diff --git a/backend/data_layer/activity_data_canon.py b/backend/data_layer/activity_data_canon.py
index 17ec223..1582173 100644
--- a/backend/data_layer/activity_data_canon.py
+++ b/backend/data_layer/activity_data_canon.py
@@ -1,8 +1,10 @@
 """
 Kanonische Aufteilung activity_log vs. EAV für Aktivitätssessions.
 
-Single Source für: welche Felder das CSV-/Registry-Modul „activity“ direkt in activity_log schreibt,
-und welche training_parameters primär über EAV laufen (mit optionalem Lesefallback auf Legacy-Spalten).
+- **Kern / Mapping-Ziele für activity_log:** ausschließlich die Keys aus
+  ``csv_parser.module_registry.MODULE_DEFINITIONS["activity"].fields`` (keine zweite hartcodierte Liste).
+- **Alle anderen Attribute:** ``training_parameters`` + Attributprofil (Kategorie/Typ) → EAV;
+  Lesefallback für bekannte Legacy-Spalten siehe unten.
 
 Normative Doku: .claude/docs/technical/ACTIVITY_PRODUCTION_ARCHITECTURE_AND_PHASES.md
 """
@@ -10,25 +12,22 @@ from __future__ import annotations
 
 from typing import Dict, Final
 
-# ── activity_log: Modul „activity“ (Universal-CSV-Kern) ───────────────────────
-# Nur diese Keys erscheinen in csv_parser.module_registry MODULE_DEFINITIONS["activity"].fields.
-# Alles Weitere: training_parameters + EAV (Import über upsert_session_metrics_from_csv_mapped).
-ACTIVITY_MODULE_REGISTRY_FIELD_KEYS: Final[frozenset[str]] = frozenset(
-    {
-        "date",
-        "start_time",
-        "end_time",
-        "activity_type",
-        "duration_min",
-        "kcal_active",
-        "kcal_resting",
-        "distance_km",
-        "hr_avg",
-        "hr_max",
-        "rpe",
-        "notes",
-    }
-)
+from csv_parser.module_registry import get_module_definition
+
+
+def get_activity_module_registry_field_keys() -> frozenset[str]:
+    """Keys des Universal-CSV-Moduls ``activity`` (= feste activity_log-Kernfelder / Mapping-Ziele)."""
+    mod = get_module_definition("activity")
+    if not mod:
+        return frozenset()
+    return frozenset((mod.get("fields") or {}).keys())
+
+
+# Gleiche Menge wie ``MODULE_DEFINITIONS["activity"].fields`` — zur Laufzeit aus der Registry abgeleitet.
+ACTIVITY_MODULE_REGISTRY_FIELD_KEYS: Final[frozenset[str]] = get_activity_module_registry_field_keys()
+
+# Teil-UPDATEs (Import): alle Kernfelder außer ``date`` (Identität / Duplikat-Key).
+ACTIVITY_LOG_PATCHABLE_COLUMNS: Final[frozenset[str]] = ACTIVITY_MODULE_REGISTRY_FIELD_KEYS - {"date"}
 
 # Parameter-Keys (training_parameters.key), die primär in EAV geführt werden; source_field nach Migration 057 NULL.
 # Lesefallback: activity_log-Spalte unter ACTIVITY_LOG_LEGACY_COLUMN_FOR_EAV_PRIMARY_PARAM, falls EAV leer.
@@ -59,20 +58,3 @@ ACTIVITY_LOG_LEGACY_COLUMN_FOR_EAV_PRIMARY_PARAM: Final[Dict[str, str]] = {
     "kcal_per_km": "kcal_per_km",
 }
 
-# Spalten, die mit training_parameters.source_field (nach Migration 057) noch activity_log abbilden.
-# Erweiterte Metriken sind EAV-primär — nicht hier auflisten.
-ACTIVITY_LOG_PATCHABLE_COLUMNS: Final[frozenset[str]] = frozenset(
-    {
-        "start_time",
-        "end_time",
-        "activity_type",
-        "duration_min",
-        "kcal_active",
-        "kcal_resting",
-        "hr_avg",
-        "hr_max",
-        "distance_km",
-        "rpe",
-        "notes",
-    }
-)
diff --git a/backend/data_layer/activity_persistence_orchestrator.py b/backend/data_layer/activity_persistence_orchestrator.py
index 6085550..6a390dd 100644
--- a/backend/data_layer/activity_persistence_orchestrator.py
+++ b/backend/data_layer/activity_persistence_orchestrator.py
@@ -15,6 +15,7 @@ from typing import Any, Dict, List, Mapping, Optional
 from models import ActivityEntry
 
 from csv_parser.module_registry import get_module_definition
+from data_layer.activity_data_canon import get_activity_module_registry_field_keys
 
 logger = logging.getLogger(__name__)
 
@@ -50,10 +51,8 @@ _ACTIVITY_CSV_REGISTRY_EXCLUDE = frozenset({"date", "start_time", "end_time", "a
 
 
 def activity_registry_field_keys() -> frozenset[str]:
-    mod = get_module_definition("activity")
-    if not mod:
-        return frozenset()
-    return frozenset((mod.get("fields") or {}).keys())
+    """Gleiche Menge wie ``ACTIVITY_MODULE_REGISTRY_FIELD_KEYS`` (Registry als Single Source)."""
+    return get_activity_module_registry_field_keys()
 
 
 def activity_csv_registry_updates_from_mapped(mapped: Mapping[str, Any]) -> Dict[str, Any]:
diff --git a/backend/data_layer/activity_session_metrics.py b/backend/data_layer/activity_session_metrics.py
index b5ef19d..3b79734 100644
--- a/backend/data_layer/activity_session_metrics.py
+++ b/backend/data_layer/activity_session_metrics.py
@@ -9,8 +9,10 @@ import logging
 from decimal import Decimal
 from typing import Any, Dict, List, Mapping, Optional, Sequence
 
-from csv_parser.module_registry import get_module_definition
-from data_layer.activity_data_canon import ACTIVITY_LOG_LEGACY_COLUMN_FOR_EAV_PRIMARY_PARAM
+from data_layer.activity_data_canon import (
+    ACTIVITY_LOG_LEGACY_COLUMN_FOR_EAV_PRIMARY_PARAM,
+    ACTIVITY_MODULE_REGISTRY_FIELD_KEYS,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -262,8 +264,6 @@ def upsert_session_metrics_from_csv_mapped(
     row = cur.fetchone()
     if not row or str(row["profile_id"]) != str(profile_id):
         return
-    mod = get_module_definition("activity") or {}
-    activity_registry_keys = frozenset((mod.get("fields") or {}).keys())
     schema = resolve_activity_attribute_schema(cur, training_category, training_type_id)
     for spec in schema:
         pkey = spec["key"]
@@ -272,7 +272,7 @@ def upsert_session_metrics_from_csv_mapped(
         raw = mapped[pkey]
         if raw is None or raw == "":
             continue
-        if pkey in activity_registry_keys:
+        if pkey in ACTIVITY_MODULE_REGISTRY_FIELD_KEYS:
             continue
         tid = spec["training_parameter_id"]
         dt = spec["data_type"]