/harness-diet

name: harness-diet
description: Measure and shrink the always-loaded context of a Claude Code harness (CLAUDE.md + rules without paths frontmatter) back under budget — migrate narrative to reference files, convert rules to path-scoped or skill-triggered loading, and verify zero governance loss with deterministic preservation checks. Use on "harness diet", "context diet", "rules diet", "CLAUDE.md too long", "always-load budget", "trim my rules", "context bloat", "하네스 다이어트", "룰 다이어트", "컨텍스트 다이어트", "always-load 줄여줘". Not for one-off prose editing or project docs cleanup.
license: MIT
metadata:
  category: harness-maintenance
  phase: v1

harness-diet — put your always-loaded context back under budget

> A harness gains weight automatically (every incident note, every boss directive, every fix lands > as another paragraph in an always-loaded rule) but only loses weight when someone runs a diet. > Field measurement on a mature harness: growth-to-reduction commit ratio of ~60:1, natural growth > of ~70KB/month, and adherence degrading as the pile grows. Anthropic's guidance is blunt: > *"target under 200 lines per CLAUDE.md file. Longer files consume more context and reduce > adherence"*, and rules without `paths` frontmatter load *"with the same priority as CLAUDE.md"* > — every session, every token ([memory docs](https://docs.claude.com/en/docs/claude-code/memory)).

**Result you should expect**: one field run took a harness from 146KB always-loaded (143% of budget) to 100.6KB (98%) with **zero governance loss** — every killswitch, decision table, trigger keyword, and canonical command verified present after the diet.

Budgets (defaults — override via flags)

| Metric | Budget | Why | |---|---|---| | CLAUDE.md | < 200 lines | Anthropic official guidance | | Per always-loaded rule file | 8,192 B | Keeps any single rule scannable; forces narrative out | | Total always-loaded rules | 102,400 B | Attention-budget ceiling; beyond this, adherence drops |

> **Bundled script paths**: commands below use `$HOME/.claude/skills/harness-diet/…` (the > `install.sh` layout). For marketplace (`/plugin install`) installs, resolve under > `${CLAUDE_PLUGIN_ROOT}/skills/harness-diet/…` instead. The scripts are stdlib-only Python; > if unavailable, perform the step manually from the described contract.

Phase 0 — Measure

DIET="$HOME/.claude/skills/harness-diet"   # or "${CLAUDE_PLUGIN_ROOT}/skills/harness-diet"
python3 "$DIET/scripts/harness_diet_audit.py"            # human summary
python3 "$DIET/scripts/harness_diet_audit.py" --json     # machine output
python3 "$DIET/scripts/harness_diet_audit.py" --strict   # exit 2 if over budget (CI/ratchet)

Auto-discovers `./.claude/rules`, `~/.claude/rules`, and CLAUDE.md files at project/user level. A rule is **always-loaded** iff its YAML frontmatter has no `paths:` key.

Phase 1 — Classify every always-loaded rule

Walk the list from largest to smallest and pick one bucket per file:

1. **Keep always-loaded** — cross-cutting behavior needed in *every* session (tone, security boundaries, routing indexes). Diet the body (Phase 2) but keep the load class. 2. **Path-scope** — the rule only matters when specific files are touched. Add `paths:` globs. ⚠ Path scoping fires on *file access*, never on spoken keywords. A rule triggered by what the user *says* cannot be path-scoped. ⚠ No literal brackets in globs (`[locale]` parses as a character class and silently never matches). 3. **Convert to skill / hook-injected** — task-specific procedure? Official guidance: *"use skills instead"*. Best case: the rule's real trigger is already a deterministic hook — have the hook inject "Read <rule> first" into context and drop the always-load. 4. **Migrate narrative to reference** — the default for oversized keepers (Phase 2).

Phase 2 — Migrate (block-level, never prose compression)

For each oversized file:

1. **Extract a preservation manifest first** (before touching anything):

   python3 "$DIET/scripts/preservation_check.py" extract rules/big-rule.md > /tmp/big-rule.manifest.json

2. **Append** the outgoing blocks to `references/<name>-ref.md` (or your repo's reference dir), verbatim under a dated section header. Append *before* rewriting the rule body, and commit both together — a slimmed body pushed without its reference content is a content hole for every mirror that pulls in between. 3. **Rewrite the rule body**: keep the verdict skeleton (what to do / never do), leave a one-line pointer to the reference for the "why" and the war stories.

**Must stay in the body** (never migrate): CRITICAL/IMPORTANT banners and their verdicts, decision tables, trigger keywords and agent names (they are a routing index, not prose), killswitch env vars, canonical command lines, IDs and threshold values.

**Migrate aggressively**: incident narratives, measurement history, duplicated explanations of the same point, long example blocks, anything already present in the reference file.

Phase 3 — Verify (two lenses, fresh checker)

1. **Loss lens (deterministic)**:

   python3 "$DIET/scripts/preservation_check.py" verify rules/big-rule.md /tmp/big-rule.manifest.json

Exit 2 = something load-bearing got migrated. Restore it before proceeding. Review the manifest by hand first — prune entries that were *intended* to move. 2. **Efficacy lens**: re-run the audit; recompute the total; confirm the savings are real (reference files are lazily `Read`, not `@`-imported — check the rule bodies contain no `@path` imports of the reference, or the "savings" still load at launch). 3. **Fresh checker**: hand the diff to an independent reviewer that didn't write it (pairs with the `review-loop` skill). Diets fail quietly: a plausible-looking slim body missing one qualifier is exactly what the maker cannot see.

Phase 4 — Guard (keep it off)

A diet without a guard regrows. Ship-with options in `