runtime

Guide to the assistant-ui runtime system, the state and action layer behind every chat surface, in @assistant-ui/react. Use when creating a runtime (useLocalRuntime with a ChatModelAdapter, useExternalStoreRuntime for Redux or Zustand backed stores, useRemoteThreadListRuntime, useCloudThreadListRuntime, useAssistantTransportRuntime), wiring AssistantRuntimeProvider, or reading and mutating thread, message, composer, and attachment state. Covers useAui, useAuiState, and useAuiEvent, including the one primitive or stable reference selector rule from hooks/state.mdx, the property scope accessors (aui.thread, aui.threads, aui.message, aui.composer, aui.part, aui.threadListItem) with source availability, the AuiConfig plus AuiProvider grammar (config, extends, isolated roots, and the config prop on AssistantRuntimeProvider), the s.optional.<scope> view, the threads.selectionChanged event and the events it replaced, RuntimeCapabilities including refetchThread, and the attachment, speech, dictation, feedback, suggestion, and history adapters. Route here for a provider error ('Cannot read property of undefined'), a removed v0.12 hook import, an infinite re-render from an object literal selector, or state not updating. For multi-thread list UI and switching between conversations use thread-list instead; for toolkit definitions and tool call UI use tools instead.

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