fix(slack): route bot mentions from legacy attachments

plugins/platforms/slack/adapter.py

@@ -389,18 +389,67 @@ def _walk(node, in_quote: bool) -> None:
     return mentions
 
 
-def _slack_mention_detection_text(event: dict) -> str:
+_SLACK_USER_MENTION_TOKEN_RE = re.compile(
+    r"<@[A-Za-z0-9_-]+(?:\|[^>\n]*)?>"
+)
+
+
+def _collect_slack_attachment_mentions(attachments: list) -> list:
+    """Return explicit user mentions authored in legacy attachment content.
+
+    Third-party Slack apps such as Datadog and PagerDuty commonly put their
+    entire notification in ``attachments`` while leaving top-level ``text``
+    empty. Only inspect authored text/fields and nested blocks here; omit
+    ``fallback`` and link-unfurl metadata so a human-shared preview cannot
+    manufacture a routing mention.
+    """
+    mentions: list[str] = []
+
+    def _append_text(value: Any) -> None:
+        if not isinstance(value, str):
+            return
+        for match in _SLACK_USER_MENTION_TOKEN_RE.findall(value):
+            if match not in mentions:
+                mentions.append(match)
+
+    for attachment in attachments or []:
+        if not isinstance(attachment, dict) or attachment.get("is_msg_unfurl"):
+            continue
+        for key in ("pretext", "title", "text"):
+            _append_text(attachment.get(key))
+        for field in attachment.get("fields") or []:
+            if not isinstance(field, dict):
+                continue
+            _append_text(field.get("title"))
+            _append_text(field.get("value"))
+        nested_blocks = attachment.get("blocks")
+        if nested_blocks:
+            for mention in _collect_slack_block_mentions(nested_blocks):
+                if mention not in mentions:
+                    mentions.append(mention)
+    return mentions
+
+
+def _slack_mention_detection_text(
+    event: dict, *, include_attachments: bool = False
+) -> str:
     """Return the text used for @mention detection on a Slack message event.
 
     Combines the flat top-level ``text`` with any ``<@UID>`` mentions recovered
     from non-quoted Block Kit blocks (#52387), so a genuine Block-Kit-only
     mention reaches the gates while quoted/forwarded mentions stay ignored.
+    Legacy attachment mentions are opt-in because they are safe routing input
+    only after the sender has independently been identified as a bot/app.
     """
     flat = event.get("text", "") or ""
     blocks = event.get("blocks")
-    if not blocks:
-        return flat
-    mentions = _collect_slack_block_mentions(blocks)
+    mentions = _collect_slack_block_mentions(blocks) if blocks else []
+    if include_attachments:
+        for mention in _collect_slack_attachment_mentions(
+            event.get("attachments") or []
+        ):
+            if mention not in mentions:
+                mentions.append(mention)
     extra = [m for m in mentions if m not in flat]
     if not extra:
         return flat
@@ -5847,12 +5896,16 @@ async def _handle_slack_message(
             if allow_bots == "none":
                 return
             elif allow_bots == "mentions":
-                # Include Block-Kit-only mentions, not just the flat text (#52387)
-                text_check = _slack_mention_detection_text(event)
+                # Bot apps often author the entire notification inside legacy
+                # attachments. The sender is already independently classified
+                # as a bot here, so those explicit mentions are safe to route.
+                text_check = _slack_mention_detection_text(
+                    event, include_attachments=True
+                )
                 if self._bot_user_id and f"<@{self._bot_user_id}>" not in text_check:
                     logger.debug(
                         "[Slack] Dropping bot message under allow_bots=mentions: "
-                        "no <@%s> mention in flat text or blocks",
+                        "no <@%s> mention in flat text, blocks, or attachments",
                         self._bot_user_id,
                     )
                     return
@@ -6121,8 +6174,15 @@ async def _handle_slack_message(
         #   3. The message is in a thread where the bot was previously @mentioned, OR
         #   4. There's an existing session for this thread (survives restarts)
         bot_uid = self._team_bot_user_ids.get(team_id, self._bot_user_id)
-        # Detect mentions authored only inside Block Kit blocks too (#52387)
-        routing_text = _slack_mention_detection_text(event) or original_text or ""
+        # Attachment mentions count only after bot/app authorship has been
+        # established; human-authored unfurls remain inert routing context.
+        routing_text = (
+            _slack_mention_detection_text(
+                event, include_attachments=sender_is_bot
+            )
+            or original_text
+            or ""
+        )
         is_mentioned = bool(
             (bot_uid and f"<@{bot_uid}>" in routing_text)
             or self._slack_message_matches_mention_patterns(routing_text)

