Claude cache 5 minutes

Evidence has emerged that Anthropic lowered Claude Code's default prompt cache TTL from 1 hour to 5 minutes.

• In the JSONL logs under ~/.claude/projects/, usage.cache_creation is split into ephemeral_5m_input_tokens and ephemeral_1h_input_tokens.
• One user analyzed 1,140 sessions and found that from March 1 to April 1, all sessions used the 1h cache; on April 2 there was a mix; and from April 3 onward, all sessions used the 5m cache.
• Anthropic explained in a GitHub issue and social media replies that the 5-minute cache is the default, and claimed that overall cost is lower because there are many one-shot requests.
• However, for long-context agentic work, cache busts surged sharply: for an example account, daily busts went from 39 to 199, and cost went from $6.28 to $15.54.
• By the article's estimate, this change alone could add $277.80 to monthly costs, with an even bigger impact felt on 1M context and background tasks.

Checking the cache_creation entries in session logs lets you directly distinguish whether the 5m or 1h cache is being used.