property=from_account)
+
+    result = list(get_caller_pairs(activity))
+
+    assert (USER_ID_KEY, "aad-wins") in result
+
+
+def test_get_caller_pairs_a2a_guid_agentic_user_id():
+    """Test userId resolves to GUID AgenticUserId in A2A scenario."""
+    from_account = ChannelAccount(
+        id="29:1sH5NArUwkWAX",
+        name="Agent Caller",
+        agentic_user_id="bef730f4-d6f5-4ffb-b759-26ffa449ed7e",
+        aad_object_id=None,
+    )
+    activity = Activity(type="message", from_property=from_account)
+    result = list(get_caller_pairs(activity))
+    assert (USER_ID_KEY, "bef730f4-d6f5-4ffb-b759-26ffa449ed7e") in result
+
+
 def test_get_conversation_pairs():
     """Test get_conversation_pairs extracts conversation information."""
     conversation = ConversationAccount(id="conversation-123")