Google’s agent now drives the Chrome you are logged into, with your saved passwords, and hands control back for payments. Payment is the one action with a chargeback window; the mailbox read, the data copied out and the recovery address changed are all on the unattended side of that line.
OpenAI is retiring the ChatGPT Atlas browser nine months after launch and moving its capabilities into a Chrome extension, an in-app browser and a server-side cloud browser. That is not a retreat from agentic browsing — it is the admission that a browser agent never needed a browser. What it needed was proximity to an authenticated session, and the three replacement surfaces are three different answers to whose session it borrows.
A "guardrail" is not one thing. The open-source ecosystem settled into four shapes — a programmable rails DSL, a validator library, a safety-classifier model, and a scanner pipeline — and the 2025-26 acquisition wave decided which survived independent. Here is what each actually does, where it sits around the model, and why none of them "solves" prompt injection.