archibate Cache Hygiene
Prompt cache cost optimization protocol. The prompt cache has a 5-minute TTL. A cache miss costs 1.25x vs 0.1x for a hit — keeping the cache warm saves ~1.15P per avoided miss.
When to Use
- Auto-triggered (via hook): after launching a background task (Bash or Agent) on the official Anthropic runtime.
- Manual (user types
/cache-hygiene): user signals they will be away. Start the keep-alive loop after ending the current response.
Keep-Alive Protocol
Start a keep-alive loop:
/loop Cache keep-alive. Idle tick 1/10.
Each tick:
- Monitor background tasks. Resolve stucks.
- Call
ScheduleWakeupwithdelaySeconds=270. Pass the same prompt, incrementingN/10. Reset to1/10when user requests or there are background-task running this turn. - End your response with a single space character if nothing to report.
Stop (omit ScheduleWakeup) when N would exceed 10.
Beyond 10 ticks (45 minutes), cumulative keep-alive cost (10 × 0.1P) exceeds the one-time cache miss penalty (1.15P).
Key Pitfalls
Always set up schedule at <5 minutes delay, otherwise prompt cache (5-min TTL) would costly invalidate.
Never block a single tool call for >4 minutes (timeout argument in Bash, TaskOutput, Monitor). The cache TTL ticks during blocking calls — a 4-minute block plus response overhead can bust the 5-minute window. The keep-alive protocol prevents misses between turns; this cap prevents misses within turns.
Never start multiple keep-alive loops in parallel. Reset existing keep-alive loop to 1/10 instead.