diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..fbad0b2
Binary files /dev/null and b/.DS_Store differ
diff --git a/src/.DS_Store b/src/.DS_Store
new file mode 100644
index 0000000..fe2507d
Binary files /dev/null and b/src/.DS_Store differ
diff --git a/src/chat_sdk/.DS_Store b/src/chat_sdk/.DS_Store
new file mode 100644
index 0000000..e7b9aa5
Binary files /dev/null and b/src/chat_sdk/.DS_Store differ
diff --git a/src/chat_sdk/adapters/slack/adapter.py b/src/chat_sdk/adapters/slack/adapter.py
index d1168ee..8358a98 100644
--- a/src/chat_sdk/adapters/slack/adapter.py
+++ b/src/chat_sdk/adapters/slack/adapter.py
@@ -1605,10 +1605,15 @@ def _handle_block_actions(self, payload: dict[str, Any], options: WebhookOptions
 
         channel = (payload.get("channel") or {}).get("id") or (payload.get("container") or {}).get("channel_id")
         message_ts = (payload.get("message") or {}).get("ts") or (payload.get("container") or {}).get("message_ts")
+        # DMs have no threads: a button click on a top-level DM message must not
+        # thread the response. Mirror _handle_message_event's DM handling — keep a
+        # real in-DM thread_ts, but never fall back to the clicked message's own
+        # ts, which would spawn a phantom "1 reply" thread in the DM.
+        is_dm = bool(channel) and channel.startswith("D")
         thread_ts = (
             (payload.get("message") or {}).get("thread_ts")
             or (payload.get("container") or {}).get("thread_ts")
-            or message_ts
+            or ("" if is_dm else message_ts)
         )
 
         is_view_action = (payload.get("container") or {}).get("type") == "view"
@@ -1619,7 +1624,7 @@ def _handle_block_actions(self, payload: dict[str, Any], options: WebhookOptions
 
         thread_id = ""
         if channel and (thread_ts or message_ts):
-            thread_id = self.encode_thread_id(SlackThreadId(channel=channel, thread_ts=thread_ts or message_ts or ""))
+            thread_id = self.encode_thread_id(SlackThreadId(channel=channel, thread_ts=thread_ts))
 
         is_ephemeral = (payload.get("container") or {}).get("is_ephemeral") is True
         response_url = payload.get("response_url")
diff --git a/tests/test_slack_webhook.py b/tests/test_slack_webhook.py
index 2638789..07fc2b6 100644
--- a/tests/test_slack_webhook.py
+++ b/tests/test_slack_webhook.py
@@ -337,6 +337,42 @@ async def test_handles_block_actions(self):
         response = await adapter.handle_webhook(req)
         assert response["status"] == 200
 
+    @pytest.mark.asyncio
+    async def test_dm_block_action_does_not_thread(self):
+        """A click on a top-level DM message must resolve to a DM-root thread_id.
+
+        Regression: _handle_block_actions fell back to message_ts for thread_ts
+        in DMs, so HITL approval result cards posted via event.thread.post became
+        phantom "1 reply" threads in the DM. DMs have no threads — the ActionEvent
+        must carry an empty thread_ts, mirroring _handle_message_event.
+        """
+        adapter = _make_adapter()
+        chat = _make_mock_chat(_make_mock_state())
+        await adapter.initialize(chat)
+
+        req = self._make_interactive_req(
+            {
+                "type": "block_actions",
+                "user": {"id": "U123", "username": "testuser", "name": "Test User"},
+                "container": {"type": "message", "message_ts": "1234567890.123456", "channel_id": "D456"},
+                "channel": {"id": "D456", "name": "directmessage"},
+                "message": {"ts": "1234567890.123456"},  # top-level DM message: no thread_ts
+                "actions": [{"type": "button", "action_id": "approve_btn", "value": "approved"}],
+            }
+        )
+        response = await adapter.handle_webhook(req)
+        assert response["status"] == 200
+
+        chat.process_action.assert_called_once()
+        action_event = chat.process_action.call_args[0][0]
+        decoded = adapter.decode_thread_id(action_event.thread_id)
+        assert decoded.channel == "D456"
+        assert decoded.thread_ts == "", (
+            f"DM block action threaded under {decoded.thread_ts!r}; a top-level DM click "
+            "must resolve to a DM-root thread_id (empty thread_ts), else the approval "
+            "result card posts as a phantom reply thread."
+        )
+
     @pytest.mark.asyncio
     async def test_returns_400_for_missing_payload(self):
         adapter = _make_adapter()