Auto-cache: Anthropic system prompt

What it does

This transform inserts an Anthropic ephemeral cache_control breakpoint on the last system or developer node of the request. The upstream then caches the stable system prefix and reads it from cache on later requests.

The transform changes nothing when the request has no system or developer node.

Reference

When to use

• The upstream is Anthropic-compatible and bills cache writes and reads at reduced rates.
• Your clients send a long, stable system prompt on every request.

Configuration

This transform has no options. Use an empty config object.

Example rule

{
  "transform": "cache_anthropic_system",
  "enabled": true,
  "phase": "request",
  "models": [
    "claude-*"
  ],
  "config": {}
}

Combine with cache_anthropic_tool_use to also cache the conversation prefix during tool loops.