Anthropic Quietly Reduces Claude Code's Prompt Cache Window from 1 Hour to 5 Minutes

Summary

Anthropic has quietly reduced Claude Code's default prompt cache time-to-live from one hour to five minutes, a change that rolled out over several weeks beginning in early April 2026. The modification was not officially announced; instead, documentation was quietly updated, and users discovered the change by analyzing their session logs and observing increased token consumption. Anthropic eventually acknowledged the shift on a GitHub issue in mid-April, with Claude Code creator Boris Cherny framing the five-minute cache as the "true default" and characterizing it as cost-effective since many Claude Code requests are single-use queries.

For developers performing long-context agentic work in large codebases, however, the reduced cache window has significant practical impact: tokens are consumed faster without corresponding benefits. The change is verifiable through session logs stored at ~/.claude/projects/, where each API response includes cache_creation fields showing either ephemeral_5m_input_tokens or ephemeral_1h_input_tokens. A Reddit user documented the timing using 1,140 sessions from their conversation database, showing a complete transition from 100% one-hour caching (through April 1) to 100% five-minute caching by April 3. Anthropic's messaging around the change has been poor, with official acknowledgment only appearing days after users detected the modification, leaving many users unaware of why their token quotas are depleting faster.

• Anthropic framed the change as cost-reducing, arguing most requests are one-shot queries—a characterization that doesn't address the impact on serious development work
• Official acknowledgment came nearly two weeks after users detected the modification, indicating poor transparency and communication