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On November 3, 2026, Anthropic launched message threads in public beta on the Messages API. According to information released by Claude Devs, this feature lets the server cache conversations between turns, so callers only need to send the new message and the previous message ID, and must add the thread parameter and beta header. 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. The same information states that after Claude Code integrated message threads, median time to first token on requests of 500K to 1M tokens dropped by about 35%; in long conversations, the median size of a single request fell from about 800 KB to 1.8 KB.
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Claude Code integrates message threads, reducing first-token latency for long requests by about 35%Developments
1 confirmed developments
Anthropic launches public beta of message threads on the Messages API
Source:Claude Devs
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Nov 3
Claude DevsFirst-partySelected
Claude Code integrates message threads, reducing first-token latency for long requests by about 35%
After Claude Code integrated message threads, on requests of 500K to 1M tokens, the median first-token latency dropped by about 35%; in long conversations, the median size of a single request fell from about 800 KB to 1.8 KB. Message threads have entered public beta in the Messages API. The server caches the conversation between turns, so callers only need to send the new message and the ID of the previous message, and must add the thread parameter and beta header. It 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.
Claude DevsFirst-party
Anthropic Opens Message Threads Beta in the Messages API
Anthropic has launched the message threads beta on its Messages API. The API caches conversations server-side, so subsequent requests only need to send the new message and the previous message ID, allowing Claude to start responding faster. The company says the feature is already integrated in Claude Code, with median time to first token for 500K to 1M token requests reduced by about 35%, and median request size for long conversations dropping from about 800 KB to 1.8 KB. To use it, add the thread parameter and beta header to requests. 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.