Vercel AI SDK, CopilotKit, AG-UI protocol, shadcn registry, 21st.dev Magic, assistant-ui, Thesys C1, Google A2UI, v0, json-render — and PieUI (Swarm AI Lab). Toggle frameworks and category filters, or search any cell. PieUI column is highlighted.
The field split into design-time codegen (v0, 21st.dev Magic, shadcn MCP — agents write component code into your repo) and runtime generative UI (Thesys C1, A2UI, json-render — agents stream a catalog-constrained JSON spec). 2026's convergence: catalog-constrained, streaming, versioned specs win on safety and brand control.
MCP (agent↔tools), A2A (agent↔agent), AG-UI (agent↔user), A2UI (agent↔widgets, rides over AG-UI/MCP/A2A). CopilotKit owns the AG-UI standard with MS/Google/AWS/Oracle adoption; Vercel pushes its own UI Message Stream and ignores AG-UI. Betting on protocol interop is now table stakes.
Almost everyone (AI Elements, 21st.dev, v0, PieUI) distributes through shadcn-compatible registries. The registry spec + namespaces + auth + MCP server is becoming the package manager of AI-generated UI — compatibility with it is the cheapest ecosystem leverage available.
Nobody else combines versioned registry + marketplace with revshare + MCP-orchestrated entity lifecycle + stable event contracts in one engine. Closest analogues: shadcn registry (distribution, but no governance/lifecycle), A2UI (stable contracts, but a spec — no marketplace), 21st.dev (marketplace, but no event contracts). PieUI's gaps to watch: no public OSS footprint/stars yet, no AG-UI/A2UI interop story, React+Telegram only vs. multi-framework incumbents.