diff --git a/Front/client/src/services/designAgentApi.ts b/Front/client/src/services/designAgentApi.ts
index f6a9240..272a0a3 100644
--- a/Front/client/src/services/designAgentApi.ts
+++ b/Front/client/src/services/designAgentApi.ts
@@ -235,6 +235,15 @@ export interface AiRepairStatus {
     unsupported_kind: number;
     error: number;
   };
+  // IMP-92 u3 — per-kind operational error aggregates plumbed from Step 12
+  // (u2 classify_operational_error). Optional for backward compatibility
+  // with pre-u3 payloads — u5 formatter treats absence as silent.
+  api_error_kinds?: {
+    quota: number;
+    billing: number;
+    auth: number;
+    other: number;
+  };
   unsupported_kind_records: Array<{
     unit_index?: number | null;
     source_section_ids: string[];
@@ -244,6 +253,8 @@ export interface AiRepairStatus {
     unit_index?: number | null;
     source_section_ids: string[];
     error: string;
+    // IMP-92 u3 — per-record operational error kind (quota|billing|auth|other|null).
+    api_error_kind?: string | null;
   }>;
   coverage_status: string;
   dropped_section_ids: string[];
@@ -267,23 +278,32 @@ export interface RunMeta {
   ai_repair_status: AiRepairStatus | null;
 }
 
+// IMP-92 u5 — Operational-only AI repair message formatter.
+//
+// Per the #84 operational-vs-non-operational replacement-plan contract, this
+// returns a user-visible toast string ONLY when ai_repair_status carries one
+// of the three actionable Anthropic API error kinds plumbed by u3
+// (quota / billing / auth). Non-operational AI failures (validation,
+// coverage_violated, unsupported_kind, or generic "other" API errors) return
+// null so the auto-pipeline stays silent per feedback_auto_pipeline_first.
+// Messages mirror the issue body copy contract exactly (429/402/401 →
+// quota/billing/auth Korean strings).
 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 (${n}건) — 다른 frame 선택 또는 수동 편집 필요`;
+  if (!ai) return null;
+  const kinds = ai.api_error_kinds;
+  if (!kinds) return null;
+  if (kinds.quota > 0) {
+    return `API quota 부족 — 충전 필요 (${kinds.quota}건)`;
   }
-  if (ai.status === "coverage_violated") {
-    const dropped = (ai.dropped_section_ids || []).join(", ");
-    return `AI 재구성 후 콘텐츠 누락 (dropped: ${dropped || "?"}) — 다른 frame 선택 또는 수동 편집 필요`;
+  if (kinds.billing > 0) {
+    return `API billing 문제 — 결제 정보 확인 (${kinds.billing}건)`;
   }
-  if (ai.status === "unsupported_kind") {
-    const n = ai.counts?.unsupported_kind ?? ai.unsupported_kind_records?.length ?? 0;
-    return `AI 제안 형식 미지원 (${n}건) — 다른 frame 선택 또는 수동 편집 필요`;
+  if (kinds.auth > 0) {
+    return `API key 무효 — .env 확인 (${kinds.auth}건)`;
   }
-  return `AI 재구성 human_review 필요 (status: ${ai.status})`;
+  return null;
 }
 
 export interface LoadRunResult {
diff --git a/Front/client/tests/imp47b_human_review_toast.test.tsx b/Front/client/tests/imp47b_human_review_toast.test.tsx
index 712e3cf..51d6a9d 100644
--- a/Front/client/tests/imp47b_human_review_toast.test.tsx
+++ b/Front/client/tests/imp47b_human_review_toast.test.tsx
@@ -1,20 +1,28 @@
-// IMP-47B u11 — Frontend ai_repair_status notification surfacing.
+// IMP-92 u5 — Frontend AI repair operational-only formatter test surface.
 //
-// Scope (Stage 2 unit u11 contract):
-//   1) loadRun → RunMeta.ai_repair_status exposes the u8 step20 payload.
-//   2) formatAiRepairHumanReviewMessage(...) returns user-facing notification
-//      text on the three failure axes (error / coverage_violated /
-//      unsupported_kind) and returns null on success / no-AI paths.
+// Scope (Stage 2 unit u5 contract):
+//   1) formatAiRepairHumanReviewMessage(...) surfaces a user-facing toast
+//      ONLY on the three operational Anthropic API error kinds (quota /
+//      billing / auth) classified by Step 12 u2
+//      (classify_operational_error) and aggregated through u3
+//      ai_repair_status.api_error_kinds.
+//   2) Non-operational AI failures (validation / coverage_violated /
+//      unsupported_kind / generic "other") return null so the
+//      auto-pipeline stays silent per feedback_auto_pipeline_first and
+//      the #84 operational-vs-non-operational replacement-plan contract.
+//   3) Replaces the prior IMP-47B u11 surface — previously rendered toasts
+//      for error / coverage_violated / unsupported_kind. After IMP-92 the
+//      ONLY operational reaches the user; non-operational stays silent.
 //
 // Pure-function unit test (no React Testing Library required — vitest is
 // already in devDependencies; @testing-library/* is NOT installed). The
-// Home.tsx wiring is a 2-line site that calls this helper after
-// setRunMeta(...); covering the helper covers the user-visible message text
-// directly without DOM rendering.
+// Home.tsx wiring is a 2-line site (`Home.tsx:438`) that calls this helper
+// after `setRunMeta(...)`; covering the helper covers the user-visible
+// message text directly without DOM rendering.
 //
-// File extension is `.tsx` per Stage 2 unit contract path; no JSX is required
-// for these assertions but the extension allows future RTL-based tests to
-// land here without renaming.
+// The test file path is preserved from IMP-47B u11 (Stage 2 plan
+// `Front/client/tests/imp47b_human_review_toast.test.tsx`); the assertions
+// inside reflect the IMP-92 u5 operational-only contract.
 
 import { describe, it, expect } from "vitest";
 import {
@@ -23,7 +31,7 @@ import {
 } from "../src/services/designAgentApi";
 
 const baseCounts = {
-  total: 1,
+  total: 0,
   applied: 0,
   no_proposal: 0,
   no_zone_match: 0,
@@ -31,16 +39,19 @@ const baseCounts = {
   error: 0,
 };
 
-describe("formatAiRepairHumanReviewMessage (IMP-47B u11)", () => {
-  it("returns null when ai_repair_status is null (legacy / pre-Step12 abort)", () => {
+const zeroKinds = { quota: 0, billing: 0, auth: 0, other: 0 };
+
+describe("formatAiRepairHumanReviewMessage (IMP-92 u5 — operational-only)", () => {
+  it("returns null when ai_repair_status is null / undefined", () => {
     expect(formatAiRepairHumanReviewMessage(null)).toBeNull();
     expect(formatAiRepairHumanReviewMessage(undefined)).toBeNull();
   });
 
-  it("returns null when human_review_required=false (success / no-AI path)", () => {
+  it("returns null on success / no-AI path (no operational kind present)", () => {
     const ok: AiRepairStatus = {
       status: "ok",
-      counts: { ...baseCounts, total: 0 },
+      counts: { ...baseCounts },
+      api_error_kinds: { ...zeroKinds },
       unsupported_kind_records: [],
       error_records: [],
       coverage_status: "ok",
@@ -57,47 +68,127 @@ describe("formatAiRepairHumanReviewMessage (IMP-47B u11)", () => {
     expect(formatAiRepairHumanReviewMessage(applied)).toBeNull();
   });
 
-  it("surfaces AI call failures with count + frame/manual guidance", () => {
-    const errored: AiRepairStatus = {
+  it("surfaces quota operational alert (Anthropic 429 / RateLimitError)", () => {
+    const ai: AiRepairStatus = {
       status: "error",
       counts: { ...baseCounts, total: 2, error: 2 },
+      api_error_kinds: { quota: 2, billing: 0, auth: 0, other: 0 },
       unsupported_kind_records: [],
       error_records: [
-        { unit_index: 0, source_section_ids: ["03-1"], error: "timeout" },
-        { unit_index: 1, source_section_ids: ["03-2"], error: "validation" },
+        {
+          unit_index: 0,
+          source_section_ids: ["03-1"],
+          error: "RateLimitError: rate_limit_exceeded",
+          api_error_kind: "quota",
+        },
+        {
+          unit_index: 1,
+          source_section_ids: ["03-2"],
+          error: "RateLimitError: rate_limit_exceeded",
+          api_error_kind: "quota",
+        },
       ],
       coverage_status: "ok",
       dropped_section_ids: [],
       human_review_required: true,
     };
-    const msg = formatAiRepairHumanReviewMessage(errored);
+    const msg = formatAiRepairHumanReviewMessage(ai);
     expect(msg).not.toBeNull();
-    expect(msg).toContain("AI 재구성 호출 실패");
+    expect(msg).toContain("API quota");
+    expect(msg).toContain("충전 필요");
     expect(msg).toContain("2");
-    expect(msg).toContain("다른 frame 선택 또는 수동 편집 필요");
   });
 
-  it("surfaces coverage violations with the dropped section ids", () => {
-    const dropped: AiRepairStatus = {
+  it("surfaces billing operational alert (Anthropic 402 / PermissionDeniedError)", () => {
+    const ai: AiRepairStatus = {
+      status: "error",
+      counts: { ...baseCounts, total: 1, error: 1 },
+      api_error_kinds: { quota: 0, billing: 1, auth: 0, other: 0 },
+      unsupported_kind_records: [],
+      error_records: [
+        {
+          unit_index: 0,
+          source_section_ids: ["03-1"],
+          error: "PermissionDeniedError: insufficient credits",
+          api_error_kind: "billing",
+        },
+      ],
+      coverage_status: "ok",
+      dropped_section_ids: [],
+      human_review_required: true,
+    };
+    const msg = formatAiRepairHumanReviewMessage(ai);
+    expect(msg).not.toBeNull();
+    expect(msg).toContain("API billing");
+    expect(msg).toContain("결제 정보 확인");
+    expect(msg).toContain("1");
+  });
+
+  it("surfaces auth operational alert (Anthropic 401 / AuthenticationError)", () => {
+    const ai: AiRepairStatus = {
+      status: "error",
+      counts: { ...baseCounts, total: 1, error: 1 },
+      api_error_kinds: { quota: 0, billing: 0, auth: 1, other: 0 },
+      unsupported_kind_records: [],
+      error_records: [
+        {
+          unit_index: 0,
+          source_section_ids: ["03-1"],
+          error: "AuthenticationError: invalid x-api-key",
+          api_error_kind: "auth",
+        },
+      ],
+      coverage_status: "ok",
+      dropped_section_ids: [],
+      human_review_required: true,
+    };
+    const msg = formatAiRepairHumanReviewMessage(ai);
+    expect(msg).not.toBeNull();
+    expect(msg).toContain("API key 무효");
+    expect(msg).toContain(".env");
+    expect(msg).toContain("1");
+  });
+
+  it("returns null on generic non-operational 'other' API error (silent)", () => {
+    const ai: AiRepairStatus = {
+      status: "error",
+      counts: { ...baseCounts, total: 1, error: 1 },
+      api_error_kinds: { quota: 0, billing: 0, auth: 0, other: 1 },
+      unsupported_kind_records: [],
+      error_records: [
+        {
+          unit_index: 0,
+          source_section_ids: ["03-1"],
+          error: "ValidationError: proposal failed schema",
+          api_error_kind: "other",
+        },
+      ],
+      coverage_status: "ok",
+      dropped_section_ids: [],
+      human_review_required: true,
+    };
+    expect(formatAiRepairHumanReviewMessage(ai)).toBeNull();
+  });
+
+  it("returns null on coverage_violated (non-operational, silent)", () => {
+    const ai: AiRepairStatus = {
       status: "coverage_violated",
       counts: { ...baseCounts, total: 1, applied: 1 },
+      api_error_kinds: { ...zeroKinds },
       unsupported_kind_records: [],
       error_records: [],
       coverage_status: "violated",
       dropped_section_ids: ["03-2"],
       human_review_required: true,
     };
-    const msg = formatAiRepairHumanReviewMessage(dropped);
-    expect(msg).not.toBeNull();
-    expect(msg).toContain("콘텐츠 누락");
-    expect(msg).toContain("03-2");
-    expect(msg).toContain("다른 frame 선택 또는 수동 편집 필요");
+    expect(formatAiRepairHumanReviewMessage(ai)).toBeNull();
   });
 
-  it("surfaces unsupported proposal kinds with the unsupported count", () => {
-    const unsupported: AiRepairStatus = {
+  it("returns null on unsupported_kind (non-operational, silent)", () => {
+    const ai: AiRepairStatus = {
       status: "unsupported_kind",
       counts: { ...baseCounts, total: 1, unsupported_kind: 1 },
+      api_error_kinds: { ...zeroKinds },
       unsupported_kind_records: [
         {
           unit_index: 0,
@@ -110,26 +201,57 @@ describe("formatAiRepairHumanReviewMessage (IMP-47B u11)", () => {
       dropped_section_ids: [],
       human_review_required: true,
     };
-    const msg = formatAiRepairHumanReviewMessage(unsupported);
-    expect(msg).not.toBeNull();
-    expect(msg).toContain("AI 제안 형식 미지원");
-    expect(msg).toContain("1");
-    expect(msg).toContain("다른 frame 선택 또는 수동 편집 필요");
+    expect(formatAiRepairHumanReviewMessage(ai)).toBeNull();
   });
 
-  it("falls back to a generic human_review message on unknown status enums", () => {
-    const future: AiRepairStatus = {
-      status: "future_axis_not_yet_mapped",
-      counts: { ...baseCounts, total: 0 },
+  it("returns null on legacy ai_repair_status without api_error_kinds (pre-u3 runs)", () => {
+    // Backward-compat: payloads emitted before u3 plumbing landed don't
+    // carry api_error_kinds. Operational-only contract treats the absence
+    // as "no operational signal" → silent (no toast).
+    const legacy: AiRepairStatus = {
+      status: "error",
+      counts: { ...baseCounts, total: 1, error: 1 },
+      // api_error_kinds intentionally omitted
       unsupported_kind_records: [],
-      error_records: [],
+      error_records: [
+        { unit_index: 0, source_section_ids: ["03-1"], error: "timeout" },
+      ],
       coverage_status: "ok",
       dropped_section_ids: [],
       human_review_required: true,
     };
-    const msg = formatAiRepairHumanReviewMessage(future);
+    expect(formatAiRepairHumanReviewMessage(legacy)).toBeNull();
+  });
+
+  it("prioritises quota when multiple operational kinds co-occur", () => {
+    // Defensive: a run that accumulated quota + billing errors across
+    // multiple AI repair attempts surfaces the quota line first (the
+    // most-frequently actionable per the issue body ordering).
+    const ai: AiRepairStatus = {
+      status: "error",
+      counts: { ...baseCounts, total: 2, error: 2 },
+      api_error_kinds: { quota: 1, billing: 1, auth: 0, other: 0 },
+      unsupported_kind_records: [],
+      error_records: [
+        {
+          unit_index: 0,
+          source_section_ids: ["03-1"],
+          error: "RateLimitError",
+          api_error_kind: "quota",
+        },
+        {
+          unit_index: 1,
+          source_section_ids: ["03-2"],
+          error: "PermissionDeniedError",
+          api_error_kind: "billing",
+        },
+      ],
+      coverage_status: "ok",
+      dropped_section_ids: [],
+      human_review_required: true,
+    };
+    const msg = formatAiRepairHumanReviewMessage(ai);
     expect(msg).not.toBeNull();
-    expect(msg).toContain("human_review");
-    expect(msg).toContain("future_axis_not_yet_mapped");
+    expect(msg).toContain("API quota");
   });
 });
diff --git a/src/config.py b/src/config.py
index fec6a38..772008e 100644
--- a/src/config.py
+++ b/src/config.py
@@ -17,7 +17,7 @@ class Settings(BaseSettings):
     # IMP-33 u1 — AI fallback policy. Fallback-path only; normal path AI=0.
     # Defaults locked by Stage 2 plan; do NOT inline literals downstream.
     ai_fallback_enabled: bool = False
-    ai_fallback_model: str = "claude-opus-4-6-20250415"
+    ai_fallback_model: str = "claude-opus-4-7"
     ai_fallback_timeout_s: float = 60.0
     ai_fallback_max_retries: int = 3
     ai_fallback_backoff_base_s: float = 1.0
diff --git a/src/phase_z2_ai_fallback/client.py b/src/phase_z2_ai_fallback/client.py
index bc126a3..61450b3 100644
--- a/src/phase_z2_ai_fallback/client.py
+++ b/src/phase_z2_ai_fallback/client.py
@@ -31,6 +31,55 @@ _TRANSIENT_ERRORS: tuple[type[BaseException], ...] = (
 # Output cap is an Anthropic API requirement, not a policy knob (u1).
 _MAX_OUTPUT_TOKENS = 4096
 
+# IMP-92 u2 — Anthropic SDK exception → operational error kind classifier.
+# Stamped onto Step 12 AI repair records (api_error_kind) so the frontend
+# operational alert formatter can surface quota / billing / auth to users
+# while keeping non-operational ("other") failures silent. The classifier
+# is type-based (not string parsing) and the four kinds are the only
+# values frontend operational formatter is allowed to render.
+_OPERATIONAL_ERROR_KIND_QUOTA = "quota"
+_OPERATIONAL_ERROR_KIND_BILLING = "billing"
+_OPERATIONAL_ERROR_KIND_AUTH = "auth"
+_OPERATIONAL_ERROR_KIND_OTHER = "other"
+
+
+def classify_operational_error(exc: BaseException) -> str:
+    """Return the operational error kind for an Anthropic SDK exception.
+
+    Dispatch combines SDK exception type with the HTTP status code so the
+    issue body's explicit operational contract (429 quota / 402 billing /
+    401 auth) is honoured even when the SDK surfaces a 402 as the generic
+    ``anthropic.APIStatusError`` rather than a typed subclass:
+
+      * ``anthropic.RateLimitError`` OR HTTP 429        → ``"quota"``
+      * ``anthropic.PermissionDeniedError`` OR HTTP 402 → ``"billing"``
+        (Anthropic Payment Required surfaces as 402; PermissionDenied/403
+        is the SDK-typed billing/permission surface)
+      * ``anthropic.AuthenticationError`` OR HTTP 401   → ``"auth"``
+      * everything else                                 → ``"other"`` (silent on UI)
+
+    The frontend formatter renders quota / billing / auth and returns
+    ``None`` for ``"other"`` so non-operational AI failures stay silent
+    per the #84 replacement-plan contract.
+    """
+    if isinstance(exc, anthropic.RateLimitError):
+        return _OPERATIONAL_ERROR_KIND_QUOTA
+    if isinstance(exc, anthropic.PermissionDeniedError):
+        return _OPERATIONAL_ERROR_KIND_BILLING
+    if isinstance(exc, anthropic.AuthenticationError):
+        return _OPERATIONAL_ERROR_KIND_AUTH
+    if isinstance(exc, anthropic.APIStatusError):
+        status_code = getattr(exc, "status_code", None)
+        if status_code is None:
+            status_code = getattr(getattr(exc, "response", None), "status_code", None)
+        if status_code == 429:
+            return _OPERATIONAL_ERROR_KIND_QUOTA
+        if status_code == 402:
+            return _OPERATIONAL_ERROR_KIND_BILLING
+        if status_code == 401:
+            return _OPERATIONAL_ERROR_KIND_AUTH
+    return _OPERATIONAL_ERROR_KIND_OTHER
+
 
