diff --git a/.env.example b/.env.example
index d02edf4..bbcab4c 100644
--- a/.env.example
+++ b/.env.example
@@ -29,6 +29,9 @@ ALERTMANAGER_URL=http://alertmanager:9093
 ALERTMANAGER_WEBHOOK_URL=
 GRAFANA_URL=http://grafana:3000
 PROMETHEUS_URL=http://prometheus:9090
+# Required: master key for encrypting service secrets (API keys/tokens) at rest.
+# Generate one with: python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
+MANAGE_ENCRYPTION_KEY=replace-with-a-fernet-key
 BACKEND_CACHE_DIR=./backend-cache
 
 # Auth
diff --git a/README.md b/README.md
index da6be81..b31a86a 100644
--- a/README.md
+++ b/README.md
@@ -89,6 +89,7 @@ export VITE_OIDC_REDIRECT_URI=https://manage.example.com/oidc/callback
 export VITE_OIDC_POST_LOGOUT_REDIRECT_URI=https://manage.example.com/
 export VITE_GRAFANA_URL=https://grafana.manage.example.com
 export VITE_PROMETHEUS_URL=https://prometheus.manage.example.com
+export MANAGE_ENCRYPTION_KEY=$(python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())")
 
 docker compose up --build
 ```
@@ -148,6 +149,10 @@ GRAFANA_URL=http://grafana:3000
 PROMETHEUS_URL=http://prometheus:9090
 VITE_GRAFANA_URL=https://grafana.manage.example.com
 VITE_PROMETHEUS_URL=https://prometheus.manage.example.com
+
+# Required: master key encrypting service secrets (API keys/tokens) at rest.
+# Generate one with: python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
+MANAGE_ENCRYPTION_KEY=replace-with-a-fernet-key
 ```
 
 ## Remote server requirements
diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index 2ffbc92..172eade 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -15,6 +15,7 @@ dependencies = [
   "python-multipart>=0.0.9",
   "prometheus-client>=0.21",
   "python-json-logger>=2.0",
+  "cryptography>=42.0",
 ]
 
 [project.optional-dependencies]
diff --git a/backend/src/media_library_viewer_api/integrations/__init__.py b/backend/src/media_library_viewer_api/integrations/__init__.py
new file mode 100644
index 0000000..7392e6b
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/__init__.py
@@ -0,0 +1 @@
+"""Closed registry of service integrations."""
diff --git a/backend/src/media_library_viewer_api/integrations/base.py b/backend/src/media_library_viewer_api/integrations/base.py
new file mode 100644
index 0000000..6dee3ce
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/base.py
@@ -0,0 +1,117 @@
+"""Base classes for service integrations.
+
+A *service definition* is a closed, compile-time description of an external service
+the app can talk to (Grafana, Jellyfin, …). Each definition declares:
+
+* its non-secret ``config_schema`` (derived from a Pydantic model),
+* the secret fields it accepts (API keys / tokens),
+* the widget kinds it can contribute to the dashboard (each with its own
+  Pydantic-derived config schema).
+
+Definitions live in :mod:`media_library_viewer_api.integrations` modules and are
+assembled into the closed :data:`~media_library_viewer_api.integrations.registry.SERVICE_DEFINITIONS`
+map. There is no runtime plugin loading.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any
+
+from pydantic import BaseModel
+
+
+class ServiceConfigBase(BaseModel):
+    """Base for per-service non-secret config models.
+
+    Subclass this in each integration module and declare the connection fields.
+    The JSON schema is derived via ``model_json_schema()`` and exposed to the UI.
+    """
+
+
+class WidgetConfigBase(BaseModel):
+    """Base for per-widget config models.
+
+    Subclass this for each widget kind a service provides. Widget configs never
+    hold secrets; credentials live on the parent service record.
+    """
+
+    model_config = {"extra": "forbid"}
+
+
+@dataclass(frozen=True)
+class SecretField:
+    """A secret field stored encrypted on the service record."""
+
+    key: str
+    label: str
+    required: bool = False
+    helper: str | None = None
+
+
+@dataclass(frozen=True)
+class WidgetKind:
+    """A widget kind contributed by a service definition."""
+
+    kind: str
+    name: str
+    description: str
+    config_schema: dict[str, Any]
+    default_config: dict[str, Any] = field(default_factory=dict)
+    refresh_interval_ms: int = 0
+
+
+@dataclass(frozen=True)
+class ServiceDefinition:
+    """Closed description of an external service type."""
+
+    service_type: str
+    name: str
+    description: str
+    config_model: type[ServiceConfigBase]
+    secret_fields: list[SecretField]
+    widget_kinds: list[WidgetKind]
+
+    @property
+    def config_schema(self) -> dict[str, Any]:
+        """JSON schema for the service's non-secret config."""
+        return self.config_model.model_json_schema()
+
+    @property
+    def secret_keys(self) -> set[str]:
+        return {sf.key for sf in self.secret_fields}
+
+    def widget_kind(self, kind: str) -> WidgetKind | None:
+        for wk in self.widget_kinds:
+            if wk.kind == kind:
+                return wk
+        return None
+
+
+def widget_kind(
+    kind: str,
+    name: str,
+    description: str,
+    model_cls: type[WidgetConfigBase],
+    *,
+    default_config: dict[str, Any] | None = None,
+    refresh_interval_ms: int = 0,
+) -> WidgetKind:
+    """Build a :class:`WidgetKind` from a Pydantic widget-config model."""
+    schema = model_cls.model_json_schema()
+    # Strip Pydantic's title noise so the exposed schema stays clean.
+    schema.pop("title", None)
+    return WidgetKind(
+        kind=kind,
+        name=name,
+        description=description,
+        config_schema=schema,
+        default_config=dict(default_config or {}),
+        refresh_interval_ms=refresh_interval_ms,
+    )
+
+
+def validate_config(model_cls: type[BaseModel], config: dict[str, Any] | None) -> dict[str, Any]:
+    """Validate a config dict against a Pydantic model and return the cleaned dict."""
+    instance = model_cls.model_validate(config or {})
+    return instance.model_dump(exclude_none=True)
diff --git a/backend/src/media_library_viewer_api/integrations/grafana.py b/backend/src/media_library_viewer_api/integrations/grafana.py
new file mode 100644
index 0000000..cf95f55
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/grafana.py
@@ -0,0 +1,46 @@
+"""Grafana service definition."""
+
+from __future__ import annotations
+
+from media_library_viewer_api.integrations.base import (
+    SecretField,
+    ServiceConfigBase,
+    ServiceDefinition,
+    WidgetConfigBase,
+    widget_kind,
+)
+
+
+class GrafanaConfig(ServiceConfigBase):
+    """Non-secret Grafana connection config."""
+
+    base_url: str
+    timeout_seconds: int = 5
+
+
+class GrafanaLinkWidgetConfig(WidgetConfigBase):
+    """Deep-link to a Grafana dashboard or panel."""
+
+    dashboard_uid: str
+    panel_id: int | None = None
+
+
+DEFINITION = ServiceDefinition(
+    service_type="grafana",
+    name="Grafana",
+    description="Dashboards, metrics, and logs.",
+    config_model=GrafanaConfig,
+    secret_fields=[
+        SecretField(key="api_key", label="API key", helper="Service account token (optional)"),
+    ],
+    widget_kinds=[
+        widget_kind(
+            kind="link",
+            name="Dashboard link",
+            description="Deep-link to a Grafana dashboard or panel.",
+            model_cls=GrafanaLinkWidgetConfig,
+            default_config={"dashboard_uid": ""},
+            refresh_interval_ms=0,
+        ),
+    ],
+)
diff --git a/backend/src/media_library_viewer_api/integrations/jellyfin.py b/backend/src/media_library_viewer_api/integrations/jellyfin.py
new file mode 100644
index 0000000..78897fd
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/jellyfin.py
@@ -0,0 +1,47 @@
+"""Jellyfin service definition."""
+
+from __future__ import annotations
+
+from media_library_viewer_api.integrations.base import (
+    SecretField,
+    ServiceConfigBase,
+    ServiceDefinition,
+    WidgetConfigBase,
+    widget_kind,
+)
+
+
+class JellyfinConfig(ServiceConfigBase):
+    """Non-secret Jellyfin connection config."""
+
+    base_url: str
+    user_id: str = ""
+    timeout_seconds: int = 10
+
+
+class JellyfinActivityWidgetConfig(WidgetConfigBase):
+    """Live Jellyfin session activity."""
+
+    # No user-overridable fields; the service record carries user_id.
+    pass
+
+
+DEFINITION = ServiceDefinition(
+    service_type="jellyfin",
+    name="Jellyfin",
+    description="Media server with live session activity.",
+    config_model=JellyfinConfig,
+    secret_fields=[
+        SecretField(key="api_key", label="API key", required=True),
+    ],
+    widget_kinds=[
+        widget_kind(
+            kind="activity",
+            name="Activity",
+            description="Live sessions and idle users.",
+            model_cls=JellyfinActivityWidgetConfig,
+            default_config={},
+            refresh_interval_ms=30_000,
+        ),
+    ],
+)
diff --git a/backend/src/media_library_viewer_api/integrations/nextcloud.py b/backend/src/media_library_viewer_api/integrations/nextcloud.py
new file mode 100644
index 0000000..dd44558
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/nextcloud.py
@@ -0,0 +1,32 @@
+"""Nextcloud service definition.
+
+Nextcloud is included as a proof-of-concept third-party service. It has no
+dashboard widgets yet; its service page holds connection config only.
+"""
+
+from __future__ import annotations
+
+from media_library_viewer_api.integrations.base import (
+    SecretField,
+    ServiceConfigBase,
+    ServiceDefinition,
+)
+
+
+class NextcloudConfig(ServiceConfigBase):
+    """Non-secret Nextcloud connection config."""
+
+    base_url: str
+    username: str = ""
+
+
+DEFINITION = ServiceDefinition(
+    service_type="nextcloud",
+    name="Nextcloud",
+    description="Self-hosted files and collaboration.",
+    config_model=NextcloudConfig,
+    secret_fields=[
+        SecretField(key="app_password", label="App password", required=True),
+    ],
+    widget_kinds=[],
+)
diff --git a/backend/src/media_library_viewer_api/integrations/prometheus.py b/backend/src/media_library_viewer_api/integrations/prometheus.py
new file mode 100644
index 0000000..458304f
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/prometheus.py
@@ -0,0 +1,45 @@
+"""Prometheus service definition."""
+
+from __future__ import annotations
+
+from media_library_viewer_api.integrations.base import (
+    SecretField,
+    ServiceConfigBase,
+    ServiceDefinition,
+    WidgetConfigBase,
+    widget_kind,
+)
+
+
+class PrometheusConfig(ServiceConfigBase):
+    """Non-secret Prometheus connection config."""
+
+    base_url: str
+    timeout_seconds: int = 10
+
+
+class PrometheusMetricWidgetConfig(WidgetConfigBase):
+    """A PromQL instant query rendered as a metric."""
+
+    promql: str
+
+
+DEFINITION = ServiceDefinition(
+    service_type="prometheus",
+    name="Prometheus",
+    description="Metrics storage and PromQL queries.",
+    config_model=PrometheusConfig,
+    secret_fields=[
+        SecretField(key="api_key", label="API key", helper="Optional bearer token"),
+    ],
+    widget_kinds=[
+        widget_kind(
+            kind="metric",
+            name="Metric",
+            description="Instant query result rendered as a metric.",
+            model_cls=PrometheusMetricWidgetConfig,
+            default_config={"promql": ""},
+            refresh_interval_ms=30_000,
+        ),
+    ],
+)
diff --git a/backend/src/media_library_viewer_api/integrations/registry.py b/backend/src/media_library_viewer_api/integrations/registry.py
new file mode 100644
index 0000000..199a2fe
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/registry.py
@@ -0,0 +1,48 @@
+"""Closed registry of service definitions.
+
+Adding a brand-new service still requires a backend deploy and a module here.
+There is no runtime plugin loading.
+"""
+
+from __future__ import annotations
+
+from media_library_viewer_api.integrations.base import ServiceDefinition, WidgetKind
+from media_library_viewer_api.integrations.grafana import DEFINITION as GRAFANA
+from media_library_viewer_api.integrations.jellyfin import DEFINITION as JELLYFIN
+from media_library_viewer_api.integrations.nextcloud import DEFINITION as NEXTCLOUD
+from media_library_viewer_api.integrations.prometheus import DEFINITION as PROMETHEUS
+from media_library_viewer_api.integrations.ssh_tasks import DEFINITION as SSH_TASKS
+
+SERVICE_DEFINITIONS: dict[str, ServiceDefinition] = {
+    GRAFANA.service_type: GRAFANA,
+    PROMETHEUS.service_type: PROMETHEUS,
+    JELLYFIN.service_type: JELLYFIN,
+    NEXTCLOUD.service_type: NEXTCLOUD,
+    SSH_TASKS.service_type: SSH_TASKS,
+}
+
+
+def list_service_types() -> list[str]:
+    """Return all registered service type names (sorted for stable output)."""
+    return sorted(SERVICE_DEFINITIONS)
+
+
+def get_service_definition(service_type: str) -> ServiceDefinition | None:
+    """Return the definition for a service type, or ``None`` if unknown."""
+    return SERVICE_DEFINITIONS.get(service_type)
+
+
+def get_widget_kind(service_type: str, widget_kind: str) -> WidgetKind | None:
+    """Return a widget kind declared by a service definition, or ``None``."""
+    definition = get_service_definition(service_type)
+    if definition is None:
+        return None
+    return definition.widget_kind(widget_kind)
+
+
+def require_service_definition(service_type: str) -> ServiceDefinition:
+    """Return the definition or raise ``ValueError`` for an unknown type."""
+    definition = get_service_definition(service_type)
+    if definition is None:
+        raise ValueError(f"Unknown service type: {service_type}")
+    return definition
diff --git a/backend/src/media_library_viewer_api/integrations/ssh_tasks.py b/backend/src/media_library_viewer_api/integrations/ssh_tasks.py
new file mode 100644
index 0000000..a2eeb89
--- /dev/null
+++ b/backend/src/media_library_viewer_api/integrations/ssh_tasks.py
@@ -0,0 +1,60 @@
+"""SSH task runner service definition.
+
+An ``ssh_tasks`` instance is an SSH endpoint that can run reusable saved tasks.
