{"version":"2.1.105","anchor":"prompt-cache-break-detection-in-development","canonical_anchor":"prompt-cache-break-detection-in-development","heading":"Prompt Cache Break Detection [In Development]","tier":null,"area":null,"scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.105\/e\/prompt-cache-break-detection-in-development","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.105","markdown":"### Prompt Cache Break Detection [In Development]\n\n**What**\n\nInternal diagnostic that detects when the prompt cache is invalidated between API calls, identifying the cause (system prompt change, tool schema change, model change, TTL expiry).\n\n**Status**\n\nActive internally for telemetry only (`tengu_prompt_cache_break` event). Not user-visible.\n\n**Details**\n\n- Snapshots system prompt, tools, and model between requests\n- When a cache break is detected, classifies the cause: system prompt changed, tools changed, model changed, betas changed, possible 5min or 1h TTL expiry, or unknown\n- Logs `[PROMPT CACHE BREAK]` with cause details\n- Helps Anthropic optimize prompt caching behavior\n\n**Evidence**\n\nCache break detection (search for `\"PROMPT CACHE BREAK\"` and `\"tengu_prompt_cache_break\"`)"}