Look into https://github.com/NVIDIA/NeMo-Guardrails and specifically to your question there are "topical rails" to ensure the conversation stays on a set of topics you greenlighted.
Also takes care of jailbreaks and allows custom conversation flow templates.
I'm curious how that works, as the documentation is a little under-specified. It seems like it requires specifying exact "utterances" from the user, but I don't think that can be the case -- wouldn't it be flatly useless that way? But it's not clear how to use it to, for example, disallow talking about politics. Or to disallow talking about topics unrelated to the dev's product, for that matter.
Look into https://github.com/NVIDIA/NeMo-Guardrails and specifically to your question there are "topical rails" to ensure the conversation stays on a set of topics you greenlighted.
Also takes care of jailbreaks and allows custom conversation flow templates.