Some offer zero data retention policies, but there can be weasel words. For example, on the individual pro plan, you can turn off the setting that lets them train models on your data, but they still have a section in their terms that allows them to evaluate your anonymized data for statistical and "research" purposes. You have to actually get a signed contract along with an enterprise plan that spells out exactly what they're going to use, and what settings enable what retention.

https://privacy.claude.com/en/articles/10023548-how-long-do-... (see the additional info section)

Or just use Azure, AWS, etc. for Claude/ChatGPT inference, where the AI labs never even get your data in their data centers at all.

You pay more for it, but if you care that much, use it.