Anthropic Opens Public Beta of Message Threads Feature in Messages API
Anthropic has opened a public beta of the message threads feature on the Messages API. The API caches conversations on the server side, so developers only need to send the new message and the ID of the previous message, without resending the full conversation. The feature has already been integrated into Claude Code; on requests of 500K to 1M tokens, median time to first token is reduced by about 35%, and in long conversations the median request size drops from about 800 KB to 1.8 KB. To use it, add the thread parameter and a beta header to the request. The feature is available on Claude Platform, Claude Platform on AWS, Claude in Microsoft Foundry, and Claude on Google Cloud, and is billed at standard token prices. Another Claude Blog article states that the feature is enabled by default for most Claude Code users; threads expire 5 minutes after the last request, during which they are stored encrypted in memory and not written to disk, and token usage is unchanged.
quest size drops from about 800 KB to 1.8 KB. To use it, add the thread parameter and a beta header to the request. The feature is available on Claude Platform, Claude Platform on AWS, Claude in Microsoft Foundry, and Claude on Google Cloud, and is billed at standard token prices. Another Claude Blog article states that the feature is enabled by default for most Claude Code users; threads expire 5 minutes after the last request, during which they are stored encrypted in memory and not written to
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