diff --git a/gateway/run.py b/gateway/run.py
index f9bf9a38b9..327f8ae32a 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -485,17 +485,21 @@ def _resolve_hermes_bin() -> Optional[list[str]]:
 def _parse_session_key(session_key: str) -> "dict | None":
     """Parse a session key into its component parts.
 
-    Session keys follow the format ``agent:main:{platform}:{chat_type}:{chat_id}``.
-    Returns a dict with ``platform``, ``chat_type``, and ``chat_id`` keys,
-    or None if the key doesn't match the expected format.
+    Session keys follow the format
+    ``agent:main:{platform}:{chat_type}:{chat_id}[:{thread_id}[:{user_id}]]``.
+    Returns a dict with ``platform``, ``chat_type``, ``chat_id``, and
+    optionally ``thread_id`` keys, or None if the key doesn't match.
     """
     parts = session_key.split(":")
     if len(parts) >= 5 and parts[0] == "agent" and parts[1] == "main":
-        return {
+        result = {
             "platform": parts[2],
             "chat_type": parts[3],
             "chat_id": parts[4],
         }
+        if len(parts) > 5:
+            result["thread_id"] = parts[5]
+        return result
     return None
 
 
@@ -1526,7 +1530,7 @@ class GatewayRunner:
 
                 # Include thread_id if present so the message lands in the
                 # correct forum topic / thread.
-                thread_id = parts[5] if len(parts) > 5 else None
+                thread_id = _parsed.get("thread_id")
                 metadata = {"thread_id": thread_id} if thread_id else None
 
                 await adapter.send(chat_id, msg, metadata=metadata)
diff --git a/tests/gateway/test_background_process_notifications.py b/tests/gateway/test_background_process_notifications.py
index 68eb5e3043..eabf92be63 100644
--- a/tests/gateway/test_background_process_notifications.py
+++ b/tests/gateway/test_background_process_notifications.py
@@ -383,9 +383,15 @@ def test_parse_session_key_valid():
 
 
 def test_parse_session_key_with_extra_parts():
-    """Extra trailing parts (thread_id etc.) are ignored — only first 5 matter."""
+    """Thread ID (6th part) is extracted; further parts are ignored."""
     result = _parse_session_key("agent:main:discord:group:chan123:thread456")
-    assert result == {"platform": "discord", "chat_type": "group", "chat_id": "chan123"}
+    assert result == {"platform": "discord", "chat_type": "group", "chat_id": "chan123", "thread_id": "thread456"}
+
+
+def test_parse_session_key_with_user_id_part():
+    """7th part (user_id) is ignored — only up to thread_id is extracted."""
+    result = _parse_session_key("agent:main:telegram:group:chat1:thread42:user99")
+    assert result == {"platform": "telegram", "chat_type": "group", "chat_id": "chat1", "thread_id": "thread42"}
 
 
 def test_parse_session_key_too_short():