fix(slack): skip @ inside email localparts when wrapping mentions

src/chat_sdk/adapters/slack/adapter.py

@@ -1651,7 +1651,7 @@ async def _resolve_outgoing_mentions(self, text: str, thread_id: str) -> str:
             return text
         state = self._chat.get_state()
 
-        mention_pattern = re.compile(r"@(\w+)")
+        mention_pattern = re.compile(r"(?<![\w<])@(\w+)")
         mentions: dict[str, list[str]] = {}
 
         for match in mention_pattern.finditer(text):

src/chat_sdk/adapters/slack/format_converter.py

@@ -200,7 +200,7 @@ def flush_text() -> None:
 
     def _convert_mentions_to_slack(self, text: str) -> str:
         """Convert @mentions to Slack format: @name -> <@name>."""
-        return re.sub(r"(?<!<)@(\w+)", r"<@\1>", text)
+        return re.sub(r"(?<![\w<])@(\w+)", r"<@\1>", text)
 
     def _node_to_mrkdwn(self, node: Content) -> str:
         """Convert a single AST node to Slack mrkdwn."""
@@ -215,7 +215,7 @@ def _node_to_mrkdwn(self, node: Content) -> str:
 
         if node_type == "text":
             value = node.get("value", "")
-            return re.sub(r"(?<!<)@(\w+)", r"<@\1>", value)
+            return re.sub(r"(?<![\w<])@(\w+)", r"<@\1>", value)
 
         if node_type == "strong":
             content = "".join(self._node_to_mrkdwn(c) for c in children)

tests/test_slack_format.py

@@ -199,6 +199,23 @@ def test_from_markdown_no_double_wrap(self):
         result = self.converter.from_markdown("Hey <@U12345>")
         assert result == "Hey <@U12345>"
 
+    def test_does_not_wrap_at_in_email_localpart(self):
+        """`@` preceded by a word char is part of an email address, not a mention.
+
+        Without the lookbehind tightening, `alice@example.com` was rewritten to
+        `alice<@example>.com`, surfacing a broken-looking mention in messages
+        that quote email addresses from upstream APIs.
+        """
+        result = self.converter.render_postable("Contact alice@example.com or bob@example.org")
+        assert "<@example>" not in result
+        assert "alice@example.com" in result
+        assert "bob@example.org" in result
+
+    def test_does_not_wrap_at_in_email_localpart_from_markdown_ast(self):
+        result = self.converter.render_postable({"markdown": "Contact alice@example.com"})
+        assert "<@example>" not in result
+        assert "alice@example.com" in result
+
 
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