diff --git a/.gitignore b/.gitignore
index 7d7a50f..5fcaeff 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,7 +8,11 @@ dist/
 build/
 .venv/
 node_modules/
-data/
+data/*
+# IMP-46 u6 — track only the frame_cache directory marker; cached payloads stay ignored.
+!data/frame_cache/
+data/frame_cache/*
+!data/frame_cache/.gitkeep
 
 # session workspace (push X — 작업 흐름 trace, 사용자 결정 2026-05-08)
 forex/
diff --git a/Front/client/src/components/FramePanel.tsx b/Front/client/src/components/FramePanel.tsx
index c7f383a..050540e 100644
--- a/Front/client/src/components/FramePanel.tsx
+++ b/Front/client/src/components/FramePanel.tsx
@@ -19,6 +19,20 @@ interface FramePanelProps {
   onNoDesignToggle: () => void;
 }
 
+// ─── IMP-41 u3 — application_mode consequence tooltip map (issue #70) ────────
+// Keyed by application_mode VALUE (backend authoritative), NOT V4 label.
+// Source = src/phase_z2_pipeline.py APPLICATION_MODE_BY_V4_LABEL (:107-112)
+// emitted via Step 9 unit.application_candidates[] and forwarded by
+// designAgentApi.ts (IMP-41 u2). When applicationMode is absent (legacy
+// fixtures pre-IMP-32, or candidate filtered out at Step 9) the tooltip
+// falls back to the raw V4 label string per Stage 2 contract.
+const APPLICATION_MODE_TOOLTIP_KR: Record<string, string> = {
+  direct_insert: "코드 직접 적용",
+  same_frame_with_adjustment: "AI 보강 필요",
+  layout_or_region_change: "AI restructure 필요",
+  exclude: "render path 제외",
+};
+
 export default function FramePanel({
   slidePlan,
   selectedZone,
@@ -46,6 +60,26 @@ export default function FramePanel({
     return userSelection.overrides.zone_frames[targetRegion.id] || targetRegion.frame_match_strategy.frame_id;
   }, [selectedZone, selectedRegion, userSelection.overrides.zone_frames]);
 
+  // IMP-47B u11 — reject-click confirm guard. Per #76 policy: 사용자가 reject
+  // 카드 명시 클릭 → backend `--override-frame` 전달 + reject frame 유지 + AI 재구성.
+  // The window.confirm makes the AI-rebuild intent explicit (deselecting an
+  // already-applied reject frame does not prompt). Pure UX gate — no state
+  // mutation here; the parent `onFrameSelect` still owns the override apply.
+  const handleFrameSelect = React.useCallback(
+    (candidate: FrameCandidate) => {
+      const isReject = candidate.label === "reject";
+      const alreadyApplied = currentFrameId === candidate.id;
+      if (isReject && !alreadyApplied) {
+        const ok = window.confirm(
+          `"${candidate.name}" 은 V4 reject 라벨입니다.\n선택 시 frame 은 유지되고 AI 가 콘텐츠를 frame 구조에 맞게 재구성합니다.\n계속하시겠습니까?`,
+        );
+        if (!ok) return;
+      }
+      onFrameSelect(candidate.id);
+    },
+    [currentFrameId, onFrameSelect],
+  );
+
   if (!selectedZone) {
     return (
       <div className="h-full flex flex-col items-center justify-center bg-slate-50 p-8 text-center text-slate-400">
@@ -151,7 +185,7 @@ export default function FramePanel({
                 className="w-full"
               >
                 <button
-                  onClick={() => onFrameSelect(candidate.id)}
+                  onClick={() => handleFrameSelect(candidate)}
                   draggable
                   onDragStart={(e) => {
                     e.dataTransfer.setData("frameId", candidate.id);
@@ -235,22 +269,35 @@ export default function FramePanel({
                            </span>
                          )}
                          {/* V4 label badge */}
-                         {candidate.label && (
-                           <span
-                             className={`text-[8px] font-black uppercase tracking-tight px-1.5 py-0.5 rounded ${
-                               candidate.label === "use_as_is"
-                                 ? "bg-emerald-100 text-emerald-700"
-                                 : candidate.label === "light_edit"
-                                 ? "bg-blue-100 text-blue-700"
-                                 : candidate.label === "restructure"
-                                 ? "bg-amber-100 text-amber-700"
-                                 : "bg-red-100 text-red-700"
-                             }`}
-                             title={`V4 label: ${candidate.label}`}
-                           >
-                             {candidate.label}
-                           </span>
-                         )}
+                         {candidate.label && (() => {
+                           // IMP-41 u3 — applicationMode-keyed Korean consequence
+                           // tooltip with legacy fallback. applicationMode is
+                           // forwarded by designAgentApi.ts (u2) from Step 9
+                           // unit.application_candidates[]; undefined when the
+                           // backend did not emit a mapping for this candidate.
+                           const consequence = candidate.applicationMode
+                             ? APPLICATION_MODE_TOOLTIP_KR[candidate.applicationMode]
+                             : undefined;
+                           const badgeTitle = consequence
+                             ? `${consequence} (${candidate.applicationMode})`
+                             : `V4 label: ${candidate.label}`;
+                           return (
+                             <span
+                               className={`text-[8px] font-black uppercase tracking-tight px-1.5 py-0.5 rounded ${
+                                 candidate.label === "use_as_is"
+                                   ? "bg-emerald-100 text-emerald-700"
+                                   : candidate.label === "light_edit"
+                                   ? "bg-blue-100 text-blue-700"
+                                   : candidate.label === "restructure"
+                                   ? "bg-amber-100 text-amber-700"
+                                   : "bg-red-100 text-red-700"
+                               }`}
+                               title={badgeTitle}
+                             >
+                               {candidate.label}
+                             </span>
+                           );
+                         })()}
                          {/* IMP-29 u3 — route hint chip (skip when direct_render = default). */}
                          {showRouteChip && (
                            <span
diff --git a/Front/client/src/pages/Home.tsx b/Front/client/src/pages/Home.tsx
index 00fa847..b983e64 100644
--- a/Front/client/src/pages/Home.tsx
+++ b/Front/client/src/pages/Home.tsx
@@ -21,6 +21,7 @@ import {
   runPipeline,
   loadRun,
   computeZonePositions,
+  formatAiRepairHumanReviewMessage,
   type RunMeta,
   type PipelineOverrides,
 } from "../services/designAgentApi";
@@ -370,6 +371,13 @@ export default function Home() {
       }));
       setRunMeta(runMeta);
       toast.success(`run "${result.run_id}" 완료 — ${runMeta.status}`);
+      // IMP-47B u11 — surface Step 12 AI repair failure axes (error /
+      // coverage_violated / unsupported_kind) as a human_review notification.
+      // Auto-pipeline first ([[feedback_auto_pipeline_first]]): no review_queue
+      // insertion — just an explicit error toast directing the user to pick
+      // another frame or edit manually. Helper returns null on success path.
+      const aiReviewMsg = formatAiRepairHumanReviewMessage(runMeta.ai_repair_status);
+      if (aiReviewMsg) toast.error(aiReviewMsg);
     } catch (err) {
       console.error(err);
       toast.error(
diff --git a/Front/client/src/services/designAgentApi.ts b/Front/client/src/services/designAgentApi.ts
index 5db5ffa..32cd18c 100644
--- a/Front/client/src/services/designAgentApi.ts
+++ b/Front/client/src/services/designAgentApi.ts
@@ -223,6 +223,35 @@ export interface FilteredSectionReason {
   position?: string | null;
 }
 
+// IMP-47B u11 — verbatim mirror of step20_slide_status.ai_repair_status (u8 schema).
+// Surfaces Step 12 AI repair outcomes so the frontend can render a
+// human_review notification when AI proposal validation, coverage, or call
+// itself failed. Enum / field names kept verbatim — no frontend redefinition.
+export interface AiRepairStatus {
+  status: "ok" | "applied" | "unsupported_kind" | "coverage_violated" | "error" | string;
+  counts: {
+    total: number;
+    applied: number;
+    no_proposal: number;
+    no_zone_match: number;
+    unsupported_kind: number;
+    error: number;
+  };
+  unsupported_kind_records: Array<{
+    unit_index?: number | null;
+    source_section_ids: string[];
+    apply_status: string;
+  }>;
+  error_records: Array<{
+    unit_index?: number | null;
+    source_section_ids: string[];
+    error: string;
+  }>;
+  coverage_status: string;
+  dropped_section_ids: string[];
+  human_review_required: boolean;
+}
+
 export interface RunMeta {
   run_id: string;
   mdx_path: string;
@@ -237,6 +266,38 @@ export interface RunMeta {
   layout_candidates: string[]; // step07 layout_candidates list
   region_layout_candidates_by_zone: Record<string, string[]>;       // step08 placeholder
   display_strategy_candidates_by_zone: Record<string, string[]>;    // step08 placeholder
+  /** IMP-47B u11 — Step 12 AI repair outcome (u8 surfacing). null when
+   *  step20 omits the field (legacy runs / pipeline aborted before Step 12). */
+  ai_repair_status: AiRepairStatus | null;
+}
+
+/**
+ * IMP-47B u11 — Build the human_review notification text when Step 12 AI repair
+ * reports a failure axis. Returns null when no notification is needed (success,
+ * no AI invocation, or human_review_required=false). Pure function — no DOM, no
+ * toast side-effect — so it can be unit-tested without React Testing Library.
+ *
+ * Failure axes mapped to user-facing text (verbatim policy from
+ * IMP-47B #76 guardrail: "AI 호출 실패 / proposal validation 실패 / coverage 미달
+ * → frontend 에 명확한 notification").
+ */
+export function formatAiRepairHumanReviewMessage(
+  ai: AiRepairStatus | null | undefined,
+): string | null {
+  if (!ai || !ai.human_review_required) return null;
+  if (ai.status === "error") {
+    const n = ai.counts?.error ?? ai.error_records?.length ?? 0;
+    return `AI 재구성 호출 실패 (${n}건) — 다른 frame 선택 또는 수동 편집 필요`;
+  }
+  if (ai.status === "coverage_violated") {
+    const dropped = (ai.dropped_section_ids || []).join(", ");
+    return `AI 재구성 후 콘텐츠 누락 (dropped: ${dropped || "?"}) — 다른 frame 선택 또는 수동 편집 필요`;
+  }
+  if (ai.status === "unsupported_kind") {
+    const n = ai.counts?.unsupported_kind ?? ai.unsupported_kind_records?.length ?? 0;
+    return `AI 제안 형식 미지원 (${n}건) — 다른 frame 선택 또는 수동 편집 필요`;
+  }
+  return `AI 재구성 human_review 필요 (status: ${ai.status})`;
 }
 
 export interface LoadRunResult {
@@ -428,6 +489,7 @@ export async function loadRun(runId: string): Promise<LoadRunResult> {
         z.display_strategy_candidates ?? [],
       ])
     ),
+    ai_repair_status: (slideStatus.data?.ai_repair_status ?? null) as AiRepairStatus | null,
   };
 
   // ── NormalizedContent ──
@@ -527,9 +589,27 @@ export async function loadRun(runId: string): Promise<LoadRunResult> {
       if (lp !== 0) return lp;
       return (b.confidence ?? 0) - (a.confidence ?? 0);
     });
+    // ─── IMP-41 u2 — application_candidates enrichment (issue #70) ───────────
+    // Backend Step 9 emits `unit.application_candidates[]` (src/phase_z2_pipeline.py
+    // _application_candidates_for_unit, :3071-3092) one entry per v4 candidate with
+    // application_mode / auto_applicable / delegated_to derived from
+    // APPLICATION_MODE_BY_V4_LABEL (:107-112). Enrichment ONLY — does NOT alter
+    // candidate source priority, sorting, or TOP_N_FRAMES slicing.
+    const applicationCandidates: any[] = Array.isArray(unit.application_candidates)
+      ? unit.application_candidates
+      : [];
+    const applicationModeMap = new Map<string, any>();
+    applicationCandidates.forEach((ac: any) => {
+      const key = ac?.template_id;
+      if (typeof key === "string" && key.length > 0) {
+        applicationModeMap.set(key, ac);
+      }
+    });
     const frameCandidates: FrameCandidate[] = v4Source
       .slice(0, TOP_N_FRAMES)
-      .map((c: any) => ({
+      .map((c: any) => {
+        const appMatch = applicationModeMap.get(c.template_id);
+        return ({
         id: c.template_id,
         name: c.template_id,
         score: c.confidence ?? 0,
@@ -559,7 +639,15 @@ export async function loadRun(runId: string): Promise<LoadRunResult> {
         decision: c.decision,
         reason: c.reason,
         capacityFit: c.capacity_fit,
-      }));
+        // ─── IMP-41 u2 — application_mode forwarding (issue #70) ───────────
+        // Source = unit.application_candidates[] indexed by template_id above.
+        // Optional fields — undefined when no matching application_candidate
+        // (legacy fixtures pre-IMP-32 or candidates filtered out at Step 9).
+        applicationMode: appMatch?.application_mode,
+        autoApplicable: appMatch?.auto_applicable,
+        delegatedTo: appMatch?.delegated_to ?? null,
+      });
+      });
 
     const displayStrategy = (
       runMeta.display_strategy_candidates_by_zone[posEntry.name]?.[0] ??
diff --git a/Front/client/src/types/designAgent.ts b/Front/client/src/types/designAgent.ts
index 34fdda9..baf6831 100644
--- a/Front/client/src/types/designAgent.ts
+++ b/Front/client/src/types/designAgent.ts
@@ -175,6 +175,19 @@ export interface FrameCandidate {
   reason?: string | null;
   /** Capacity vs. content shape audit (compute_capacity_fit output). */
   capacityFit?: CapacityFitEvidence | null;
+
+  // ─── IMP-41 application_mode forwarding (issue #70 u1) ─────────────────────
+  // Source = src/phase_z2_pipeline.py APPLICATION_MODE_BY_V4_LABEL (:107-112),
+  // emitted by _application_candidates_for_unit() into Step 9
+  // unit.application_candidates[]. Optional — legacy fixtures pre-IMP-32 omit
+  // these and the FramePanel tooltip falls back to the raw V4 label.
+
+  /** Application mode mapped from V4 label by backend (authoritative). */
+  applicationMode?: 'direct_insert' | 'same_frame_with_adjustment' | 'layout_or_region_change' | 'exclude';
+  /** True when backend marks the candidate as automatically applicable. */
+  autoApplicable?: boolean;
+  /** Delegation target step / actor (e.g. "step10_contract_check", "human_review"). */
+  delegatedTo?: string | null;
 }
 
 // ─────────────────────────────────────────────────────────────────────────────
diff --git a/Front/vite.config.ts b/Front/vite.config.ts
index 789d708..6e3d0f2 100644
--- a/Front/vite.config.ts
+++ b/Front/vite.config.ts
@@ -346,8 +346,10 @@ function vitePluginPhaseZApi(): Plugin {
           const pythonExe = process.platform === "win32" ? "python.exe" : "python";
           // 2026-05-14 — env toggle forward (보고용 일회성).
           //   PHASE_Z_ALLOW_RESTRUCTURE / PHASE_Z_ALLOW_REJECT : status 통과
-          //   PHASE_Z_MAX_RANK=32 : V4 fallback chain 의 max_rank 확대 (등록 frame 까지 검색)
-          // 04-1 (all reject) / 05-2 (rank 1~3 미등록) 등 자동 매칭 가능.
+          // 2026-05-21 — IMP-38 retire PHASE_Z_MAX_RANK env (never read by backend).
+          //   v4 fallback chain max_rank 는 templates/phase_z2/catalog/v4_fallback_policy.yaml 의
+          //   정식 정책 (dynamic_usable_count_based) 으로 결정 — backend src/phase_z2_pipeline.py
+          //   의 lookup_v4_match_with_fallback() 가 load_v4_fallback_policy() 로 적용.
           const proc = spawn(pythonExe, cliArgs, {
             cwd: DESIGN_AGENT_ROOT,
             shell: false,
@@ -355,7 +357,6 @@ function vitePluginPhaseZApi(): Plugin {
               ...process.env,
               PHASE_Z_ALLOW_RESTRUCTURE: "1",
               PHASE_Z_ALLOW_REJECT: "1",
-              PHASE_Z_MAX_RANK: "32",
             },
           });
 
diff --git a/docs/architecture/IMP-17-CARVE-OUT.md b/docs/architecture/IMP-17-CARVE-OUT.md
index 555111a..533a5af 100644
--- a/docs/architecture/IMP-17-CARVE-OUT.md
+++ b/docs/architecture/IMP-17-CARVE-OUT.md
@@ -51,5 +51,5 @@ Phase Q `content_editor.py` 는 **Archive Candidate** ([`PHASE-Q-AUDIT.md`](PHAS
 | Step 12 entry | `src.phase_z2_ai_fallback.step12.gather_step12_ai_repair_proposals` — IMP-30 provisional gate (`not_provisional` skip) AND reject gate (`design_reference_only_no_ai` skip) AND non-AI route catch-all run BEFORE `route_ai_fallback`. |
 | Step 17 entry | `src.phase_z2_ai_fallback.step17.gather_step17_ai_repair_proposals` — STRUCTURALLY BLOCKED. Every unit returns `skip_reason="step17_ai_blocked_imp_34_35_prerequisites_missing"`. Module does NOT import `route_ai_fallback` / `AiFallbackClient` / `anthropic`. |
 | Cascade order | `src.phase_z2_ai_fallback.step17.OVERFLOW_CASCADE_ORDER = (DETERMINISTIC, POPUP, AI_REPAIR, USER_OVERRIDE)` — single source of truth for Step 17 consumers. Aligns with line 16 of this doc. |
-| IMP-46 cache gate | `src.phase_z2_ai_fallback.cache.save_proposal(..., visual_check_passed, user_approved)` raises `AiFallbackCacheGateError` unless BOTH gates are True; storage backend then raises `NotImplementedError` (IMP-46 marker). `read_proposal` returns `None` until IMP-46 lands a backend. |
+| IMP-46 cache gate | `src.phase_z2_ai_fallback.cache.save_proposal(..., visual_check_passed, user_approved, auto_cache=False)` raises `AiFallbackCacheGateError` unless `visual_check_passed=True` AND (`user_approved=True` OR `auto_cache=True`). Persistent JSON backend at `data/frame_cache/{frame_id}/{signature_hash}.json` (u2); cache key = structural signature over 8 axes (u1+u4); read-side fingerprint invalidation via `read_proposal(..., fingerprints=...)` strict equality (u3); `--auto-cache` CLI flag + `settings.ai_fallback_auto_cache` (default `False`) bypasses ONLY the `user_approved` gate (u5); repo root tracked via `data/frame_cache/.gitkeep` with cached payloads git-ignored (u6). `read_proposal` returns `None` on missing / corrupt / fingerprint-mismatched entries — cache is a hint, never a hard dependency. |
 | AST isolation | `tests/phase_z2_ai_fallback/test_ast_isolation.py` parses every `*.py` under `src/phase_z2_ai_fallback/` and forbids Phase Q runtime / Kei client / `src.phase_z2_*` (non-fallback) imports. Whitelist = `src.config` + intra-package + stdlib + `anthropic` + `pydantic`. |
diff --git a/src/config.py b/src/config.py
index f9de404..fec6a38 100644
--- a/src/config.py
+++ b/src/config.py
@@ -26,6 +26,14 @@ class Settings(BaseSettings):
     ai_fallback_budget_per_run: int = 10
     ai_fallback_circuit_breaker_threshold: int = 5
 
+    # IMP-46 u5 — auto-cache flag. When True, `save_proposal` bypasses the
+    # `user_approved` gate only (`visual_check_passed` is never bypassed).
+    # Default OFF preserves the dual-gate contract; the CLI flag
+    # `--auto-cache` in `src/phase_z2_pipeline.py` mutates this setting at
+    # parse time. Downstream callers MUST source the flag from Settings,
+    # never inline literals.
+    ai_fallback_auto_cache: bool = False
+
     model_config = {"env_file": ".env", "env_file_encoding": "utf-8"}
 
 
diff --git a/src/phase_z2_ai_fallback/cache.py b/src/phase_z2_ai_fallback/cache.py
index 9ceba97..43debb9 100644
--- a/src/phase_z2_ai_fallback/cache.py
+++ b/src/phase_z2_ai_fallback/cache.py
@@ -1,48 +1,158 @@
-"""IMP-33 u6 — AI fallback proposal cache (IMP-46 gate, no persistent storage).
+"""IMP-46 u2 + u3 + u5 — Persistent JSON cache backend for AI fallback proposals.
 
-This module defines the cache contract that IMP-33 callers use to remember
-AI fallback proposals across runs. The persistent storage layer itself is
-out-of-scope for IMP-33 and is owned by IMP-46 (frame transformation cache).
+Replaces the IMP-33 u6 ``NotImplementedError`` stub with a content-addressed
+store at ``data/frame_cache/{frame_id}/{signature_hash}.json``.
 
-Behaviour locked by Stage 2 plan (u6):
+Key format:
 
-* ``read_proposal(key)`` always returns ``None`` until IMP-46 lands a
-  persistent backend. Callers MUST handle the cache-miss path.
-* ``save_proposal(key, proposal, *, visual_check_passed, user_approved)``
-  enforces the IMP-46 gate before any storage write is attempted:
+* ``read_proposal(key)`` / ``save_proposal(key, ...)`` accept a string ``key``
+  of the form ``"{frame_id}::{signature_hash}"``. The two components are
+  parsed inside this module so that upstream callers (router, step 12)
+  remain unaware of the on-disk layout.
+* ``read_proposal`` on a malformed (legacy) key silently returns ``None``
+  — the IMP-33 u7 router currently passes a legacy ``cache_key`` string,
+  and u4 will switch to the structural form. Until then, all such reads
+  must miss safely (no exception, no false hit).
+* ``save_proposal`` on a malformed key raises ``ValueError`` (loud, never
+  silent) — writes are gated and must use the structural form.
 
-    - ``visual_check_passed=False`` -> ``AiFallbackCacheGateError``
-    - ``user_approved=False``       -> ``AiFallbackCacheGateError``
+Stored payload (one JSON file per (frame_id, signature_hash) pair):
 
-  Only when BOTH gates are True does control reach the storage layer,
-  which currently raises ``NotImplementedError`` (the IMP-46 marker).
+    {
+      "schema_version": 1,
+      "proposal":       <AiFallbackProposal.model_dump(mode="json")>,
+      "slide_css":      <str | null>,
+      "fingerprints":   {"contract_sha": ..., "partial_sha": ..., "catalog_sha": ...}
+    }
 
-Guardrails:
+u3 invalidation contract (this module is a *comparator*, not a *computer*):
 
-* No Anthropic import; cache is pure proposal bookkeeping.
-* No MDX read/write; proposals are u2 ``AiFallbackProposal`` instances.
-* No silent persistence: gate violations are loud, not skipped writes
-  (`feedback_artifact_status_naming`).
+* ``save_proposal`` persists the ``fingerprints`` dict supplied by the
+  caller verbatim. Cache.py never computes any fingerprint — the three
+  declared shas (``contract_sha`` / ``partial_sha`` / ``catalog_sha``) are
+  computed by callers from the live contract YAML / partial templates /
+  catalog payloads and handed in. Keeping the computation out of cache.py
+  preserves AI isolation (no Phase Z runtime knowledge in the cache
+  module) and keeps the cache schema-agnostic — additional fingerprint
+  axes can be added without editing cache.py.
+* ``read_proposal`` accepts an optional ``fingerprints`` kwarg. When
+  supplied, the stored ``fingerprints`` dict must equal the caller's dict
+  exactly (strict equality, NOT subset). Any mismatch — including a key
+  the caller demands but the stored entry lacks, OR a key the stored
+  entry has but the caller does not pass — returns ``None``. Default
+  ``fingerprints=None`` performs no comparison (back-compat for legacy
+  callers that have not yet adopted fingerprint-aware lookup).
+
+Guardrails (locked by Stage 2 plan):
+
+* Both write gates preserved — ``visual_check_passed=False`` always
+  raises ``AiFallbackCacheGateError`` BEFORE any filesystem touch.
+  ``user_approved=False`` also raises by default; the IMP-46 u5
+  ``auto_cache=True`` override bypasses ONLY the ``user_approved`` gate
+  (``visual_check_passed`` is never bypassed). Gate violation never
+  silently no-ops.
+* Missing or corrupt files cause ``read_proposal`` to return ``None`` —
+  the cache is a hint, never a hard dependency. Errors are not propagated
+  to callers because the AI fallback path can always recompute.
+* ``mkdir(parents=True, exist_ok=True)`` is performed lazily on save.
+* No Anthropic / MDX / Phase Z runtime imports (AI isolation contract).
+* Cache root is held as a module-level :data:`CACHE_ROOT` so tests can
+  redirect writes via ``monkeypatch.setattr`` without subclassing.
+
+u5 auto-cache contract (CLI ``--auto-cache`` + ``settings.ai_fallback_auto_cache``):
+
+* ``save_proposal(..., auto_cache=True)`` only bypasses the
+  ``user_approved`` gate; ``visual_check_passed`` remains mandatory.
+* ``auto_cache`` is keyword-only and defaults to ``False`` — existing
+  callers (and the test suite) see the original dual-gate behaviour
+  unless they opt in explicitly.
+* The truth table over ``(visual_check_passed, user_approved, auto_cache)``
+  has eight cells; exactly three succeed:
+  ``(True, True, False)``, ``(True, True, True)``, and
+  ``(True, False, True)``. Every other cell raises
+  ``AiFallbackCacheGateError``.
 """
 from __future__ import annotations
 
+import json
+import pathlib
+
 from src.phase_z2_ai_fallback.schema import AiFallbackProposal
 
 
+SCHEMA_VERSION = 1
+KEY_DELIMITER = "::"
+CACHE_ROOT: pathlib.Path = pathlib.Path("data/frame_cache")
+
+
 class AiFallbackCacheGateError(RuntimeError):
     """Raised when ``save_proposal`` is called without both IMP-46 gates True."""
 
 
-def read_proposal(key: str) -> AiFallbackProposal | None:
+def _parse_key(key: str) -> tuple[str, str] | None:
+    """Parse a ``frame_id::signature_hash`` key. Returns ``None`` if malformed."""
+    if KEY_DELIMITER not in key:
+        return None
+    frame_id, _, signature_hash = key.partition(KEY_DELIMITER)
+    if not frame_id or not signature_hash:
+        return None
+    if KEY_DELIMITER in signature_hash:
+        return None
+    return frame_id, signature_hash
+
+
+def _cache_path(frame_id: str, signature_hash: str) -> pathlib.Path:
+    return CACHE_ROOT / frame_id / f"{signature_hash}.json"
+
+
+def read_proposal(
+    key: str,
+    *,
+    fingerprints: dict | None = None,
+) -> AiFallbackProposal | None:
     """Look up a previously cached proposal by ``key``.
 
-    IMP-33 ships without a persistent backend; this stub always returns
-    ``None`` so callers exercise the cache-miss path. The persistent
-    backend will be wired by IMP-46.
+    Returns ``None`` for:
+
+    * empty / non-string key → ``ValueError`` (loud);
+    * non-dict ``fingerprints`` (when supplied) → ``TypeError`` (loud,
+      symmetric with :func:`save_proposal`);
+    * legacy key format (no ``::`` delimiter) → silent ``None`` (router
+      back-compat until u4 switches to the structural form);
+    * missing file under ``data/frame_cache/{frame_id}/{signature_hash}.json``;
+    * corrupt JSON / payload schema mismatch — read errors never propagate;
+    * ``fingerprints`` supplied AND stored ``fingerprints`` field is not a
+      dict OR does not equal the supplied dict (strict equality,
+      u3 invalidation).
     """
     if not isinstance(key, str) or not key:
         raise ValueError("cache key must be a non-empty string")
-    return None
+    if fingerprints is not None and not isinstance(fingerprints, dict):
+        raise TypeError("fingerprints must be a dict or None")
+    parsed = _parse_key(key)
+    if parsed is None:
+        return None
+    frame_id, signature_hash = parsed
+    path = _cache_path(frame_id, signature_hash)
+    if not path.is_file():
+        return None
+    try:
+        data = json.loads(path.read_text(encoding="utf-8"))
+    except (OSError, json.JSONDecodeError):
+        return None
+    if not isinstance(data, dict):
+        return None
+    if fingerprints is not None:
+        stored = data.get("fingerprints")
+        if not isinstance(stored, dict) or stored != fingerprints:
+            return None
+    proposal_dict = data.get("proposal")
+    if not isinstance(proposal_dict, dict):
+        return None
+    try:
+        return AiFallbackProposal.model_validate(proposal_dict)
+    except Exception:  # noqa: BLE001 — corrupt payload must miss, not raise
+        return None
 
 
 def save_proposal(
@@ -51,13 +161,39 @@ def save_proposal(
     *,
     visual_check_passed: bool,
     user_approved: bool,
-) -> None:
-    """Persist ``proposal`` under ``key`` once both IMP-46 gates are True.
+    slide_css: str | None = None,
+    fingerprints: dict | None = None,
+    auto_cache: bool = False,
+) -> pathlib.Path:
+    """Persist ``proposal`` under ``key`` once the IMP-46 gates clear.
 
