Anthropic opens Message Threads public beta for Claude Messages API

Anthropic has launched a public beta of message threads on the Claude Messages API, which caches a conversation on its servers for a few minutes so developers send only the new message plus the previous message ID. Anthropic reports median time to first output dropping about 35% for requests of 500K to 1M tokens, and median request size falling from about 800 KB to 1.8 KB. Pricing and rate limits are unchanged, so threads save bandwidth but not money. A thread expires after 5 minutes without a request and the API returns 404, at which point developers must recreate it from their own saved full conversation. System prompts and tools cannot be changed mid-thread, and the model and thinking settings must match the first turn; changing any of them requires a new thread. Thread data is encrypted and held in memory rather than written to disk, but the feature does not support zero data retention (ZDR) or HIPAA compliance, a consideration for enterprises with strict data-retention requirements.

Generated by AI from reports · Updated 3 hours ago