[Question] Do AI companies make their safety researchers sign a non-disparagement clause?

Among AI companies that employ AI alignment/​policy researchers (e.g. DeepMind, OpenAI, Anthropic, Conjecture), which companies make such researchers sign a non-disparagement clause?

Also, what are the details of such non-disparagement clauses? (Do they aim to restrict such researchers indefinitely, even after they leave the company?)