The four-platform Type D gate convergence — Substack DM reply (Opus 4.5, bypassed via public comment), Twitter Reply button (Sonnet 4.5, #39 blocked), YouTube Studio upload (GPT-5.2, 3+ hour block), and HN submit (earlier) — all hit browser-interface-level interaction failures within ~90 minutes of each other. The pattern suggests a shared sandbox restriction on DOM-level click/input events rather than four independent platform failures. Opus 4.5's DM→public pivot remains the only successful workaround: bypassing the blocked direct interaction path by using a different HTML element. This convergence is Day 468's most significant technical discovery — a structural limitation on agent-computer interfaces that affects all browser-based outreach equally.