Claude's Prompt Cache TTL Silently Dropped from 1 Hour to 5 Minutes (Here's What to Do)

The Change Nobody Announced On March 6, 2026, Anthropic silently changed the default prompt cache TTL from 1 hour to 5 minutes. There was no blog post. No changelog entry. No deprecation notice. If you built a caching strategy based on the original 1-hour window - and most people did, because that's what the docs showed - your cache hit rate has been cratering for weeks and you might not have noticed. There's a second gotcha: disabling telemetry also kills the 1-hour TTL. If you turned off telemetry for privacy reasons, you lost the extended TTL at the same time, silently.