+Tasks themselves stay in the global saved-task registry; the instance only owns
+transport (host/port/user/key). Every run is recorded in ``service_task_runs``
+and shown as history on the instance's service page.
+"""
+
+from __future__ import annotations
+
+from media_library_viewer_api.integrations.base import (
+    SecretField,
+    ServiceConfigBase,
+    ServiceDefinition,
+    WidgetConfigBase,
+    widget_kind,
+)
+
+
+class SshTasksConfig(ServiceConfigBase):
+    """Non-secret SSH task runner config.
+
+    The SSH key itself lives in the saved SSH-key registry and is referenced by
+    ``ssh_key_id``. An optional ``passphrase`` is stored as a secret.
+    """
+
+    host: str
+    port: int = 22
+    username: str = ""
+    ssh_key_id: str = ""
+    timeout_seconds: int = 30
+
+
+class SshTaskOutputWidgetConfig(WidgetConfigBase):
+    """Output of a saved task run on this instance."""
+
+    task_id: str
+    # service_id is implicit (the widget's service); allow overriding per-widget.
+    service_id: str | None = None
+
+
+DEFINITION = ServiceDefinition(
+    service_type="ssh_tasks",
+    name="SSH task runner",
+    description="Run reusable saved tasks over SSH and keep run history.",
+    config_model=SshTasksConfig,
+    secret_fields=[
+        SecretField(key="passphrase", label="Key passphrase", helper="Optional"),
+    ],
+    widget_kinds=[
+        widget_kind(
+            kind="task_output",
+            name="Task output",
+            description="Output of a saved task run.",
+            model_cls=SshTaskOutputWidgetConfig,
+            default_config={"task_id": ""},
+            refresh_interval_ms=0,
+        ),
+    ],
+)
diff --git a/backend/src/media_library_viewer_api/main.py b/backend/src/media_library_viewer_api/main.py
index e424e9b..8cbe679 100644
--- a/backend/src/media_library_viewer_api/main.py
+++ b/backend/src/media_library_viewer_api/main.py
@@ -23,6 +23,7 @@ from media_library_viewer_api.observability import (
 )
 from media_library_viewer_api.routers import backups as backups_router
 from media_library_viewer_api.routers import dashboard, files, jobs, media, monitoring, tasks, users
+from media_library_viewer_api.routers import services as services_router
 from media_library_viewer_api.routers import widgets as widgets_router
 from media_library_viewer_api.routers.settings import router as settings_router
 
@@ -38,6 +39,9 @@ async def lifespan(app: FastAPI):
     settings = get_settings()
     configure_logging(settings.log_level, settings.log_format)
     validate_auth_settings(settings)
+    from media_library_viewer_api.services.secrets import validate_encryption_key
+
+    validate_encryption_key()
     logger.info("Backend startup complete: %s", describe_settings(settings))
     logger.info("Managed known_hosts will be populated lazily on first successful SSH connection")
     try:
@@ -143,6 +147,7 @@ app.include_router(tasks.router)
 app.include_router(settings_router)
 app.include_router(backups_router.router)
 app.include_router(widgets_router.router)
+app.include_router(services_router.router)
 
 
 @app.get("/api/health")
diff --git a/backend/src/media_library_viewer_api/models/services.py b/backend/src/media_library_viewer_api/models/services.py
new file mode 100644
index 0000000..d9cb3a9
--- /dev/null
+++ b/backend/src/media_library_viewer_api/models/services.py
@@ -0,0 +1,96 @@
+"""Pydantic models for the service registry API."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import BaseModel, Field, field_validator
+
+
+def _validate_config_keys(config: dict[str, Any]) -> dict[str, Any]:
+    """Reject credential keys in non-secret service config.
+
+    Secrets are sent in the separate ``secrets`` mapping; the plain ``config``
+    object must never hold them.
+    """
+    forbidden = {
+        "password",
+        "token",
+        "secret",
+        "api_key",
+        "apikey",
+        "private_key",
+        "passphrase",
+        "credential",
+    }
+
+    def _check(value: Any) -> None:
+        if isinstance(value, dict):
+            for key, child in value.items():
+                if key.lower() in forbidden:
+                    raise ValueError(
+                        f"Credential key '{key}' is not allowed in service config"
+                    )
+                _check(child)
+        elif isinstance(value, list):
+            for item in value:
+                _check(item)
+
+    _check(config)
+    return config
+
+
+class ServiceInstanceInput(BaseModel):
+    """Payload for creating or updating a service instance."""
+
+    id: str | None = None
+    service_type: str = Field(..., min_length=1)
+    name: str = Field(..., min_length=1)
+    config: dict[str, Any] = Field(default_factory=dict)
+    secrets: dict[str, str] = Field(default_factory=dict)
+    enabled: bool = True
+
+    @field_validator("config")
+    @classmethod
+    def reject_credential_keys(cls, value: dict[str, Any]) -> dict[str, Any]:
+        return _validate_config_keys(value or {})
+
+
+class ServiceInstance(BaseModel):
+    """Persisted service instance returned by the API (no plaintext secrets)."""
+
+    id: str
+    service_type: str
+    name: str
+    config: dict[str, Any]
+    secrets_set: dict[str, bool]
+    enabled: bool
+    created_at: int
+    updated_at: int
+
+
+class SecretFieldInfo(BaseModel):
+    key: str
+    label: str
+    required: bool = False
+    helper: str | None = None
+
+
+class WidgetKindInfo(BaseModel):
+    kind: str
+    name: str
+    description: str
+    config_schema: dict[str, Any]
+    default_config: dict[str, Any]
+    refresh_interval_ms: int
+
+
+class ServiceTypeInfo(BaseModel):
+    """Metadata about a registered service type."""
+
+    service_type: str
+    name: str
+    description: str
+    config_schema: dict[str, Any]
+    secret_fields: list[SecretFieldInfo]
+    widget_kinds: list[WidgetKindInfo]
diff --git a/backend/src/media_library_viewer_api/routers/services.py b/backend/src/media_library_viewer_api/routers/services.py
new file mode 100644
index 0000000..df00631
--- /dev/null
+++ b/backend/src/media_library_viewer_api/routers/services.py
@@ -0,0 +1,182 @@
+"""REST API for the service registry.
+
+Service instances hold non-secret config and encrypted secrets. Plaintext
+secrets are never returned; only the boolean ``secrets_set`` map is exposed.
+"""
+
+from __future__ import annotations
+
+import logging
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException, status
+
+from media_library_viewer_api.dependencies import get_settings_store
+from media_library_viewer_api.integrations.base import validate_config
+from media_library_viewer_api.integrations.registry import (
+    SERVICE_DEFINITIONS,
+    get_service_definition,
+    require_service_definition,
+)
+from media_library_viewer_api.models.services import (
+    SecretFieldInfo,
+    ServiceInstance,
+    ServiceInstanceInput,
+    ServiceTypeInfo,
+    WidgetKindInfo,
+)
+from media_library_viewer_api.services.settings_store import SettingsStore
+
+router = APIRouter(prefix="/api/services", tags=["services"])
+
+logger = logging.getLogger(__name__)
+
+
+def _to_type_info(service_type: str) -> ServiceTypeInfo:
+    definition = require_service_definition(service_type)
+    return ServiceTypeInfo(
+        service_type=definition.service_type,
+        name=definition.name,
+        description=definition.description,
+        config_schema=definition.config_schema,
+        secret_fields=[
+            SecretFieldInfo(
+                key=sf.key,
+                label=sf.label,
+                required=sf.required,
+                helper=sf.helper,
+            )
+            for sf in definition.secret_fields
+        ],
+        widget_kinds=[
+            WidgetKindInfo(
+                kind=wk.kind,
+                name=wk.name,
+                description=wk.description,
+                config_schema=wk.config_schema,
+                default_config=wk.default_config,
+                refresh_interval_ms=wk.refresh_interval_ms,
+            )
+            for wk in definition.widget_kinds
+        ],
+    )
+
+
+def _to_instance(row: dict[str, Any]) -> ServiceInstance:
+    """Build an API response model, surfacing only secret 'set' flags."""
