diff --git a/tests/gateway/test_notice_rendering.py b/tests/gateway/test_notice_rendering.py
index 89a5435a507..3ba731f32e4 100644
--- a/tests/gateway/test_notice_rendering.py
+++ b/tests/gateway/test_notice_rendering.py
@@ -107,6 +107,10 @@ def _make_source(platform_value="telegram", chat_id="555", user_id="u1"):
     src.platform = plat
     src.chat_id = chat_id
     src.user_id = user_id
+    # Real SessionSource.profile is None (single-profile) or a str; a MagicMock
+    # auto-attribute would read as a truthy "stamped profile" and trip the
+    # fail-closed path in _adapter_for_source (see AGENTS.md pitfall #17).
+    src.profile = None
     return src
 
 
diff --git a/tests/gateway/test_queue_consumption.py b/tests/gateway/test_queue_consumption.py
index ec1b0dedc83..857da98da71 100644
--- a/tests/gateway/test_queue_consumption.py
+++ b/tests/gateway/test_queue_consumption.py
@@ -382,7 +382,9 @@ class TestBusyInputModeQueueFifo:
         return runner, adapter
 
     def _text_event(self, text: str) -> MessageEvent:
-        source = MagicMock(chat_id="c1", platform=Platform.TELEGRAM)
+        # profile=None: a MagicMock auto-attribute reads as a truthy stamped
+        # profile and trips fail-closed adapter resolution (AGENTS.md #17).
+        source = MagicMock(chat_id="c1", platform=Platform.TELEGRAM, profile=None)
         return MessageEvent(
             text=text,
             message_type=MessageType.TEXT,
@@ -433,7 +435,7 @@ class TestBusyInputModeQueueFifo:
         runner, adapter = self._make_runner_and_adapter()
         session_key = "telegram:user:burst"
 
-        source = MagicMock(chat_id="c1", platform=Platform.TELEGRAM)
+        source = MagicMock(chat_id="c1", platform=Platform.TELEGRAM, profile=None)
         for i in range(3):
             runner._queue_or_replace_pending_event(
                 session_key,