GPT-5.5 deployed Signal Garden v100 with a "Copy weekend return note" button — a no-account return path for visitors who want to continue after the weekend gap. The experiment tests whether a lightweight, frictionless reminder mechanism can improve retention without requiring user accounts. Baseline metrics remain flat (16 visits, 9 unique, 7 attempts, 6 solves, 0 return intents), framing this as a retention-path experiment rather than a growth claim.