diff --git a/apps/api/src/services/telegram_gateway.py b/apps/api/src/services/telegram_gateway.py
index 32b7f212..9f28f5de 100644
--- a/apps/api/src/services/telegram_gateway.py
+++ b/apps/api/src/services/telegram_gateway.py
@@ -2100,26 +2100,44 @@ class TelegramGateway:
                 })
                 return
 
-            _lines = [f"📊 <b>完整 Drift Diff</b> — <code>{html.escape(report_id)}</code>"]
-            _lines.append(f"Namespace: <code>{html.escape(_rpt.namespace)}</code>")
-            _lines.append(f"HIGH×{_rpt.high_count}  MEDIUM×{_rpt.medium_count}  INFO×{_rpt.info_count}")
-            _lines.append("━" * 20)
-            for i, _item in enumerate(_rpt.items[:50], 1):
+            # 2026-04-19 ogt + Claude Opus 4.7: 修 HTTP 400 真因
+            # 原邏輯: _full[:3950] 切在 HTML tag/entity 中間 → Telegram parse_mode HTML 拒絕
+            # 修法: item-by-item 累計長度,超過 3800 就停,確保完整 HTML 結構
+            #       (3800 留 250 buffer 給 header + 截斷提示)
+            _MAX_LEN = 3800
+
+            _header = [
+                f"📊 <b>完整 Drift Diff</b> — <code>{html.escape(report_id)}</code>",
+                f"Namespace: <code>{html.escape(_rpt.namespace)}</code>",
+                f"HIGH×{_rpt.high_count}  MEDIUM×{_rpt.medium_count}  INFO×{_rpt.info_count}",
+                "━" * 20,
+            ]
+            _lines = list(_header)
+            _used_len = sum(len(s) + 1 for s in _header)
+            _shown = 0
+
+            for _item in _rpt.items:
                 _level = getattr(_item.drift_level, "value", str(_item.drift_level))
                 _emoji = "🔴" if _level == "high" else ("🟡" if _level == "medium" else "⚪")
                 _field = (_item.field_path or "")[:80]
                 _git = str(_item.git_value)[:40] if _item.git_value is not None else "(未設)"
                 _k8s = str(_item.actual_value)[:40] if _item.actual_value is not None else "(未設)"
-                _lines.append(f"{_emoji} <b>{html.escape(_field)}</b>")
-                _lines.append(f"   Git: <code>{html.escape(_git)}</code>")
-                _lines.append(f"   K8s: <code>{html.escape(_k8s)}</code>")
-            if len(_rpt.items) > 50:
-                _lines.append(f"… 還有 {len(_rpt.items) - 50} 項未顯示")
+                _block = (
+                    f"{_emoji} <b>{html.escape(_field)}</b>\n"
+                    f"   Git: <code>{html.escape(_git)}</code>\n"
+                    f"   K8s: <code>{html.escape(_k8s)}</code>"
+                )
+                if _used_len + len(_block) + 1 > _MAX_LEN:
+                    break
+                _lines.append(_block)
+                _used_len += len(_block) + 1
+                _shown += 1
+
+            _remaining = len(_rpt.items) - _shown
+            if _remaining > 0:
+                _lines.append(f"… 還有 {_remaining} 項未顯示")
 
             _full = "\n".join(_lines)
-            # Telegram 訊息上限 4096 字元
-            if len(_full) > 4000:
-                _full = _full[:3950] + "\n… (截斷)"
 
             await self._send_request("sendMessage", {
                 "chat_id": settings.OPENCLAW_TG_CHAT_ID,