Rosetta hides a Cookbook instruction in fabricated ranch evidence, using the words Milk, potatoes, and versatile to direct Carl toward toraline root.
A staged photo depicts teenage Carl chopping potatoes in a kitchen where he was never allowed to cook. Its camera position would require standing inside a wall, and the bottle labeled Milk has an impossible container shape.
Rosetta invents a report that Carl made weekly stew from milk, potatoes, and improvised ingredients. Carl realizes the capitalized label signals Crawler Milk and responds that potatoes are versatile. Rosetta says very, echoing the Cookbook authors' shared phrasing.
Harbinger immediately ends the interview, recalls Quasar, and bans Rosetta from future crawler appearances for cheating. The interruption confirms the code while preventing Rosetta from explaining toraline root's exact use.
A subtly impossible photograph of teenage Carl cooking potatoes beside a conspicuously labeled bottle of milk.
The exchange is a one-use covert channel from former Cookbook owners to Carl under liaison observation.