diff --git a/apps/api/src/main.py b/apps/api/src/main.py
index f2cd5e56..d96d2094 100644
--- a/apps/api/src/main.py
+++ b/apps/api/src/main.py
@@ -230,6 +230,15 @@ async def lifespan(_app: FastAPI) -> AsyncGenerator[None, None]:
     register_all_providers()
     logger.info("mcp_providers_registered")
 
+    # ADR-081 Phase 1: MCPToolRegistry 初始化（PreDecisionInvestigator 感官工具）
+    # 2026-04-16 ogt + Claude Sonnet 4.6: 修復 sensors=0/0 根因 — init 從未在 startup 被呼叫
+    try:
+        from src.services.mcp_tool_registry import init_mcp_tool_registry
+        await init_mcp_tool_registry()
+        logger.info("mcp_tool_registry_initialized")
+    except Exception as e:
+        logger.warning("mcp_tool_registry_init_failed", error=str(e))
+
     # Phase 6.5: Telegram 心跳監控（每 30 分鐘發送到 SRE 戰情室群組）
     # 2026-04-16 ogt + Claude Sonnet 4.6: 恢復 — 使用者確認必須繼續在 SRE 戰情室發送
     #   上次停用原因（forwarded_to_separate_group）有誤，群組就是 SRE_GROUP_CHAT_ID
diff --git a/apps/api/src/services/signal_producer.py b/apps/api/src/services/signal_producer.py
index fa58631b..1a4e3ec4 100644
--- a/apps/api/src/services/signal_producer.py
+++ b/apps/api/src/services/signal_producer.py
@@ -12,6 +12,7 @@ Signal Producer Service - Phase 17 P0 Router 層違規修復
 - Router -> Service -> Redis
 """
 
+import json
 from dataclasses import dataclass
 from typing import Any
 
@@ -74,8 +75,8 @@ class SignalProducerService:
             "namespace": signal.namespace,
             "target": signal.target,
             "message": signal.message,
-            "labels": str(signal.labels or {}),
-            "annotations": str(signal.annotations or {}),
+            "labels": json.dumps(signal.labels or {}),
+            "annotations": json.dumps(signal.annotations or {}),
             "received_at": now_taipei().isoformat(),
         }
 
diff --git a/packages/lewooogo-brain/src/lewooogo_brain/engines/incident_engine.py b/packages/lewooogo-brain/src/lewooogo_brain/engines/incident_engine.py
index d5317f33..991d22d7 100644
--- a/packages/lewooogo-brain/src/lewooogo_brain/engines/incident_engine.py
+++ b/packages/lewooogo-brain/src/lewooogo_brain/engines/incident_engine.py
@@ -30,6 +30,22 @@ from lewooogo_brain.interfaces.incident_processor import (
 )
 
 
+def _parse_dict_field(value: Any) -> dict:
+    """將 Redis 讀回的欄位（可能是 JSON 字串或 dict）轉為 dict。
+    signal_producer 以 json.dumps() 寫入；舊資料可能是 str(dict) repr，一律 fallback 空 dict。
+    2026-04-16 ogt + Claude Sonnet 4.6: 修復 labels/annotations 永遠為 {} 的根因
+    """
+    if isinstance(value, dict):
+        return value
+    if isinstance(value, str) and value:
+        try:
+            result = json.loads(value)
+            return result if isinstance(result, dict) else {}
+        except (json.JSONDecodeError, ValueError):
+            return {}
+    return {}
+
+
 # =============================================================================
 # Memory Provider Protocol (依賴注入用)
 # =============================================================================
@@ -237,8 +253,8 @@ class IncidentEngine(IIncidentProcessor):
             severity=severity,
             source=data.get("source", "unknown"),
             fired_at=datetime.now(timezone.utc),
-            labels=data.get("labels", {}) if isinstance(data.get("labels"), dict) else {},
-            annotations=data.get("annotations", {}) if isinstance(data.get("annotations"), dict) else {},
+            labels=_parse_dict_field(data.get("labels")),
+            annotations=_parse_dict_field(data.get("annotations")),
         )
 
     def _compute_fingerprint(self, data: dict[str, Any]) -> str: