primitives

Builds and customizes assistant-ui chat UI from composable, unstyled @assistant-ui/react primitives that follow Radix-style part composition. Use when assembling or styling a custom Thread, Composer, message rendering, action bar, or branch picker from building blocks: ThreadPrimitive (.Root, .Viewport, .Messages, .Empty, .ScrollToBottom), ComposerPrimitive (.Input, .Send, .Cancel, .Attachments), MessagePrimitive (.Parts/.Content, .Error), ActionBarPrimitive (.Copy, .Edit, .Reload, .Speak, feedback, .ExportMarkdown), BranchPickerPrimitive, AttachmentPrimitive, ThreadListPrimitive, ThreadListItemPrimitive. Covers MessagePrimitive.Parts children render functions for text, image, reasoning, and tool-call parts; conditional rendering with AuiIf (deprecated .If); and gotchas like wrapping in AssistantRuntimeProvider and adding className since primitives ship unstyled. For prebuilt drop-in UI and scaffolding use setup; for multi-thread sidebar behavior use thread-list.