A build cache reuses the result of an instruction when its relevant inputs still match. Changing an earlier layer invalidates later dependent layers. Put stable dependency inputs before frequently edited application files when that ordering fits the build. A source edit can then reuse dependency work, while a dependency edit rebuilds what follows it. A forced fresh build bypasses reuse and answers a different operational question. This workspace reports cached and rebuilt layers using a deterministic local model. The tasks compare repeated builds, application edits and dependency edits; they check the layer boundary rather than treating every successful build as equivalent.