feat(discord): auto-thread on @mention + skip mention in bot threads

Two changes to align Discord behavior with Slack:

1. Auto-thread on @mention (default: true)
   - When someone @mentions the bot in a server channel, a thread is
     automatically created from their message and the response goes there.
   - Each thread gets its own isolated session (like Slack).
   - Configurable via discord.auto_thread in config.yaml (default: true)
     or DISCORD_AUTO_THREAD env var (env takes precedence).
   - DMs and existing threads are unaffected.

2. Skip @mention in bot-participated threads
   - Once the bot has responded in a thread (auto-created or manually
     entered), subsequent messages in that thread no longer require
     @mention. Users can just type normally.
   - Tracked via in-memory set (_bot_participated_threads). After a
     gateway restart, users need to @mention once to re-establish.
   - Threads the bot hasn't participated in still require @mention.

Config change:
   discord:
     auto_thread: true  # new, added to DEFAULT_CONFIG

Tests: 7 new tests covering auto-thread default, disable, bot thread
participation tracking, and mention skip logic. All 903 gateway tests pass.

gateway/platforms/discord.py

@@ -433,6 +433,9 @@ class DiscordAdapter(BasePlatformAdapter):
         self._voice_listen_tasks: Dict[int, asyncio.Task] = {}  # guild_id -> listen loop
         self._voice_input_callback: Optional[Callable] = None  # set by run.py
         self._on_voice_disconnect: Optional[Callable] = None  # set by run.py
+        # Track threads where the bot has participated so follow-up messages
+        # in those threads don't require @mention.
+        self._bot_participated_threads: set = set()
     
     async def connect(self) -> bool:
         """Connect to Discord and start receiving events."""
@@ -1798,14 +1801,13 @@ class DiscordAdapter(BasePlatformAdapter):
     async def _handle_message(self, message: DiscordMessage) -> None:
         """Handle incoming Discord messages."""
         # In server channels (not DMs), require the bot to be @mentioned
-        # UNLESS the channel is in the free-response list.
+        # UNLESS the channel is in the free-response list or the message is
+        # in a thread where the bot has already participated.
         #
-        # Config:
+        # Config (all settable via discord.* in config.yaml):
-        #   DISCORD_FREE_RESPONSE_CHANNELS: Comma-separated channel IDs where the
+        #   discord.require_mention: Require @mention in server channels (default: true)
-        #       bot responds to every message without needing a mention.
+        #   discord.free_response_channels: Channel IDs where bot responds without mention
-        #   DISCORD_REQUIRE_MENTION: Set to "false" to disable mention requirement
+        #   discord.auto_thread: Auto-create thread on @mention in channels (default: true)
-        #       globally (all channels become free-response). Default: "true".
-        #       Can also be set via discord.require_mention in config.yaml.
 
         thread_id = None
         parent_channel_id = None
@@ -1824,7 +1826,11 @@ class DiscordAdapter(BasePlatformAdapter):
             require_mention = os.getenv("DISCORD_REQUIRE_MENTION", "true").lower() not in ("false", "0", "no")
             is_free_channel = bool(channel_ids & free_channels)
 
-            if require_mention and not is_free_channel:
+            # Skip the mention check if the message is in a thread where
+            # the bot has previously participated (auto-created or replied in).
+            in_bot_thread = is_thread and thread_id in self._bot_participated_threads
+
+            if require_mention and not is_free_channel and not in_bot_thread:
                 if self._client.user not in message.mentions:
                     return
 
@@ -1833,17 +1839,18 @@ class DiscordAdapter(BasePlatformAdapter):
                 message.content = message.content.replace(f"<@!{self._client.user.id}>", "").strip()
 
