diff --git a/app/api/dashboard.py b/app/api/dashboard.py
index d591437..912fae6 100644
--- a/app/api/dashboard.py
+++ b/app/api/dashboard.py
@@ -50,12 +50,15 @@ class QueueLag(BaseModel):
 
 
 class TierHealthStack(BaseModel):
-    """PR-B B-3 — tier 관측성 3종 카드 소스 (24h 윈도우).
+    """PR-B B-3 — tier 관측성 카드 소스 (24h 윈도우).
 
-    대시보드 카드:
-      - "에스컬레이션 비율": escalated_total / triage_total (>20% 적색, <1% 회색)
+    대시보드 카드 (Day 4 튜닝 — 2026-04-27 임계치 재조정):
+      - "에스컬레이션 비율": escalated_total / triage_total
+        · <80% 적색 (정책 매칭 실패 증가 — 진짜 튜닝 필요)
+        · 80~99% 정상 (safety/health 정책 의도)
       - "triage JSON 건강도": triage_json_invalid / triage_total (>5% 적색)
       - "Backlog Suppression": suppressed_total / triage_total (>10% 주황)
+      - "Deep summary 안정성": deep_err_total / deep_total (>5% 적색)
     """
     triage_total: int = 0
     escalated_total: int = 0
@@ -63,6 +66,9 @@ class TierHealthStack(BaseModel):
     escalation_by_domain: dict[str, int] = {}     # safety_reference / news_item / ...
     triage_json_invalid: int = 0                  # error_code='triage_json_invalid'
     suppressed_total: int = 0                     # suppressed_reason IS NOT NULL
+    # Day 4 튜닝 신규 — deep_summary 호출 안정성
+    deep_total: int = 0                           # mode='summary_deep' 전체
+    deep_err_total: int = 0                       # error_code IS NOT NULL (call_failed / parse:*)
 
 
 class DashboardResponse(BaseModel):
@@ -216,13 +222,15 @@ async def get_dashboard(
         for row in lag_result.all()
     ]
 
-    # ─── PR-B B-3 — tier 관측성 (24h) ───
+    # ─── PR-B B-3 — tier 관측성 (24h) + Day 4 deep_err 추가 ───
     tier_rows = (await session.execute(text("""
         SELECT
           COUNT(*) FILTER (WHERE mode = 'summary_triage')                                   AS triage_total,
           COUNT(*) FILTER (WHERE mode = 'summary_triage' AND escalated_to_26b = true)       AS escalated_total,
           COUNT(*) FILTER (WHERE mode = 'summary_triage' AND error_code = 'triage_json_invalid') AS json_invalid,
-          COUNT(*) FILTER (WHERE mode = 'summary_triage' AND suppressed_reason IS NOT NULL) AS suppressed_total
+          COUNT(*) FILTER (WHERE mode = 'summary_triage' AND suppressed_reason IS NOT NULL) AS suppressed_total,
+          COUNT(*) FILTER (WHERE mode = 'summary_deep')                                     AS deep_total,
+          COUNT(*) FILTER (WHERE mode = 'summary_deep' AND error_code IS NOT NULL)          AS deep_err_total
         FROM analyze_events
         WHERE created_at > NOW() - INTERVAL '24 hours'
     """))).one()
@@ -253,6 +261,8 @@ async def get_dashboard(
         escalated_total=int(tier_rows.escalated_total or 0),
         triage_json_invalid=int(tier_rows.json_invalid or 0),
         suppressed_total=int(tier_rows.suppressed_total or 0),
+        deep_total=int(tier_rows.deep_total or 0),
+        deep_err_total=int(tier_rows.deep_err_total or 0),
         escalation_by_reason=escalation_by_reason,
         escalation_by_domain=escalation_by_domain,
     )
diff --git a/frontend/src/lib/stores/system.ts b/frontend/src/lib/stores/system.ts
index 74bfa25..77a41f0 100644
--- a/frontend/src/lib/stores/system.ts
+++ b/frontend/src/lib/stores/system.ts
@@ -41,6 +41,9 @@ export interface TierHealthStack {
   escalation_by_domain: Record<string, number>;
   triage_json_invalid: number;
   suppressed_total: number;
+  // Day 4 신규 — deep_summary 호출 안정성
+  deep_total?: number;
+  deep_err_total?: number;
 }
 