+    definition = get_service_definition(row["service_type"])
+    known_secrets = definition.secret_keys if definition else set()
+    secrets_blob = row.get("secrets") or {}
+    secrets_set = {key: (key in secrets_blob and bool(secrets_blob[key])) for key in known_secrets}
+    return ServiceInstance(
+        id=row["id"],
+        service_type=row["service_type"],
+        name=row["name"],
+        config=row.get("config") or {},
+        secrets_set=secrets_set,
+        enabled=row["enabled"],
+        created_at=row["created_at"],
+        updated_at=row["updated_at"],
+    )
+
+
+def _validate_input(body: ServiceInstanceInput) -> None:
+    """Validate service_type, config, and secret keys against the definition."""
+    definition = get_service_definition(body.service_type)
+    if definition is None:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=f"Unknown service type: {body.service_type}",
+        )
+    try:
+        validate_config(definition.config_model, body.config)
+    except Exception as exc:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=f"Invalid service config: {exc}",
+        ) from exc
+    unknown_secrets = set(body.secrets) - definition.secret_keys
+    if unknown_secrets:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=f"Unknown secret fields for {body.service_type}: {sorted(unknown_secrets)}",
+        )
+
+
+@router.get("/types")
+def list_types() -> list[ServiceTypeInfo]:
+    """Return metadata for every registered service type."""
+    return [_to_type_info(service_type) for service_type in sorted(SERVICE_DEFINITIONS)]
+
+
+@router.get("/instances")
+def list_instances(
+    service_type: str | None = None,
+    store: SettingsStore = Depends(get_settings_store),
+) -> list[ServiceInstance]:
+    """Return all persisted service instances (no plaintext secrets)."""
+    rows = store.list_services(service_type)
+    return [_to_instance(row) for row in rows]
+
+
+@router.post("/instances", status_code=status.HTTP_201_CREATED)
+def create_instance(
+    body: ServiceInstanceInput,
+    store: SettingsStore = Depends(get_settings_store),
+) -> ServiceInstance:
+    """Create a new service instance."""
+    _validate_input(body)
+    row = store.upsert_service(
+        {
+            "id": body.id,
+            "service_type": body.service_type,
+            "name": body.name,
+            "config": body.config,
+            "enabled": body.enabled,
+        },
+        secret_values=body.secrets,
+    )
+    return _to_instance(row)
+
+
+@router.put("/instances/{service_id}")
+def update_instance(
+    service_id: str,
+    body: ServiceInstanceInput,
+    store: SettingsStore = Depends(get_settings_store),
+) -> ServiceInstance:
+    """Update an existing service instance."""
+    existing = store.get_service(service_id)
+    if not existing:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Service not found")
+    if body.id is not None and body.id != service_id:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="ID in path does not match ID in body",
+        )
+    _validate_input(body)
+    row = store.upsert_service(
+        {
+            "id": service_id,
+            "service_type": body.service_type,
+            "name": body.name,
+            "config": body.config,
+            "enabled": body.enabled,
+        },
+        secret_values=body.secrets,
+        service_id=service_id,
+    )
+    return _to_instance(row)
+
+
+@router.delete("/instances/{service_id}")
+def delete_instance(
+    service_id: str,
+    store: SettingsStore = Depends(get_settings_store),
+) -> dict[str, str]:
+    """Delete a service instance (cascade-deletes widgets referencing it)."""
+    existing = store.get_service(service_id)
+    if not existing:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Service not found")
+    store.delete_service(service_id)
+    return {"status": "deleted"}
diff --git a/backend/src/media_library_viewer_api/services/secrets.py b/backend/src/media_library_viewer_api/services/secrets.py
new file mode 100644
index 0000000..fe26347
--- /dev/null
+++ b/backend/src/media_library_viewer_api/services/secrets.py
@@ -0,0 +1,97 @@
+"""Encryption-at-rest for service secrets.
+
+Service API keys / tokens are stored encrypted in the ``services.secrets_json``
+column. Encryption uses Fernet (symmetric authenticated encryption) with a single
+master key provided via the ``MANAGE_ENCRYPTION_KEY`` environment variable.
+
+* The key **must** be a urlsafe base64-encoded 32-byte value (Fernet format).
+* The key is **always required** — there is no development fallback, so secrets
+  are never accidentally stored in plaintext.
+* Secrets are encrypted field-by-field; the ``"which secrets are set"`` metadata
+  can be derived from the ciphertext blob without decrypting.
+"""
+
+from __future__ import annotations
+
+import os
+from functools import lru_cache
+
+from cryptography.fernet import Fernet, InvalidToken
+
+ENCRYPTION_KEY_ENV = "MANAGE_ENCRYPTION_KEY"
+
+
+class EncryptionKeyError(RuntimeError):
+    """Raised when the encryption key is missing or invalid."""
+
+
+@lru_cache(maxsize=1)
+def get_encryption_key() -> bytes:
+    """Return the raw Fernet key, or raise if missing/invalid.
+
+    The result is cached for the process lifetime. Tests should call
+    :func:`reset_encryption_key_cache` after changing the environment.
+    """
+    raw = os.environ.get(ENCRYPTION_KEY_ENV)
+    if not raw:
+        raise EncryptionKeyError(
+            f"{ENCRYPTION_KEY_ENV} is required to store service secrets"
+        )
+    key = raw.strip().encode()
+    try:
+        Fernet(key)
+    except (ValueError, TypeError) as exc:  # pragma: no cover - validated by tests
+        raise EncryptionKeyError(
+            f"{ENCRYPTION_KEY_ENV} must be a valid Fernet key"
+        ) from exc
+    return key
+
+
+def reset_encryption_key_cache() -> None:
+    """Drop the cached encryption key (used by tests that swap keys)."""
+    get_encryption_key.cache_clear()
+
+
+def _fernet() -> Fernet:
+    return Fernet(get_encryption_key())
+
+
+def encrypt_value(plaintext: str) -> str:
+    """Encrypt a single secret value and return the ciphertext string."""
+    return _fernet().encrypt(plaintext.encode()).decode()
+
+
+def decrypt_value(ciphertext: str) -> str:
+    """Decrypt a single ciphertext value."""
+    try:
+        return _fernet().decrypt(ciphertext.encode()).decode()
+    except InvalidToken as exc:
+        raise EncryptionKeyError("Service secret could not be decrypted") from exc
+
+
+def encrypt_secrets(values: dict[str, str]) -> dict[str, str]:
+    """Encrypt every provided secret value."""
