OpenAI’s plan to allow employees and former staff to sell $6 billion in private stock to investors was already slated to become one of the biggest such employee tenders in Silicon Valley history. Now, that sale could be even bigger.

The ChatGPT maker will allow current and former employees to sell up to $8 billion at a valuation of $500 billion, according to two people with knowledge of the proposed sale. If finalized, the sale would amount to nearly the entire volume of shares sold by startup employees and other stakeholders last year. The final size of the share sale will depend on how much stock eligible employees and former staff decide to sell, one of the people said.