 export interface DashboardSummary {
diff --git a/frontend/src/routes/+page.svelte b/frontend/src/routes/+page.svelte
index 9d82145..2b8d6a1 100644
--- a/frontend/src/routes/+page.svelte
+++ b/frontend/src/routes/+page.svelte
@@ -357,10 +357,15 @@
         {@const esc_rate = th.triage_total > 0 ? th.escalated_total / th.triage_total : 0}
         {@const json_rate = th.triage_total > 0 ? th.triage_json_invalid / th.triage_total : 0}
         {@const sup_rate = th.triage_total > 0 ? th.suppressed_total / th.triage_total : 0}
-        {@const esc_tone = esc_rate > 0.20 ? 'text-error' : (esc_rate < 0.01 ? 'text-dim' : 'text-text')}
+        {@const deep_total = th.deep_total ?? 0}
+        {@const deep_err_rate = deep_total > 0 ? (th.deep_err_total ?? 0) / deep_total : 0}
+        <!-- Day 4 튜닝 (2026-04-27): 운영 패턴 실측 후 임계치 재조정.
+             3일 telemetry 기준 escalate 97% 가 정상 (safety 정책 의도) → <80% 가 진짜 신호. -->
+        {@const esc_tone = esc_rate < 0.80 ? 'text-error' : 'text-text'}
         {@const json_tone = json_rate > 0.05 ? 'text-error' : 'text-text'}
         {@const sup_tone = sup_rate > 0.10 ? 'text-warning' : 'text-text'}
-        <div class="grid grid-cols-1 md:grid-cols-3 gap-4 mb-5">
+        {@const deep_tone = deep_err_rate > 0.05 ? 'text-error' : 'text-text'}
+        <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-4 mb-5">
           <!-- 에스컬레이션 비율 -->
           <Card class="h-full">
             <div class="flex items-start justify-between">
@@ -372,9 +377,9 @@
             </p>
             <p class="text-xs text-dim mt-1">
               {th.escalated_total} / {th.triage_total}
-              {#if esc_rate > 0.20}<span class="text-error ml-1">(튜닝 필요)</span>{/if}
-              {#if esc_rate < 0.01}<span class="text-dim ml-1">(false negative?)</span>{/if}
+              {#if esc_rate < 0.80}<span class="text-error ml-1">(매칭 실패 증가)</span>{/if}
             </p>
+            <p class="text-[10px] text-faint mt-1">safety 정책상 95~100% 가 정상</p>
             {#if Object.keys(th.escalation_by_reason).length > 0}
               <div class="mt-2 flex flex-wrap gap-1">
                 {#each Object.entries(th.escalation_by_reason).slice(0, 4) as [reason, n]}
@@ -417,6 +422,22 @@
             </p>
             <p class="text-[10px] text-faint mt-1">10% 초과 시 ratio/pending threshold 조정</p>
           </Card>
+
+          <!-- Deep summary 안정성 (Day 4 신규) -->
+          <Card class="h-full">
+            <div class="flex items-start justify-between">
+              <p class="text-sm text-dim">Deep summary 안정성 (24h)</p>
+              <Sparkles size={18} class="text-faint" />
+            </div>
+            <p class="text-2xl font-bold mt-2 {deep_tone}">
+              {(deep_err_rate * 100).toFixed(1)}%
+            </p>
+            <p class="text-xs text-dim mt-1">
+              실패 {th.deep_err_total ?? 0} / {deep_total}
+              {#if deep_err_rate > 0.05}<span class="text-error ml-1">(MLX 안정성 점검)</span>{/if}
+            </p>
+            <p class="text-[10px] text-faint mt-1">call_failed / parse:* 합계, 5% 초과 시 점검</p>
+          </Card>
         </div>
       {/if}