With Opus 4.8, you can add system instructions mid-conversation without breaking the prompt cache.
More cache hits means lower cost and latency for your API requests.
Claude Opus 4.8 is out today. It's our strongest coding model yet: up on SWE-bench Pro (from 64.3 to 69.2) and noticeably more honest about its own work. It tells you when it's unsure and catches its own bugs instead of declaring victory early. Same price as 4.7.
Useful tip to cut time-to-first-token on longer prompts in the API: pre-warm the prompt cache.
Send your system prompt before the user prompt. Claude writes it to the cache, but skips generating any output.
When the real user request lands, it'll hit a warm cache.
Claude Code 2.1.139 added /goal
You set a completion condition and Claude keeps working across turns until it's met
Works in interactive, -p, and Remote Control 👏