How does Claude Opus 5's prompt caching minimum affect short system prompts?

Because the minimum cacheable prompt length dropped from 1,024 tokens on Opus 4.8 to 512 tokens on Opus 5, system prompts that fell in that 512-1,024 token range - too short to cache before - now qualify for caching automatically.

This applies with no code changes required: simply moving the same request to Opus 5 makes previously-uncacheable short prompts eligible, rather than needing any explicit reconfiguration.

For high-volume agentic workloads that reuse a relatively short, consistent system prompt across many requests, this can translate into a real, if incidental, cost reduction purely as a side effect of migrating models rather than any deliberate prompt engineering.

Invest now in Acorns!!! 🚀
Join Acorns and get your $5 bonus!

Acorns is a micro-investing app that automatically invests your "spare change" from daily purchases into diversified, expert-built portfolios of ETFs. It is designed for beginners, allowing you to start investing with as little as $5. The service automates saving and investing. Disclosure: I may receive a referral bonus.

Invest now!!! Get Free equity stock (US, UK only)!

Use Robinhood app to invest in stocks. It is safe and secure. Use the Referral link to claim your free stock when you sign up!.

The Robinhood app makes it easy to trade stocks, crypto and more.

Webull! Receive free stock by signing up using the link: Webull signup.