diff --git a/.gitignore b/.gitignore
index f1653ef..816fcb1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -131,6 +131,9 @@ $RECYCLE.BIN/
 # MemPalace per-project files (issue #185)
 mempalace.yaml
 entities.json
-
-# Runtime photo store (uploaded/imported gerbil photos) — never commit
-GerbilManagerWebAPI/photo-storage/
+
+# Runtime photo store (uploaded/imported gerbil photos) — never commit
+GerbilManagerWebAPI/photo-storage/
+
+# AR-3: Data Protection key ring (dev-only ephemeral keys) — never commit
+GerbilManagerWebAPI/.data-protection-keys/
diff --git a/GerbilManagerWebAPI/Program.cs b/GerbilManagerWebAPI/Program.cs
index e2a47b0..b7ee181 100644
--- a/GerbilManagerWebAPI/Program.cs
+++ b/GerbilManagerWebAPI/Program.cs
@@ -1,5 +1,6 @@
 using System.Text.Json.Serialization;
 using GerbilManagerWebAPI.Endpoints;
+using Microsoft.AspNetCore.DataProtection;
 using Microsoft.EntityFrameworkCore;
 using Scalar.AspNetCore;
 
@@ -46,7 +47,17 @@ builder.Services.AddHttpClient<GerbilManagerWebAPI.Inbox.DraftReplyService>(
     http => http.Timeout = TimeSpan.FromSeconds(60));
 
 // INBOX-0: Gmail inbox. App Password encrypted at rest via Data Protection.
-builder.Services.AddDataProtection();
+// AR-3: persist the key ring so encrypted passwords survive image redeployments.
+// In prod the path is mounted to a persistent volume (compose DataProtection__KeyRingPath).
+// In dev (Aspire) keys live in the content root — ephemeral, which is fine there.
+{
+    var keyRingPath = builder.Configuration["DataProtection:KeyRingPath"]
+        ?? Path.Combine(builder.Environment.ContentRootPath, ".data-protection-keys");
+    Directory.CreateDirectory(keyRingPath);
+    builder.Services.AddDataProtection()
+        .PersistKeysToFileSystem(new DirectoryInfo(keyRingPath))
+        .SetApplicationName("GerbilManager");
+}
 builder.Services.AddScoped<GerbilManagerWebAPI.Inbox.MailSettingsService>();
 builder.Services.AddScoped<GerbilManagerWebAPI.Inbox.IGmailMailReader, GerbilManagerWebAPI.Inbox.GmailMailReader>();
 builder.Services.AddScoped<GerbilManagerWebAPI.Inbox.RequestSyncService>();
diff --git a/deploy/truenas/.env.example b/deploy/truenas/.env.example
index f005d37..1fe057b 100644
--- a/deploy/truenas/.env.example
+++ b/deploy/truenas/.env.example
@@ -15,9 +15,15 @@ TAG=latest
 PGDATA_PATH=/mnt/SSD/gerbil/pgdata
 PHOTOS_PATH=/mnt/SSD/gerbil/photos
 BACKUPS_PATH=/mnt/SSD/gerbil/backups
+# AR-3: Data Protection Key-Ring (Gmail-App-Passwort-Verschlüsselung)
+KEYS_PATH=/mnt/SSD/gerbil/keys
 
 # Backup-Rotation: Anzahl Tage (Standard: 7)
 BACKUP_KEEP_DAYS=7
 
-# Claude-API-Key fuer KI-Verkaufstext (FEAT-12a; leer lassen wenn nicht vorhanden)
-ANTHROPIC_API_KEY=
+# KI-Funktionen (Verkaufstext + Posteingang-Entwurf)
+# Beliebiger OpenAI-kompatibler Anbieter — Optionen in docs/ai-provider.md
+# Leer lassen = KI deaktiviert (kein Fehler, nur 503 AiKeyMissing)
+AI__BaseUrl=
+AI__ApiKey=
+AI__Model=gemini-2.0-flash
diff --git a/deploy/truenas/compose.yaml b/deploy/truenas/compose.yaml
index 6810c8b..4c19904 100644
--- a/deploy/truenas/compose.yaml
+++ b/deploy/truenas/compose.yaml
@@ -40,10 +40,17 @@ services:
       ConnectionStrings__gerbilmanager: "Host=db;Port=5432;Database=gerbilmanager;Username=postgres;Password=${POSTGRES_PASSWORD}"
       # Speicherort der hochgeladenen Fotos (NAS-Dataset gemounted unter /data/photos)
       Photos__RootPath: /data/photos
-      # KI-Verkaufstext (FEAT-12a stub; leer lassen wenn kein Key vorhanden)
-      ANTHROPIC_API_KEY: "${ANTHROPIC_API_KEY:-}"
+      # AR-3: Data Protection Key-Ring (persistiert Gmail-App-Passwort-Verschlüsselung über Redeployments)
+      DataProtection__KeyRingPath: /data/keys
+      # AR-4: KI-Funktionen (Verkaufstext + Posteingang-Entwurf, Sektion AI; beliebiger OpenAI-kompatibler Anbieter)
+      # Anbieter-Optionen und Schlüssel-Beispiele: docs/ai-provider.md
+      # Leer lassen = KI deaktiviert (503 AiKeyMissing statt Fehler)
+      AI__BaseUrl: "${AI__BaseUrl:-}"
+      AI__ApiKey: "${AI__ApiKey:-}"
+      AI__Model: "${AI__Model:-gemini-2.0-flash}"
     volumes:
       - photos:/data/photos
+      - keys:/data/keys
     depends_on:
       db:
         condition: service_healthy
@@ -101,6 +108,14 @@ volumes:
       type: none
       o: bind
       device: "${PHOTOS_PATH:-/mnt/gerbil/photos}"
+  # AR-3: Data Protection key ring — persistiert Gmail-App-Passwort-Verschlüsselung.
+  # Muss ein persistentes NAS-Dataset sein (nicht dasselbe wie photos).
+  keys:
+    driver: local
+    driver_opts:
+      type: none
+      o: bind
+      device: "${KEYS_PATH:-/mnt/gerbil/keys}"
   backups:
     driver: local
     driver_opts: