diff --git a/apps/api/src/services/alert_grouping_service.py b/apps/api/src/services/alert_grouping_service.py
index cd167ce6..fc9beac3 100644
--- a/apps/api/src/services/alert_grouping_service.py
+++ b/apps/api/src/services/alert_grouping_service.py
@@ -36,6 +36,17 @@ if TYPE_CHECKING:
 logger = structlog.get_logger(__name__)
 
 
+def _decode_redis_member(value: object, fallback: str) -> str:
+    """Redis client 可能回 bytes 或 str；統一成 str 供 DB / log 使用。"""
+    if isinstance(value, bytes):
+        return value.decode("utf-8", errors="replace")
+    if isinstance(value, str):
+        return value
+    if value is None:
+        return fallback
+    return str(value)
+
+
 # =============================================================================
 # Data Types
 # =============================================================================
@@ -189,7 +200,10 @@ class AlertGroupingService:
 
         count = results[2]
         first_members = results[3]
-        parent_fingerprint = first_members[0] if first_members else fingerprint
+        parent_fingerprint = _decode_redis_member(
+            first_members[0] if first_members else None,
+            fallback=fingerprint,
+        )
 
         # 是否為父告警（第一個）
         is_parent = parent_fingerprint == fingerprint or count == 1
diff --git a/apps/api/src/services/channel_hub.py b/apps/api/src/services/channel_hub.py
index 07f12122..93ca04db 100644
--- a/apps/api/src/services/channel_hub.py
+++ b/apps/api/src/services/channel_hub.py
@@ -28,6 +28,7 @@ from __future__ import annotations
 
 import asyncio
 import hashlib
+import html
 import json
 from datetime import datetime, timezone
 from typing import Any
@@ -167,6 +168,111 @@ def format_grouped_alert_event_content(
     )
 
 
+def format_grouped_alert_digest_text(
+    *,
+    alertname: str,
+    severity: str,
+    namespace: str,
+    target_resource: str,
+    group_key: str,
+    count: int,
+) -> str:
+    """格式化要回覆到父告警卡的短 digest。"""
+    safe_alert = html.escape(alertname or "unknown")
+    safe_severity = html.escape(severity or "unknown")
+    safe_namespace = html.escape(namespace or "default")
+    safe_target = html.escape(target_resource or "unknown")
+    safe_group = html.escape(group_key or "unknown")
+
+    return "\n".join(
+        [
+            "🧩 <b>告警已收斂到父卡</b>",
+            f"├ 類型：<code>{safe_alert}</code>",
+            f"├ 等級：<code>{safe_severity}</code>",
+            f"├ 範圍：<code>{safe_namespace}</code>",
+            f"├ 最新目標：<code>{safe_target}</code>",
+            f"├ 群組：<code>{safe_group}</code>",
+            f"└ 目前視窗：<b>{count}</b> 筆同組告警",
+            "",
+            "完整子告警請看 AwoooP Run 監控，不再逐筆發 Telegram。",
+        ]
+    )
+
+
+async def maybe_send_grouped_alert_digest(
+    *,
+    project_id: str,
+    alertname: str,
+    severity: str,
+    namespace: str,
+    target_resource: str,
+    group_key: str,
+    count: int,
+    parent_fingerprint: str | None,
+) -> bool:
+    """若父告警卡已存在，回覆一則低頻 digest；找不到父卡則安靜降級。"""
+    if not parent_fingerprint:
+        return False
+
+    try:
+        from sqlalchemy import select
+
+        from src.db.base import get_db_context
+        from src.db.models import ApprovalRecord
+        from src.services.telegram_gateway import get_telegram_gateway
+
+        async with get_db_context(project_id) as db:
+            result = await db.execute(
+                select(ApprovalRecord.incident_id)
+                .where(ApprovalRecord.fingerprint == parent_fingerprint)
+                .where(ApprovalRecord.incident_id.is_not(None))
+                .order_by(ApprovalRecord.created_at.desc())
+                .limit(1)
+            )
+            incident_id = result.scalar_one_or_none()
+
+        if not incident_id:
+            logger.info(
+                "grouped_alert_digest_parent_not_ready",
+                project_id=project_id,
+                group_key=group_key,
+                parent_fingerprint=parent_fingerprint,
+            )
+            return False
+
+        digest_text = format_grouped_alert_digest_text(
+            alertname=alertname,
+            severity=severity,
+            namespace=namespace,
+            target_resource=target_resource,
+            group_key=group_key,
+            count=count,
+        )
+        sent = await get_telegram_gateway().append_grouped_alert_digest(
+            incident_id=str(incident_id),
+            group_key=group_key,
+            digest_text=digest_text,
+        )
+        logger.info(
+            "grouped_alert_digest_result",
+            project_id=project_id,
+            incident_id=str(incident_id),
+            group_key=group_key,
+            count=count,
+            sent=sent,
+        )
+        return sent
+    except Exception as exc:
+        logger.warning(
+            "grouped_alert_digest_failed",
+            project_id=project_id,
+            group_key=group_key,
+            parent_fingerprint=parent_fingerprint,
+            error=str(exc),
+        )
+        return False
+
+
 async def record_grouped_alert_event(
     *,
     project_id: str,
@@ -226,6 +332,16 @@ async def record_grouped_alert_event(
             group_key=group_key,
             count=count,
         )
+        await maybe_send_grouped_alert_digest(
+            project_id=project_id,
+            alertname=alertname,
+            severity=severity,
+            namespace=namespace,
+            target_resource=target_resource,
+            group_key=group_key,
+            count=count,
+            parent_fingerprint=parent_fingerprint,
+        )
         return event_id
     except Exception as exc:
         logger.warning(
diff --git a/apps/api/src/services/telegram_gateway.py b/apps/api/src/services/telegram_gateway.py
index e6153882..0a1e619f 100644
--- a/apps/api/src/services/telegram_gateway.py
+++ b/apps/api/src/services/telegram_gateway.py
@@ -56,6 +56,8 @@ INCIDENT_UPDATE_DEDUP_PREFIX = "awoooi:tg_update_dedup:"  # {incident_id}:{statu
 INCIDENT_UPDATE_DEDUP_TTL_SECONDS = 5 * 60  # 5 分鐘內相同狀態不重複洗版
 INCIDENT_UPDATE_GLOBAL_FAILURE_DEDUP_PREFIX = "awoooi:tg_update_global_failure_dedup:"
 INCIDENT_UPDATE_GLOBAL_FAILURE_DEDUP_TTL_SECONDS = 10 * 60  # 相同失敗摘要跨 incident 10 分鐘只推一次
+GROUPED_ALERT_DIGEST_DEDUP_PREFIX = "awoooi:tg_group_digest:"  # {group_key}
+GROUPED_ALERT_DIGEST_DEDUP_TTL_SECONDS = 5 * 60  # 同一告警群組 5 分鐘只推一則 digest
 
 # 2026-04-01 Claude Code: Long Polling 分散式 Leader Election
 # 防止多 Pod 同時 getUpdates → 409 Conflict 互搶問題
@@ -4765,6 +4767,91 @@ class TelegramGateway:
         )
         return True
 
