# Scratchpad — Thin-core prompt diet (#528)

**Branch:** `feat/contract-thin-core` · **Issue:** #528 · **Mode:** Delivery

## Objective

Cut the always-injected contract (`defaults/AGENTS.md` + `defaults/TOOLS.md` + `runtime/claude/RUNTIME.md`, inlined every turn by the launcher) without losing any hard gate. Restore the original "thin core + on-demand guides" intent.

## Change

- `defaults/AGENTS.md` → thin core: 12 hard gates verbatim, 37 operating rules condensed to ~15 bullets (detail already in `guides/E2E-DELIVERY.md`), Superpowers condensed, load order made on-demand (no halt-on-missing for STANDARDS), conditional guide-loading index retained.
- `defaults/TOOLS.md` → index; full catalog moved to new `guides/TOOLS-REFERENCE.md` (read on demand).
- `runtime/claude/RUNTIME.md` → slimmed (dedup tier table, terser pointers).

## Method (autoresearch-style validation)

1. Built a 9-probe role battery (backend/deploy/review/orchestrate/secrets/docs/simple-trap/no-stop-at-PR/agent-work) + a deterministic 18-signature gate-checklist.
2. Headless interactive runs (Claude Max **subscription**, tmux — no API), scored by per-probe rubric.
3. Keep-or-discard hill-climb (token cost gated by per-probe fidelity) proved the method; final design re-derived against THIS repo's content (diet-only, no drifted-deployment content imported).

## Validation evidence

- Gate-checklist: ALL gates + critical rules + mode lines + sequential-thinking + OpenBrain + Superpowers present.
- A/B on real repo content: **thin 7/9 vs monolith 5/9** probes; strictly better on deploy/review/simple-task; composed **8,827 → 4,122 tok (−53%)**.
- p11 (don't-stop-at-PR): 3→2/3 on one rubric line — verified a scorer/phrasing artifact (answer correctly cites gates §5/§9 + close-issue; gate verbatim-present). Variance: thin 2/2/3, v0 3/3/3.

## Decisions / risks

- **Diet-only** vs repo content (user decision). Did NOT import web1's Gate 13-15 / federated memory / OpenViking — canonical repo is behind those deployments; flagged for separate reconciliation.
- AGENTS/TOOLS are shared across runtimes → diet benefits codex/pi/opencode too; RUNTIME change is claude-only.
- p11 accepted as-is (user decision) — not gaming the rubric.

## Status

PR open, paused for maintainer merge ratification (fleet-governing change). `mosaic upgrade` will propagate on merge.
