Follow-up requests are new messages only… Claude API Thread Beta Documentation

Anthropic has documented a beta "message threads" feature in its Claude API that lets developers store conversation state server-side, so follow-up requests can continue a dialogue with only a new message plus a previous response ID rather than resending the full conversation history. The API defines thread as an optional parameter: setting create on an initial request saves the conversation state linked to a response ID, while subsequent requests pass continue with a previous_message_id to resume from that state. This replaces the existing pattern in the Messages API, where prior user and assistant messages must be re-sent in the messages array to maintain context. The feature matters for developers because it can reduce token usage and payload size in multi-turn applications, lowering inference costs and latency for chat-style products. It is a beta, optional capability, and requests that do not use it continue to work as before. What to watch next: whether the feature moves from beta to general availability, its pricing implications for stored state, and adoption by agent and chat application builders on the Claude platform.