 class AiFallbackBudgetExceeded(RuntimeError):
     """Per-run AI call budget (u1 ai_fallback_budget_per_run) exhausted."""
diff --git a/src/phase_z2_ai_fallback/step12.py b/src/phase_z2_ai_fallback/step12.py
index b2406ef..7915e2f 100644
--- a/src/phase_z2_ai_fallback/step12.py
+++ b/src/phase_z2_ai_fallback/step12.py
@@ -56,6 +56,7 @@ import hashlib
 import json
 from typing import Any, Callable, Iterable
 
+from src.phase_z2_ai_fallback.client import classify_operational_error
 from src.phase_z2_ai_fallback.router import route_ai_fallback
 from src.phase_z2_ai_fallback.signature import bucket_char_count, build_signature
 
@@ -96,6 +97,7 @@ def gather_step12_ai_repair_proposals(
           "skip_reason": str | None,
           "proposal": dict | None,
           "error": str | None,
+          "api_error_kind": str | None,   # IMP-92 u2 (quota|billing|auth|other)
           "cache_key": str | None,        # IMP-46 u4
           "fingerprints": dict | None,    # IMP-46 u4
         }
@@ -130,6 +132,7 @@ def gather_step12_ai_repair_proposals(
             "skip_reason": None,
             "proposal": None,
             "error": None,
+            "api_error_kind": None,
             "cache_key": None,
             "fingerprints": None,
         }
@@ -205,6 +208,7 @@ def gather_step12_ai_repair_proposals(
         except Exception as exc:  # noqa: BLE001 — record + continue, no AI re-raise
             record["ai_called"] = True
             record["error"] = f"{type(exc).__name__}: {exc}"
+            record["api_error_kind"] = classify_operational_error(exc)
             records.append(record)
             continue
         if proposal is None:
diff --git a/src/phase_z2_pipeline.py b/src/phase_z2_pipeline.py
index 1ba04cf..be46bc4 100644
--- a/src/phase_z2_pipeline.py
+++ b/src/phase_z2_pipeline.py
@@ -789,6 +789,14 @@ def _summarize_ai_repair_status(
     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.
+
+    IMP-92 u3 — propagate ``api_error_kind`` (quota / billing / auth /
+    other) stamped by Step 12 (u2 ``classify_operational_error``) through
+    ``ai_repair_status`` so the frontend operational formatter can route
+    only operational kinds (quota / billing / auth) to user-visible
+    alerts. ``api_error_kinds`` aggregates counts by kind at the summary
+    level; ``error_records[i]["api_error_kind"]`` retains the per-record
+    kind for unit-level surfacing.
     """
     counts = {
         "total": len(ai_repair_records),
@@ -798,15 +806,20 @@ def _summarize_ai_repair_status(
         "unsupported_kind": 0,
         "error": 0,
     }
+    api_error_kinds = {"quota": 0, "billing": 0, "auth": 0, "other": 0}
     unsupported_records: list[dict] = []
     error_records: list[dict] = []
     for record in ai_repair_records:
         if record.get("error"):
             counts["error"] += 1
+            kind = record.get("api_error_kind")
+            if kind in api_error_kinds:
+                api_error_kinds[kind] += 1
             error_records.append({
                 "unit_index": record.get("unit_index"),
                 "source_section_ids": list(record.get("source_section_ids") or []),
                 "error": record.get("error"),
+                "api_error_kind": kind,
             })
             continue
         apply_status = record.get("apply_status") or ""
@@ -838,6 +851,7 @@ def _summarize_ai_repair_status(
     return {
         "status": status,
         "counts": counts,
+        "api_error_kinds": api_error_kinds,
         "unsupported_kind_records": unsupported_records,
         "error_records": error_records,
         "coverage_status": coverage_status,
@@ -3588,6 +3602,114 @@ def _build_application_plan_unit(
 
 # ─── Main entry ────────────────────────────────────────────────
 
+
+class Step0PreflightError(RuntimeError):
+    """IMP-92 u4 — Step 0 AI preflight fail-fast surface.
+
+    Raised at boot when ``settings.ai_fallback_enabled`` is True and the
+    Anthropic API ping reveals a persistent setup problem (invalid API
+    key, invalid model ID, billing / permission denied). Transient errors
+    (429 / 5xx) do NOT fail boot — they are recorded as ``"transient"``
+    in the Step 0 artifact and the pipeline proceeds; the in-pipeline
+    retry layer + u2 operational classifier handle them downstream.
+    """
+
+
+def _run_step0_ai_preflight() -> dict:
+    """IMP-92 u4 — Boot-time AI fallback preflight ping (gated).
+
+    When ``settings.ai_fallback_enabled`` is False (default), returns
+    ``{"status": "skipped", "reason": "ai_fallback_disabled", ...}``
+    without instantiating ``anthropic.Anthropic`` — preserves the PZ-1
+    AI=0 normal path and the ``feedback_demo_env_toggle_policy``
+    default-OFF contract (no API call on normal runs).
+
+    When enabled, issues a single 1-token Anthropic ``messages.create``
+    to validate the configured ``(ai_fallback_model, anthropic_api_key)``
+    pair. Persistent setup errors raise ``Step0PreflightError`` so the
+    pipeline fails fast at boot rather than at first AI repair attempt.
+    Transient errors are recorded as ``"transient"`` and the pipeline
+    continues.
+
+    Setup errors (fail-fast):
+      * ``anthropic.AuthenticationError`` (401)     — invalid API key
+      * ``anthropic.PermissionDeniedError`` (403)   — billing / permission
+      * ``anthropic.NotFoundError`` (404)           — invalid model ID
+      * generic ``anthropic.APIStatusError`` (402)  — billing / payment
+        required (Anthropic surfaces 402 without a typed subclass;
+        dispatched here by HTTP status code, mirroring u2
+        ``classify_operational_error``).
+
+    Transient (record + continue):
+      * ``anthropic.RateLimitError`` (429)
+      * ``anthropic.InternalServerError`` (5xx)
+      * generic ``anthropic.APIStatusError`` with HTTP 429 / 5xx
+    """
+    import anthropic
+
+    from src.config import settings as _settings
+
+    if not _settings.ai_fallback_enabled:
+        return {
+            "status": "skipped",
+            "reason": "ai_fallback_disabled",
+            "model": _settings.ai_fallback_model,
+        }
+    try:
+        client = anthropic.Anthropic(
+            api_key=_settings.anthropic_api_key,
+            timeout=_settings.ai_fallback_timeout_s,
+        )
+        client.messages.create(
+            model=_settings.ai_fallback_model,
+            max_tokens=1,
+            messages=[{"role": "user", "content": "ping"}],
+        )
+    except (
+        anthropic.AuthenticationError,
+        anthropic.PermissionDeniedError,
+        anthropic.NotFoundError,
+    ) as exc:
+        raise Step0PreflightError(
+            f"Anthropic API preflight failed for model "
+            f"{_settings.ai_fallback_model!r}: "
+            f"{type(exc).__name__}: {exc}. "
+            "Check ANTHROPIC_API_KEY / ai_fallback_model in .env."
+        ) from exc
+    except (anthropic.RateLimitError, anthropic.InternalServerError) as exc:
+        return {
+            "status": "transient",
+            "model": _settings.ai_fallback_model,
+            "transient_error": f"{type(exc).__name__}: {exc}",
+        }
+    except anthropic.APIStatusError as exc:
+        # IMP-92 u4 — fall back to HTTP status code dispatch when the SDK
+        # surfaces a setup error as the generic ``APIStatusError`` instead
+        # of a typed subclass. Mirrors u2 ``classify_operational_error``
+        # so HTTP 402 (Payment Required / billing) becomes a fail-fast
+        # Step0PreflightError, matching the issue body's explicit
+        # operational contract.
+        status_code = getattr(exc, "status_code", None)
+        if status_code is None:
+            status_code = getattr(getattr(exc, "response", None), "status_code", None)
+        if status_code == 429 or (status_code is not None and 500 <= status_code < 600):
+            return {
+                "status": "transient",
+                "model": _settings.ai_fallback_model,
+                "transient_error": f"{type(exc).__name__}: {exc}",
+            }
+        raise Step0PreflightError(
+            f"Anthropic API preflight failed for model "
+            f"{_settings.ai_fallback_model!r}: "
+            f"HTTP {status_code} {type(exc).__name__}: {exc}. "
+            "Check ANTHROPIC_API_KEY / ai_fallback_model in .env."
+        ) from exc
+    return {
+        "status": "passed",
+        "model": _settings.ai_fallback_model,
+    }
+
+
 def run_phase_z2_mvp1(
     mdx_path: Path,
     run_id: Optional[str] = None,
@@ -3629,6 +3751,10 @@ def run_phase_z2_mvp1(
     print(f"[Phase Z-2 MVP-1.5b] start — mdx={mdx_path.name}, run_id={run_id}")
 
     # ─── Step 0: 사전 준비 (precondition snapshot) ───
+    # IMP-92 u4 — boot-time AI fallback preflight (gated on
+    # settings.ai_fallback_enabled; default OFF = skipped, no API call).
+    # Persistent setup errors raise Step0PreflightError before Step 1.
+    ai_preflight = _run_step0_ai_preflight()
     _write_step_artifact(
         run_dir, 0, "preconditions",
         data={
@@ -3639,6 +3765,7 @@ def run_phase_z2_mvp1(
             "frame_contracts_template_ids": sorted(load_frame_contracts().keys()),
             "v4_label_to_phase_z_status": V4_LABEL_TO_PHASE_Z_STATUS,
             "mvp1_allowed_statuses": sorted(MVP1_ALLOWED_STATUSES),
+            "ai_preflight": ai_preflight,
         },
         step_status="partial",
         pipeline_path_connected=True,
diff --git a/tests/phase_z2/test_pipeline_step0_preflight.py b/tests/phase_z2/test_pipeline_step0_preflight.py
new file mode 100644
index 0000000..c98bb81
--- /dev/null
+++ b/tests/phase_z2/test_pipeline_step0_preflight.py
@@ -0,0 +1,214 @@
+"""IMP-92 u4 — Step 0 AI preflight unit tests.
+
+Scope (Stage 2 plan, u4):
+  - ``settings.ai_fallback_enabled=False`` → preflight short-circuits to
+    ``"skipped"`` without instantiating ``anthropic.Anthropic`` (PZ-1
+    AI=0 normal path + ``feedback_demo_env_toggle_policy`` default-OFF).
+  - ``settings.ai_fallback_enabled=True`` + valid (key, model) → preflight
+    returns ``"passed"`` after a 1-token ``messages.create`` ping.
+  - Persistent setup errors (Authentication / PermissionDenied /
+    NotFound) raise ``Step0PreflightError`` so boot fails fast.
+  - Transient errors (RateLimit / InternalServer) are recorded as
+    ``"transient"`` without failing boot.
+
+Cross-references:
+  - u1 default model literal: ``src/config.py:20``
+    + ``tests/test_phase_z2_ai_fallback_config.py:5,31``
+  - u2 SDK operational classifier:
+    ``src/phase_z2_ai_fallback/client.py:46``
+    + ``tests/phase_z2_ai_fallback/test_step12.py``
+  - u3 ``api_error_kind`` summary plumbing:
+    ``src/phase_z2_pipeline.py:_summarize_ai_repair_status``
+    + ``tests/test_imp47b_failure_surface.py``
+"""
+from __future__ import annotations
+
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import anthropic
+import httpx
+import pytest
+
+from src import phase_z2_pipeline as pipeline_mod
+from src.config import settings
+
+
+@pytest.fixture(autouse=True)
+def _restore_settings():
+    snapshot = settings.model_dump()
+    yield
+    for key, value in snapshot.items():
+        setattr(settings, key, value)
+
+
+def _ok_response() -> SimpleNamespace:
+    return SimpleNamespace(content=[SimpleNamespace(text="")])
+
+
+def _status_error(
+    cls: type[anthropic.APIStatusError],
+    status_code: int,
+    message: str,
+) -> anthropic.APIStatusError:
+    req = httpx.Request("POST", "https://api.anthropic.com/v1/messages")
+    return cls(
+        message=message,
+        response=httpx.Response(status_code, request=req),
+        body=None,
+    )
+
+
+def test_preflight_skipped_when_disabled(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", False)
+    spy = MagicMock()
+    monkeypatch.setattr(anthropic, "Anthropic", spy)
+    result = pipeline_mod._run_step0_ai_preflight()
+    assert result["status"] == "skipped"
+    assert result["reason"] == "ai_fallback_disabled"
+    assert result["model"] == settings.ai_fallback_model
+    spy.assert_not_called()
+
+
+def test_preflight_passed_when_enabled_with_valid_credentials(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.return_value = _ok_response()
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    result = pipeline_mod._run_step0_ai_preflight()
+    assert result == {
+        "status": "passed",
+        "model": settings.ai_fallback_model,
+    }
+    fake_client.messages.create.assert_called_once()
+    kwargs = fake_client.messages.create.call_args.kwargs
+    assert kwargs["model"] == settings.ai_fallback_model
+    assert kwargs["max_tokens"] == 1
+
+
+def test_preflight_fail_fast_on_invalid_api_key(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.AuthenticationError, 401, "invalid x-api-key"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    with pytest.raises(pipeline_mod.Step0PreflightError) as ei:
+        pipeline_mod._run_step0_ai_preflight()
+    assert "AuthenticationError" in str(ei.value)
+
+
+def test_preflight_fail_fast_on_invalid_model(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.NotFoundError, 404, "model not found"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    with pytest.raises(pipeline_mod.Step0PreflightError) as ei:
+        pipeline_mod._run_step0_ai_preflight()
+    msg = str(ei.value)
+    assert "NotFoundError" in msg
+    assert settings.ai_fallback_model in msg
+
+
+def test_preflight_fail_fast_on_billing_permission_denied(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.PermissionDeniedError, 403, "billing required"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    with pytest.raises(pipeline_mod.Step0PreflightError) as ei:
+        pipeline_mod._run_step0_ai_preflight()
+    assert "PermissionDeniedError" in str(ei.value)
+
+
+def test_preflight_transient_rate_limit_does_not_fail_boot(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.RateLimitError, 429, "rate limited"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    result = pipeline_mod._run_step0_ai_preflight()
+    assert result["status"] == "transient"
+    assert result["model"] == settings.ai_fallback_model
+    assert "RateLimitError" in result["transient_error"]
+
+
+def test_preflight_transient_internal_server_error_does_not_fail_boot(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.InternalServerError, 500, "upstream 500"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    result = pipeline_mod._run_step0_ai_preflight()
+    assert result["status"] == "transient"
+    assert "InternalServerError" in result["transient_error"]
+
+
+def test_preflight_fail_fast_on_generic_billing_402(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """IMP-92 u4 — HTTP 402 (Payment Required) surfaces as the generic
+    ``anthropic.APIStatusError`` (no typed subclass). The preflight MUST
+    dispatch by status code and raise ``Step0PreflightError`` so a
+    billing setup problem fails boot fast, matching the issue body's
+    operational contract.
+    """
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.APIStatusError, 402, "payment required"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    with pytest.raises(pipeline_mod.Step0PreflightError) as ei:
+        pipeline_mod._run_step0_ai_preflight()
+    msg = str(ei.value)
+    assert "402" in msg
+    assert settings.ai_fallback_model in msg
+    assert "Check ANTHROPIC_API_KEY / ai_fallback_model in .env." in msg
+
+
+def test_preflight_generic_status_429_treated_as_transient(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """IMP-92 u4 — a generic ``APIStatusError`` with HTTP 429 must follow
+    the same transient policy as the typed ``RateLimitError`` branch.
+    """
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.APIStatusError, 429, "rate limited (generic)"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    result = pipeline_mod._run_step0_ai_preflight()
+    assert result["status"] == "transient"
+    assert "APIStatusError" in result["transient_error"]
+
+
+def test_preflight_generic_status_5xx_treated_as_transient(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """IMP-92 u4 — a generic ``APIStatusError`` with HTTP 5xx must follow
+    the same transient policy as the typed ``InternalServerError`` branch.
+    """
+    monkeypatch.setattr(settings, "ai_fallback_enabled", True)
+    fake_client = MagicMock()
+    fake_client.messages.create.side_effect = _status_error(
+        anthropic.APIStatusError, 503, "upstream 503 (generic)"
+    )
+    monkeypatch.setattr(anthropic, "Anthropic", lambda **kwargs: fake_client)
+    result = pipeline_mod._run_step0_ai_preflight()
+    assert result["status"] == "transient"
+    assert "APIStatusError" in result["transient_error"]
diff --git a/tests/phase_z2_ai_fallback/test_step12.py b/tests/phase_z2_ai_fallback/test_step12.py
index 1ad16c6..8206a19 100644
--- a/tests/phase_z2_ai_fallback/test_step12.py
+++ b/tests/phase_z2_ai_fallback/test_step12.py
@@ -17,6 +17,9 @@ from dataclasses import dataclass, field
 from typing import Any
 from unittest.mock import MagicMock
 
+import anthropic
+import httpx
+
 from src.phase_z2_ai_fallback import step12 as step12_mod
 from src.phase_z2_ai_fallback.schema import AiFallbackProposal, ProposalKind
 
@@ -176,6 +179,9 @@ def test_router_exception_is_captured_per_record(monkeypatch):
     assert rec["ai_called"] is True
     assert rec["proposal"] is None
     assert rec["error"] == "RuntimeError: transient_boom"
+    # IMP-92 u2 — generic (non-Anthropic) exceptions classify as "other"
+    # so the frontend operational formatter stays silent for them.
+    assert rec["api_error_kind"] == "other"
     router.assert_called_once()
 