+    fernet = _fernet()
+    return {key: fernet.encrypt(value.encode()).decode() for key, value in values.items()}
+
+
+def decrypt_secrets(blob: dict[str, str]) -> dict[str, str]:
+    """Decrypt every secret value in a blob."""
+    fernet = _fernet()
+    result: dict[str, str] = {}
+    for key, ciphertext in blob.items():
+        try:
+            result[key] = fernet.decrypt(ciphertext.encode()).decode()
+        except InvalidToken as exc:
+            raise EncryptionKeyError(f"Service secret '{key}' could not be decrypted") from exc
+    return result
+
+
+def generate_development_key() -> str:
+    """Return a freshly generated Fernet key (helper for operators/docs)."""
+    return Fernet.generate_key().decode()
+
+
+def validate_encryption_key() -> None:
+    """Eagerly validate that the encryption key is present and well-formed."""
+    get_encryption_key()  # raises EncryptionKeyError on failure
diff --git a/backend/src/media_library_viewer_api/services/settings_store.py b/backend/src/media_library_viewer_api/services/settings_store.py
index d021f26..5a27e98 100644
--- a/backend/src/media_library_viewer_api/services/settings_store.py
+++ b/backend/src/media_library_viewer_api/services/settings_store.py
@@ -226,6 +226,45 @@ class SettingsStore:
             """)
             conn.execute("CREATE INDEX IF NOT EXISTS idx_backup_alerts_job_id ON backup_alerts(job_id)")
             conn.execute("CREATE INDEX IF NOT EXISTS idx_backup_alerts_acknowledged ON backup_alerts(acknowledged)")
+            conn.execute(
+                """
+                CREATE TABLE IF NOT EXISTS services (
+                    id TEXT PRIMARY KEY,
+                    service_type TEXT NOT NULL,
+                    name TEXT NOT NULL,
+                    config_json TEXT NOT NULL DEFAULT '{}',
+                    secrets_json TEXT NOT NULL DEFAULT '{}',
+                    enabled INTEGER NOT NULL DEFAULT 1,
+                    created_at INTEGER NOT NULL,
+                    updated_at INTEGER NOT NULL
+                )
+                """
+            )
+            conn.execute("CREATE INDEX IF NOT EXISTS idx_services_type ON services(service_type)")
+            conn.execute(
+                """
+                CREATE TABLE IF NOT EXISTS service_task_runs (
+                    id TEXT PRIMARY KEY,
+                    task_id TEXT NOT NULL,
+                    service_id TEXT NOT NULL,
+                    status TEXT NOT NULL,
+                    exit_status INTEGER,
+                    duration_ms INTEGER,
+                    stdout_tail TEXT NOT NULL DEFAULT '',
+                    stderr_tail TEXT NOT NULL DEFAULT '',
+                    error TEXT NOT NULL DEFAULT '',
+                    created_at INTEGER NOT NULL
+                )
+                """
+            )
+            conn.execute(
+                "CREATE INDEX IF NOT EXISTS idx_service_task_runs_service "
+                "ON service_task_runs(service_id, created_at DESC)"
+            )
+            conn.execute(
+                "CREATE INDEX IF NOT EXISTS idx_service_task_runs_task "
+                "ON service_task_runs(task_id, created_at DESC)"
+            )
 
     @staticmethod
     def _normalize_services(value: Any, fallback: list[str] | None = None) -> list[str]:
@@ -1476,6 +1515,211 @@ class SettingsStore:
         with self.connect() as conn:
             conn.execute("DELETE FROM dashboard_widgets WHERE id = ?", (widget_id,))
 
+    # ------------------------------------------------------------------
+    # Service registry
+    # ------------------------------------------------------------------
+
+    def _row_to_service(self, row: sqlite3.Row) -> dict[str, Any]:
+        secrets_blob = json.loads(row["secrets_json"] or "{}")
+        return {
+            "id": row["id"],
+            "service_type": row["service_type"],
+            "name": row["name"],
+            "config": json.loads(row["config_json"] or "{}"),
+            "secrets": secrets_blob,
+            "enabled": bool(row["enabled"]),
+            "created_at": row["created_at"],
+            "updated_at": row["updated_at"],
+        }
+
+    def list_services(self, service_type: str | None = None) -> list[dict[str, Any]]:
+        self.init_schema()
+        with self.connect() as conn:
+            if service_type:
+                rows = conn.execute(
+                    "SELECT * FROM services WHERE service_type = ? ORDER BY name ASC",
+                    (service_type,),
+                ).fetchall()
+            else:
+                rows = conn.execute("SELECT * FROM services ORDER BY name ASC").fetchall()
+        return [self._row_to_service(row) for row in rows]
+
+    def get_service(self, service_id: str) -> dict[str, Any] | None:
+        self.init_schema()
+        with self.connect() as conn:
+            row = conn.execute(
+                "SELECT * FROM services WHERE id = ?", (service_id,)
+            ).fetchone()
+        return self._row_to_service(row) if row else None
+
+    def _normalize_service_payload(
+        self,
+        payload: dict[str, Any],
+        service_id: str | None = None,
+    ) -> dict[str, Any]:
+        current = self.get_service(service_id) if service_id else None
+        service_id = (
+            str(payload.get("id") or service_id or uuid.uuid4().hex[:12]).strip()
+            or uuid.uuid4().hex[:12]
+        )
+        service_type = str(
+            payload.get("service_type") or (current or {}).get("service_type", "")
+        ).strip()
+        name = str(payload.get("name") or (current or {}).get("name", "") or "").strip()
+        config = payload.get("config", (current or {}).get("config", {}))
+        if not isinstance(config, dict):
+            config = {}
+        enabled = bool(payload.get("enabled", (current or {}).get("enabled", True)))
+        return {
+            "id": service_id,
+            "service_type": service_type,
+            "name": name,
+            "config": config,
+            "enabled": enabled,
+        }
+
+    def upsert_service(
+        self,
+        payload: dict[str, Any],
+        secret_values: dict[str, str] | None = None,
+        service_id: str | None = None,
+    ) -> dict[str, Any]:
+        """Insert or update a service instance.
+
+        ``secret_values`` carries plaintext secrets to encrypt and store. A key
+        absent from ``secret_values`` preserves the existing ciphertext; a key
+        mapped to an empty string clears it.
+        """
+        self.init_schema()
+        service = self._normalize_service_payload(payload, service_id)
+        now = int(time.time())
+
+        existing = self.get_service(service["id"])
+        secrets_blob: dict[str, str]
+        if existing is not None:
+            secrets_blob = dict(existing["secrets"])
+        else:
+            secrets_blob = {}
+        if secret_values:
+            from media_library_viewer_api.services.secrets import encrypt_value
+
+            for key, value in secret_values.items():
+                if value == "":
+                    secrets_blob.pop(key, None)
+                else:
+                    secrets_blob[key] = encrypt_value(value)
+
+        with self.connect() as conn:
+            created_at = int(existing["created_at"]) if existing else now
+            conn.execute(
+                """
+                INSERT INTO services (
+                    id, service_type, name, config_json, secrets_json,
+                    enabled, created_at, updated_at
+                )
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+                ON CONFLICT(id) DO UPDATE SET
+                    service_type = excluded.service_type,
+                    name = excluded.name,
+                    config_json = excluded.config_json,
+                    secrets_json = excluded.secrets_json,
+                    enabled = excluded.enabled,
+                    updated_at = excluded.updated_at
+                """,
+                (
+                    service["id"],
+                    service["service_type"],
+                    service["name"],
+                    json.dumps(service["config"]),
+                    json.dumps(secrets_blob),
+                    1 if service["enabled"] else 0,
+                    created_at,
+                    now,
+                ),
+            )
+        return self.get_service(service["id"]) or service
+
+    def delete_service(self, service_id: str) -> None:
+        """Delete a service and cascade-delete widgets referencing it."""
+        self.init_schema()
+        with self.connect() as conn:
+            # The service_id column on dashboard_widgets is added in a later
+            # slice; only cascade when it is present.
+            widget_cols = {row[1] for row in conn.execute("PRAGMA table_info(dashboard_widgets)").fetchall()}
+            if "service_id" in widget_cols:
+                conn.execute(
+                    "DELETE FROM dashboard_widgets WHERE service_id = ?",
+                    (service_id,),
+                )
+            conn.execute("DELETE FROM services WHERE id = ?", (service_id,))
+
+    def record_service_task_run(self, payload: dict[str, Any]) -> dict[str, Any]:
+        """Append a service task run history row."""
+        self.init_schema()
+        run_id = str(payload.get("id") or uuid.uuid4().hex[:12])
+        now = int(time.time())
+        with self.connect() as conn:
+            conn.execute(
+                """
+                INSERT INTO service_task_runs (
+                    id, task_id, service_id, status, exit_status, duration_ms,
+                    stdout_tail, stderr_tail, error, created_at
+                )
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+                """,
+                (
+                    run_id,
+                    str(payload.get("task_id") or ""),
+                    str(payload.get("service_id") or ""),
+                    str(payload.get("status") or "error"),
+                    payload.get("exit_status"),
+                    payload.get("duration_ms"),
+                    str(payload.get("stdout_tail") or "")[:8000],
+                    str(payload.get("stderr_tail") or "")[:8000],
+                    str(payload.get("error") or "")[:1000],
+                    int(payload.get("created_at") or now),
+                ),
+            )
+        return {"id": run_id}
+
+    def list_service_task_runs(
+        self,
+        service_id: str | None = None,
+        task_id: str | None = None,
+        limit: int = 50,
+    ) -> list[dict[str, Any]]:
+        self.init_schema()
+        clauses: list[str] = []
+        params: list[Any] = []
+        if service_id:
+            clauses.append("service_id = ?")
+            params.append(service_id)
+        if task_id:
+            clauses.append("task_id = ?")
+            params.append(task_id)
+        where = ("WHERE " + " AND ".join(clauses)) if clauses else ""
+        params.append(int(limit))
+        with self.connect() as conn:
+            rows = conn.execute(
+                f"SELECT * FROM service_task_runs {where} ORDER BY created_at DESC LIMIT ?",
+                params,
+            ).fetchall()
+        return [
+            {
+                "id": row["id"],
+                "task_id": row["task_id"],
+                "service_id": row["service_id"],
+                "status": row["status"],
+                "exit_status": row["exit_status"],
+                "duration_ms": row["duration_ms"],
+                "stdout_tail": row["stdout_tail"],
+                "stderr_tail": row["stderr_tail"],
+                "error": row["error"],
+                "created_at": row["created_at"],
+            }
+            for row in rows
+        ]
+
 
 _store: SettingsStore | None = None
 
diff --git a/backend/tests/test_services.py b/backend/tests/test_services.py
new file mode 100644
index 0000000..d5295a6
--- /dev/null
+++ b/backend/tests/test_services.py
@@ -0,0 +1,360 @@
+"""Tests for the service registry: definitions, encryption, CRUD, cascade delete."""
+
+from __future__ import annotations
+
+from types import SimpleNamespace
+from unittest.mock import patch
+
+import pytest
+from cryptography.fernet import Fernet
+from fastapi.testclient import TestClient
+
+from media_library_viewer_api.dependencies import get_settings_store
+from media_library_viewer_api.integrations.registry import (
+    SERVICE_DEFINITIONS,
+    get_service_definition,
+    get_widget_kind,
+)
+from media_library_viewer_api.main import app
+from media_library_viewer_api.services.secrets import (
+    EncryptionKeyError,
+    decrypt_secrets,
+    decrypt_value,
+    encrypt_secrets,
+    encrypt_value,
+    get_encryption_key,
+    reset_encryption_key_cache,
+)
+from media_library_viewer_api.services.settings_store import SettingsStore
+
+TEST_KEY = Fernet.generate_key().decode()
+
+
+@pytest.fixture(autouse=True)
+def _encryption_key(monkeypatch):
+    """Provide a stable MANAGE_ENCRYPTION_KEY for every test."""
+    monkeypatch.setenv("MANAGE_ENCRYPTION_KEY", TEST_KEY)
+    reset_encryption_key_cache()
+    yield
+    reset_encryption_key_cache()
+
+
+@pytest.fixture
+def client(tmp_path):
+    """FastAPI test client with a fresh settings store and auth disabled."""
+    store = SettingsStore(tmp_path / "settings.sqlite")
+    store.ensure_defaults()
+    app.dependency_overrides[get_settings_store] = lambda: store
+    auth_settings = SimpleNamespace(auth_enabled=False)
+    with patch("media_library_viewer_api.auth.get_settings", return_value=auth_settings):
+        yield TestClient(app)
+    app.dependency_overrides.clear()
+
+
+# ---------------------------------------------------------------------------
+# Registry
+# ---------------------------------------------------------------------------
+
+
+def test_registry_contains_five_service_types():
+    assert set(SERVICE_DEFINITIONS) == {
+        "grafana",
+        "prometheus",
+        "jellyfin",
+        "nextcloud",
+        "ssh_tasks",
+    }
+
+
+def test_definitions_declare_widget_kinds():
+    assert {wk.kind for wk in get_service_definition("grafana").widget_kinds} == {"link"}
+    assert {wk.kind for wk in get_service_definition("prometheus").widget_kinds} == {"metric"}
+    assert {wk.kind for wk in get_service_definition("jellyfin").widget_kinds} == {"activity"}
+    assert get_service_definition("nextcloud").widget_kinds == []
+    assert {wk.kind for wk in get_service_definition("ssh_tasks").widget_kinds} == {"task_output"}
+
+
+def test_widget_kind_lookup():
+    assert get_widget_kind("grafana", "link") is not None
+    assert get_widget_kind("grafana", "missing") is None
+    assert get_widget_kind("unknown", "link") is None
+
+
+def test_service_config_schema_is_json_schema():
+    schema = get_service_definition("grafana").config_schema
+    assert schema["type"] == "object"
+    assert "base_url" in schema["properties"]
+
+
+# ---------------------------------------------------------------------------
+# Encryption
+# ---------------------------------------------------------------------------
+
+
+def test_encrypt_decrypt_round_trip():
+    cipher = encrypt_value("hunter2")
+    assert cipher != "hunter2"
+    assert decrypt_value(cipher) == "hunter2"
+
+
+def test_encrypt_decrypt_secrets_dict():
+    blob = encrypt_secrets({"api_key": "abc", "token": "xyz"})
+    assert decrypt_secrets(blob) == {"api_key": "abc", "token": "xyz"}
+
+
+def test_missing_encryption_key_raises(monkeypatch):
+    monkeypatch.delenv("MANAGE_ENCRYPTION_KEY", raising=False)
+    reset_encryption_key_cache()
+    with pytest.raises(EncryptionKeyError):
+        get_encryption_key()
+    reset_encryption_key_cache()
+
+
+def test_decrypt_with_wrong_key_raises(monkeypatch):
+    blob = encrypt_secrets({"api_key": "abc"})
+    monkeypatch.setenv("MANAGE_ENCRYPTION_KEY", Fernet.generate_key().decode())
+    reset_encryption_key_cache()
+    with pytest.raises(EncryptionKeyError):
+        decrypt_secrets(blob)
+    reset_encryption_key_cache()
+
+
+def test_invalid_ciphertext_raises():
+    with pytest.raises(EncryptionKeyError):
+        decrypt_value("not-a-real-token")
+
+
+# ---------------------------------------------------------------------------
+# Service type metadata endpoint
+# ---------------------------------------------------------------------------
+
+
+def test_list_service_types(client):
+    response = client.get("/api/services/types")
+    assert response.status_code == 200
+    types = {item["service_type"] for item in response.json()}
+    assert types == {"grafana", "prometheus", "jellyfin", "nextcloud", "ssh_tasks"}
+
+
+def test_service_type_includes_secret_and_widget_metadata(client):
+    response = client.get("/api/services/types")
+    grafana = next(item for item in response.json() if item["service_type"] == "grafana")
+    assert [sf["key"] for sf in grafana["secret_fields"]] == ["api_key"]
+    assert [wk["kind"] for wk in grafana["widget_kinds"]] == ["link"]
+
+
+# ---------------------------------------------------------------------------
+# CRUD
+# ---------------------------------------------------------------------------
+
+
+def _grafana_payload(**overrides):
+    payload = {
+        "service_type": "grafana",
+        "name": "Production Grafana",
+        "config": {"base_url": "https://grafana.example.com"},
+        "secrets": {"api_key": "secret-token"},
+        "enabled": True,
+    }
+    payload.update(overrides)
+    return payload
+
+
+def test_create_and_list_service(client):
+    response = client.post("/api/services/instances", json=_grafana_payload())
+    assert response.status_code == 201
+    created = response.json()
+    assert created["service_type"] == "grafana"
+    assert created["config"]["base_url"] == "https://grafana.example.com"
+    # Plaintext secrets are never returned.
+    assert "secrets" not in created
+    assert created["secrets_set"] == {"api_key": True}
+
+    response = client.get("/api/services/instances")
+    assert response.status_code == 200
+    assert len(response.json()) == 1
+
+
+def test_list_instances_filters_by_type(client):
+    client.post("/api/services/instances", json=_grafana_payload())
+    client.post(
+        "/api/services/instances",
+        json={
+            "service_type": "prometheus",
+            "name": "Prom",
+            "config": {"base_url": "http://prometheus:9090"},
+        },
+    )
+    response = client.get("/api/services/instances?service_type=grafana")
+    assert response.status_code == 200
+    assert len(response.json()) == 1
+    assert response.json()[0]["service_type"] == "grafana"
+
+
+def test_update_service_preserves_unsent_secrets(client):
+    created = client.post("/api/services/instances", json=_grafana_payload()).json()
+    # Update without sending secrets; the existing key should remain set.
+    updated = client.put(
+        f"/api/services/instances/{created['id']}",
+        json={
+            "service_type": "grafana",
+            "name": "Renamed Grafana",
+            "config": {"base_url": "https://grafana.example.com", "timeout_seconds": 10},
+        },
+    ).json()
+    assert updated["name"] == "Renamed Grafana"
+    assert updated["secrets_set"] == {"api_key": True}
+
+
+def test_update_service_can_clear_secret(client):
+    created = client.post("/api/services/instances", json=_grafana_payload()).json()
+    updated = client.put(
+        f"/api/services/instances/{created['id']}",
+        json={
+            "service_type": "grafana",
+            "name": "Production Grafana",
+            "config": {"base_url": "https://grafana.example.com"},
+            "secrets": {"api_key": ""},
+        },
+    ).json()
+    assert updated["secrets_set"] == {"api_key": False}
+
+
+def test_unknown_service_type_rejected(client):
+    response = client.post(
+        "/api/services/instances",
+        json={"service_type": "bogus", "name": "x", "config": {}},
+    )
+    assert response.status_code == 422
+
+
+def test_invalid_config_rejected(client):
+    response = client.post(
+        "/api/services/instances",
+        json={"service_type": "grafana", "name": "x", "config": {"base_url": ""}},
+    )
+    # Pydantic accepts empty string; force a real validation error via bad type.
+    response = client.post(
+        "/api/services/instances",
+        json={"service_type": "grafana", "name": "x", "config": {"timeout_seconds": "fast"}},
+    )
+    assert response.status_code == 422
+
+
+def test_unknown_secret_field_rejected(client):
+    response = client.post(
+        "/api/services/instances",
+        json={
+            "service_type": "grafana",
+            "name": "x",
+            "config": {"base_url": "https://grafana.example.com"},
+            "secrets": {"password": "leak"},
+        },
+    )
+    assert response.status_code == 422
+
+
+def test_credential_key_in_config_rejected(client):
+    response = client.post(
+        "/api/services/instances",
+        json={
+            "service_type": "grafana",
+            "name": "x",
+            "config": {"base_url": "https://grafana.example.com", "api_key": "leak"},
+        },
+    )
+    assert response.status_code == 422
+
+
+def test_update_nonexistent_returns_404(client):
+    response = client.put(
+        "/api/services/instances/missing",
+        json=_grafana_payload(id="missing"),
+    )
+    assert response.status_code == 404
+
+
+def test_update_id_mismatch_returns_400(client):
+    created = client.post("/api/services/instances", json=_grafana_payload()).json()
+    response = client.put(
+        f"/api/services/instances/{created['id']}",
+        json=_grafana_payload(id="other-id"),
+    )
+    assert response.status_code == 400
+
+
+def test_delete_service(client):
+    created = client.post("/api/services/instances", json=_grafana_payload()).json()
+    response = client.delete(f"/api/services/instances/{created['id']}")
+    assert response.status_code == 200
+    assert client.get("/api/services/instances").json() == []
+
+
+def test_delete_nonexistent_returns_404(client):
+    assert client.delete("/api/services/instances/missing").status_code == 404
+
+
+# ---------------------------------------------------------------------------
+# Cascade delete
+# ---------------------------------------------------------------------------
+
+
+def test_delete_service_cascades_to_widgets(client, tmp_path):
+    """Once widgets carry service_id (Slice 2), deleting a service removes them.
+
+    This test seeds a widget row directly with the column present to prove the
+    cascade path; the column is added defensively here so the test is meaningful
+    even before Slice 2 lands.
+    """
+    store = app.dependency_overrides[get_settings_store]()
+    service = store.upsert_service(
+        {"service_type": "grafana", "name": "Grafana", "config": {"base_url": "u"}, "enabled": True}
+    )
+
+    # Ensure the service_id column exists and seed a referencing widget.
+    with store.connect() as conn:
+        cols = {row[1] for row in conn.execute("PRAGMA table_info(dashboard_widgets)").fetchall()}
+        if "service_id" not in cols:
+            conn.execute("ALTER TABLE dashboard_widgets ADD COLUMN service_id TEXT")
+        conn.execute(
+            """
+            INSERT INTO dashboard_widgets (id, addon_id, widget_type, title, config_json,
+                                           enabled, sort_order, created_at, updated_at, service_id)
+            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+            """,
+            ("w1", "grafana", "grafana.link", "Link", "{}", 1, 0, 1, 1, service["id"]),
+        )
+
+    store.delete_service(service["id"])
+    assert store.get_service(service["id"]) is None
+    with store.connect() as conn:
+        remaining = conn.execute(
+            "SELECT COUNT(*) FROM dashboard_widgets WHERE service_id = ?",
+            (service["id"],),
+        ).fetchone()
+    assert int(remaining[0]) == 0
+
+
+# ---------------------------------------------------------------------------
+# Service task run history
+# ---------------------------------------------------------------------------
+
+
+def test_record_and_list_service_task_runs(client):
+    store = app.dependency_overrides[get_settings_store]()
+    service = store.upsert_service(
+        {"service_type": "ssh_tasks", "name": "box", "config": {"host": "h"}, "enabled": True}
+    )
+    store.record_service_task_run(
+        {
+            "task_id": "t1",
+            "service_id": service["id"],
+            "status": "success",
+            "exit_status": 0,
+            "stdout_tail": "ok",
+        }
+    )
+    runs = store.list_service_task_runs(service_id=service["id"])
+    assert len(runs) == 1
+    assert runs[0]["status"] == "success"
+    assert runs[0]["stdout_tail"] == "ok"
diff --git a/docker-compose.dev.yml b/docker-compose.dev.yml
index ff3b15e..5038064 100644
--- a/docker-compose.dev.yml
+++ b/docker-compose.dev.yml
@@ -19,6 +19,7 @@ services:
       ALERTMANAGER_WEBHOOK_URL: ${ALERTMANAGER_WEBHOOK_URL:-}
       GRAFANA_URL: ${GRAFANA_URL:-http://grafana:3000}
       PROMETHEUS_URL: ${PROMETHEUS_URL:-http://prometheus:9090}
+      MANAGE_ENCRYPTION_KEY: ${MANAGE_ENCRYPTION_KEY:?set MANAGE_ENCRYPTION_KEY in your .env}
     ports:
       - "8000:8000"
     volumes:
diff --git a/docker-compose.yml b/docker-compose.yml
index a4706b9..e2b6827 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -30,6 +30,7 @@ services:
       ALERTMANAGER_WEBHOOK_URL: ${ALERTMANAGER_WEBHOOK_URL:-}
       GRAFANA_URL: ${GRAFANA_URL:-http://grafana:3000}
       PROMETHEUS_URL: ${PROMETHEUS_URL:-http://prometheus:9090}
+      MANAGE_ENCRYPTION_KEY: ${MANAGE_ENCRYPTION_KEY:?generate one with python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"}
     volumes:
       - ${BACKEND_CACHE_DIR:-./backend-cache}:/app/backend/.cache
     restart: unless-stopped
diff --git a/openspec/changes/service-registry/apply-progress.md b/openspec/changes/service-registry/apply-progress.md
new file mode 100644
index 0000000..ea07b56
--- /dev/null
+++ b/openspec/changes/service-registry/apply-progress.md
@@ -0,0 +1,79 @@
+# Apply Progress: Runtime Service Registry
+
+**Change:** `service-registry`
+**Apply run:** PR 1 / Slice 1 — Backend service foundation
+**Date:** 2026-06-19
+
+## Completed tasks (Slice 1)
+
+- [x] 1.1 Add encryption helper (`services/secrets.py`)
+- [x] 1.2 Add integrations base classes (`integrations/base.py`)
+- [x] 1.3 Add five service definitions + registry
+- [x] 1.4 Add `services` + `service_task_runs` tables + store CRUD with cascade delete
+- [x] 1.5 Add service Pydantic models + `/api/services*` router
+- [x] 1.6 Validate `MANAGE_ENCRYPTION_KEY` on startup
+- [x] 1.7 Add backend tests (`tests/test_services.py`)
+- [x] 1.8 Verify (ruff + pytest green)
+
+## Files changed (Slice 1)
+
+### New files
+
+- `backend/src/media_library_viewer_api/integrations/__init__.py` — package marker.
+- `backend/src/media_library_viewer_api/integrations/base.py` — `ServiceConfigBase`,
+  `WidgetConfigBase`, `SecretField`, `WidgetKind`, `ServiceDefinition`, `widget_kind()`,
+  `validate_config()`.
+- `backend/src/media_library_viewer_api/integrations/{grafana,prometheus,jellyfin,nextcloud,ssh_tasks}.py`
+  — one Pydantic-config + widget-config definition per service.
+- `backend/src/media_library_viewer_api/integrations/registry.py` — closed
+  `SERVICE_DEFINITIONS` + helpers.
+- `backend/src/media_library_viewer_api/services/secrets.py` — Fernet encrypt/decrypt
+  - key validation.
+- `backend/src/media_library_viewer_api/models/services.py` — request/response models.
+- `backend/src/media_library_viewer_api/routers/services.py` — `/api/services/types`
+  - `/api/services/instances` CRUD.
+- `backend/tests/test_services.py` — 25 tests.
+
+### Modified files
+
+- `backend/src/media_library_viewer_api/services/settings_store.py` — `services` and
+  `service_task_runs` tables; service CRUD; cascade delete (defensive against the
+  not-yet-present `dashboard_widgets.service_id` column); task-run history helpers.
+- `backend/src/media_library_viewer_api/main.py` — register `services_router`;
+  validate encryption key on startup.
+- `backend/pyproject.toml` — declare `cryptography>=42.0` direct dependency.
+- `docker-compose.yml`, `docker-compose.dev.yml`, `.env.example`, `README.md` — require
+  and document `MANAGE_ENCRYPTION_KEY`.
+
+## Verification (Slice 1)
+
+```bash
+cd backend
+.venv/bin/ruff check .                                      # All checks passed
+PYTHONPATH=src .venv/bin/python -m pytest                   # 225 passed
+cd ../frontend
+npm run lint                                                # 0 errors
+npm run build                                               # success
+```
+
+Smoke: encryption round-trip OK; missing `MANAGE_ENCRYPTION_KEY` raises on startup.
+
+## Deviations from design
+
+- Service-config and widget-config schemas are derived from **Pydantic models**
+  (`model_json_schema()`), matching the user's "proper pydantic config definitions"
+  request. The design's hand-written JSON schemas were replaced by model-derived ones.
+- Service-table CRUD lives on `SettingsStore` (not a separate `service_store.py`) to
+  match how widgets/saved_tasks/ssh_keys are already handled there. This keeps a single
+  store owner for all tables.
+- The cascade delete defensively checks for `dashboard_widgets.service_id` (added in
+  Slice 2) so Slice 1 stays green without the column.
+
+## Remaining work
+
+- Slice 2: Backend widget rebind to services (add `service_id`/`widget_kind`, refactor
+  adapters to take a `ServiceRecord`, retire old widget registry, SSH run logging).
+- Slice 3: Frontend services runtime (types, API, hooks, frontend registry, service
+  pages, route swap).
+- Slice 4: Dashboard picker, settings rework, remove `grafana_url`/`prometheus_url`
+  env vars, stop default seeding, docs + changelog.