+    async def append_grouped_alert_digest(
+        self,
+        *,
+        incident_id: str,
+        group_key: str,
+        digest_text: str,
+    ) -> bool:
+        """
+        將同組告警收斂摘要回覆到父告警卡，不移除原卡按鈕。
+
+        與 append_incident_update 不同：digest 是觀測訊息，不代表執行狀態改變，
+        因此不能動 approve/reject/silence 按鈕。
+        """
+        redis = get_redis()
+        stored = await redis.get(f"tg_msg:{incident_id}")
+        if not stored:
+            logger.info(
+                "grouped_alert_digest_no_parent_message",
+                incident_id=incident_id,
+                group_key=group_key,
+            )
+            return False
+
+        try:
+            message_id = int(stored)
+        except (ValueError, TypeError):
+            logger.warning(
+                "grouped_alert_digest_invalid_parent_message",
+                incident_id=incident_id,
+                stored=stored,
+            )
+            return False
+
+        dedup_key = f"{GROUPED_ALERT_DIGEST_DEDUP_PREFIX}{group_key}"
+        try:
+            was_set = await redis.set(
+                dedup_key,
+                incident_id,
+                ex=GROUPED_ALERT_DIGEST_DEDUP_TTL_SECONDS,
+                nx=True,
+            )
+            if not was_set:
+                logger.info(
+                    "grouped_alert_digest_dedup_suppressed",
+                    incident_id=incident_id,
+                    group_key=group_key,
+                )
+                return True
+        except Exception as exc:
+            logger.warning(
+                "grouped_alert_digest_dedup_failed",
+                incident_id=incident_id,
+                group_key=group_key,
+                error=str(exc),
+            )
+
+        try:
+            await self._send_request("sendMessage", {
+                "chat_id": self.alert_chat_id,
+                "text": digest_text[:1400],
+                "parse_mode": "HTML",
+                "reply_parameters": {
+                    "message_id": message_id,
+                    "allow_sending_without_reply": True,
+                },
+                "disable_web_page_preview": True,
+            })
+        except TelegramGatewayError as exc:
+            logger.warning(
+                "grouped_alert_digest_reply_failed",
+                incident_id=incident_id,
+                group_key=group_key,
+                message_id=message_id,
+                error=str(exc),
+            )
+            return False
+
+        logger.info(
+            "grouped_alert_digest_reply_sent",
+            incident_id=incident_id,
+            group_key=group_key,
+            message_id=message_id,
+        )
+        return True
+
     async def _dispatch_category_action(
         self,
         callback_query_id: str,
diff --git a/apps/api/tests/test_alert_grouping_service.py b/apps/api/tests/test_alert_grouping_service.py
index 70151a3e..6c0a343f 100644
--- a/apps/api/tests/test_alert_grouping_service.py
+++ b/apps/api/tests/test_alert_grouping_service.py
@@ -12,7 +12,11 @@ ADR-076: 告警聚合引擎 — 告警風暴防禦
 
 import pytest
 
-from src.services.alert_grouping_service import AlertGroupingService, GroupingResult
+from src.services.alert_grouping_service import (
+    AlertGroupingService,
+    GroupingResult,
+    _decode_redis_member,
+)
 
 
 class TestBuildGroupKey:
@@ -116,6 +120,16 @@ class TestGroupingResultDataclass:
         assert len(parts) == 2
 
 
+class TestRedisMemberDecode:
+    """測試 Redis zrange member 正規化。"""
+
+    def test_decode_bytes_member(self):
+        assert _decode_redis_member(b"fp-parent", "fallback") == "fp-parent"
+
+    def test_decode_none_uses_fallback(self):
+        assert _decode_redis_member(None, "fallback") == "fallback"
+
+
 class TestAlertGroupingServiceConstants:
     """測試服務常量設定"""
 
diff --git a/apps/api/tests/test_channel_hub_grouped_alert_events.py b/apps/api/tests/test_channel_hub_grouped_alert_events.py
index c16020d6..1cae72ea 100644
--- a/apps/api/tests/test_channel_hub_grouped_alert_events.py
+++ b/apps/api/tests/test_channel_hub_grouped_alert_events.py
@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from src.services.channel_hub import (
     build_grouped_alert_provider_event_id,
+    format_grouped_alert_digest_text,
     format_grouped_alert_event_content,
 )
 
@@ -34,3 +35,20 @@ def test_format_grouped_alert_event_content_keeps_operator_context() -> None:
     assert "Target: sentry-self-hosted-events-consumer-1" in content
     assert "Group Count: 4" in content
     assert "Parent Fingerprint: parent-fp" in content
+
+
+def test_format_grouped_alert_digest_text_is_html_safe() -> None:
+    content = format_grouped_alert_digest_text(
+        alertname="Docker<Restart>",
+        severity="critical",
+        namespace="default",
+        target_resource="sentry&snuba",
+        group_key="Docker<Restart>:default",
+        count=7,
+    )
+
+    assert "告警已收斂到父卡" in content
+    assert "Docker&lt;Restart&gt;" in content
+    assert "sentry&amp;snuba" in content
+    assert "<b>7</b> 筆同組告警" in content
+    assert "AwoooP Run 監控" in content