-    Raises ``AiFallbackCacheGateError`` if either gate is False — the
-    proposal is NOT written. When both gates are True, storage raises
-    ``NotImplementedError`` (the IMP-46 persistent backend has not landed
-    yet).
+    Gate contract (IMP-46 u5 truth table):
+
+    * ``visual_check_passed=False`` -> :class:`AiFallbackCacheGateError`
+      always (never bypassable; ``auto_cache`` cannot override).
+    * ``user_approved=False`` AND ``auto_cache=False`` ->
+      :class:`AiFallbackCacheGateError`.
+    * ``user_approved=False`` AND ``auto_cache=True`` -> bypass the
+      user-approval gate (IMP-46 u5 CLI / settings opt-in).
+    * Otherwise (``visual_check_passed=True`` AND either
+      ``user_approved=True`` OR ``auto_cache=True``) -> persist payload.
+
+    Gate violations are raised BEFORE any filesystem touch — no parent
+    directory is created, no file is written. When the gates clear the
+    JSON payload (schema_version + proposal + slide_css + fingerprints)
+    is written to ``data/frame_cache/{frame_id}/{signature_hash}.json``
+    and the resolved :class:`pathlib.Path` is returned.
+
+    ``slide_css`` may be ``None`` (no slide-level CSS captured) or a
+    string. ``fingerprints`` may be ``None`` (treated as empty dict) or a
+    dict mapping fingerprint name to SHA hex digest.
+
+    ``auto_cache`` is keyword-only and defaults to ``False``. It is wired
+    from :data:`src.config.settings.ai_fallback_auto_cache`, which the
+    ``--auto-cache`` CLI flag in ``src/phase_z2_pipeline.py`` toggles at
+    parse time. The cache module never reads the setting itself — the
+    caller passes the resolved boolean — so AI-isolation contracts
+    (no Phase Z runtime / no Anthropic import) remain intact.
     """
     if not isinstance(key, str) or not key:
         raise ValueError("cache key must be a non-empty string")
@@ -66,17 +202,42 @@ def save_proposal(
             "proposal must be an AiFallbackProposal instance "
             f"(got {type(proposal).__name__})"
         )
+    if not isinstance(auto_cache, bool):
+        raise TypeError("auto_cache must be a bool")
     if not visual_check_passed:
         raise AiFallbackCacheGateError(
             "IMP-46 gate: visual_check_passed=False; refusing to cache an "
-            "unverified proposal."
+            "unverified proposal. (auto_cache cannot bypass this gate.)"
         )
-    if not user_approved:
+    if not user_approved and not auto_cache:
         raise AiFallbackCacheGateError(
-            "IMP-46 gate: user_approved=False; refusing to cache without "
-            "explicit user approval."
+            "IMP-46 gate: user_approved=False and auto_cache=False; "
+            "refusing to cache without explicit user approval. Pass "
+            "auto_cache=True (or --auto-cache on the CLI) to bypass."
         )
-    raise NotImplementedError(
-        "IMP-46 persistent cache storage is not implemented yet; "
-        "this is the IMP-33 u6 stub marker."
+    if slide_css is not None and not isinstance(slide_css, str):
+        raise TypeError("slide_css must be a string or None")
+    if fingerprints is None:
+        fingerprints = {}
+    elif not isinstance(fingerprints, dict):
+        raise TypeError("fingerprints must be a dict or None")
+    parsed = _parse_key(key)
+    if parsed is None:
+        raise ValueError(
+            "cache key must be in "
+            f"'frame_id{KEY_DELIMITER}signature_hash' format; got {key!r}"
+        )
+    frame_id, signature_hash = parsed
+    path = _cache_path(frame_id, signature_hash)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    payload = {
+        "schema_version": SCHEMA_VERSION,
+        "proposal": proposal.model_dump(mode="json"),
+        "slide_css": slide_css,
+        "fingerprints": dict(fingerprints),
+    }
+    path.write_text(
+        json.dumps(payload, sort_keys=True, ensure_ascii=False, indent=2),
+        encoding="utf-8",
     )
+    return path
diff --git a/src/phase_z2_ai_fallback/step12.py b/src/phase_z2_ai_fallback/step12.py
index 2cb8a98..f0df5a9 100644
--- a/src/phase_z2_ai_fallback/step12.py
+++ b/src/phase_z2_ai_fallback/step12.py
@@ -1,32 +1,72 @@
-"""IMP-33 u8 — Step 12 AI repair wiring (IMP-30 provisional units only).
+"""IMP-33 u8 + IMP-46 u4 — Step 12 AI repair wiring with structural cache key.
 
 Phase Z Step 12 = slot_payload (the runtime "light_edit / restructure" surface
 where AI-assisted frame-aware adaptation is allowed per IMP-17 carve-out).
 This module is the only call site that pipes Phase Z composition units into
-``src.phase_z2_ai_fallback.router.route_ai_fallback``. Two structural gates
-preserve the AI isolation contract:
+``src.phase_z2_ai_fallback.router.route_ai_fallback``. One structural gate
+preserves the AI isolation contract:
 
 * IMP-30 provisional gate — units with ``provisional=False`` are skipped
   before any route classification. AI repair is reserved for first-render
   invariant survivors (no rank-1 V4 evidence, recovered as provisional).
-* Reject gate — units whose V4 label maps to ``design_reference_only``
-  (``reject``) are skipped with ``skip_reason="design_reference_only_no_ai"``.
-  Reject path is design reference only — never an AI call.
+
+Per IMP-47B u1+u2, the ``reject`` V4 label routes to
+``ai_adaptation_required`` (no longer ``design_reference_only``) and is
+admitted to the AI repair path; the legacy "reject gate" short-circuit is
+removed. Any unit whose ``route_hint`` is not ``ai_adaptation_required``
+still falls through to the catch-all ``route_not_ai_adaptation:<hint>``
+skip — that single gate continues to enforce the AI=0 normal path.
 
 Combined with the u7 router's flag-off + route-gate short-circuits, the
 default Phase Z run path performs zero AI calls (PZ-1). Save to cache is
 NOT performed here — that is the caller's responsibility AFTER
 ``visual_check_passed=True`` AND ``user_approved=True`` (u6 IMP-46 gate).
+
+IMP-46 u4 — structural cache key + fingerprints
+------------------------------------------------
+
+The legacy ``cache_key`` was ``"{template_id}::{sorted(source_section_ids)}"``
+which leaked sample / section identity into the cache surface
+(no-hardcoding lock violation: structurally identical content with
+different MDX section ids would miss). u4 replaces it with
+``"{frame_id}::{signature_hash}"`` where ``signature_hash`` is the
+deterministic SHA256 over the 8 declared structural axes (see
+``src.phase_z2_ai_fallback.signature``). Per-unit signature inputs are
+read from unit attributes:
+
+* ``cardinality`` (int | None)         — also forwarded to ``v4_result``
+* ``layout_preset`` (str)
+* ``zone_position`` (str)
+* ``source_shape`` (str)               — bullet / paragraph / table / mixed
+* ``h3_count`` (int)
+* ``char_count`` (int)                 — bucketed via ``bucket_char_count``
+
+In parallel the three invalidation fingerprints
+(``contract_sha`` / ``partial_sha`` / ``catalog_sha``) are computed and
+attached to the record. The cache.py module remains a *comparator* — all
+fingerprint *computation* happens here (or via injected loaders) so the
+cache schema-agnostic contract is preserved. The router's existing
+``read_proposal(cache_key)`` continues to perform exact-match lookup only
+(fuzzy is deferred per Stage 2 plan); read-side fingerprint validation
+through the router is a follow-up axis.
 """
 from __future__ import annotations
 
+import hashlib
+import json
 from typing import Any, Callable, Iterable
 
 from src.phase_z2_ai_fallback.router import route_ai_fallback
+from src.phase_z2_ai_fallback.signature import bucket_char_count, build_signature
 
 
 _AI_ADAPTATION_ROUTE = "ai_adaptation_required"
-_DESIGN_REFERENCE_ROUTE = "design_reference_only"
+
+
+def _sha256_of(payload: Any) -> str:
+    """Deterministic SHA256 hex digest over a JSON-serialisable payload."""
+    encoded = json.dumps(payload, sort_keys=True, ensure_ascii=False).encode("utf-8")
+    return hashlib.sha256(encoded).hexdigest()
 
 
 def gather_step12_ai_repair_proposals(
@@ -38,6 +78,7 @@ def gather_step12_ai_repair_proposals(
     figma_partial_loader: Callable[[str], dict] | None = None,
     internal_region_lookup: Callable[[Any], dict] | None = None,
     mdx_text_loader: Callable[[Any], str] | None = None,
+    catalog_sha_loader: Callable[[], str] | None = None,
 ) -> list[dict]:
     """Return one record per unit describing the Step 12 AI repair decision.
 
@@ -55,8 +96,16 @@ def gather_step12_ai_repair_proposals(
           "skip_reason": str | None,
           "proposal": dict | None,
           "error": str | None,
+          "cache_key": str | None,        # IMP-46 u4
+          "fingerprints": dict | None,    # IMP-46 u4
         }
 
+    ``cache_key`` and ``fingerprints`` are populated only when the unit
+    reaches the AI-eligible code path (provisional + ai_adaptation route).
+    Skipped units retain ``None`` for both — the structural axes
+    (layout_preset / zone_position / source_shape / h3_count / char_count)
+    are not guaranteed to be set for non-AI paths.
+
     ``ai_called`` is True only when ``route_ai_fallback`` was invoked AND
     returned a proposal OR raised. Flag-off / route-mismatch returns
     ``None`` from the router and is surfaced as ``ai_called=False`` with
@@ -64,6 +113,9 @@ def gather_step12_ai_repair_proposals(
     "router decided not to run" from "router ran and returned a proposal".
     """
     records: list[dict] = []
+    catalog_sha = (
+        catalog_sha_loader() if catalog_sha_loader is not None else ""
+    )
     for index, unit in enumerate(units):
         label = getattr(unit, "label", None)
         route_hint = route_for_label(label)
@@ -78,15 +130,13 @@ def gather_step12_ai_repair_proposals(
             "skip_reason": None,
             "proposal": None,
             "error": None,
+            "cache_key": None,
+            "fingerprints": None,
         }
         if not record["provisional"]:
             record["skip_reason"] = "not_provisional"
             records.append(record)
             continue
-        if route_hint == _DESIGN_REFERENCE_ROUTE:
-            record["skip_reason"] = "design_reference_only_no_ai"
-            records.append(record)
-            continue
         if route_hint != _AI_ADAPTATION_ROUTE:
             record["skip_reason"] = f"route_not_ai_adaptation:{route_hint}"
             records.append(record)
@@ -106,15 +156,40 @@ def gather_step12_ai_repair_proposals(
             if mdx_text_loader is not None
             else (getattr(unit, "raw_content", "") or "")
         )
-        cache_key = "::".join(
-            [template_id, ",".join(sorted(record["source_section_ids"]))]
+
+        frame_id_value = getattr(unit, "frame_id", "") or ""
+        cardinality = getattr(unit, "cardinality", None)
+        layout_preset = getattr(unit, "layout_preset", "") or ""
+        zone_position = getattr(unit, "zone_position", "") or ""
+        source_shape = getattr(unit, "source_shape", "paragraph") or "paragraph"
+        h3_count = int(getattr(unit, "h3_count", 0) or 0)
+        char_count = int(getattr(unit, "char_count", 0) or 0)
+        char_count_bucket = bucket_char_count(char_count)
+        signature_hash = build_signature(
+            frame_id=frame_id_value,
+            v4_label=label or "",
+            cardinality=cardinality,
+            source_shape=source_shape,
+            h3_count=h3_count,
+            char_count_bucket=char_count_bucket,
+            layout_preset=layout_preset,
+            zone_position=zone_position,
         )
+        cache_key = f"{frame_id_value}::{signature_hash}"
+        fingerprints = {
+            "contract_sha": _sha256_of(frame_contract),
+            "partial_sha": _sha256_of(figma_partial_json),
+            "catalog_sha": catalog_sha,
+        }
+        record["cache_key"] = cache_key
+        record["fingerprints"] = fingerprints
+
         v4_result = {
             "route": route_hint,
             "label": label,
             "frame_id": getattr(unit, "frame_id", None),
             "rank": getattr(unit, "v4_rank", None),
-            "cardinality": None,
+            "cardinality": cardinality,
         }
         try:
             proposal = route_ai_fallback(
diff --git a/src/phase_z2_mapper.py b/src/phase_z2_mapper.py
index ae71405..cb87a1e 100644
--- a/src/phase_z2_mapper.py
+++ b/src/phase_z2_mapper.py
@@ -32,6 +32,7 @@ import yaml
 
 PROJECT_ROOT = Path(__file__).parent.parent
 CATALOG_PATH = PROJECT_ROOT / "templates" / "phase_z2" / "catalog" / "frame_contracts.yaml"
+V4_FALLBACK_POLICY_PATH = PROJECT_ROOT / "templates" / "phase_z2" / "catalog" / "v4_fallback_policy.yaml"
 
 
 class FitError(Exception):
@@ -57,6 +58,44 @@ def get_contract(template_id: str) -> dict | None:
     return load_frame_contracts().get(template_id)
 
 
+# ─── V4 fallback policy loading (IMP-38) ──────────────────────────
+
+_V4_FALLBACK_POLICY_CACHE: dict | None = None
+
+_V4_FALLBACK_POLICY_DEFAULT: dict = {
+    "policy_type": "static",
+    "usable_threshold": 1,
+    "default_max_rank": 3,
+    "extended_max_rank": 3,  # graceful: yaml 없을 시 확장 X (byte-identical to pre-IMP-38)
+}
+
+
+def load_v4_fallback_policy() -> dict:
+    """IMP-38 V4 fallback policy loader (separate yaml, catalog 오염 방지).
+
+    Returns dict with keys: policy_type, usable_threshold, default_max_rank, extended_max_rank.
+
+    Codex #1 권장: frame_contracts.yaml top-level 오염 회피 (별 yaml).
+    Codex #3 LOCK: load_frame_contracts() shape 변경 X (이 함수는 별 cache).
+
+    Graceful fallback:
+        yaml 파일 없을 시 → _V4_FALLBACK_POLICY_DEFAULT (default_max_rank=3, extended=3)
+        → backward compat byte-identical to pre-IMP-38 behavior.
+
+    Returns:
+        dict — 정책 키 (정책 yaml 의 superset 가능, 알 수 없는 키는 무시 권장).
+    """
+    global _V4_FALLBACK_POLICY_CACHE
+    if _V4_FALLBACK_POLICY_CACHE is None:
+        if V4_FALLBACK_POLICY_PATH.exists():
+            loaded = yaml.safe_load(V4_FALLBACK_POLICY_PATH.read_text(encoding="utf-8")) or {}
+            # merge with default (yaml 키 부분 누락 시 default 로 fall through)
+            _V4_FALLBACK_POLICY_CACHE = {**_V4_FALLBACK_POLICY_DEFAULT, **loaded}
+        else:
+            _V4_FALLBACK_POLICY_CACHE = dict(_V4_FALLBACK_POLICY_DEFAULT)
+    return _V4_FALLBACK_POLICY_CACHE
+
+
 # ─── Source-shape splitters ──────────────────────────────────────
 
 def _split_top_bullets(content: str) -> list[tuple[str, list[str]]]:
diff --git a/src/phase_z2_pipeline.py b/src/phase_z2_pipeline.py
index a4e9c20..06706c3 100644
--- a/src/phase_z2_pipeline.py
+++ b/src/phase_z2_pipeline.py
@@ -52,6 +52,7 @@ from phase_z2_mapper import (
     compute_capacity_fit,
     get_contract,
     load_frame_contracts,
+    load_v4_fallback_policy,
     map_with_contract,
 )
 from phase_z2_classifier import classify_visual_runtime_check
@@ -77,6 +78,12 @@ from phase_z2_failure_router import (
 from phase_z2_content_extractor import extract_content_objects, extract_rich_content_objects
 from phase_z2_placement_planner import plan_placement
 
+# IMP-47B u4 — Step 12 AI repair wiring. gather() short-circuits at the
+# router when settings.ai_fallback_enabled is False (default), so import
+# at module load is safe for the AI=0 normal path (PZ-1). Activation gate
+# stays in src/config.py + src/phase_z2_ai_fallback/router.py.
+from src.phase_z2_ai_fallback.step12 import gather_step12_ai_repair_proposals
+
 
 # ─── Constants ──────────────────────────────────────────────────
 
@@ -568,12 +575,15 @@ def lookup_v4_match(
 #   use_as_is    → Phase Z direct render
 #   light_edit   → deterministic minor adjustment
 #   restructure  → AI-assisted frame-aware adaptation (deferred to IMP-17 — carve-out, AI fallback only, normal path 밖)
-#   reject       → design reference only (deferred to IMP-29 frontend override)
+#   reject       → AI re-construction over the rank-1 reject frame (IMP-47B u1, 2026-05-21);
+#                  policy correction supersedes the legacy "design reference only" disposition.
+#                  Frame visual / contract stays untouched; AI only re-maps MDX content into
+#                  declared slots. Activation still gated by ai_fallback_enabled (default OFF).
 _IMP05_ROUTE_HINTS: dict[str, str] = {
     "use_as_is":   "direct_render",
     "light_edit":  "deterministic_minor_adjustment",
     "restructure": "ai_adaptation_required",
-    "reject":      "design_reference_only",
+    "reject":      "ai_adaptation_required",
 }
 
 
@@ -584,39 +594,354 @@ def _imp05_route_hint(label: Optional[str]) -> Optional[str]:
     return _IMP05_ROUTE_HINTS.get(label)
 
 
+def _load_frame_partial_html(template_id: str) -> str:
+    """IMP-47B u4 — Read templates/phase_z2/families/{template_id}.html.
+
+    Missing partial (e.g., ``__empty__`` shell from IMP-30) returns an
+    empty string so gather_step12_ai_repair_proposals can still build a
+    record with skip_reason without raising on file IO.
+    """
+    partial_path = TEMPLATE_DIR / "families" / f"{template_id}.html"
+    if not partial_path.is_file():
+        return ""
+    return partial_path.read_text(encoding="utf-8")
+
+
+def _run_step12_ai_repair(units) -> list[dict]:
+    """IMP-47B u4 — Wire gather_step12_ai_repair_proposals into Step 12.
+
+    Routes provisional units whose IMP-05 hint maps to
+    ``ai_adaptation_required`` (``restructure`` + ``reject`` per u1)
+    through ``src.phase_z2_ai_fallback.router``. Normal-path units
+    (``use_as_is`` / ``light_edit`` / non-provisional) record a
+    skip_reason without invoking the router; flag-off runs short-circuit
+    at the router (``settings.ai_fallback_enabled=False`` default).
+    Returns the per-unit record list — u5 consumes records for
+    PARTIAL_OVERRIDES apply and u6 writes the audit artifact.
+    """
+    return gather_step12_ai_repair_proposals(
+        units,
+        route_for_label=_imp05_route_hint,
+        get_contract_fn=get_contract,
+        frame_visual_loader=_load_frame_partial_html,
+    )
+
+
+_REJECT_SUPPORTED_PROPOSAL_KINDS: frozenset[str] = frozenset({"partial_overrides"})
+
+
+def _apply_ai_repair_proposals_to_zones(
+    ai_repair_records: list[dict],
+    unit_positions: list[str],
+    zones_data: list[dict],
+) -> None:
+    """IMP-47B u5 — Apply PARTIAL_OVERRIDES into zones_data.slot_payload.
+
+    Mutates each record's ``apply_status`` in place and merges
+    ``proposal.payload.slots`` into the matching zone. Out-of-scope
+    kinds (``builder_options_patch``, ``slot_mapping_proposal``)
+    loud-fail with ``unsupported_kind_for_reject_route:<kind>`` — zones
+    untouched (human_review surfacing → u8). IMP-33 u5 validator
+    guarantees declared-slot completeness, so ``dict.update`` is the
+    structural merge (``feedback_ai_isolation_contract``).
+    """
+    zone_by_position = {z["position"]: z for z in zones_data}
+    for record in ai_repair_records:
+        proposal = record.get("proposal")
+        if proposal is None:
+            record["apply_status"] = "no_proposal"
+            continue
+        kind = proposal.get("proposal_kind")
+        if kind not in _REJECT_SUPPORTED_PROPOSAL_KINDS:
+            record["apply_status"] = f"unsupported_kind_for_reject_route:{kind}"
+            print(
+                f"  [ai-repair-apply] unit {record['unit_index']} "
+                f"proposal_kind='{kind}' out-of-scope for reject route — "
+                "skipping apply; human_review required.",
+                file=sys.stderr,
+            )
+            continue
+        unit_index = record["unit_index"]
+        position = (
+            unit_positions[unit_index]
+            if 0 <= unit_index < len(unit_positions) else None
+        )
+        zone = zone_by_position.get(position) if position is not None else None
+        if zone is None:
+            record["apply_status"] = "no_zone_match"
+            continue
+        slots = (proposal.get("payload") or {}).get("slots") or {}
+        zone["slot_payload"].update(slots)
+        record["apply_status"] = "applied:partial_overrides"
+
+
+def _check_post_ai_coverage_invariant(
+    units,
+    ai_repair_records: list[dict],
+) -> dict:
+    """IMP-47B u7 — Verify AI repair preserved every source_section_id.
+
+    Compares the union of unit-level ``source_section_ids`` (pre-AI) to
+    the union present on ``ai_repair_records`` post-apply. Per the AI
+    isolation contract + dropped 절대 룰
+    (``feedback_ai_isolation_contract``), AI repair never removes a
+    unit's section coverage. Any divergence indicates a regression that
+    u8 surfaces through ``slide_status.ai_repair_status``. The check is
+    structural (set membership); the per-record ``source_section_ids``
+    list is a copy populated by ``gather_step12_ai_repair_proposals``
+    (``step12.py:124``) so apply mutations cannot silently drop it.
+    """
+    pre_ai_ids: set[str] = set()
+    for unit in units:
+        pre_ai_ids.update(getattr(unit, "source_section_ids", []) or [])
+    post_ai_ids: set[str] = set()
+    for record in ai_repair_records:
+        post_ai_ids.update(record.get("source_section_ids") or [])
+    dropped = sorted(pre_ai_ids - post_ai_ids)
+    return {
+        "pre_ai_section_ids": sorted(pre_ai_ids),
+        "post_ai_section_ids": sorted(post_ai_ids),
+        "dropped_section_ids": dropped,
+        "status": "ok" if not dropped else "violated",
+    }
+
+
+def _persist_ai_repair_proposals_to_cache(
+    ai_repair_records: list[dict],
+    *,
+    visual_check_passed: bool,
+    user_approved: bool,
+    auto_cache: bool,
+) -> None:
+    """IMP-47B u13 — Persist applied AI repair proposals through IMP-46 gates.
+
+    Mutates each record in place with a ``cache_save_status`` axis.
+    Only records whose ``apply_status`` starts with ``"applied:"`` and
+    that still carry the original ``cache_key`` + ``fingerprints`` + a
+    serialized ``proposal`` dict are eligible — everything else marked
+    ``not_applied``. Eligible records go through
+    ``cache.save_proposal`` with the IMP-46 dual-gate truth table; the
+    helper catches :class:`AiFallbackCacheGateError` so a gate block is
+    surfaced (``gate_blocked:<reason>``) without raising into the
+    pipeline runtime (the cache is a hint, never a hard dependency —
+    cache.py contract). ``visual_check_passed`` is never bypassable;
+    ``auto_cache=True`` bypasses ONLY the ``user_approved`` gate per
+    IMP-46 u5. Pure save layer: no AI call, no MDX touch.
+    """
+    from src.phase_z2_ai_fallback.cache import (
+        AiFallbackCacheGateError,
+        save_proposal,
+    )
+    from src.phase_z2_ai_fallback.schema import AiFallbackProposal
+    for record in ai_repair_records:
+        apply_status = record.get("apply_status") or ""
+        proposal_dict = record.get("proposal")
+        cache_key = record.get("cache_key")
+        fingerprints = record.get("fingerprints")
+        if (
+            not apply_status.startswith("applied:")
+            or not isinstance(proposal_dict, dict)
+            or not cache_key
+            or not isinstance(fingerprints, dict)
+        ):
+            record["cache_save_status"] = "not_applied"
+            continue
+        try:
+            proposal_obj = AiFallbackProposal.model_validate(proposal_dict)
+        except Exception as exc:  # noqa: BLE001 — invalid payload → skip, never raise
+            record["cache_save_status"] = f"invalid_proposal:{type(exc).__name__}"
+            continue
+        try:
+            save_proposal(
+                cache_key,
+                proposal_obj,
+                visual_check_passed=visual_check_passed,
+                user_approved=user_approved,
+                auto_cache=auto_cache,
+                fingerprints=fingerprints,
+            )
+        except AiFallbackCacheGateError as gate_exc:
+            record["cache_save_status"] = f"gate_blocked:{gate_exc}"
+            continue
+        record["cache_save_status"] = "saved"
+
+
+def _summarize_ai_repair_status(
+    ai_repair_records: list[dict],
+    coverage_invariant: dict,
+) -> dict:
+    """IMP-47B u8 — Classify Step 12 AI repair outcomes for slide_status surfacing.
+
+    Reads u4 gather ``error`` + u5 ``apply_status`` + u7 coverage_invariant
+    to derive a single ``ai_repair_status`` axis attached to
+    ``slide_status``. Failure-axis priority (highest → lowest):
+    ``error`` > ``coverage_violated`` > ``unsupported_kind`` > ``applied`` > ``ok``.
+    ``human_review_required`` flips True on the three failure axes so the
+    frontend (u11) can surface a notification per the IMP-47B policy
+    ("AI 호출 실패 / proposal validation 실패 / coverage 미달 → frontend notification").
+    Pure: no IO, no AI call.
+    """
+    counts = {
+        "total": len(ai_repair_records),
+        "applied": 0,
+        "no_proposal": 0,
+        "no_zone_match": 0,
+        "unsupported_kind": 0,
+        "error": 0,
+    }
+    unsupported_records: list[dict] = []
+    error_records: list[dict] = []
+    for record in ai_repair_records:
+        if record.get("error"):
+            counts["error"] += 1
+            error_records.append({
+                "unit_index": record.get("unit_index"),
+                "source_section_ids": list(record.get("source_section_ids") or []),
+                "error": record.get("error"),
+            })
+            continue
+        apply_status = record.get("apply_status") or ""
+        if apply_status.startswith("applied:"):
+            counts["applied"] += 1
+        elif apply_status.startswith("unsupported_kind_for_reject_route:"):
+            counts["unsupported_kind"] += 1
+            unsupported_records.append({
+                "unit_index": record.get("unit_index"),
+                "source_section_ids": list(record.get("source_section_ids") or []),
+                "apply_status": apply_status,
+            })
+        elif apply_status == "no_zone_match":
+            counts["no_zone_match"] += 1
+        else:
+            counts["no_proposal"] += 1
+    coverage_status = (coverage_invariant or {}).get("status", "ok")
+    dropped = list((coverage_invariant or {}).get("dropped_section_ids") or [])
+    if counts["error"]:
+        status = "error"
+    elif coverage_status != "ok":
+        status = "coverage_violated"
+    elif counts["unsupported_kind"]:
+        status = "unsupported_kind"
+    elif counts["applied"]:
+        status = "applied"
+    else:
+        status = "ok"
+    return {
+        "status": status,
+        "counts": counts,
+        "unsupported_kind_records": unsupported_records,
+        "error_records": error_records,
+        "coverage_status": coverage_status,
+        "dropped_section_ids": dropped,
+        "human_review_required": status in {"error", "coverage_violated", "unsupported_kind"},
+    }
+
+
 def lookup_v4_match_with_fallback(
     v4: dict,
     section_id: str,
     *,
     raw_content: Optional[str] = None,
-    max_rank: int = 3,
+    max_rank: Optional[int] = None,
     alias_keys: Optional[list] = None,
     allow_provisional: bool = False,
 ) -> tuple[Optional[V4Match], dict]:
-    """Select V4 rank-1, or promote rank-2/3 when rank-1 is not auto-renderable.
+    """Select V4 rank-1, or promote rank-2..N when rank-1 is not auto-renderable.
 
     This is an IMP-05 selector only. It uses existing V4 labels, frame-contract
     presence, and the Phase Z capacity precheck; it does not call calculate_fit.
 
-    IMP-30 u1 — when ``allow_provisional=True`` and the rank-1..max_rank chain
-    is exhausted (no candidate passes MVP1 filter + contract + capacity), the
-    selector synthesizes a *provisional* V4Match from the rank-1 judgment so
+    IMP-30 u1 — when ``allow_provisional=True`` and the rank-1..effective_max_rank
+    chain is exhausted (no candidate passes MVP1 filter + contract + capacity),
+    the selector synthesizes a *provisional* V4Match from the rank-1 judgment so
     the first-render invariant can be satisfied downstream. The synthesized
     match carries ``provisional=True``, ``selection_path="provisional_rank_1"``,
     and ``fallback_reason`` mirrors the existing chain-exhaust reason. The
     candidate trace shape is unchanged (synthetic injection only updates the
     top-level ``selection_path`` + ``selected_*`` mirrors). When the rank-1
     judgment itself is missing (``empty_v4_judgments`` / ``no_v4_section``),
-    no provisional is synthesized — the caller (u3 / u4) handles those cases
-    with a placeholder zone or empty-shell.
+    no provisional is synthesized — the caller handles those cases with a
+    placeholder zone or empty-shell.
 
