Glossary · term139 of 202
prefix stability
Keeping the leading portion of a prompt byte-identical across turns so it keeps qualifying for cheap cache reads instead of triggering an expensive cache rewrite.
also written as byte-identical prefix · stable cached prefix · stable prefix
Related terms
cache missA request whose prompt prefix no longer matches what was cached, forcing the full prefix to be billed again at the cache-write rate instead of the cheaper cache-read rate.view termcache readA token served from a prior prompt's cached context instead of being processed fresh, billed at a fraction of the base input price. Most tokens in a long agent session are cache reads, not new context.view termcache writeThe cost of storing a prompt's context so later requests can read it from cache instead of reprocessing it. Billed above base input price, with the rate depending on how long the write stays valid.view termcontext-tier boundaryA pricing threshold where a task's context size crosses into a different billing tier, which can make measured per-request token savings disappear once a task grows past it.view term
At a glance
- cited by
- 2 posts
- categories
- 2
- first used
- jul 2026
Token-Compression Skills Do Not Survive MeasurementToken compression skills report savings the invoice never shows. Cache reads carry 87 percent of an agent bill, and cutting tokens can push the cost up.
Ways to Make the Most Out of Claude Fable 5 (2026)Get more from Claude Fable 5: pick the right effort level, plan with Fable while cheaper models implement, and claw back costs with caching and batching.