Anthropic launches message threads in public beta, letting Messages API apps send only new messages

Anthropic introduced message threads in public beta on November 2, 2026. Messages API applications on the Claude Platform can now send only new messages after an initial full-conversation request, according to a summary published by Unite.AI.

What changed

Under the new feature, an application sends the full conversation once. After that, requests within the same session carry only the new messages.

Target use cases

Anthropic describes message threads as intended for active sessions where latency matters. The use cases named are:

• Long-running coding agents
• Computer-use agents, whose screenshots remain with the thread
• Document- and image-heavy workflows

Anthropic also reports that message threads are on by default for most Claude Code users. The summary is cut off at that point, so further details on that claim are not available here.

Not a new model

Message threads is an API feature, not a new model. No context window, pricing, benchmark or model version details accompany the announcement.

What this means

Message threads change how applications send conversation state to the Messages API. Instead of resending the full conversation on each request, an app sends it once and then sends only new messages. Anthropic positions this for sessions where latency matters, including agents that accumulate screenshots, documents or images over time. Because the feature is in public beta, developers building such workflows on the Claude Platform can test it now.