feat: make DM topic skill binding functional

- Add auto_skill field to MessageEvent for topic-skill bindings
- Gateway auto-loads the bound skill on new sessions via _load_skill_payload
- Skill content is injected into the first message (same as /skill commands)
- Subsequent messages in the session see it in conversation history
- Clean chat_topic (no [skill: ...] suffix) — skill flows via auto_skill field
- Add 3 tests for _build_message_event auto_skill behavior

gateway/platforms/base.py

@@ -296,6 +296,9 @@ class MessageEvent:
     reply_to_message_id: Optional[str] = None
     reply_to_text: Optional[str] = None  # Text of the replied-to message (for context injection)
     
+    # Auto-loaded skill for topic/channel bindings (e.g., Telegram DM Topics)
+    auto_skill: Optional[str] = None
+    
     # Timestamps
     timestamp: datetime = field(default_factory=datetime.now)
     

gateway/platforms/telegram.py

@@ -1791,19 +1791,17 @@ class TelegramAdapter(BasePlatformAdapter):
         elif chat.type == ChatType.CHANNEL:
             chat_type = "channel"
 
-        # Resolve DM topic name for chat_topic context injection
+        # Resolve DM topic name and skill binding
         thread_id_raw = message.message_thread_id
         thread_id_str = str(thread_id_raw) if thread_id_raw else None
         chat_topic = None
+        topic_skill = None
 
         if chat_type == "dm" and thread_id_str:
             topic_info = self._get_dm_topic_info(str(chat.id), thread_id_str)
             if topic_info:
                 chat_topic = topic_info.get("name")
-                # If topic has a skill, inject it as context hint
                 topic_skill = topic_info.get("skill")
-                if topic_skill:
-                    chat_topic = f"{chat_topic} [skill: {topic_skill}]"
 
             # Also check forum_topic_created service message for topic discovery
             if hasattr(message, "forum_topic_created") and message.forum_topic_created:
@@ -1839,5 +1837,6 @@ class TelegramAdapter(BasePlatformAdapter):
             message_id=str(message.message_id),
             reply_to_message_id=reply_to_id,
             reply_to_text=reply_to_text,
+            auto_skill=topic_skill,
             timestamp=message.date,
         )

gateway/run.py

@@ -1957,7 +1957,39 @@ class GatewayRunner:
 
             session_entry.was_auto_reset = False
             session_entry.auto_reset_reason = None
-        
+
+        # Auto-load skill for DM topic bindings (e.g., Telegram Private Chat Topics)
+        # Only inject on NEW sessions — for ongoing conversations the skill content
+        # is already in the conversation history from the first message.
+        if _is_new_session and getattr(event, "auto_skill", None):
+            try:
+                from agent.skill_commands import _load_skill_payload, _build_skill_message
+                _skill_name = event.auto_skill
+                _loaded = _load_skill_payload(_skill_name, task_id=_quick_key)
+                if _loaded:
+                    _loaded_skill, _skill_dir, _display_name = _loaded
+                    _activation_note = (
+                        f'[SYSTEM: This conversation is in a topic with the "{_display_name}" skill '
+                        f"auto-loaded. Follow its instructions for the duration of this session.]"
+                    )
+                    _skill_msg = _build_skill_message(
+                        _loaded_skill, _skill_dir, _activation_note,
+                        user_instruction=event.text,
+                    )
+                    if _skill_msg:
+                        event.text = _skill_msg
+                        logger.info(
+                            "[Gateway] Auto-loaded skill '%s' for DM topic session %s",
+                            _skill_name, session_key,
+                        )
+                else:
+                    logger.warning(
+                        "[Gateway] DM topic skill '%s' not found in available skills",
+                        _skill_name,
+                    )
+            except Exception as e:
+                logger.warning("[Gateway] Failed to auto-load topic skill '%s': %s", event.auto_skill, e)
+
         # Load conversation history from transcript
         history = self.session_store.load_transcript(session_entry.session_id)
         

tests/gateway/test_dm_topics.py

@@ -395,3 +395,90 @@ def test_cache_dm_topic_from_message_no_overwrite():
     adapter._cache_dm_topic_from_message("111", "999", "General")
 
     assert adapter._dm_topics["111:General"] == 100  # unchanged
+
+
+# ── _build_message_event: auto_skill binding ──
+
+
+def _make_mock_message(chat_id=111, chat_type="private", text="hello", thread_id=None,
+                       user_id=42, user_name="Test User", forum_topic_created=None):
+    """Create a mock Telegram Message for _build_message_event tests."""
+    chat = SimpleNamespace(
+        id=chat_id,
+        type=chat_type,
+        title=None,
+    )
+    # Add full_name attribute for DM chats
+    if not hasattr(chat, "full_name"):
+        chat.full_name = user_name
+
+    user = SimpleNamespace(
+        id=user_id,
+        full_name=user_name,
+    )
+
+    msg = SimpleNamespace(
+        chat=chat,
+        from_user=user,
+        text=text,
+        message_thread_id=thread_id,
+        message_id=1001,
+        reply_to_message=None,
+        date=None,
+        forum_topic_created=forum_topic_created,
+    )
+    return msg
+
+
+def test_build_message_event_sets_auto_skill():
+    """When topic has a skill binding, auto_skill should be set on the event."""
+    from gateway.platforms.base import MessageType
+
+    adapter = _make_adapter([
+        {
+            "chat_id": 111,
+            "topics": [
+                {"name": "My Project", "skill": "accessibility-auditor", "thread_id": 100},
+            ],
+        }
+    ])
+    adapter._dm_topics["111:My Project"] = 100
+
+    msg = _make_mock_message(chat_id=111, thread_id=100, text="check this page")
+    event = adapter._build_message_event(msg, MessageType.TEXT)
+
+    assert event.auto_skill == "accessibility-auditor"
+    # chat_topic should be the clean topic name, no [skill: ...] suffix
+    assert event.source.chat_topic == "My Project"
+
+
+def test_build_message_event_no_auto_skill_without_binding():
+    """Topics without skill binding should have auto_skill=None."""
+    from gateway.platforms.base import MessageType
+
+    adapter = _make_adapter([
+        {
+            "chat_id": 111,
+            "topics": [
+                {"name": "General", "thread_id": 200},
+            ],
+        }
+    ])
+    adapter._dm_topics["111:General"] = 200
+
+    msg = _make_mock_message(chat_id=111, thread_id=200)
+    event = adapter._build_message_event(msg, MessageType.TEXT)
+
+    assert event.auto_skill is None
+    assert event.source.chat_topic == "General"
+
+
+def test_build_message_event_no_auto_skill_without_thread():
+    """Regular DM messages (no thread_id) should have auto_skill=None."""
+    from gateway.platforms.base import MessageType
+
+    adapter = _make_adapter()
+    msg = _make_mock_message(chat_id=111, thread_id=None)
+    event = adapter._build_message_event(msg, MessageType.TEXT)
+
+    assert event.auto_skill is None