{"version":"2.1.261","anchor":"detailed-prompt-cache-break-diagnostics-message0-shapesect","canonical_anchor":"detailed-prompt-cache-break-diagnostics-message0-shapesect","heading":"Detailed prompt-cache-break diagnostics (message0 shape\/section diffing) sampled off by default","tier":"soon","area":"Prompt Caching","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.261\/e\/detailed-prompt-cache-break-diagnostics-message0-shapesect","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.261","markdown":"### Detailed prompt-cache-break diagnostics (message0 shape\/section diffing) sampled off by default\n\nDetailed prompt-cache-break diffing telemetry exists but is sampled at zero by default.\n\nNew telemetry can capture a detailed structural snapshot of the first request message, including block kinds, lengths, hashes, named sections like `preamble`, `claudeMd`, and `workerToolsContext`, and worker tool\/MCP-server counts, diffing it on a cache break to report changed, added, and removed sections and blocks. This collection is sampled via the gate `tengu_iridescent_gem`, which defaults to a sample rate of 0, so none of this data is captured unless that rate is raised remotely.\n\n- Area: Prompt Caching\n- Names: `tengu_iridescent_gem`\n- Tier: Nothing to try yet\n- Useful: 3\/5\n- Signal: 3\/5\n- Present in the build but not switched on"}