 
@@ -405,6 +411,7 @@ def test_record_shape_contract_is_stable_with_u4_fields(monkeypatch):
         "skip_reason",
         "proposal",
         "error",
+        "api_error_kind",
         "cache_key",
         "fingerprints",
     }
@@ -602,3 +609,146 @@ def test_mixed_units_router_receives_fingerprints_only_for_ai_eligible(monkeypat
     # Skipped records carry None.
     assert recs[0]["fingerprints"] is None
     assert recs[1]["fingerprints"] is None
+
+
+# ---------------------------------------------------------------------------
+# IMP-92 u2 — Anthropic SDK exception → api_error_kind classification
+# ---------------------------------------------------------------------------
+# Step 12 stamps each AI-called record with api_error_kind so the frontend
+# operational alert formatter can render quota / billing / auth surfaces
+# while keeping "other" failures silent (the #84 replacement-plan contract).
+# Classification is type-based (no string parsing); only AI-eligible units
+# that actually hit ``route_ai_fallback`` and raise can produce a non-None
+# api_error_kind. Skipped units (not_provisional / non-AI route) retain
+# api_error_kind=None alongside cache_key/fingerprints=None.
+
+
+def _anthropic_status_error(
+    error_cls: type[anthropic.APIStatusError], status_code: int
+) -> anthropic.APIStatusError:
+    """Construct an Anthropic SDK status error suitable for side_effect.
+
+    The SDK error constructors require ``response`` and ``body`` kwargs; an
+    ``httpx.Response`` bound to a stub request is the minimum that satisfies
+    isinstance dispatch in ``classify_operational_error``.
+    """
+    request = httpx.Request("POST", "https://api.anthropic.com/v1/messages")
+    response = httpx.Response(status_code, request=request)
+    return error_cls("simulated", response=response, body=None)
+
+
+def test_router_rate_limit_error_classifies_as_quota(monkeypatch):
+    """RateLimitError (HTTP 429) → api_error_kind='quota'."""
+    err = _anthropic_status_error(anthropic.RateLimitError, 429)
+    router = MagicMock(side_effect=err)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["api_error_kind"] == "quota"
+    assert rec["error"].startswith("RateLimitError: ")
+
+
+def test_router_permission_denied_classifies_as_billing(monkeypatch):
+    """PermissionDeniedError (HTTP 403) → api_error_kind='billing'."""
+    err = _anthropic_status_error(anthropic.PermissionDeniedError, 403)
+    router = MagicMock(side_effect=err)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["api_error_kind"] == "billing"
+    assert rec["error"].startswith("PermissionDeniedError: ")
+
+
+def test_router_payment_required_classifies_as_billing(monkeypatch):
+    """Generic APIStatusError with HTTP 402 → api_error_kind='billing'.
+
+    The Anthropic SDK has no dedicated PaymentRequired subclass; a 402
+    response surfaces as the base ``APIStatusError``. The issue body's
+    explicit operational contract requires 402 to render as billing,
+    so the classifier must fall through to ``status_code`` dispatch when
+    the typed subclass branches miss.
+    """
+    err = _anthropic_status_error(anthropic.APIStatusError, 402)
+    router = MagicMock(side_effect=err)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["api_error_kind"] == "billing"
+    assert rec["error"].startswith("APIStatusError: ")
+
+
+def test_router_authentication_error_classifies_as_auth(monkeypatch):
+    """AuthenticationError (HTTP 401) → api_error_kind='auth'."""
+    err = _anthropic_status_error(anthropic.AuthenticationError, 401)
+    router = MagicMock(side_effect=err)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["api_error_kind"] == "auth"
+    assert rec["error"].startswith("AuthenticationError: ")
+
+
+def test_router_bad_request_classifies_as_other(monkeypatch):
+    """BadRequestError (HTTP 400) is non-operational → api_error_kind='other'."""
+    err = _anthropic_status_error(anthropic.BadRequestError, 400)
+    router = MagicMock(side_effect=err)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["api_error_kind"] == "other"
+
+
+def test_router_internal_server_error_classifies_as_other(monkeypatch):
+    """InternalServerError (HTTP 5xx) is non-operational → api_error_kind='other'."""
+    err = _anthropic_status_error(anthropic.InternalServerError, 500)
+    router = MagicMock(side_effect=err)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["api_error_kind"] == "other"
+
+
+def test_router_success_leaves_api_error_kind_none(monkeypatch):
+    """Successful proposal record keeps api_error_kind=None (no error to classify)."""
+    proposal = AiFallbackProposal(
+        proposal_kind=ProposalKind.PARTIAL_OVERRIDES,
+        payload={"slots": {"s": "x"}},
+        rationale="r",
+    )
+    router = MagicMock(return_value=proposal)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["ai_called"] is True
+    assert rec["error"] is None
+    assert rec["api_error_kind"] is None
+
+
+def test_skipped_records_keep_api_error_kind_none(monkeypatch):
+    """Non-AI-eligible records never see the router, so api_error_kind stays None."""
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", MagicMock(return_value=None))
+    units = [
+        FakeUnit(label="restructure", provisional=False),  # not_provisional
+        FakeUnit(label="light_edit", provisional=True),    # non-AI route
+        FakeUnit(label="reject", provisional=True),        # legacy non-AI route
+    ]
+    recs = _call(units)
+    for rec in recs:
+        assert rec["api_error_kind"] is None
+        assert rec["error"] is None
+
+
+def test_router_short_circuit_keeps_api_error_kind_none(monkeypatch):
+    """Router short-circuit (None return) is not an error path → api_error_kind=None."""
+    router = MagicMock(return_value=None)
+    monkeypatch.setattr(step12_mod, "route_ai_fallback", router)
+    recs = _call([_ai_unit()])
+    rec = recs[0]
+    assert rec["skip_reason"] == "router_short_circuit"
+    assert rec["api_error_kind"] is None
diff --git a/tests/test_imp47b_failure_surface.py b/tests/test_imp47b_failure_surface.py
index 8862214..a7ad4e8 100644
--- a/tests/test_imp47b_failure_surface.py
+++ b/tests/test_imp47b_failure_surface.py
@@ -26,13 +26,19 @@ def _record(
     apply_status: str | None = None,
     error: str | None = None,
     source_section_ids: list[str] | None = None,
+    api_error_kind: str | None = None,
 ) -> dict:
-    """Minimal Step 12 AI repair record stub — fields u8 reads."""
+    """Minimal Step 12 AI repair record stub — fields u8 reads.
+
+    IMP-92 u3 — ``api_error_kind`` is stamped by Step 12 (u2 classifier)
+    on the exception path; non-error paths leave it ``None``.
+    """
     return {
         "unit_index": unit_index,
         "source_section_ids": source_section_ids or [f"MOCK_S{unit_index}"],
         "apply_status": apply_status,
         "error": error,
+        "api_error_kind": api_error_kind,
     }
 