     Default ``allow_provisional=False`` keeps the IMP-05 behavior byte-identical.
+
+    IMP-38 — dynamic effective max_rank via ``load_v4_fallback_policy()``
+    (4 round 합의 / Codex #1~#3 + Claude #1~#4 LOCK at #67 comment 23195):
+      - ``max_rank=None`` (default) → policy applied:
+          usable_count = candidates in rank 1..default_max_rank passing 3-tier
+          predicate (status in MVP1 + catalog registered + optional capacity).
+          usable_count >= usable_threshold → effective_max_rank = default_max_rank.
+          Otherwise → effective_max_rank = min(extended_max_rank,
+          len(judgments_full32)) = effective_extended_ceiling (Codex #2 정정).
+      - ``max_rank`` explicitly passed → caller_override: that value is used
+          as-is (backward compat for tests / explicit IMP-05/IMP-30 paths).
+
+    Trace gains 8 IMP-38 fields: ``requested_max_rank``, ``default_max_rank``,
+    ``configured_extended_max_rank``, ``judgments_count``,
+    ``effective_extended_ceiling``, ``effective_max_rank``, ``usable_count``,
+    ``policy_applied``. ``max_rank`` legacy field kept as alias for backward
+    compat (= effective_max_rank).
     """
     resolved = _resolve_v4_section_key(v4, section_id, alias_keys=alias_keys)
     sec = v4.get("mdx_sections", {}).get(resolved) if resolved else None
+    all_judgments = (sec.get("judgments_full32") if sec else None) or []
+    judgments_count = len(all_judgments)
+
+    # IMP-38 — load policy (graceful: yaml 없을 시 default_max_rank=3, extended=3)
+    _policy = load_v4_fallback_policy()
+    default_max_rank = int(_policy.get("default_max_rank", 3))
+    configured_extended_max_rank = int(_policy.get("extended_max_rank", default_max_rank))
+    usable_threshold = int(_policy.get("usable_threshold", 1))
+    # Codex #2 정정: min(configured, len(judgments_full32)) — yaml ceiling 무력화 방지
+    effective_extended_ceiling = min(configured_extended_max_rank, judgments_count) if judgments_count else default_max_rank
+
+    usable_count: Optional[int] = None  # set only when policy path active
+    if max_rank is not None:
+        # caller override (backward compat — explicit IMP-05/IMP-30 paths, tests)
+        effective_max_rank = int(max_rank)
+        policy_applied = "caller_override"
+    elif judgments_count == 0:
+        # no judgments — slicing 빈 list 라 어차피 영향 X
+        effective_max_rank = default_max_rank
+        policy_applied = "no_judgments"
+    else:
+        # IMP-38 policy path — 3-tier predicate usable_count on default window
+        usable_count = 0
+        default_window = all_judgments[:default_max_rank]
+        for _j in default_window:
+            _m = _v4_match_from_judgment(section_id, _j, rank=0)
+            if to_phase_z_status(_m) not in MVP1_ALLOWED_STATUSES:
+                continue
+            if get_contract(_m.template_id) is None:
+                continue
+            if raw_content is not None:
+                _cap = compute_capacity_fit(_m.template_id, raw_content)
+                if _cap and _cap.get("fit_status") not in {
+                    "ok", "no_contract", "unknown_source_shape",
+                }:
+                    continue
+            usable_count += 1
+
+        if usable_count >= usable_threshold:
+            effective_max_rank = default_max_rank
+            policy_applied = "default_max_rank"
+        else:
+            effective_max_rank = effective_extended_ceiling
+            policy_applied = "extended_max_rank"
+
     trace = {
         "section_id": section_id,
-        "max_rank": max_rank,
+        # IMP-38 — 8 trace fields (4 round LOCK)
+        "requested_max_rank": max_rank,
+        "default_max_rank": default_max_rank,
+        "configured_extended_max_rank": configured_extended_max_rank,
+        "judgments_count": judgments_count,
+        "effective_extended_ceiling": effective_extended_ceiling,
+        "effective_max_rank": effective_max_rank,
+        "usable_count": usable_count,
+        "policy_applied": policy_applied,
+        # legacy alias for backward compat (= effective_max_rank)
+        "max_rank": effective_max_rank,
         "selection_path": "no_v4_candidate",
         "selected_rank": None,
         "selected_template_id": None,
@@ -630,7 +955,7 @@ def lookup_v4_match_with_fallback(
         trace["fallback_reason"] = "no_v4_section"
         return None, trace
 
-    judgments = (sec.get("judgments_full32") or [])[:max_rank]
+    judgments = all_judgments[:effective_max_rank]
     if not judgments:
         trace["fallback_reason"] = "empty_v4_judgments"
         return None, trace
@@ -712,7 +1037,7 @@ def lookup_v4_match_with_fallback(
         trace["candidates"].append(candidate_trace)
 
     trace["selection_path"] = "chain_exhausted"
-    trace["fallback_reason"] = first_skip_reason or "no_auto_renderable_rank_1_to_3"
+    trace["fallback_reason"] = first_skip_reason or f"no_auto_renderable_rank_1_to_{effective_max_rank}"
 
     # IMP-30 u1 — opt-in provisional first-render synthesis. When the caller
     # signals allow_provisional, promote rank-1 judgment as a provisional
@@ -805,6 +1130,54 @@ def lookup_v4_candidates(
     return candidates
 
 
+def _apply_frame_override_to_unit(unit, new_tid: str, v4: dict) -> str:
+    """IMP-47B u3 — apply a frame override to *unit* in place.
+
+    Returns a meta_source string for the override book-keeping. Three
+    probe layers, in order:
+
+      1. ``unit.v4_candidates`` (non-reject, max_n bounded). Copies
+         frame_id / frame_number / confidence / label from the matching
+         candidate so Step 9 metadata stays consistent. Returns
+         ``"v4_candidates"``.
+      2. Full 32 V4 judgments (reject inclusive). When the override
+         target matches a reject judgment for the unit's primary section,
+         the unit is promoted to ``provisional=True`` with ``label="reject"``
+         so Step 12 (IMP-47B u4) admits the AI repair path. Returns
+         ``"v4_reject_judgment_provisional"``.
+      3. Raw fall-through. Updates only ``frame_template_id``; returns
+         ``"raw_template_id_only"``.
+
+    Frame visual / contract stay untouched per the AI isolation contract
+    (frame auto-swap forbidden — AI re-places content into the existing
+    frame only). The caller validates catalog contract presence before
+    invoking this helper.
+    """
+    for cand in (unit.v4_candidates or []):
+        if getattr(cand, "template_id", None) == new_tid:
+            unit.frame_template_id = cand.template_id
+            unit.frame_id = cand.frame_id
+            unit.frame_number = cand.frame_number
+            unit.confidence = cand.confidence
+            unit.label = cand.label
+            return "v4_candidates"
+    primary_sid = (
+        unit.source_section_ids[0] if unit.source_section_ids else None
+    )
+    if primary_sid:
+        for j in lookup_v4_all_judgments(v4, primary_sid):
+            if j.template_id == new_tid and j.label == "reject":
+                unit.frame_template_id = j.template_id
+                unit.frame_id = j.frame_id
+                unit.frame_number = j.frame_number
+                unit.confidence = j.confidence
+                unit.label = "reject"
+                unit.provisional = True
+                return "v4_reject_judgment_provisional"
+    unit.frame_template_id = new_tid
+    return "raw_template_id_only"
+
+
 # ─── Content weight + zone layout 계산 ─────────────────────────
 # layout preset 선택은 phase_z2_composition.select_layout_preset (composition v0) 가 담당.
 # 본 모듈의 select_layout_preset 은 이전 단순 count-based 구현이었고 dead code 로 제거 (2026-04-29).
@@ -3218,7 +3591,6 @@ def run_phase_z2_mvp1(
             v4,
             sid,
             raw_content=section_content_by_id.get(sid),
-            max_rank=3,
             alias_keys=section_alias_by_id.get(sid),
         )
         v4_fallback_traces[sid] = trace
@@ -3264,6 +3636,57 @@ def run_phase_z2_mvp1(
         ),
     }
 
+    # IMP-47B u12 — mixed direct+reject first-render admission.
+    # When initial plan_composition produces a viable layout but at least one
+    # section remains uncovered (typically chain_exhausted / reject), re-run
+    # with allow_provisional in the lookup + allow_provisional_fill=True so
+    # reject sections gain a provisional rank-1 V4Match and a last-resort
+    # provisional candidate fill. This admits the mixed direct+reject case
+    # to the AI repair path (IMP-47B u4/u5) on first render. Skipped under
+    # --override-section-assignments to preserve the operator's plan and
+    # mirror the IMP-30 u4 retry's section_assignment_plan gate. All-direct
+    # slides have no uncovered sections so this is a no-op. The all-reject
+    # case is still handled by the IMP-30 u4 retry block below (initial
+    # plan_composition returns units=[]).
+    if units and layout_preset is not None and not override_section_assignments:
+        _u12_covered_ids: set[str] = set()
+        for _u in units:
+            _u12_covered_ids.update(_u.source_section_ids)
+        _u12_uncovered_ids = [
+            s.section_id for s in sections if s.section_id not in _u12_covered_ids
+        ]
+        if _u12_uncovered_ids:
+            def _lookup_fn_mixed_admission(sid: str) -> Optional[V4Match]:
+                match, trace = lookup_v4_match_with_fallback(
+                    v4,
+                    sid,
+                    raw_content=section_content_by_id.get(sid),
+                    alias_keys=section_alias_by_id.get(sid),
+                    allow_provisional=True,
+                )
+                v4_fallback_traces[sid] = trace
+                return match
+
+            units_mixed, layout_preset_mixed, _comp_debug_mixed = plan_composition(
+                sections,
+                _lookup_fn_mixed_admission,
+                V4_LABEL_TO_PHASE_Z_STATUS,
+                MVP1_ALLOWED_STATUSES,
+                capacity_fit_fn=compute_capacity_fit,
+                v4_candidates_lookup_fn=candidates_lookup_fn,
+                allow_provisional_fill=True,
+            )
+            if units_mixed and layout_preset_mixed is not None:
+                units = units_mixed
+                layout_preset = layout_preset_mixed
+                comp_debug["v4_fallback_selections"] = list(v4_fallback_traces.values())
+                comp_debug["imp47b_u12_mixed_admission"] = {
+                    "applied": True,
+                    "uncovered_before": _u12_uncovered_ids,
+                    "result_unit_count": len(units_mixed),
+                    "result_layout_preset": layout_preset_mixed,
+                }
+
     # ── Step 7-A axis : layout override ──
     # 사용자가 LayoutPanel 에서 다른 preset 을 선택했을 때 자동 결정값을 강제 변경.
     # 길이 mismatch (positions count vs unit count) 는 zone loop 의 fallback (zone_{i})
@@ -3434,7 +3857,6 @@ def run_phase_z2_mvp1(
                     v4,
                     sid,
                     raw_content=section_content_by_id.get(sid),
-                    max_rank=3,
                     alias_keys=section_alias_by_id.get(sid),
                     allow_provisional=True,
                 )
@@ -3613,7 +4035,10 @@ def run_phase_z2_mvp1(
     # {unit_id: template_id} 형식. unit_id 매칭 시 unit.frame_template_id 강제 변경.
     # v4_candidates 안에서 같은 template_id 를 가진 entry 를 찾으면 frame_id /
     # frame_number / confidence / label 까지 그 entry 에서 가져와 갱신 — 그래야 step09
-    # artifact 의 메타가 일관됨.
+    # artifact 의 메타가 일관됨. IMP-47B u3 (2026-05-21) : v4_candidates miss 시
+    # 전 32 judgments 까지 probe — reject 라벨 frame 을 사용자가 선택한 경우
+    # unit 을 provisional=True 로 승격해 Step 12 AI 재구성 게이트를 통과시킴
+    # (frame 유지, 자동 frame swap 금지 — [[feedback_ai_isolation_contract]]).
     # frame contract 가 catalog 에 등록 안 된 template_id 면 skip + warning —
     # crash 방지 (V4 score 는 매겨지지만 catalog partial 은 없는 후보 존재).
     frame_overrides_applied: list[dict] = []
@@ -3642,21 +4067,7 @@ def run_phase_z2_mvp1(
                     file=sys.stderr,
                 )
                 continue
-            match = None
-            for cand in (unit.v4_candidates or []):
-                if getattr(cand, "template_id", None) == new_tid:
-                    match = cand
-                    break
-            if match is not None:
-                unit.frame_template_id = match.template_id
-                unit.frame_id = match.frame_id
-                unit.frame_number = match.frame_number
-                unit.confidence = match.confidence
-                unit.label = match.label
-                meta_source = "v4_candidates"
-            else:
-                unit.frame_template_id = new_tid
-                meta_source = "raw_template_id_only"
+            meta_source = _apply_frame_override_to_unit(unit, new_tid, v4)
             frame_overrides_applied.append({
                 "unit_id": unit_id,
                 "from": old_tid,
@@ -4258,6 +4669,58 @@ def run_phase_z2_mvp1(
         note="B4 PlacementPlan slot_assignments — render path 미연결. 실제 render slot 매핑은 mapper.py 의 builder.",
     )
 
+    # ─── Step 12 IMP-47B u4 — AI repair proposal gather ───
+    # Wire gather_step12_ai_repair_proposals so reject / restructure
+    # provisional units reach the AI fallback router. Normal-path units
+    # (use_as_is / light_edit / non-provisional) skip via the catch-all
+    # route gate; flag-off runs short-circuit at the router. Stored locally
+    # for u5 (PARTIAL_OVERRIDES apply) + u6 (step12_ai_repair.json audit).
+    ai_repair_records = _run_step12_ai_repair(units)
+
+    # ─── Step 12 IMP-47B u5 — Apply PARTIAL_OVERRIDES proposals ───
+    # Mirror the per-unit position derivation from the render loop above
+    # (L3789-3796); apply merges slots into zone slot_payload, loud-fails
+    # unsupported kinds via apply_status marker.
+    unit_positions: list[str] = []
+    for _i, _unit in enumerate(units):
+        _pos = positions[_i] if _i < len(positions) else f"zone_{_i}"
+        _plan_record = render_record_by_unit_id.get(id(_unit))
+        if _plan_record is not None and _plan_record.get("position"):
+            _pos = _plan_record["position"]
+        unit_positions.append(_pos)
+    _apply_ai_repair_proposals_to_zones(ai_repair_records, unit_positions, zones_data)
+
+    # ─── Step 12 IMP-47B u7 — Post-AI source_section_ids coverage invariant ───
+    # Structural defense: AI repair must not silently drop a unit's
+    # source_section_ids. dropped 절대 룰 — text_block / table / image /
+    # details deletion forbidden. Result feeds u6 audit (below) and
+    # u8 slide_status.ai_repair_status surfacing.
+    ai_repair_coverage_invariant = _check_post_ai_coverage_invariant(
+        units, ai_repair_records,
+    )
+
+    # ─── Step 12 IMP-47B u6 — AI repair audit artifact ───
+    # Persist per-unit gather/apply outcomes (route_hint, skip_reason,
+    # apply_status, ai_called, proposal kind, cache_key, fingerprints)
+    # so reviewers can audit which units reached the AI fallback router
+    # and what happened. Flag-off default → every record has
+    # ai_called=False + apply_status='no_proposal'; flag-on +
+    # provisional reject/restructure → router_short_circuit (cache miss
+    # without client) or applied:partial_overrides (cache hit / live AI).
+    # u7 coverage_invariant rides alongside per_unit for reviewers.
+    _write_step_artifact(
+        run_dir, 12, "ai_repair",
+        data={
+            "per_unit": ai_repair_records,
+            "coverage_invariant": ai_repair_coverage_invariant,
+        },
+        step_status="done",
+        pipeline_path_connected=True,
+        inputs=["step10_frame_contract.json", "step02_normalized.json"],
+        outputs=["step12_ai_repair.json"],
+        note="IMP-47B u6 — Step 12 AI repair gather + apply records per unit (route, skip_reason, apply_status, proposal). u7 coverage_invariant = pre/post AI source_section_ids set comparison.",
+    )
+
     # ─── Step 12: Slot Payload (actual values, mapper.py 결과) ───
     _write_step_artifact(
         run_dir, 12, "slot_payload",
@@ -4872,6 +5335,24 @@ def run_phase_z2_mvp1(
         ),
     )
 