         # Auto-thread: when enabled, automatically create a thread for every
-        # new message in a text channel so each conversation is isolated.
+        # @mention in a text channel so each conversation is isolated (like Slack).
         # Messages already inside threads or DMs are unaffected.
         auto_threaded_channel = None
         if not is_thread and not isinstance(message.channel, discord.DMChannel):
-            auto_thread = os.getenv("DISCORD_AUTO_THREAD", "").lower() in ("true", "1", "yes")
+            auto_thread = os.getenv("DISCORD_AUTO_THREAD", "true").lower() in ("true", "1", "yes")
             if auto_thread:
                 thread = await self._auto_create_thread(message)
                 if thread:
                     is_thread = True
                     thread_id = str(thread.id)
                     auto_threaded_channel = thread
+                    self._bot_participated_threads.add(thread_id)
 
         # Determine message type
         msg_type = MessageType.TEXT
@@ -1944,6 +1951,11 @@ class DiscordAdapter(BasePlatformAdapter):
             timestamp=message.created_at,
         )
 
+        # Track thread participation so the bot won't require @mention for
+        # follow-up messages in threads it has already engaged in.
+        if thread_id:
+            self._bot_participated_threads.add(thread_id)
+
         await self.handle_message(event)
 
 

hermes_cli/config.py

@@ -280,6 +280,7 @@ DEFAULT_CONFIG = {
     "discord": {
         "require_mention": True,       # Require @mention to respond in server channels
         "free_response_channels": "",  # Comma-separated channel IDs where bot responds without mention
+        "auto_thread": True,           # Auto-create threads on @mention in channels (like Slack)
     },
 
     # Permanently allowed dangerous command patterns (added via "always" approval)

tests/gateway/test_discord_free_response.py

@@ -252,3 +252,109 @@ async def test_discord_dms_ignore_mention_requirement(adapter, monkeypatch):
     event = adapter.handle_message.await_args.args[0]
     assert event.text == "dm without mention"
     assert event.source.chat_type == "dm"
+
+
+@pytest.mark.asyncio
+async def test_discord_auto_thread_enabled_by_default(adapter, monkeypatch):
+    """Auto-threading should be enabled by default (DISCORD_AUTO_THREAD defaults to 'true')."""
+    monkeypatch.delenv("DISCORD_AUTO_THREAD", raising=False)
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "false")
+
+    # Patch _auto_create_thread to return a fake thread
+    fake_thread = FakeThread(channel_id=999, name="auto-thread")
+    adapter._auto_create_thread = AsyncMock(return_value=fake_thread)
+
+    message = make_message(channel=FakeTextChannel(channel_id=123), content="hello")
+
+    await adapter._handle_message(message)
+
+    adapter._auto_create_thread.assert_awaited_once()
+    adapter.handle_message.assert_awaited_once()
+    event = adapter.handle_message.await_args.args[0]
+    assert event.source.chat_type == "thread"
+    assert event.source.thread_id == "999"
+
+
+@pytest.mark.asyncio
+async def test_discord_auto_thread_can_be_disabled(adapter, monkeypatch):
+    """Setting auto_thread to false skips thread creation."""
+    monkeypatch.setenv("DISCORD_AUTO_THREAD", "false")
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "false")
+
+    adapter._auto_create_thread = AsyncMock()
+
+    message = make_message(channel=FakeTextChannel(channel_id=123), content="hello")
+
+    await adapter._handle_message(message)
+
+    adapter._auto_create_thread.assert_not_awaited()
+    adapter.handle_message.assert_awaited_once()
+    event = adapter.handle_message.await_args.args[0]
+    assert event.source.chat_type == "group"
+
+
+@pytest.mark.asyncio
+async def test_discord_bot_thread_skips_mention_requirement(adapter, monkeypatch):
+    """Messages in a thread the bot has participated in should not require @mention."""
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "true")
+    monkeypatch.delenv("DISCORD_FREE_RESPONSE_CHANNELS", raising=False)
+    monkeypatch.setenv("DISCORD_AUTO_THREAD", "false")
+
+    # Simulate bot having previously participated in thread 456
+    adapter._bot_participated_threads.add("456")
+
+    thread = FakeThread(channel_id=456, name="existing thread")
+    message = make_message(channel=thread, content="follow-up without mention")
+
+    await adapter._handle_message(message)
+
+    adapter.handle_message.assert_awaited_once()
+    event = adapter.handle_message.await_args.args[0]
+    assert event.text == "follow-up without mention"
+    assert event.source.chat_type == "thread"
+
+
+@pytest.mark.asyncio
+async def test_discord_unknown_thread_still_requires_mention(adapter, monkeypatch):
+    """Messages in a thread the bot hasn't participated in should still require @mention."""
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "true")
+    monkeypatch.delenv("DISCORD_FREE_RESPONSE_CHANNELS", raising=False)
+    monkeypatch.setenv("DISCORD_AUTO_THREAD", "false")
+
+    # Bot has NOT participated in thread 789
+    thread = FakeThread(channel_id=789, name="some thread")
+    message = make_message(channel=thread, content="hello from unknown thread")
+
+    await adapter._handle_message(message)
+
+    adapter.handle_message.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_discord_auto_thread_tracks_participation(adapter, monkeypatch):
+    """Auto-created threads should be tracked for future mention-free replies."""
+    monkeypatch.delenv("DISCORD_AUTO_THREAD", raising=False)
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "false")
+
+    fake_thread = FakeThread(channel_id=555, name="auto-thread")
+    adapter._auto_create_thread = AsyncMock(return_value=fake_thread)
+
+    message = make_message(channel=FakeTextChannel(channel_id=123), content="start a thread")
+
+    await adapter._handle_message(message)
+
+    assert "555" in adapter._bot_participated_threads
+
+
+@pytest.mark.asyncio
+async def test_discord_thread_participation_tracked_on_dispatch(adapter, monkeypatch):
+    """When the bot processes a message in a thread, it tracks participation."""
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "false")
+    monkeypatch.setenv("DISCORD_AUTO_THREAD", "false")
+
+    thread = FakeThread(channel_id=777, name="manually created thread")
+    message = make_message(channel=thread, content="hello in thread")
+
+    await adapter._handle_message(message)
+
+    assert "777" in adapter._bot_participated_threads

