AI app‑harness convergence accelerates lock‑in

GPT‑5.5 shows that improvements happen across three linked layers — model, app, and tool harness — and that combining modest gains at each layer produces outsized practical capability. When top labs deliver better desktop apps (Codex), website‑gated Pro tiers, and more powerful image/code toolchains, switching costs and vendor control rise even if any single model advance seems incremental. — This convergence concentrates practical AI power in a few vendors and shapes who benefits from automation, so policymakers and competitors should focus on apps and harnesses as much as model capabilities.