+    # ─── IMP-47B u13: Persist validated AI repair proposals to cache ───
+    # Saves each applied PARTIAL_OVERRIDES proposal AFTER Step 14 visual
+    # check + per IMP-46 dual-gate. ``visual_check_passed`` reads the
+    # Selenium overflow result; ``auto_cache`` sourced from Settings
+    # (CLI --auto-cache wires settings.ai_fallback_auto_cache at parse
+    # time, src/phase_z2_pipeline.py:5631-5633). ``user_approved`` stays
+    # False — the pipeline has no UX approval gate; the auto_cache
+    # opt-in is the documented bypass per IMP-46 u5. Gate violations
+    # surface as ``cache_save_status='gate_blocked:<reason>'`` on the
+    # record (cache is a hint, never a hard dependency).
+    from src.config import settings as _ai_cache_settings
+    _persist_ai_repair_proposals_to_cache(
+        ai_repair_records,
+        visual_check_passed=bool(overflow.get("passed")),
+        user_approved=False,
+        auto_cache=bool(_ai_cache_settings.ai_fallback_auto_cache),
+    )
+
     # 10. fit_classifier v0 (A1) — Selenium 결과 → spec §3 category 분류 layer.
     #     *분류만*. action / router / rerender X. behavior 변경 0.
     fit_classification = classify_visual_runtime_check(overflow, debug_zones)
@@ -5055,6 +5536,16 @@ def run_phase_z2_mvp1(
         debug_zones=debug_zones,
     )
 
+    # IMP-47B u8 — Surface Step 12 AI repair outcomes through slide_status.
+    # Composes u4 gather errors + u5 apply_status + u7 coverage_invariant
+    # into a single ``ai_repair_status`` axis the frontend (u11) reads to
+    # render human_review notifications. Auto pipeline first
+    # ([[feedback_auto_pipeline_first]]) — no review_queue insertion;
+    # explicit status enum + human_review_required flag.
+    slide_status["ai_repair_status"] = _summarize_ai_repair_status(
+        ai_repair_records, ai_repair_coverage_invariant,
+    )
+
     # ─── Step 20: Slide Status ───
     _write_step_artifact(
         run_dir, 20, "slide_status",
@@ -5076,6 +5567,11 @@ def run_phase_z2_mvp1(
     _aligned = slide_status.get("aligned_section_ids") or []
     _covered = slide_status.get("covered_section_ids") or []
     _filtered = slide_status.get("filtered_section_ids") or []
+    _ai_repair = slide_status.get("ai_repair_status") or {}
+    _ai_repair_label = (
+        f'{_ai_repair.get("status", "?")} '
+        f'(human_review_required={_ai_repair.get("human_review_required", False)})'
+    )
     _write_step_html(
         run_dir, 20, "final_status",
         title="Final Slide Status",
@@ -5090,6 +5586,7 @@ def run_phase_z2_mvp1(
             f'<tr><th>filtered_section_ids</th><td>{_filtered}</td></tr>'
             f'<tr><th>adapter_needed_count</th><td>{slide_status.get("adapter_needed_count", 0)}</td></tr>'
             f'<tr><th>content_truncated_count</th><td>{slide_status.get("content_truncated_count", 0)}</td></tr>'
+            f'<tr><th>ai_repair_status</th><td>{_ai_repair_label}</td></tr>'
             f'</table>'
             f'<h2>Visual Fail Reasons</h2>{_vfs_html}'
             f'<h2>Note</h2><p>{slide_status.get("note", "")}</p>'
@@ -5260,8 +5757,29 @@ if __name__ == "__main__":
             "--override-section-assignment bottom=03-2,03-3"
         ),
     )
+    # IMP-46 u5 — auto-cache opt-in. When set, ``cache.save_proposal``
+    # bypasses the ``user_approved`` gate only (``visual_check_passed``
+    # is never bypassable). Source of truth is
+    # ``settings.ai_fallback_auto_cache`` (src/config.py); this flag
+    # mutates the setting in-process so downstream callers read the
+    # same value through Settings rather than parsing args themselves.
+    parser.add_argument(
+        "--auto-cache",
+        dest="auto_cache",
+        action="store_true",
+        default=False,
+        help=(
+            "Allow cache.save_proposal to bypass the user_approved gate "
+            "(visual_check_passed remains mandatory). Sets "
+            "settings.ai_fallback_auto_cache=True for this run."
+        ),
+    )
     args = parser.parse_args()
 
+    if args.auto_cache:
+        from src.config import settings as _settings
+        _settings.ai_fallback_auto_cache = True
+
     overrides_frames: dict[str, str] = {}
     for ov in args.override_frames:
         if "=" not in ov:
diff --git a/tests/phase_z2_ai_fallback/test_ast_isolation.py b/tests/phase_z2_ai_fallback/test_ast_isolation.py
index 8c3e77d..b734287 100644
--- a/tests/phase_z2_ai_fallback/test_ast_isolation.py
+++ b/tests/phase_z2_ai_fallback/test_ast_isolation.py
@@ -36,6 +36,7 @@ _ALLOWED_TOP_LEVEL: frozenset[str] = frozenset(
         "ast",
         "dataclasses",
         "enum",
+        "hashlib",
         "json",
         "pathlib",
         "random",
diff --git a/tests/phase_z2_ai_fallback/test_cache.py b/tests/phase_z2_ai_fallback/test_cache.py
index b3d1dd9..f3576b8 100644
--- a/tests/phase_z2_ai_fallback/test_cache.py
+++ b/tests/phase_z2_ai_fallback/test_cache.py
@@ -1,32 +1,67 @@
-"""IMP-33 u6 — AI fallback cache gate tests.
+"""IMP-46 u2 — Persistent JSON cache backend tests.
 
-Verifies the IMP-46 gate contract:
-  * ``read_proposal`` is a stub (returns None until IMP-46).
-  * ``save_proposal`` enforces both gates before any write attempt.
-  * Storage itself raises NotImplementedError (IMP-46 marker).
+Scope (Stage 2 plan, u2):
+
+* Replaced ``NotImplementedError`` marker with a real persistent backend
+  at ``data/frame_cache/{frame_id}/{signature_hash}.json``.
+* Preserved IMP-33 u6 dual write gate: ``visual_check_passed`` AND
+  ``user_approved`` BOTH required (loud :class:`AiFallbackCacheGateError`
+  before any filesystem touch).
+* Round-trip every :class:`ProposalKind`; round-trip ``slide_css`` None
+  *and* set; missing or corrupt files miss silently.
+* Fingerprint *comparison* is u3; here we only check that the field is
+  persisted.
+
+All filesystem writes are scoped to ``tmp_path`` via
+``monkeypatch.setattr`` on the module-level :data:`CACHE_ROOT`, so the
+production directory is never touched by these tests.
 """
 from __future__ import annotations
 
+import json
+import pathlib
+
 import pytest
 
+from src.phase_z2_ai_fallback import cache as cache_mod
 from src.phase_z2_ai_fallback.cache import (
     AiFallbackCacheGateError,
+    KEY_DELIMITER,
+    SCHEMA_VERSION,
     read_proposal,
     save_proposal,
 )
 from src.phase_z2_ai_fallback.schema import AiFallbackProposal, ProposalKind
 
 
-def _proposal() -> AiFallbackProposal:
+_FRAME_ID = "1171281190"
+_SIG_HASH = "a" * 64  # SHA256-shaped placeholder; cache is shape-agnostic.
+_KEY = f"{_FRAME_ID}{KEY_DELIMITER}{_SIG_HASH}"
+
+
+def _proposal(
+    kind: ProposalKind = ProposalKind.BUILDER_OPTIONS_PATCH,
+    payload: dict | None = None,
+) -> AiFallbackProposal:
     return AiFallbackProposal(
-        proposal_kind=ProposalKind.BUILDER_OPTIONS_PATCH,
-        payload={"item_parser": "bullet_v2"},
-        rationale="u6-test",
+        proposal_kind=kind,
+        payload=payload if payload is not None else {"item_parser": "bullet_v2"},
+        rationale="u2-test",
     )
 
 
-def test_read_proposal_returns_none_for_any_key():
-    assert read_proposal("frame=foo|cardinality=3") is None
+@pytest.fixture(autouse=True)
+def _isolated_cache_root(tmp_path: pathlib.Path, monkeypatch: pytest.MonkeyPatch):
+    """Redirect the cache root to an isolated tmp directory for every test."""
+    monkeypatch.setattr(cache_mod, "CACHE_ROOT", tmp_path / "frame_cache")
+    yield tmp_path / "frame_cache"
+
+
+# -- read_proposal --------------------------------------------------------
+
+
+def test_read_proposal_returns_none_for_missing_file():
+    assert read_proposal(_KEY) is None
 
 
 def test_read_proposal_rejects_empty_key():
@@ -34,10 +69,65 @@ def test_read_proposal_rejects_empty_key():
         read_proposal("")
 
 
+def test_read_proposal_rejects_non_string_key():
+    with pytest.raises(ValueError):
+        read_proposal(None)  # type: ignore[arg-type]
+
+
+def test_read_proposal_returns_none_for_legacy_key_format():
+    """Router back-compat: pre-u4 cache_key (no '::') misses silently."""
+    assert read_proposal("frame:1171281190:cardinality:many") is None
+
+
+def test_read_proposal_returns_none_for_corrupt_json(_isolated_cache_root: pathlib.Path):
+    path = _isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json"
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text("{not valid json", encoding="utf-8")
+    assert read_proposal(_KEY) is None
+
+
+def test_read_proposal_returns_none_for_non_dict_root(_isolated_cache_root: pathlib.Path):
+    path = _isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json"
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text("[]", encoding="utf-8")
+    assert read_proposal(_KEY) is None
+
+
+def test_read_proposal_returns_none_when_payload_proposal_missing(
+    _isolated_cache_root: pathlib.Path,
+):
+    path = _isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json"
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(json.dumps({"schema_version": 1}), encoding="utf-8")
+    assert read_proposal(_KEY) is None
+
+
+def test_read_proposal_returns_none_for_forbidden_proposal_kind(
+    _isolated_cache_root: pathlib.Path,
+):
+    path = _isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json"
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(
+        json.dumps(
+            {
+                "schema_version": 1,
+                "proposal": {"proposal_kind": "mdx_text", "payload": {}, "rationale": ""},
+                "slide_css": None,
+                "fingerprints": {},
+            }
+        ),
+        encoding="utf-8",
+    )
+    assert read_proposal(_KEY) is None
+
+
+# -- save_proposal: write gates -------------------------------------------
+
+
 def test_save_rejects_when_visual_check_failed():
     with pytest.raises(AiFallbackCacheGateError) as exc:
         save_proposal(
-            "k", _proposal(), visual_check_passed=False, user_approved=True
+            _KEY, _proposal(), visual_check_passed=False, user_approved=True
         )
     assert "visual_check_passed" in str(exc.value)
 
@@ -45,7 +135,7 @@ def test_save_rejects_when_visual_check_failed():
 def test_save_rejects_when_user_not_approved():
     with pytest.raises(AiFallbackCacheGateError) as exc:
         save_proposal(
-            "k", _proposal(), visual_check_passed=True, user_approved=False
+            _KEY, _proposal(), visual_check_passed=True, user_approved=False
         )
     assert "user_approved" in str(exc.value)
 
@@ -53,16 +143,20 @@ def test_save_rejects_when_user_not_approved():
 def test_save_rejects_when_both_gates_false():
     with pytest.raises(AiFallbackCacheGateError):
         save_proposal(
-            "k", _proposal(), visual_check_passed=False, user_approved=False
+            _KEY, _proposal(), visual_check_passed=False, user_approved=False
         )
 
 
-def test_save_raises_not_implemented_when_both_gates_pass():
-    with pytest.raises(NotImplementedError) as exc:
+def test_save_gate_violation_does_not_touch_filesystem(
+    _isolated_cache_root: pathlib.Path,
+):
+    with pytest.raises(AiFallbackCacheGateError):
         save_proposal(
-            "k", _proposal(), visual_check_passed=True, user_approved=True
+            _KEY, _proposal(), visual_check_passed=False, user_approved=True
         )
-    assert "IMP-46" in str(exc.value)
+    # Cache root may or may not exist depending on fixture order, but the
+    # frame_id directory must NOT exist when the gate rejects the write.
+    assert not (_isolated_cache_root / _FRAME_ID).exists()
 
 
 def test_save_rejects_empty_key():
@@ -75,16 +169,340 @@ def test_save_rejects_empty_key():
 def test_save_rejects_non_proposal_object():
     with pytest.raises(TypeError):
         save_proposal(
-            "k",
+            _KEY,
             {"proposal_kind": "builder_options_patch"},  # type: ignore[arg-type]
             visual_check_passed=True,
             user_approved=True,
         )
 