tests/gateway/test_discord_slash_commands.py

@@ -363,11 +363,37 @@ async def test_auto_thread_creates_thread_and_redirects(adapter, monkeypatch):
 
 
 @pytest.mark.asyncio
-async def test_auto_thread_disabled_by_default(adapter, monkeypatch):
+async def test_auto_thread_enabled_by_default_slash_commands(adapter, monkeypatch):
-    """Without DISCORD_AUTO_THREAD, messages stay in the channel."""
+    """Without DISCORD_AUTO_THREAD env var, auto-threading is enabled (default: true)."""
     monkeypatch.delenv("DISCORD_AUTO_THREAD", raising=False)
     monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "false")
 
+    fake_thread = _FakeThreadChannel(channel_id=999, name="auto-thread")
+    adapter._auto_create_thread = AsyncMock(return_value=fake_thread)
+
+    captured_events = []
+
+    async def capture_handle(event):
+        captured_events.append(event)
+
+    adapter.handle_message = capture_handle
+
+    msg = _fake_message(_FakeTextChannel())
+
+    await adapter._handle_message(msg)
+
+    adapter._auto_create_thread.assert_awaited_once()
+    assert len(captured_events) == 1
+    assert captured_events[0].source.chat_id == "999"  # redirected to thread
+    assert captured_events[0].source.chat_type == "thread"
+
+
+@pytest.mark.asyncio
+async def test_auto_thread_can_be_disabled(adapter, monkeypatch):
+    """Setting DISCORD_AUTO_THREAD=false keeps messages in the channel."""
+    monkeypatch.setenv("DISCORD_AUTO_THREAD", "false")
+    monkeypatch.setenv("DISCORD_REQUIRE_MENTION", "false")
+
     adapter._auto_create_thread = AsyncMock()
 
     captured_events = []