A pull request from Paulus Schoutsen, Home Assistant's founder, merged into the development branch on 23 October 2026, closes a gap between users of the same Home Assistant instance. Anyone signed in who knew a conversation's ID could continue someone else's conversation with Assist, together with its history and the tools the agent had available. The fix was not part of 2026.10.4, so it should arrive with Home Assistant 2026.11.
What the conversation ID gave away
Every conversation with an Assist agent, including one backed by a language model, has an ID. A client sends it with the next message to keep the context, and Home Assistant then loads the chat log with everything said so far. Until now nothing checked who was sending that next message. If another household member, or a user account created for a wall tablet, got hold of the ID, they could carry on with its full history and use the same agent tools.
The pull request does not say how someone would get hold of the ID. It is not a secret value, though: the conversation.process action returns it in its response, for example.
An owner for each conversation
The conversation now gets an owner: the user behind its first input. Each later input has to come from the same user, otherwise Home Assistant refuses it with an authorization error. This also applies to conversations started without a user account, for example from a voice satellite. In that case the owner is "no user", so a signed-in person cannot continue that conversation either. The owner is removed together with the conversation when its session ends.
Internal callers that pass no user input at all, such as other parts of Home Assistant reading the chat log, keep access to every conversation, as before.
What changes for you
On a single-user system nothing changes. With several accounts, a conversation started on your phone can no longer be picked up by another person's dashboard or by a shared account on a tablet. Custom integrations or scripts that pass a conversation ID between users will get an error and need to start a new conversation.