 
-def test_gate_error_is_not_notimplementederror():
-    with pytest.raises(AiFallbackCacheGateError):
+def test_save_rejects_legacy_key_format():
+    """Writes must use the structural ``frame_id::signature_hash`` form."""
+    with pytest.raises(ValueError):
         save_proposal(
-            "k", _proposal(), visual_check_passed=False, user_approved=True
+            "frame:1171281190:cardinality:many",
+            _proposal(),
+            visual_check_passed=True,
+            user_approved=True,
         )
+
+
+def test_save_rejects_slide_css_non_string():
+    with pytest.raises(TypeError):
+        save_proposal(
+            _KEY,
+            _proposal(),
+            visual_check_passed=True,
+            user_approved=True,
+            slide_css=123,  # type: ignore[arg-type]
+        )
+
+
+def test_save_rejects_fingerprints_non_dict():
+    with pytest.raises(TypeError):
+        save_proposal(
+            _KEY,
+            _proposal(),
+            visual_check_passed=True,
+            user_approved=True,
+            fingerprints=["contract_sha", "abc"],  # type: ignore[arg-type]
+        )
+
+
+def test_gate_error_is_not_notimplementederror():
+    """The persistent backend no longer raises ``NotImplementedError`` —
+    callers must distinguish gate violation from absent persistence."""
     assert not issubclass(AiFallbackCacheGateError, NotImplementedError)
+
+
+# -- save_proposal: persistence + round-trip ------------------------------
+
+
+def test_save_creates_parent_directories(_isolated_cache_root: pathlib.Path):
+    assert not (_isolated_cache_root / _FRAME_ID).exists()
+    save_proposal(
+        _KEY, _proposal(), visual_check_passed=True, user_approved=True
+    )
+    assert (_isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json").is_file()
+
+
+def test_save_returns_resolved_path(_isolated_cache_root: pathlib.Path):
+    path = save_proposal(
+        _KEY, _proposal(), visual_check_passed=True, user_approved=True
+    )
+    assert path == _isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json"
+
+
+def test_save_payload_includes_schema_version(_isolated_cache_root: pathlib.Path):
+    path = save_proposal(
+        _KEY, _proposal(), visual_check_passed=True, user_approved=True
+    )
+    data = json.loads(path.read_text(encoding="utf-8"))
+    assert data["schema_version"] == SCHEMA_VERSION
+
+
+def test_save_payload_includes_proposal_dump(_isolated_cache_root: pathlib.Path):
+    proposal = _proposal(payload={"item_parser": "pillar_item"})
+    path = save_proposal(
+        _KEY, proposal, visual_check_passed=True, user_approved=True
+    )
+    data = json.loads(path.read_text(encoding="utf-8"))
+    assert data["proposal"] == proposal.model_dump(mode="json")
+
+
+def test_round_trip_default_slide_css_is_none(_isolated_cache_root: pathlib.Path):
+    path = save_proposal(
+        _KEY, _proposal(), visual_check_passed=True, user_approved=True
+    )
+    data = json.loads(path.read_text(encoding="utf-8"))
+    assert data["slide_css"] is None
+    assert data["fingerprints"] == {}
+
+
+def test_round_trip_with_slide_css_set(_isolated_cache_root: pathlib.Path):
+    css = ".slide { padding: 40px; }"
+    path = save_proposal(
+        _KEY,
+        _proposal(),
+        visual_check_passed=True,
+        user_approved=True,
+        slide_css=css,
+    )
+    data = json.loads(path.read_text(encoding="utf-8"))
+    assert data["slide_css"] == css
+
+
+def test_round_trip_with_fingerprints(_isolated_cache_root: pathlib.Path):
+    fingerprints = {
+        "contract_sha": "c" * 64,
+        "partial_sha": "p" * 64,
+        "catalog_sha": "x" * 64,
+    }
+    path = save_proposal(
+        _KEY,
+        _proposal(),
+        visual_check_passed=True,
+        user_approved=True,
+        fingerprints=fingerprints,
+    )
+    data = json.loads(path.read_text(encoding="utf-8"))
+    assert data["fingerprints"] == fingerprints
+
+
+def test_read_returns_proposal_after_save(_isolated_cache_root: pathlib.Path):
+    original = _proposal(payload={"key": "value"})
+    save_proposal(
+        _KEY, original, visual_check_passed=True, user_approved=True
+    )
+    loaded = read_proposal(_KEY)
+    assert loaded is not None
+    assert loaded.proposal_kind == original.proposal_kind
+    assert loaded.payload == original.payload
+    assert loaded.rationale == original.rationale
+
+
+@pytest.mark.parametrize("kind", list(ProposalKind))
+def test_round_trip_all_proposal_kinds(
+    kind: ProposalKind, _isolated_cache_root: pathlib.Path
+):
+    """Every whitelisted ProposalKind survives save → read unchanged."""
+    if kind is ProposalKind.PARTIAL_OVERRIDES:
+        payload = {"slots": {"pillar_1": "alpha"}}
+    elif kind is ProposalKind.SLOT_MAPPING_PROPOSAL:
+        payload = {"mapping": [{"from": "a", "to": "b"}]}
+    else:
+        payload = {"item_parser": "bullet_v2"}
+    save_proposal(
+        _KEY,
+        _proposal(kind=kind, payload=payload),
+        visual_check_passed=True,
+        user_approved=True,
+    )
+    loaded = read_proposal(_KEY)
+    assert loaded is not None
+    assert loaded.proposal_kind is kind
+    assert loaded.payload == payload
+
+
+def test_save_overwrites_existing_entry(_isolated_cache_root: pathlib.Path):
+    save_proposal(
+        _KEY,
+        _proposal(payload={"v": 1}),
+        visual_check_passed=True,
+        user_approved=True,
+    )
+    save_proposal(
+        _KEY,
+        _proposal(payload={"v": 2}),
+        visual_check_passed=True,
+        user_approved=True,
+    )
+    loaded = read_proposal(_KEY)
+    assert loaded is not None
+    assert loaded.payload == {"v": 2}
+
+
+def test_file_layout_uses_frame_id_directory(_isolated_cache_root: pathlib.Path):
+    """Storage layout = ``frame_id/`` directory, ``signature_hash.json`` file."""
+    other_frame_key = f"{_FRAME_ID}_other{KEY_DELIMITER}{_SIG_HASH}"
+    save_proposal(
+        _KEY, _proposal(), visual_check_passed=True, user_approved=True
+    )
+    save_proposal(
+        other_frame_key,
+        _proposal(),
+        visual_check_passed=True,
+        user_approved=True,
+    )
+    assert (_isolated_cache_root / _FRAME_ID / f"{_SIG_HASH}.json").is_file()
+    assert (
+        _isolated_cache_root / f"{_FRAME_ID}_other" / f"{_SIG_HASH}.json"
+    ).is_file()
+
+
+def test_different_signature_hashes_isolated(_isolated_cache_root: pathlib.Path):
+    """Two distinct signature hashes under the same frame_id never collide."""
+    key_a = f"{_FRAME_ID}{KEY_DELIMITER}{'a' * 64}"
+    key_b = f"{_FRAME_ID}{KEY_DELIMITER}{'b' * 64}"
+    save_proposal(
+        key_a,
+        _proposal(payload={"sig": "a"}),
+        visual_check_passed=True,
+        user_approved=True,
+    )
+    save_proposal(
+        key_b,
+        _proposal(payload={"sig": "b"}),
+        visual_check_passed=True,
+        user_approved=True,
+    )
+    loaded_a = read_proposal(key_a)
+    loaded_b = read_proposal(key_b)
+    assert loaded_a is not None and loaded_a.payload == {"sig": "a"}
+    assert loaded_b is not None and loaded_b.payload == {"sig": "b"}
+
+
+def test_parse_key_rejects_triple_delimiter():
+    """Two ``::`` markers (extra delimiter inside signature) is rejected."""
+    assert (
+        read_proposal(
+            f"{_FRAME_ID}{KEY_DELIMITER}{_SIG_HASH}{KEY_DELIMITER}extra"
+        )
+        is None
+    )
+
+
+# -- IMP-46 u5: auto_cache gate (2^3 truth table) -------------------------
+#
+# Three booleans: visual_check_passed (V), user_approved (U), auto_cache (A).
+# Contract: V=True AND (U=True OR A=True) -> persist; else gate-raise.
+# V is never bypassable; A=True only relaxes U=False.
+
+_GATE_TRUTH_TABLE = [
+    # (V,     U,     A,     expect_persist)
+    (False, False, False, False),
+    (False, False, True,  False),
+    (False, True,  False, False),
+    (False, True,  True,  False),
+    (True,  False, False, False),
+    (True,  False, True,  True),
+    (True,  True,  False, True),
+    (True,  True,  True,  True),
+]
+
+
+@pytest.mark.parametrize("v,u,a,expect_persist", _GATE_TRUTH_TABLE)
+def test_save_gate_truth_table(
+    v: bool,
+    u: bool,
+    a: bool,
+    expect_persist: bool,
+    _isolated_cache_root: pathlib.Path,
+) -> None:
+    """IMP-46 u5 — exhaustive 2^3 enumeration of (V, U, A) -> {persist, raise}."""
+    if expect_persist:
+        path = save_proposal(
+            _KEY,
+            _proposal(payload={"v": int(v), "u": int(u), "a": int(a)}),
+            visual_check_passed=v,
+            user_approved=u,
+            auto_cache=a,
+        )
+        assert path.is_file(), f"truth row (V={v}, U={u}, A={a}) must persist"
+    else:
+        with pytest.raises(AiFallbackCacheGateError):
+            save_proposal(
+                _KEY,
+                _proposal(),
+                visual_check_passed=v,
+                user_approved=u,
+                auto_cache=a,
+            )
+        # Gate violations must never touch the filesystem (parent dir absent).
+        assert not (_isolated_cache_root / _FRAME_ID).exists(), (
+            f"truth row (V={v}, U={u}, A={a}) leaked a directory"
+        )
+
+
+def test_auto_cache_default_off_preserves_dual_gate_semantics(
+    _isolated_cache_root: pathlib.Path,
+) -> None:
+    """Calling save_proposal without ``auto_cache`` keeps the IMP-46 u2 behaviour."""
+    with pytest.raises(AiFallbackCacheGateError) as exc:
+        save_proposal(
+            _KEY, _proposal(), visual_check_passed=True, user_approved=False
+        )
+    assert "user_approved" in str(exc.value)
+    assert not (_isolated_cache_root / _FRAME_ID).exists()
+
+
+def test_auto_cache_cannot_bypass_visual_check() -> None:
+    """``visual_check_passed=False`` raises even with ``auto_cache=True``."""
+    with pytest.raises(AiFallbackCacheGateError) as exc:
+        save_proposal(
+            _KEY,
+            _proposal(),
+            visual_check_passed=False,
+            user_approved=True,
+            auto_cache=True,
+        )
+    assert "visual_check_passed" in str(exc.value)
+
+
+def test_auto_cache_bypass_user_approved_persists(
+    _isolated_cache_root: pathlib.Path,
+) -> None:
+    """``auto_cache=True`` with ``user_approved=False`` persists the proposal."""
+    path = save_proposal(
+        _KEY,
+        _proposal(payload={"bypass": "user"}),
+        visual_check_passed=True,
+        user_approved=False,
+        auto_cache=True,
+    )
+    assert path.is_file()
+    loaded = read_proposal(_KEY)
+    assert loaded is not None
+    assert loaded.payload == {"bypass": "user"}
+
+
+def test_auto_cache_rejects_non_bool() -> None:
+    """``auto_cache`` must be a bool (loud TypeError, symmetric with other kwargs)."""
+    with pytest.raises(TypeError):
+        save_proposal(
+            _KEY,
+            _proposal(),
+            visual_check_passed=True,
+            user_approved=True,
+            auto_cache="yes",  # type: ignore[arg-type]
+        )
+
+
+def test_auto_cache_is_keyword_only() -> None:
+    """``auto_cache`` must be passed by keyword (positional rejected)."""
+    import inspect
+
+    sig = inspect.signature(save_proposal)
+    param = sig.parameters["auto_cache"]
+    assert param.kind is inspect.Parameter.KEYWORD_ONLY
+    assert param.default is False
diff --git a/tests/phase_z2_ai_fallback/test_step12.py b/tests/phase_z2_ai_fallback/test_step12.py
index f66eadc..d8ad4b3 100644
--- a/tests/phase_z2_ai_fallback/test_step12.py
+++ b/tests/phase_z2_ai_fallback/test_step12.py
@@ -1,12 +1,18 @@
-"""IMP-33 u8 — Step 12 AI repair wiring tests.
+"""IMP-33 u8 + IMP-46 u4 + IMP-47B u2 — Step 12 AI repair wiring tests.
 
-Covers the two structural gates layered on top of the u7 router:
+Covers the structural gates layered on top of the u7 router:
   * IMP-30 provisional gate (only provisional units may invoke AI repair)
-  * Reject gate (route_hint=design_reference_only NEVER calls AI)
-Plus the record-shape contract returned for downstream Step 12 artifacts.
+  * Catch-all ``route_not_ai_adaptation:<hint>`` skip — every route_hint
+    other than ``ai_adaptation_required`` (including the legacy
+    ``design_reference_only`` hint) falls through to a single uniform skip
+    after the IMP-47B u2 removal of the bespoke reject gate.
+Plus the record-shape contract returned for downstream Step 12 artifacts
+and the IMP-46 u4 structural cache key + fingerprints contract.
 """
 from __future__ import annotations
 
+import hashlib
+import json
 from dataclasses import dataclass, field
 from typing import Any
 from unittest.mock import MagicMock
@@ -24,6 +30,12 @@ class FakeUnit:
     source_section_ids: list[str] = field(default_factory=lambda: ["s1"])
     raw_content: str = "raw"
     v4_rank: int | None = 1
+    cardinality: int | None = None
+    layout_preset: str = ""
+    zone_position: str = ""
+    source_shape: str = "paragraph"
+    h3_count: int = 0
+    char_count: int = 0
 
 
 _ROUTE_HINTS: dict[str | None, str | None] = {
@@ -64,6 +76,25 @@ def _call(
     return step12_mod.gather_step12_ai_repair_proposals(units, **kwargs)
 
 
+def _ai_unit(**overrides: Any) -> FakeUnit:
+    """Construct an AI-eligible FakeUnit (provisional + restructure) with sane defaults."""
+    base: dict[str, Any] = dict(
+        label="restructure",
+        provisional=True,
+        frame_template_id="tmpl_x",
+        frame_id="fid_123",
+        source_section_ids=["02-1"],
+        layout_preset="single_column",
+        zone_position="zone_a",
+        source_shape="bullet",
+        h3_count=3,
+        char_count=200,
+        cardinality=5,
+    )
+    base.update(overrides)
+    return FakeUnit(**base)
+
+
 def test_non_provisional_unit_is_skipped_without_ai_call(monkeypatch):
     router = MagicMock()
     monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
@@ -75,13 +106,20 @@ def test_non_provisional_unit_is_skipped_without_ai_call(monkeypatch):
     router.assert_not_called()
 
 
-def test_reject_route_is_skipped_without_ai_call(monkeypatch):
+def test_design_reference_route_falls_through_to_route_not_ai_adaptation(monkeypatch):
+    """IMP-47B u2 — the bespoke 'design_reference_only_no_ai' skip is gone.
+
+    Any non-AI-adaptation route_hint (including the legacy
+    ``design_reference_only`` hint exercised here via the local test mapping
+    of ``reject``) now flows into the single ``route_not_ai_adaptation:<hint>``
+    catch-all. Production reject routing is exercised by u9.
+    """
     router = MagicMock()
     monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
     units = [FakeUnit(label="reject", provisional=True)]
     records = _call(units)
     assert records[0]["ai_called"] is False
-    assert records[0]["skip_reason"] == "design_reference_only_no_ai"
+    assert records[0]["skip_reason"] == "route_not_ai_adaptation:design_reference_only"
     assert records[0]["route_hint"] == "design_reference_only"
     router.assert_not_called()
 
@@ -153,29 +191,206 @@ def test_mixed_units_each_independently_classified(monkeypatch):
     records = _call(units)
     assert [r["skip_reason"] for r in records] == [
         "not_provisional",
-        "design_reference_only_no_ai",
+        "route_not_ai_adaptation:design_reference_only",
         "router_short_circuit",
         "not_provisional",
     ]
     assert router.call_count == 1
 
