I Evaluated Every AI Chat UI Library in 2026. Here's What I Found (and What I Built)

TL;DR: React stack → assistant-ui Full agent framework → CopilotKit Quick prototype or non-React → Deep Chat Python backend → Chainlit (check project status first) Multi-framework + composable, early adopter → Loquix (no production deployments yet — read the limitations) ⚠️ Conflict of interest: I'm the author of Loquix, one of the libraries reviewed here. The independent reviews come first. Loquix gets its own clearly-labeled section at the end, written by me about my own work — treat it accordingly. If you want the quick take: for most teams, assistant-ui (React) or Deep Chat (everything else) is the more pragmatic answer. Before the reviews: four types of lock-in After evaluating all of these libraries, the biggest insight wasn't about any specific tool — it was that "lock-in" isn't one thing. There are at least four distinct flavors, and understanding which one you're accepting changes how much it matters: Type Example When it bites Framework assistant-ui (React-only) When you need