design-evolve — the self-improvement loop

The other harness components make a single page good. design-evolve makes the generators themselves better over time — it treats a generator skill's rules and templates as the thing to optimize, and lets the system propose changes, test them against the frozen evaluator, and keep only measurable winners.

This is the component that answers "is the system allowed to invent something better than what we wrote by hand?" — yes, but only if it measurably wins. The ratchet is exactly what makes open-ended creative mutation safe: a wild idea is allowed to be tried, and survives only if the frozen evaluator scores it higher and no existing page regresses. (EvolveR's result: self-distilled principles beat a larger teacher model's hand-written ones — because selection, not authorship, decides.)

The one invariant: the evaluator is FROZEN

The loop may mutate generator rules / templates / canonicals. It must never edit the evaluator in the same breath: not verify.py, not visual-audit.mjs, not the critic rubric/weights, not the known-bugs thresholds. If the optimizer can change the test, it will "improve" by loosening the test (reward hacking — autoresearch bans editing prepare.py for exactly this reason). Evaluator changes are a separate, human-gated path, never an automatic loop step.

Corollary: the generator must not score its own work. Scoring always runs the unchanged design-review evaluator as an independent step.

What you may mutate (the editable asset)

One per round, picked by diagnosis:

• a ~/.claude/skills/<skill>-design/references/dos-and-donts.md rule,
• a ~/.claude/skills/<skill>-design/references/*.md craft guideline,
• a skills/<skill>-design/templates/... template,
• a canonical page (only via the human-gated exploratory rewrite, below).

NOT the page output itself — that is what /design-loop does. Here the page is just the measurement instrument for a rule change.

The loop (one round)

Run from repo root. S=skill, P=page-type, B=a fixed test brief for S×P.

0. Lock the baseline. Generate S×P from B with the current rules, run the full evaluator, record the critic score as base. Snapshot the held-out set: regression-gate.mjs --baseline --skill=S. Both are now the bar to beat. Start a git branch evolve/<skill>-<page>-<date>.
1. Diagnose the weakest axis. From the multi-critic verdict take the lowest-scoring axis (composition / copy / illustration / brand). That axis, and the specific issues under it, decide what to change. Never mutate randomly — diagnosis-directed only.
2. Propose ONE change aimed at that axis. One change per round so the score delta is attributable. Priority order (most to least likely to move the needle): effectiveness (does the rule change what the generator actually produces?) → structure → specificity → readability. Register it: evolve-rules.mjs --register --id=<id> --surface=dos|known-bug|visual-audit --text="…". A change that only adds words without changing output is rejected on sight (the size-ceiling guard — rules accrete toward over-constraint otherwise).
3. Apply + regenerate. Edit the one asset, commit it on the branch, then regenerate S×P from the same brief B with the new rules.
4. Score with the frozen evaluator. Run ~/.claude/skills/design-review/dr-cli <page> (the 4 machine gates MUST stay green — a change that breaks a gate is an instant revert) then the multi-critic. To beat critic noise, average N≥3 renders and require the gain to clear the margin, not a single lucky sample.
5. Held-out regression check. regression-gate.mjs --check --skill=S. If any existing canonical lost ground (more errors/warnings), the change overfit the target page — revert regardless of the target's score.
6. Decide (the ratchet). Keep iff new − base ≥ MARGIN and step 5 clean.
   • keep → advance the baseline to new; the branch now carries the new best.
   • else → git revert the change (not reset --hard — keep the failed attempt in history as a diagnostic), baseline stays. Append the row: evolve-ledger.mjs --append --skill=S --page=P --axis=<axis> --change="…" --base=<base> --new=<new> --decision=keep|revert.
7. Update the rule's track record. evolve-rules.mjs --fire=<id> always; add --catch when the change was kept (the rule earned its place). This is what lets the catalog self-prune: rules that fire without ever correlating with a real gain sink in score and become prune candidates.
8. Repeat from step 1 until --max-rounds (default 5) or a plateau.

Escaping local optima (human-gated)

Pure hill-climbing gets stuck — and design taste has valleys (the best layout may need a temporarily-worse intermediate). When the loop plateaus (two consecutive rounds with no keep on the same S×P), do an exploratory rewrite: a wholesale rewrite of the template/canonical rather than a tweak, scored against the stashed champion and adopted only if it beats it. Because this can move many things at once and touches a canonical, it is proposed to the human, not auto-applied (Darwin Phase 2.5, gated).

Guardrails (why this can't quietly go wrong)

• Noise margin — require Δ ≥ 2 on the averaged score; a +1 is sampling noise, and the ratchet would otherwise lock in lucky renders.
• Mechanical gates are the floor — any green→red on verify.py / visual-audit.mjs is an automatic revert, no matter the critic score. The mechanical checks are far harder to game than the LLM critics; weight them.
• Anti-gaming audit — for each critic axis, name the laziest score-raising fake (e.g. "more decorative SVGs → higher craft", "more sections → higher composition") and confirm a mechanical counter-check exists (orphan-figure, text-desert, hollow-card…). If a proposed rule's gain comes from the lazy move, reject it.
• The SPIN bound — the system can never get better than the evaluator can discriminate. So when progress stalls, the higher-leverage move is improving the evaluator (human-gated), not torturing the generator.
• Human-in-the-loop stays load-bearing for two things only: editing the evaluator/rubric, and exploratory rewrites of a whole skill/canonical. Per-rule edits that pass all gates + the regression check + the margin may auto-keep.
• Stop conditions — --max-rounds reached; plateau with no human-approved rewrite; or a regression the loop can't resolve in one revert → escalate to a human with the ledger frontier and the score trajectory.

Tools

• ~/.claude/skills/design-review/dr-cli --evolve — prints this loop's entry checklist + current ledger frontier (orientation before a run).
• evolve-ledger.mjs — append-only experiment log; --frontier shows the running-best curve, keep-rate, and biggest gains (autoresearch's progress.png as text). Lives at skills/design-review/evolution/ledger.tsv.
• evolve-rules.mjs — rule registry + EvolveR success score s=(catches+1)/(fires+2); --report flags prune candidates, --lint finds dead/duplicate rules.
• regression-gate.mjs — --baseline / --check the held-out canonicals (mechanical evaluator only — deterministic, so a regression is a real signal).
• The frozen evaluator it scores against: ~/.claude/skills/design-review/dr-cli (verify.py + visual-audit.mjs) and --multi-critic (the 4 weighted specialist critics).

When NOT to use

• A single page needs to be good now → use /design-loop, not this.
• Fewer than ~3 real critic verdicts exist for the S×P you want to optimize → there's nothing to diagnose yet; ship pages first.
• You want to change what "good" means (new gate, new rubric axis) → that's an evaluator change: do it by hand, then re-baseline. Never let the loop do it.