fix(gateway): make group session isolation configurable

default group and channel sessions to per-user isolation, allow opting back into shared room sessions via config.yaml, and document Discord gateway routing and session behavior.

website/docs/user-guide/configuration.md

@@ -848,6 +848,21 @@ voice:
 
 Use `/voice on` in the CLI to enable microphone mode, `record_key` to start/stop recording, and `/voice tts` to toggle spoken replies. See [Voice Mode](/docs/user-guide/features/voice-mode) for end-to-end setup and platform-specific behavior.
 
+## Group Chat Session Isolation
+
+Control whether shared chats keep one conversation per room or one conversation per participant:
+
+```yaml
+group_sessions_per_user: true  # true = per-user isolation in groups/channels, false = one shared session per chat
+```
+
+- `true` is the default and recommended setting. In Discord channels, Telegram groups, Slack channels, and similar shared contexts, each sender gets their own session when the platform provides a user ID.
+- `false` reverts to the old shared-room behavior. That can be useful if you explicitly want Hermes to treat a channel like one collaborative conversation, but it also means users share context, token costs, and interrupt state.
+- Direct messages are unaffected. Hermes still keys DMs by chat/DM ID as usual.
+- Threads stay isolated from their parent channel either way; with `true`, each participant also gets their own session inside the thread.
+
+For the behavior details and examples, see [Sessions](/docs/user-guide/sessions) and the [Discord guide](/docs/user-guide/messaging/discord).
+
 ## Quick Commands
 
 Define custom commands that run shell commands without invoking the LLM — zero token usage, instant execution. Especially useful from messaging platforms (Telegram, Discord, etc.) for quick server checks or utility scripts.