feat: add /voice slash command to Discord + fix cross-platform send_voice

- Register /voice as Discord slash command with mode choices
- Fix _send_voice_reply to handle adapters that don't accept metadata
  parameter (Discord) by inspecting the method signature at runtime

gateway/platforms/discord.py

@@ -627,6 +627,23 @@ class DiscordAdapter(BasePlatformAdapter):
         async def slash_reload_mcp(interaction: discord.Interaction):
             await self._run_simple_slash(interaction, "/reload-mcp")
 
+        @tree.command(name="voice", description="Toggle voice reply mode")
+        @discord.app_commands.describe(mode="Voice mode: on, off, tts, or status")
+        @discord.app_commands.choices(mode=[
+            discord.app_commands.Choice(name="on — voice reply to voice messages", value="on"),
+            discord.app_commands.Choice(name="tts — voice reply to all messages", value="tts"),
+            discord.app_commands.Choice(name="off — text only", value="off"),
+            discord.app_commands.Choice(name="status — show current mode", value="status"),
+        ])
+        async def slash_voice(interaction: discord.Interaction, mode: str = ""):
+            await interaction.response.defer(ephemeral=True)
+            event = self._build_slash_event(interaction, f"/voice {mode}".strip())
+            await self.handle_message(event)
+            try:
+                await interaction.followup.send("Done~", ephemeral=True)
+            except Exception as e:
+                logger.debug("Discord followup failed: %s", e)
+
         @tree.command(name="update", description="Update Hermes Agent to the latest version")
         async def slash_update(interaction: discord.Interaction):
             await self._run_simple_slash(interaction, "/update", "Update initiated~")

gateway/run.py

@@ -2175,16 +2175,19 @@ class GatewayRunner:
 
             adapter = self.adapters.get(event.source.platform)
             if adapter and hasattr(adapter, "send_voice"):
-                _thread_md = (
-                    {"thread_id": event.source.thread_id}
-                    if event.source.thread_id else None
-                )
-                await adapter.send_voice(
-                    event.source.chat_id,
-                    audio_path=ogg_path,
-                    reply_to=event.message_id,
-                    metadata=_thread_md,
-                )
+                send_kwargs: Dict[str, Any] = {
+                    "chat_id": event.source.chat_id,
+                    "audio_path": ogg_path,
+                    "reply_to": event.message_id,
+                }
+                if event.source.thread_id:
+                    send_kwargs["metadata"] = {"thread_id": event.source.thread_id}
+                # Only pass metadata if the adapter accepts it
+                import inspect
+                sig = inspect.signature(adapter.send_voice)
+                if "metadata" not in sig.parameters:
+                    send_kwargs.pop("metadata", None)
+                await adapter.send_voice(**send_kwargs)
             try:
                 os.unlink(ogg_path)
             except OSError:

tests/gateway/test_voice_command.py

@@ -229,7 +229,7 @@ class TestSendVoiceReply:
 
         mock_adapter.send_voice.assert_called_once()
         call_args = mock_adapter.send_voice.call_args
-        assert call_args[0][0] == "123"  # chat_id
+        assert call_args.kwargs.get("chat_id") == "123"
 
     @pytest.mark.asyncio
     async def test_empty_text_after_strip_skips(self, runner):