 
@@ -45,7 +51,11 @@ _VIOLATED_COVERAGE = {"status": "violated", "dropped_section_ids": ["MOCK_S2"]}
 
 def test_empty_records_returns_ok_no_human_review():
     """No AI work executed → status='ok', human_review_required=False.
-    The flag-off default (no provisional units) lands here."""
+    The flag-off default (no provisional units) lands here.
+
+    IMP-92 u3 — ``api_error_kinds`` aggregation is always present with
+    every kind initialised to 0 so the frontend operational formatter
+    can read the bucket structure unconditionally."""
     result = _summarize_ai_repair_status([], _OK_COVERAGE)
     assert result["status"] == "ok"
     assert result["human_review_required"] is False
@@ -53,6 +63,12 @@ def test_empty_records_returns_ok_no_human_review():
     assert result["unsupported_kind_records"] == []
     assert result["error_records"] == []
     assert result["dropped_section_ids"] == []
+    assert result["api_error_kinds"] == {
+        "quota": 0,
+        "billing": 0,
+        "auth": 0,
+        "other": 0,
+    }
 
 
 # ─── Case 2 : applied → status='applied', no human_review ───────────
@@ -102,7 +118,11 @@ def test_unsupported_kind_marks_human_review_required():
 def test_gather_error_marks_status_error_with_records():
     """``record['error']`` set means ``gather_step12_ai_repair_proposals``
     caught a router exception (AI call / validator). status='error'
-    is the highest-priority failure axis."""
+    is the highest-priority failure axis.
+
+    IMP-92 u3 — non-Anthropic exception path leaves ``api_error_kind``
+    as ``None``; the summary retains ``None`` per-record and does not
+    increment any operational kind bucket."""
     records = [_record(
         unit_index=2,
         error="ValueError: missing slot 'title'",
@@ -117,8 +137,74 @@ def test_gather_error_marks_status_error_with_records():
             "unit_index": 2,
             "source_section_ids": ["MOCK_S2"],
             "error": "ValueError: missing slot 'title'",
+            "api_error_kind": None,
         }
     ]
+    assert result["api_error_kinds"] == {
+        "quota": 0,
+        "billing": 0,
+        "auth": 0,
+        "other": 0,
+    }
+
+
+# ─── IMP-92 u3 : api_error_kind propagation + aggregation ───────────
+
+
+def test_api_error_kind_quota_propagates_to_summary_and_record():
+    """Step 12 (u2) stamps ``api_error_kind='quota'`` on a 429
+    Anthropic exception path. u8 must surface that kind per-record
+    and increment the ``quota`` bucket in ``api_error_kinds``."""
+    records = [_record(
+        unit_index=3,
+        error="RateLimitError: 429",
+        source_section_ids=["MOCK_S3"],
+        api_error_kind="quota",
+    )]
+    result = _summarize_ai_repair_status(records, _OK_COVERAGE)
+    assert result["status"] == "error"
+    assert result["human_review_required"] is True
+    assert result["error_records"] == [
+        {
+            "unit_index": 3,
+            "source_section_ids": ["MOCK_S3"],
+            "error": "RateLimitError: 429",
+            "api_error_kind": "quota",
+        }
+    ]
+    assert result["api_error_kinds"] == {
+        "quota": 1,
+        "billing": 0,
+        "auth": 0,
+        "other": 0,
+    }
+
+
+def test_api_error_kinds_aggregate_across_all_operational_axes():
+    """Mixed batch — one of each operational kind (quota / billing /
+    auth / other). Aggregation must count each axis exactly once and
+    keep per-record kinds intact (order preserved)."""
+    records = [
+        _record(unit_index=0, error="RateLimitError", api_error_kind="quota"),
+        _record(unit_index=1, error="PermissionDeniedError", api_error_kind="billing"),
+        _record(unit_index=2, error="AuthenticationError", api_error_kind="auth"),
+        _record(unit_index=3, error="BadRequestError", api_error_kind="other"),
+    ]
+    result = _summarize_ai_repair_status(records, _OK_COVERAGE)
+    assert result["status"] == "error"
+    assert result["counts"]["error"] == 4
+    assert result["api_error_kinds"] == {
+        "quota": 1,
+        "billing": 1,
+        "auth": 1,
+        "other": 1,
+    }
+    assert [rec["api_error_kind"] for rec in result["error_records"]] == [
+        "quota",
+        "billing",
+        "auth",
+        "other",
+    ]
 
 
 # ─── Case 5 : coverage violated → status='coverage_violated' ────────
diff --git a/tests/test_phase_z2_ai_fallback_config.py b/tests/test_phase_z2_ai_fallback_config.py
index ee80048..0eac3ba 100644
--- a/tests/test_phase_z2_ai_fallback_config.py
+++ b/tests/test_phase_z2_ai_fallback_config.py
@@ -2,7 +2,7 @@
 
 These defaults are the binding contract from Stage 2 plan (per-unit u1):
   - ai_fallback_enabled        = False        (master flag OFF; fallback path only)
-  - ai_fallback_model          = "claude-opus-4-6-20250415"
+  - ai_fallback_model          = "claude-opus-4-7"
   - ai_fallback_timeout_s      = 60.0
   - ai_fallback_max_retries    = 3
   - ai_fallback_backoff_base_s = 1.0
@@ -28,7 +28,7 @@ def test_ai_fallback_master_flag_default_off() -> None:
 
 def test_ai_fallback_model_default_locked() -> None:
     s = Settings()
-    assert s.ai_fallback_model == "claude-opus-4-6-20250415"
+    assert s.ai_fallback_model == "claude-opus-4-7"
 
 
 def test_ai_fallback_retry_timeout_backoff_defaults_locked() -> None: