Skills and MEMORY.md grow by accretion, and the cost is not spread evenly. MEMORY.md and every skill description load into every session; bodies load only when the skill fires; memory files only on recall. A 200-line body that fires twice a month costs less than four bloated pointers. essence ranks the work that way and reports the saving for the always-loaded surface separately, because that is the number the run exists for.
A health pass runs before anything is cut: pointers without a file and files without a pointer, dead wikilinks, memories citing a file:line that no longer exists, one rule restated across several skills, a first-party skill shadowing a locked one, and a description that says what a skill does but never when it fires. Dead entries are deleted rather than compacted, and nothing is compacted around a stale citation, or the error survives in denser form.
Two things are never cut: the evidence behind a memory, because a rule stripped of its incident degrades into an exhortation and stops changing behaviour, and any fact with no other home. Two memories whose evidence differs are never merged.
Writing is in place, since an essence beside the original saves nothing. Guarded by a clean git status for the rewritten paths, .pre-essence copies for ~/.claude and ~/.agents which are not under git, and a diff with the saved lines and characters before one confirmation. Scope is asked with checkboxes and nothing outside it is touched.
autotune routes its optimisation step here instead of trimming by hand. essence still asks for its scope on that path; the operator answers with the skill being optimised.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
