diff --git a/docs/DEPLOYMENT_OPERATOR_GUIDE.md b/docs/DEPLOYMENT_OPERATOR_GUIDE.md
index 9b1f3a2..6a6a1fd 100644
--- a/docs/DEPLOYMENT_OPERATOR_GUIDE.md
+++ b/docs/DEPLOYMENT_OPERATOR_GUIDE.md
@@ -153,16 +153,24 @@ on throwaway databases.
 | --- | --- | --- |
 | `REDIS_URL` | `redis://redis:6379/0` | Celery broker/result backend when async workers are enabled. |
 | `CELERY_ENABLED` | `false` | Local/dev can send synchronously. Production campaign delivery should run workers and set this to `true`. |
-| `CELERY_QUEUES` | `send_email,append_sent,default` | Queue list expected by worker/process manager definitions. |
+| `CELERY_QUEUES` | `send_email,append_sent,notifications,calendar,default` | Queue list expected by worker/process manager definitions. The Calendar queue drains durable external-calendar operations. |
 
 Worker command:
 
 ```bash
 python -m celery -A govoplan_core.celery_app:celery worker \
-  --queues send_email,append_sent,default \
+  --queues send_email,append_sent,notifications,calendar,default \
   --loglevel INFO
 ```
 
+Run Celery beat as a separately supervised process. Its built-in one-minute
+schedule recovers Calendar outbox rows left behind by broker failures, process
+crashes, and expired worker leases:
+
+```bash
+python -m celery -A govoplan_core.celery_app:celery beat --loglevel INFO
+```
+
 ### Storage
 
 | Setting | Default | Notes |
@@ -275,7 +283,7 @@ the checked in `.env.example`. It runs:
 - explicit `ENABLED_MODULES`
 - explicit migrations and `--with-dev-data` bootstrap
 - API via the module-aware devserver
-- a Celery worker for `send_email,append_sent,default`
+- a Celery worker for `send_email,append_sent,notifications,calendar,default`
 - WebUI through the Vite dev server
 - durable local files under `runtime/production-like/files`
 
diff --git a/src/govoplan_core/core/install_config.py b/src/govoplan_core/core/install_config.py
index 784cf40..b12d465 100644
--- a/src/govoplan_core/core/install_config.py
+++ b/src/govoplan_core/core/install_config.py
@@ -5,7 +5,7 @@ import json
 import os
 from collections.abc import Mapping
 from dataclasses import dataclass
-from typing import Any, Literal
+from typing import Literal
 
 from cryptography.fernet import Fernet
 from sqlalchemy.engine import make_url
@@ -274,7 +274,8 @@ ENABLED_MODULES=tenancy,organizations,identity,access,admin,dashboard,policy,aud
 
 CELERY_ENABLED=true
 REDIS_URL=redis://127.0.0.1:6379/0
-CELERY_QUEUES=send_email,append_sent,default
+CELERY_QUEUES=send_email,append_sent,notifications,calendar,default
+CALENDAR_OUTBOX_TERMINAL_RETENTION_DAYS=90
 
 CORS_ORIGINS=https://govoplan.example.org
 AUTH_COOKIE_SECURE=true
@@ -317,7 +318,8 @@ DATABASE_URL=postgresql+psycopg://govoplan:govoplan-dev@127.0.0.1:55433/govoplan
 GOVOPLAN_DATABASE_URL_PGTOOLS=postgresql://govoplan:govoplan-dev@127.0.0.1:55433/govoplan
 REDIS_URL=redis://127.0.0.1:56379/0
 CELERY_ENABLED=true
-CELERY_QUEUES=send_email,append_sent,default
+CELERY_QUEUES=send_email,append_sent,notifications,calendar,default
+CALENDAR_OUTBOX_TERMINAL_RETENTION_DAYS=90
 
 ENABLED_MODULES=tenancy,organizations,identity,access,admin,dashboard,policy,audit,campaigns,files,mail,calendar,docs,ops
 CORS_ORIGINS=http://127.0.0.1:5173,http://localhost:5173
diff --git a/tests/test_install_config.py b/tests/test_install_config.py
index 5c9a479..0890cf4 100644
--- a/tests/test_install_config.py
+++ b/tests/test_install_config.py
@@ -3,11 +3,24 @@ from __future__ import annotations
 import unittest
 
 from cryptography.fernet import Fernet
+from pydantic import ValidationError
 
 from govoplan_core.core.install_config import env_template, validate_runtime_configuration
+from govoplan_core.settings import Settings
 
 
 class InstallConfigTests(unittest.TestCase):
+    def test_calendar_outbox_retention_setting_is_validated(self) -> None:
+        self.assertEqual(Settings().calendar_outbox_terminal_retention_days, 90)
+        self.assertEqual(
+            Settings(
+                CALENDAR_OUTBOX_TERMINAL_RETENTION_DAYS="0"
+            ).calendar_outbox_terminal_retention_days,
+            0,
+        )
+        with self.assertRaises(ValidationError):
+            Settings(CALENDAR_OUTBOX_TERMINAL_RETENTION_DAYS="-1")
+
     def test_self_hosted_validation_reports_actionable_missing_settings(self) -> None:
         result = validate_runtime_configuration({}, profile="self-hosted")
 
@@ -68,8 +81,10 @@ class InstallConfigTests(unittest.TestCase):
 
         self.assertIn("GOVOPLAN_INSTALL_PROFILE=self-hosted", self_hosted)
         self.assertIn("MASTER_KEY_B64=<generate", self_hosted)
+        self.assertIn("CALENDAR_OUTBOX_TERMINAL_RETENTION_DAYS=90", self_hosted)
         self.assertIn("GOVOPLAN_INSTALL_PROFILE=production-like", production_like)
         self.assertNotIn("MASTER_KEY_B64=<generate", production_like)
+        self.assertIn("CALENDAR_OUTBOX_TERMINAL_RETENTION_DAYS=90", production_like)
 
 
 if __name__ == "__main__":