tests/gateway/test_slack.py

@@ -1931,6 +1931,55 @@ async def test_allow_bots_mentions_ignores_bot_user_without_current_mention(
 
         adapter.handle_message.assert_not_called()
 
+    @pytest.mark.asyncio
+    async def test_allow_bots_mentions_accepts_bot_attachment_mention(self, adapter):
+        """Datadog-style attachment-only alerts can explicitly summon the bot."""
+        adapter.config.extra["allow_bots"] = "mentions"
+        event = {
+            "text": "",
+            "user": "U_DATADOG_BOT",
+            "bot_id": "B_DATADOG",
+            "app_id": "A_DATADOG",
+            "subtype": "bot_message",
+            "channel": "C123",
+            "channel_type": "channel",
+            "ts": "1234567890.000001",
+            "attachments": [
+                {
+                    "title": "Triggered: API failures",
+                    "title_link": "https://app.datadoghq.com/monitors/123",
+                    "text": "Service is failing. <@U_BOT>",
+                }
+            ],
+        }
+
+        await adapter._handle_slack_message(event)
+
+        adapter.handle_message.assert_awaited_once()
+        msg_event = adapter.handle_message.await_args.args[0]
+        assert "Triggered: API failures" in msg_event.text
+        assert "Service is failing" in msg_event.text
+
+    @pytest.mark.asyncio
+    async def test_human_attachment_mention_does_not_route(self, adapter):
+        """Human attachments remain inert even if their text has a mention."""
+        event = {
+            "text": "please review",
+            "user": "U_USER",
+            "channel": "C123",
+            "channel_type": "channel",
+            "ts": "1234567890.000001",
+            "attachments": [
+                {
+                    "text": "Copied alert text <@U_BOT>",
+                }
+            ],
+        }
+
+        await adapter._handle_slack_message(event)
+
+        adapter.handle_message.assert_not_called()
+
 
     @pytest.mark.asyncio
     async def test_message_edit_with_new_mention_processed(self, adapter):

tests/gateway/test_slack_mention.py

@@ -616,3 +616,39 @@ def test_mention_detection_text_ignores_quoted_blockkit_mention():
         ],
     }
     assert f"<@{BOT_USER_ID}>" not in _slack_mention_detection_text(event)
+
+
+def test_mention_detection_text_requires_opt_in_for_legacy_attachments():
+    """Attachment mentions are routing input only for verified bot senders."""
+    event = {
+        "text": "",
+        "attachments": [
+            {
+                "title": "Triggered: API failures",
+                "text": f"Investigate this alert <@{BOT_USER_ID}>",
+            }
+        ],
+    }
+
+    assert f"<@{BOT_USER_ID}>" not in _slack_mention_detection_text(event)
+    assert f"<@{BOT_USER_ID}>" in _slack_mention_detection_text(
+        event, include_attachments=True
+    )
+
+
+def test_mention_detection_text_ignores_unfurl_attachment_mentions():
+    """A link preview cannot manufacture an attachment routing mention."""
+    event = {
+        "text": "please review",
+        "attachments": [
+            {
+                "is_msg_unfurl": True,
+                "fallback": f"quoted <@{BOT_USER_ID}>",
+                "text": f"quoted <@{BOT_USER_ID}>",
+            }
+        ],
+    }
+
+    assert f"<@{BOT_USER_ID}>" not in _slack_mention_detection_text(
+        event, include_attachments=True
+    )