fix(discord): properly route slash event handling in threads

Cherry-picked from PR #2017 by @simpolism. Fixes #2011.

Discord slash commands in threads were missing thread_id in the
SessionSource, causing them to route to the parent channel session.
Commands like /usage and /reset returned wrong data or affected the
wrong session.

Detects discord.Thread channels in _build_slash_event and sets
chat_type='thread' with thread_id. Two tests added.

gateway/platforms/discord.py

@@ -1500,7 +1500,17 @@ class DiscordAdapter(BasePlatformAdapter):
     def _build_slash_event(self, interaction: discord.Interaction, text: str) -> MessageEvent:
         """Build a MessageEvent from a Discord slash command interaction."""
         is_dm = isinstance(interaction.channel, discord.DMChannel)
-        chat_type = "dm" if is_dm else "group"
+        is_thread = isinstance(interaction.channel, discord.Thread)
+        thread_id = None
+
+        if is_dm:
+            chat_type = "dm"
+        elif is_thread:
+            chat_type = "thread"
+            thread_id = str(interaction.channel_id)
+        else:
+            chat_type = "group"
+
         chat_name = ""
         if not is_dm and hasattr(interaction.channel, "name"):
             chat_name = interaction.channel.name
@@ -1516,6 +1526,7 @@ class DiscordAdapter(BasePlatformAdapter):
             chat_type=chat_type,
             user_id=str(interaction.user.id),
             user_name=interaction.user.display_name,
+            thread_id=thread_id,
             chat_topic=chat_topic,
         )
 

tests/gateway/test_discord_slash_commands.py

@@ -241,6 +241,42 @@ async def test_dispatch_thread_session_builds_thread_event(adapter):
     assert "TestGuild" in event.source.chat_name
 
 
+# ------------------------------------------------------------------
+# _build_slash_event — preserve thread context for native slash commands
+# ------------------------------------------------------------------
+
+
+def test_build_slash_event_preserves_thread_context(adapter):
+    interaction = SimpleNamespace(
+        channel=_FakeThreadChannel(channel_id=555, name="Planning"),
+        channel_id=555,
+        user=SimpleNamespace(display_name="Jezza", id=42),
+    )
+
+    event = adapter._build_slash_event(interaction, "/status")
+
+    assert event.text == "/status"
+    assert event.source.chat_id == "555"
+    assert event.source.chat_type == "thread"
+    assert event.source.thread_id == "555"
+    assert "TestGuild" in event.source.chat_name
+
+
+def test_build_slash_event_uses_group_context_for_channels(adapter):
+    interaction = SimpleNamespace(
+        channel=_FakeTextChannel(channel_id=123, name="general"),
+        channel_id=123,
+        user=SimpleNamespace(display_name="Jezza", id=42),
+    )
+
+    event = adapter._build_slash_event(interaction, "/status")
+
+    assert event.source.chat_id == "123"
+    assert event.source.chat_type == "group"
+    assert event.source.thread_id is None
+    assert "TestGuild / #general" == event.source.chat_name
+
+
 # ------------------------------------------------------------------
 # Auto-thread: _auto_create_thread
 # ------------------------------------------------------------------