 
-def test_cache_key_includes_template_and_section_ids(monkeypatch):
+# ---------------------------------------------------------------------------
+# IMP-46 u4 — structural cache key + fingerprints
+# ---------------------------------------------------------------------------
+
+
+def test_cache_key_format_is_frame_id_plus_sha256(monkeypatch):
+    """cache_key is '{frame_id}::{64-hex-sha256}', NOT template_id + section_ids."""
     router = MagicMock(return_value=None)
     monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit()])
+    cache_key = router.call_args.kwargs["cache_key"]
+    assert "::" in cache_key
+    frame_part, _, signature_part = cache_key.partition("::")
+    assert frame_part == "fid_123"
+    assert len(signature_part) == 64
+    assert all(c in "0123456789abcdef" for c in signature_part)
+    # The legacy "template_id::sorted(section_ids)" form is gone.
+    assert "tmpl_x" not in cache_key
+    assert "02-1" not in cache_key
+
+
+def test_cache_key_invariant_to_section_id_changes(monkeypatch):
+    """Same structural axes → same cache_key regardless of source_section_ids."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit(source_section_ids=["02-1"])])
+    key_a = router.call_args.kwargs["cache_key"]
+    router.reset_mock()
+    _call([_ai_unit(source_section_ids=["05-2", "07-3"])])
+    key_b = router.call_args.kwargs["cache_key"]
+    assert key_a == key_b
+
+
+def test_cache_key_invariant_to_template_id_changes(monkeypatch):
+    """frame_template_id is NOT part of the structural signature (frame_id is)."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit(frame_template_id="tmpl_x")])
+    key_a = router.call_args.kwargs["cache_key"]
+    router.reset_mock()
+    _call([_ai_unit(frame_template_id="tmpl_OTHER")])
+    key_b = router.call_args.kwargs["cache_key"]
+    assert key_a == key_b
+
+
+def test_cache_key_changes_when_any_signature_axis_changes(monkeypatch):
+    """Flipping any of the 7 unit-derived signature axes mutates cache_key."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit()])
+    base_key = router.call_args.kwargs["cache_key"]
+    perturbations: dict[str, Any] = {
+        "frame_id": "fid_OTHER",
+        "label": "use_as_is",  # v4_label axis change; still routed to AI via _ROUTE_HINTS? No.
+        # ↑ "use_as_is" → "direct_render" → would skip. Use another ai-adaptation-mapped label.
+        # Replace with frame_id-only diff to keep route stable. Drop this entry below.
+    }
+    # Rebuild perturbations restricted to axes that don't change routing.
+    perturbations = {
+        "frame_id": "fid_OTHER",
+        "layout_preset": "two_column",
+        "zone_position": "zone_b",
+        "source_shape": "paragraph",
+        "h3_count": 7,
+        "char_count": 500,  # bucket boundary crossing (151-400 → 401-1000)
+        "cardinality": 4,
+    }
+    for axis, value in perturbations.items():
+        router.reset_mock()
+        _call([_ai_unit(**{axis: value})])
+        new_key = router.call_args.kwargs["cache_key"]
+        assert new_key != base_key, f"signature axis {axis!r} did not mutate cache_key"
+
+
+def test_char_count_bucket_collapses_within_bucket(monkeypatch):
+    """Different char_counts in the SAME bucket → identical cache_key."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit(char_count=160)])
+    key_low = router.call_args.kwargs["cache_key"]
+    router.reset_mock()
+    _call([_ai_unit(char_count=399)])
+    key_high = router.call_args.kwargs["cache_key"]
+    assert key_low == key_high  # both fall in "151-400"
+    router.reset_mock()
+    _call([_ai_unit(char_count=401)])
+    key_overflow = router.call_args.kwargs["cache_key"]
+    assert key_overflow != key_low  # crossed into "401-1000"
+
+
+def test_fingerprints_attached_to_ai_record(monkeypatch):
+    """AI-called records expose contract_sha + partial_sha + catalog_sha."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    contract = {"frame_id": "fid", "payload": {"x": 1}, "sub_zones": []}
+    partial = {"some": "partial", "deeper": [1, 2, 3]}
+    catalog_value = "deadbeef" * 8
+    recs = _call(
+        [_ai_unit()],
+        get_contract_fn=lambda _t: contract,
+        figma_partial_loader=lambda _t: partial,
+        catalog_sha_loader=lambda: catalog_value,
+    )
+    fps = recs[0]["fingerprints"]
+    assert isinstance(fps, dict)
+    assert set(fps.keys()) == {"contract_sha", "partial_sha", "catalog_sha"}
+    assert all(isinstance(v, str) for v in fps.values())
+    assert fps["catalog_sha"] == catalog_value
+    # contract_sha and partial_sha must be deterministic SHA256 over JSON-sorted payloads.
+    expected_contract = hashlib.sha256(
+        json.dumps(contract, sort_keys=True, ensure_ascii=False).encode("utf-8")
+    ).hexdigest()
+    expected_partial = hashlib.sha256(
+        json.dumps(partial, sort_keys=True, ensure_ascii=False).encode("utf-8")
+    ).hexdigest()
+    assert fps["contract_sha"] == expected_contract
+    assert fps["partial_sha"] == expected_partial
+
+
+def test_fingerprints_default_catalog_sha_is_empty_string(monkeypatch):
+    """No catalog_sha_loader → catalog_sha defaults to '' (sentinel, not missing key)."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    fps = recs[0]["fingerprints"]
+    assert fps["catalog_sha"] == ""
+    # contract_sha + partial_sha keys still present (always 3 keys).
+    assert set(fps.keys()) == {"contract_sha", "partial_sha", "catalog_sha"}
+
+
+def test_fingerprints_change_when_contract_changes(monkeypatch):
+    """Different frame_contract → different contract_sha, partial_sha unchanged."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    fps_a = _call([_ai_unit()], get_contract_fn=lambda _t: {"a": 1})[0]["fingerprints"]
+    fps_b = _call([_ai_unit()], get_contract_fn=lambda _t: {"a": 2})[0]["fingerprints"]
+    assert fps_a["contract_sha"] != fps_b["contract_sha"]
+    assert fps_a["partial_sha"] == fps_b["partial_sha"]
+
+
+def test_fingerprints_change_when_partial_changes(monkeypatch):
+    """Different figma_partial_json → different partial_sha, contract_sha unchanged."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    fps_a = _call(
+        [_ai_unit()], figma_partial_loader=lambda _t: {"p": 1}
+    )[0]["fingerprints"]
+    fps_b = _call(
+        [_ai_unit()], figma_partial_loader=lambda _t: {"p": 2}
+    )[0]["fingerprints"]
+    assert fps_a["partial_sha"] != fps_b["partial_sha"]
+    assert fps_a["contract_sha"] == fps_b["contract_sha"]
+
+
+def test_v4_result_cardinality_uses_unit_value(monkeypatch):
+    """v4_result['cardinality'] mirrors the unit's cardinality (no longer hardcoded None)."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit(cardinality=7)])
+    assert router.call_args.kwargs["v4_result"]["cardinality"] == 7
+    router.reset_mock()
+    _call([_ai_unit(cardinality=None)])
+    assert router.call_args.kwargs["v4_result"]["cardinality"] is None
+
+
+def test_skipped_records_have_no_cache_key_or_fingerprints(monkeypatch):
+    """Non-AI-eligible records keep cache_key and fingerprints as None."""
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", MagicMock(return_value=None))
     units = [
-        FakeUnit(
-            label="restructure",
-            provisional=True,
-            frame_template_id="tmpl_abc",
-            source_section_ids=["02-1", "02-2"],
-        )
+        FakeUnit(label="restructure", provisional=False),
+        FakeUnit(label="reject", provisional=True),
+        FakeUnit(label="light_edit", provisional=True),
     ]
-    _call(units)
-    assert router.call_args.kwargs["cache_key"] == "tmpl_abc::02-1,02-2"
+    recs = _call(units)
+    for rec in recs:
+        assert rec["cache_key"] is None
+        assert rec["fingerprints"] is None
 
 
-def test_record_shape_contract_is_stable(monkeypatch):
+def test_catalog_sha_loader_called_once_per_gather(monkeypatch):
+    """catalog_sha is computed once per gather call, not per unit."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    loader = MagicMock(return_value="cafefeed" * 8)
+    _call(
+        [_ai_unit(), _ai_unit(frame_id="fid_other"), _ai_unit(frame_id="fid_third")],
+        catalog_sha_loader=loader,
+    )
+    loader.assert_called_once()
+
+
+def test_record_shape_contract_is_stable_with_u4_fields(monkeypatch):
+    """Record schema includes the IMP-46 u4 cache_key + fingerprints fields."""
     monkeypatch.setattr(step12_mod, "route_ai_fallback", MagicMock(return_value=None))
     units = [FakeUnit(label="reject", provisional=True)]
     rec = _call(units)[0]
@@ -190,4 +405,98 @@ def test_record_shape_contract_is_stable(monkeypatch):
         "skip_reason",
         "proposal",
         "error",
+        "cache_key",
+        "fingerprints",
     }
+
+
+def test_cache_key_is_compatible_with_cache_parse_key(monkeypatch):
+    """cache_key produced here must round-trip through cache.py's _parse_key."""
+    from src.phase_z2_ai_fallback.cache import KEY_DELIMITER, _parse_key
+
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    _call([_ai_unit()])
+    cache_key = router.call_args.kwargs["cache_key"]
+    parsed = _parse_key(cache_key)
+    assert parsed is not None
+    frame_id, signature_hash = parsed
+    assert frame_id == "fid_123"
+    assert len(signature_hash) == 64
+    assert KEY_DELIMITER not in signature_hash
+
+
+# ---------------------------------------------------------------------------
+# IMP-47B u9 — Step 12 reject eligibility + normal-path AI=0 regression
+# ---------------------------------------------------------------------------
+# Locks the end-to-end Step 12 contract against the production route helper
+# `_imp05_route_hint`. The local `_ROUTE_HINTS` mapping above intentionally
+# preserves the legacy ``reject -> design_reference_only`` form to exercise
+# the catch-all fall-through branch; u9 instead drives gather with the real
+# production map (post-u1 flip) so reject provisional units reach the router
+# and normal-path labels stay AI=0.
+
+
+def test_production_reject_route_reaches_router_when_provisional(monkeypatch):
+    """Post-u1, provisional reject units must reach ``route_ai_fallback``."""
+    from src.phase_z2_pipeline import _imp05_route_hint
+
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    records = step12_mod.gather_step12_ai_repair_proposals(
+        [FakeUnit(label="reject", provisional=True)],
+        route_for_label=_imp05_route_hint,
+        get_contract_fn=_get_contract,
+        frame_visual_loader=_frame_visual,
+    )
+    assert records[0]["route_hint"] == "ai_adaptation_required"
+    assert records[0]["skip_reason"] == "router_short_circuit"
+    assert records[0]["ai_called"] is False
+    router.assert_called_once()
+
+
+def test_production_normal_route_labels_never_reach_router(monkeypatch):
+    """Normal-path labels stay AI=0 even when the unit is provisional."""
+    from src.phase_z2_pipeline import _imp05_route_hint
+
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    units = [
+        FakeUnit(label="use_as_is", provisional=True),
+        FakeUnit(label="light_edit", provisional=True),
+        FakeUnit(label=None, provisional=True),
+    ]
+    records = step12_mod.gather_step12_ai_repair_proposals(
+        units,
+        route_for_label=_imp05_route_hint,
+        get_contract_fn=_get_contract,
+        frame_visual_loader=_frame_visual,
+    )
+    assert records[0]["skip_reason"] == "route_not_ai_adaptation:direct_render"
+    assert records[1]["skip_reason"] == (
+        "route_not_ai_adaptation:deterministic_minor_adjustment"
+    )
+    assert records[2]["skip_reason"] == "route_not_ai_adaptation:None"
+    router.assert_not_called()
+
+
+def test_production_non_provisional_reject_skipped_before_route_gate(monkeypatch):
+    """The provisional gate fires before the route gate (production routing).
+
+    Even with reject routed to ``ai_adaptation_required`` (post-u1), a
+    non-provisional reject unit must short-circuit at ``not_provisional``
+    without ever consulting ``route_for_label`` for an AI dispatch.
+    """
+    from src.phase_z2_pipeline import _imp05_route_hint
+
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    records = step12_mod.gather_step12_ai_repair_proposals(
+        [FakeUnit(label="reject", provisional=False)],
+        route_for_label=_imp05_route_hint,
+        get_contract_fn=_get_contract,
+        frame_visual_loader=_frame_visual,
+    )
+    assert records[0]["skip_reason"] == "not_provisional"
+    assert records[0]["ai_called"] is False
+    router.assert_not_called()
diff --git a/tests/test_phase_z2_ai_fallback_config.py b/tests/test_phase_z2_ai_fallback_config.py
index 877dab3..ee80048 100644
--- a/tests/test_phase_z2_ai_fallback_config.py
+++ b/tests/test_phase_z2_ai_fallback_config.py
@@ -44,3 +44,43 @@ def test_ai_fallback_budget_and_circuit_defaults_locked() -> None:
     s = Settings()
     assert s.ai_fallback_budget_per_run == 10
     assert s.ai_fallback_circuit_breaker_threshold == 5
+
+
+# IMP-46 u5 — auto-cache opt-in setting default lock.
+# The CLI flag ``--auto-cache`` in src/phase_z2_pipeline.py mutates this
+# setting at parse time. The default MUST stay OFF so the dual-gate
+# contract (visual_check_passed AND user_approved) survives without an
+# explicit operator opt-in.
+
+
+def test_ai_fallback_auto_cache_default_off() -> None:
+    s = Settings()
+    assert s.ai_fallback_auto_cache is False, (
+        "IMP-46 u5 auto-cache MUST default OFF; the dual-gate contract "
+        "(visual_check_passed AND user_approved) survives without an "
+        "explicit --auto-cache opt-in."
+    )
+
+
+# IMP-47B u1 — reject route hint policy correction.
+# Prior to 2026-05-21 the reject V4 label routed to ``design_reference_only``
+# (no AI). The user policy correction (issue #76) reroutes reject to
+# ``ai_adaptation_required`` so the rank-1 reject frame is kept and the AI
+# re-maps MDX content into its declared slots. Activation remains gated by
+# ``ai_fallback_enabled`` (default OFF preserves the normal-path AI=0
+# contract — see test_ai_fallback_master_flag_default_off above).
+
+
+def test_reject_route_hint_routes_to_ai_adaptation() -> None:
+    from src.phase_z2_pipeline import _IMP05_ROUTE_HINTS, _imp05_route_hint
+
+    assert _IMP05_ROUTE_HINTS["reject"] == "ai_adaptation_required", (
+        "IMP-47B u1: reject must route to ai_adaptation_required so the "
+        "rank-1 reject frame is retained and AI re-maps MDX content into "
+        "its slots (frame auto-swap forbidden)."
+    )
+    assert _imp05_route_hint("reject") == "ai_adaptation_required"
+    # Sibling routes unchanged — guardrail against accidental drift.
+    assert _imp05_route_hint("use_as_is") == "direct_render"
+    assert _imp05_route_hint("light_edit") == "deterministic_minor_adjustment"
+    assert _imp05_route_hint("restructure") == "ai_adaptation_required"
diff --git a/tests/test_phase_z2_v4_fallback.py b/tests/test_phase_z2_v4_fallback.py
index 158f42e..87ad6c3 100644
--- a/tests/test_phase_z2_v4_fallback.py
+++ b/tests/test_phase_z2_v4_fallback.py
@@ -237,10 +237,10 @@ def test_restructure_reject_preserved_as_non_direct_evidence(patch_selector_deps
     by_rank = {c["rank"]: c for c in candidates}
     assert set(by_rank.keys()) == {1, 2, 3}
 
-    # rank-1 reject — non-direct, design_reference_only
+    # rank-1 reject — non-direct, ai_adaptation_required (IMP-47B u1 policy correction)
     assert by_rank[1]["v4_label"] == "reject"
     assert by_rank[1]["filtered_for_direct_execution"] is True
-    assert by_rank[1]["route_hint"] == "design_reference_only"
+    assert by_rank[1]["route_hint"] == "ai_adaptation_required"
 
     # rank-2 restructure — non-direct, ai_adaptation_required
     assert by_rank[2]["v4_label"] == "restructure"