# Phase 5 checkpoint — Resolution Frontier Search

## What changed

1. **Resolution Frontier Engine** — `POST /api/runs/{run_id}/resolution-search` ranks **residual** and **attention-head** sites using a **quick LIS scan** then full **causal ladder** on the top budget (TransformerLens).
2. **Probe ladder** — Each candidate stores **baseline → ablation → restoration (activation patch) → neighbor control** with `OutputView` + first-step top-k per step.
3. **MicroScope metrics** — LIS, SSS, RF, NC, PSS (with real **benchmark families**), CP, CRS — documented in `RESOLUTION_METRICS.md`; CRS weights exposed in API + exports.
4. **Benchmark families** — `GET /api/benchmark-families` + ZIP export; four families with prompt variants for **PSS**.
5. **Resolution Map UI** — Heatmap (layer×position), head table, sortable candidate table, detail drawer, bundle links — **evidence-backed only**.
6. **Claims** — Extended `MechanismClaim` metadata; **hypothesized** for top ranks; **intervention_supported** / **benchmark_reproduced** only under explicit ladder + family rules (`claims/resolution_synthesis.py`).
7. **Exports** — `resolution_search.bundle.zip`, `ladder-evidence.zip`, `benchmark_family.bundle.zip`.

## What is genuinely new vs Phase 4

- From single probes to **multi-step causal ladder + restoration + controls**.
- From isolated benchmarks to **families** driving **real** PSS computation.
- From artifact truth to **search ranking** with **declared non-truth composites**.

## What counts as a candidate resolution zone

A tuple **(target kind, layer, head?, position?)** with stored ladder evidence and decomposed scores — a **hypothesis** for where explanation-relevant computation may concentrate under our probes.

## What remains speculative

- CRS ordering; compressibility proxy; narrow families; greedy multi-step hooks; single model family.

## Strongest defensible claim now

MicroScope can **search, score, and export** candidate internal sites using **real ablation, restoration, and neighbor controls** on supported local models, with **explicit metrics and conservative reporting**.

## Strongest claim still not allowed

**Full** black-box resolution, **unique** minimal circuits, or **provider** causal internals without true access.