diff --git a/gateway/platforms/slack.py b/gateway/platforms/slack.py
index d35b703f..f60b6bee 100644
--- a/gateway/platforms/slack.py
+++ b/gateway/platforms/slack.py
@@ -2695,9 +2695,14 @@ class SlackAdapter(BasePlatformAdapter):
             # gateway command dispatcher by prepending the slash.
             text = f"/{slash_name} {text}".strip()
 
+        # Slack slash commands can originate from DMs or shared channels.
+        # Preserve DM semantics only for DM channel IDs; shared channels must
+        # keep group semantics so different users do not collide into one
+        # session key.
+        is_dm = str(channel_id).startswith("D")
         source = self.build_source(
             chat_id=channel_id,
-            chat_type="dm",  # Slash commands are always in DM-like context
+            chat_type="dm" if is_dm else "group",
             user_id=user_id,
         )
 
diff --git a/tests/gateway/test_slack.py b/tests/gateway/test_slack.py
index 35c49d1c..c45cc53a 100644
--- a/tests/gateway/test_slack.py
+++ b/tests/gateway/test_slack.py
@@ -92,6 +92,46 @@ def _redirect_cache(tmp_path, monkeypatch):
     )
 
 
+# ---------------------------------------------------------------------------
+# TestSlashCommandSessionIsolation
+# ---------------------------------------------------------------------------
+
+class TestSlashCommandSessionIsolation:
+    @pytest.mark.asyncio
+    async def test_channel_slash_command_uses_group_session_semantics(self, adapter):
+        command = {
+            "text": "hello",
+            "user_id": "U123",
+            "channel_id": "C123",
+            "team_id": "T123",
+        }
+
+        await adapter._handle_slash_command(command)
+
+        adapter.handle_message.assert_awaited_once()
+        event = adapter.handle_message.await_args.args[0]
+        assert event.source.chat_type == "group"
+        assert event.source.chat_id == "C123"
+        assert event.source.user_id == "U123"
+
+    @pytest.mark.asyncio
+    async def test_dm_slash_command_keeps_dm_session_semantics(self, adapter):
+        command = {
+            "text": "hello",
+            "user_id": "U123",
+            "channel_id": "D123",
+            "team_id": "T123",
+        }
+
+        await adapter._handle_slash_command(command)
+
+        adapter.handle_message.assert_awaited_once()
+        event = adapter.handle_message.await_args.args[0]
+        assert event.source.chat_type == "dm"
+        assert event.source.chat_id == "D123"
+        assert event.source.user_id == "U123"
+
+
 # ---------------------------------------------------------------------------
 # TestAppMentionHandler
 # ---------------------------------------------------------------------------