diff --git a/apps/api/src/jobs/rule_stats_updater_job.py b/apps/api/src/jobs/rule_stats_updater_job.py
new file mode 100644
index 00000000..da0bc5de
--- /dev/null
+++ b/apps/api/src/jobs/rule_stats_updater_job.py
@@ -0,0 +1,180 @@
+"""
+Rule Stats Updater Job — ADR-090 § Rule Quality Analysis
+=========================================================
+每 1h 計算 alert_rule_catalog 的運作統計,解鎖 E3 Hermes 規則品質分析.
+
+更新欄位:
+  - last_fired_at       = max(incidents.created_at WHERE alertname=rule_name)
+  - true_positive_count = count incidents.status='RESOLVED' past 30d
+  - false_positive_count = count approval_records.status='EXPIRED' past 30d
+                          (EXPIRED = 48h 無人處理,視為假警報 proxy)
+  - noise_rate          = fp / (tp + fp) 若有資料,否則 NULL
+
+職責邊界 (MVP):
+  ✅ 從 incidents.alertname + approval_records.incident_id JOIN 計算
+  ✅ UPDATE alert_rule_catalog 統計欄位
+  ⏳ TODO: Hermes AI agent 基於 noise_rate > 0.5 提案 deprecate 規則 (下一階段)
+
+設計鐵律:
+  - 只 UPDATE,不 INSERT (依賴 rule_catalog_sync 先建 rule)
+  - 計算窗口固定 30d (可未來配置化)
+  - 失敗 → log warning,下次重試
+
+排程:
+  - 首次延遲 240s (rule_catalog_sync 先跑完)
+  - 每 1h
+
+2026-04-19 ogt + Claude Opus 4.7 (1M context) Asia/Taipei
+ADR-090 § Rule Quality
+"""
+from __future__ import annotations
+
+import asyncio
+import json as _json
+import time as _time
+
+import structlog
+
+logger = structlog.get_logger(__name__)
+
+_UPDATE_INTERVAL_SEC = 3600
+_FIRST_DELAY_SEC = 240
+_LOOP_BACKOFF_SEC = 600
+_WINDOW_DAYS = 30
+
+
+async def run_rule_stats_updater_loop() -> None:
+    """每 1h 更新 alert_rule_catalog 統計欄位."""
+    logger.info("rule_stats_updater_loop_started", interval_sec=_UPDATE_INTERVAL_SEC)
+    await asyncio.sleep(_FIRST_DELAY_SEC)
+
+    while True:
+        try:
+            await update_once()
+        except Exception as e:
+            logger.exception("rule_stats_updater_loop_error", error=str(e))
+            await asyncio.sleep(_LOOP_BACKOFF_SEC)
+            continue
+        await asyncio.sleep(_UPDATE_INTERVAL_SEC)
+
+
+async def update_once() -> dict[str, int]:
+    """跑一次 update 全表 alert_rule_catalog."""
+    started_ms = _time.time()
+    stats = {"rules_updated": 0, "rules_with_fires": 0, "rules_noisy": 0}
+    error_msg: str | None = None
+
+    try:
+        stats = await _do_update()
+    except Exception as e:
+        error_msg = f"{type(e).__name__}: {e}"[:1000]
+        logger.exception("rule_stats_update_once_failed", error=error_msg)
+
+    duration_ms = int((_time.time() - started_ms) * 1000)
+    await _log_aol(stats, duration_ms, error_msg)
+
+    logger.info(
+        "rule_stats_update_once_done",
+        rules_updated=stats.get("rules_updated", 0),
+        rules_with_fires=stats.get("rules_with_fires", 0),
+        rules_noisy=stats.get("rules_noisy", 0),
+        duration_ms=duration_ms,
+    )
+    return stats
+
+
+async def _do_update() -> dict[str, int]:
+    """一次 UPDATE 更新所有 rule 的統計."""
+    from sqlalchemy import text as _sql
+    from src.db.base import get_db_context
+
+    async with get_db_context() as db:
+        # 一次性 UPDATE 全表 — 對每 rule 計算 stats
+        # 使用 LATERAL 避免 N+1 queries
+        result = await db.execute(
+            _sql(f"""
+                UPDATE alert_rule_catalog arc
+                SET true_positive_count = COALESCE(s.tp_count, 0),
+                    false_positive_count = COALESCE(s.fp_count, 0),
+                    last_fired_at = s.last_fired,
+                    noise_rate = CASE
+                        WHEN COALESCE(s.tp_count, 0) + COALESCE(s.fp_count, 0) > 0
+                        THEN COALESCE(s.fp_count, 0)::numeric
+                             / (COALESCE(s.tp_count, 0) + COALESCE(s.fp_count, 0))::numeric
+                        ELSE NULL
+                    END,
+                    updated_at = NOW()
+                FROM (
+                    SELECT
+                        arc_inner.rule_name,
+                        (SELECT count(*) FROM incidents i
+                           WHERE i.alertname = arc_inner.rule_name
+                             AND i.status = 'RESOLVED'
+                             AND i.created_at > NOW() - INTERVAL '{_WINDOW_DAYS} days'
+                        ) AS tp_count,
+                        (SELECT count(*) FROM approval_records ar
+                           JOIN incidents i2 ON ar.incident_id = i2.incident_id
+                           WHERE i2.alertname = arc_inner.rule_name
+                             AND ar.status = 'EXPIRED'
+                             AND ar.created_at > NOW() - INTERVAL '{_WINDOW_DAYS} days'
+                        ) AS fp_count,
+                        (SELECT max(created_at) FROM incidents i3
+                           WHERE i3.alertname = arc_inner.rule_name
+                        ) AS last_fired
+                    FROM alert_rule_catalog arc_inner
+                ) s
+                WHERE arc.rule_name = s.rule_name
+            """),
+        )
+        rules_updated = result.rowcount or 0
+
+        # 再查統計摘要
+        row = await db.execute(
+            _sql(f"""
+                SELECT
+                    count(*) FILTER (WHERE last_fired_at > NOW() - INTERVAL '{_WINDOW_DAYS} days') AS with_fires,
+                    count(*) FILTER (WHERE noise_rate IS NOT NULL AND noise_rate > 0.5) AS noisy
+                FROM alert_rule_catalog
+            """),
+        )
+        r = row.one()
+
+        return {
+            "rules_updated": rules_updated,
+            "rules_with_fires": int(r.with_fires or 0),
+            "rules_noisy": int(r.noisy or 0),
+        }
+
+
+async def _log_aol(stats: dict[str, int], duration_ms: int, error: str | None) -> None:
+    try:
+        from sqlalchemy import text as _sql
+        from src.db.base import get_db_context
+
+        aol_status = "failed" if error else "success"
+        async with get_db_context() as db:
+            await db.execute(
+                _sql("""
+                    INSERT INTO automation_operation_log (
+                        operation_type, actor, status,
+                        input, output, duration_ms, error, tags
+                    ) VALUES (
+                        'rule_updated',
+                        'rule_stats_updater',
+                        :st,
+                        CAST(:input AS jsonb),
+                        CAST(:output AS jsonb),
+                        :dur, :err, :tags
+                    )
+                """),
+                {
+                    "st": aol_status,
+                    "input": _json.dumps({"window_days": _WINDOW_DAYS}, ensure_ascii=False),
+                    "output": _json.dumps(stats, ensure_ascii=False),
+                    "dur": duration_ms,
+                    "err": (error or "")[:2000] if error else None,
+                    "tags": ["rule_catalog", "stats", "quality"],
+                },
+            )
+    except Exception as e:
+        logger.warning("rule_stats_aol_write_failed", error=str(e))
diff --git a/apps/api/src/main.py b/apps/api/src/main.py
index b42422a1..5d27985b 100644
--- a/apps/api/src/main.py
+++ b/apps/api/src/main.py
@@ -420,6 +420,16 @@ async def lifespan(_app: FastAPI) -> AsyncGenerator[None, None]:
     except Exception as e:
         logger.warning("coverage_evaluator_loop_schedule_failed", error=str(e))
 
+    # ADR-090 § Rule Stats Updater (2026-04-19 ogt + Claude Opus 4.7 Asia/Taipei)
+    # 每 1h 從 incidents + approval_records 計算 rule 統計
+    # 解鎖 E3 Hermes: noise_rate > 0.5 的 rule 可被 AI 提案 deprecate
+    try:
+        from src.jobs.rule_stats_updater_job import run_rule_stats_updater_loop
+        asyncio.create_task(run_rule_stats_updater_loop())
+        logger.info("rule_stats_updater_loop_scheduled", interval_sec=3600)
+    except Exception as e:
+        logger.warning("rule_stats_updater_loop_schedule_failed", error=str(e))
+
     # ADR-076 Task 4: 每日 08:00 台北時間自動日度巡檢報告
     # 2026-04-14 Claude Haiku 4.5 Asia/Taipei
     try: