Plugin Guide

A camera.ui plugin is a Python package the host loads at runtime to extend cameras with new capabilities — a detection model, a vendor camera integration, a notifier, a smart-home bridge. This guide is the single reference for shipping one. You should be comfortable with modern Python (3.11+) and have the SDK installed (pip install camera-ui-sdk).

1. Plugin anatomy

A plugin is a folder with two files the host expects:

• contract.py — the manifest. A static object describing what the plugin is.
• main.py — the runtime. A class extending BasePlugin, returned by a __main__() factory.

The minimal runnable plugin:

# contract.py
from camera_ui_sdk import PluginContract, PluginRole

contract: PluginContract = {
    "name": "My Plugin",
    "role": PluginRole.SensorProvider,
    "provides": [],
    "consumes": [],
    "interfaces": [],
}

# main.py
from camera_ui_sdk import BasePlugin, CameraDevice


class MyPlugin(BasePlugin):
    async def configureCameras(self, cameraDevices: list[CameraDevice]) -> None: ...
    async def onCameraAdded(self, camera: CameraDevice) -> None: ...
    async def onCameraReleased(self, cameraId: str) -> None: ...


def __main__() -> type[MyPlugin]:
    return MyPlugin

The host instantiates the class with three arguments: a LoggerService, a PluginAPI, and a typed DeviceStorage. Everything else — sensors, discovery, schemas — is opt-in.

2. The contract

PluginContract is the static manifest the host reads before starting the plugin. The fields:

• name — stable identifier; doubles as log prefix and storage namespace.
• role — what the plugin does at the highest level (see table below).
• provides — sensor types the plugin attaches to cameras (e.g. [SensorType.Motion]).
• consumes — sensor types the plugin reads from other plugins.
• interfaces — capability flags (DiscoveryProvider, Notifier, detection types, …).
• pythonVersion (optional) — "3.11" or "3.12". The host picks a matching interpreter from its venv pool. Ignored by Node / Go plugins.
• dependencies (optional) — extra PyPI packages installed into the plugin's venv at adoption time.

Role	Use when
SensorProvider	You add detection or smart-home sensors to existing cameras (motion plugin, classifier, contact sensor).
CameraController	You bring your own cameras and own their streams (RTSP, ONVIF, vendor SDK), but produce no sensors.
CameraAndSensorProvider	You bring your own cameras AND want to attach sensors to them. Most vendor integrations land here.
Hub	Cloud-service integration that owns its cameras end-to-end via a vendor account, OR a bridge plugin that consumes other plugins' sensors and forwards them to an external system (HomeKit, MQTT, automations) or implements a Notifier.

Examples:

from camera_ui_sdk import PluginInterface, PluginRole, SensorType

# Detection plugin attaching motion sensors
{
    "name": "My Motion",
    "role": PluginRole.SensorProvider,
    "provides": [SensorType.Motion],
    "consumes": [],
    "interfaces": [PluginInterface.MotionDetection],
}

# ONVIF-style integration with discovery
{
    "name": "ACME Cameras",
    "role": PluginRole.CameraAndSensorProvider,
    "provides": [SensorType.Motion],
    "consumes": [],
    "interfaces": [PluginInterface.DiscoveryProvider],
}

# HomeKit bridge consuming sensor state from other plugins
{
    "name": "HomeKit Bridge",
    "role": PluginRole.Hub,
    "provides": [],
    "consumes": [SensorType.Motion, SensorType.Doorbell],
    "interfaces": [],
}

The SDK also carries a plugin protocol level (PROTOCOL_LEVEL). The CLI stamps the level your plugin was built against into the bundle, and the server refuses to start a plugin whose level it does not support, telling the user whether the plugin or the server needs an update. You never set it yourself: rebuilding against the current SDK is all it takes.

3. The plugin class

BasePlugin[StorageT] is generic over your storage shape so self.storage.values["X"] is typed. Its constructor takes the three host-injected dependencies in order: logger, api, storage.

from typing import TypedDict

from camera_ui_sdk import API_EVENT, BasePlugin, CameraDevice, DeviceStorage, LoggerService, PluginAPI


class MyStorage(TypedDict):
    pollIntervalSec: int


class MyPlugin(BasePlugin[MyStorage]):
    def __init__(self, logger: LoggerService, api: PluginAPI, storage: DeviceStorage[MyStorage]) -> None:
        super().__init__(logger, api, storage)
        self.state: dict[str, MyCameraState] = {}
        self.api.on(API_EVENT.SHUTDOWN, self._shutdown)

    async def configureCameras(self, cameraDevices: list[CameraDevice]) -> None:
        for camera in cameraDevices:
            await self._attach(camera)

    async def onCameraAdded(self, camera: CameraDevice) -> None:
        await self._attach(camera)

    async def onCameraReleased(self, cameraId: str) -> None:
        if state := self.state.pop(cameraId, None):
            state.dispose()

    async def _attach(self, camera: CameraDevice) -> None: ...
    def _shutdown(self) -> None: ...  # drop timers, close sockets

Things to internalize:

• configureCameras runs once at startup with the cameras already assigned to the plugin. A raised exception aborts plugin startup.
• onCameraAdded runs whenever the user assigns a new camera at runtime. Set up the same per-camera state as configureCameras.
• onCameraReleased runs when a camera is removed or reassigned. Drop timers, close vendor sessions.
• A dict[str, X] keyed by camera.id is the conventional pattern for per-camera state — cheap to look up, trivial to clean up.
• API_EVENT.SHUTDOWN fires when the host tears the plugin down (reload, server stop). Listeners must release everything synchronously enough for the host to stop the process. There is also API_EVENT.FINISH_LAUNCHING, fired once after configureCameras returns — useful for kicking off background work that should wait until the camera set is stable.

4. Sensors

A sensor is the smallest smart-home unit in camera.ui. Detection sensors push results from analyzing video; control sensors expose user-toggleable hardware (lights, sirens, locks); event sensors fire one-shot triggers (doorbell).

Every sensor is a persisted entity of its own. The plugin supplies the durable identity, everything else belongs to the user: camera assignments, display name and whether the sensor is exported to consumers. There are two ways to register one:

• camera.addSensor(sensor) — the sensor belongs to this camera's hardware (spotlight, siren, battery, PTZ). The host locks the assignment to the camera; users cannot re-assign it.
• api.sensorManager.addSensor(sensor) — standalone device (smart plug, hub, imported smart-home device). The user assigns it to zero or more cameras in the UI.

Either way, pass a native_id (e.g. the upstream device id) in the constructor so the host can reconcile the sensor across restarts by (pluginId, nativeId). Without it, identity falls back to (type, name) and a rename creates a new sensor.

For detection, subclass the matching *DetectorSensor and implement the detect method. The host pushes one frame at the configured rate:

from camera_ui_sdk import MotionDetectorSensor, MotionResult, VideoFrameData


class MyMotionSensor(MotionDetectorSensor):
    def __init__(self) -> None:
        super().__init__("My Motion")

    async def detectMotion(self, frame: VideoFrameData) -> MotionResult:
        # analyze frame["data"], return detections
        return {"detected": False, "detections": []}

Then attach it from the plugin's _attach() helper:

sensor = MyMotionSensor()
await camera.addSensor(sensor)

Other detector base classes follow the same shape. ObjectDetectorSensor.detectObjects(frame) takes a single frame; FaceDetectorSensor.detectFaces(frames), LicensePlateDetectorSensor.detectLicensePlates(frames), ClassifierDetectorSensor.detectClassifications(frames), ClipDetectorSensor.detectEmbeddings(frames) all take a batch (list[VideoFrameData]); AudioDetectorSensor.detectAudio(audio) takes one AudioFrameData. The frame-based detectors also expose an abstract modelSpec property — return the input dimensions and (for classifier) the trigger labels. Smart-home sensors expose semantic methods instead — LightControl gives you setOn() / setOff() / setBrightness(value), ContactSensor gives you setDetected(value), DoorbellTrigger gives you trigger(). You construct them, register them, and then call those methods when your hardware reports a change.

A standalone sensor works exactly the same, it just goes through the sensor manager instead of a camera:

from camera_ui_sdk import LockControl

lock = LockControl("Front Door", native_id="lock.front_door")
await self.api.sensorManager.addSensor(lock)

Every sensor also has a lifecycle pair: on_start() runs once the sensor is registered and its storage is ready — start pollers, subscriptions, timers there. on_stop() is the counterpart and runs on removal, plugin shutdown and cleanup. Both may be plain def or async def:

class PollingContact(ContactSensor):
    def on_start(self) -> None:
        self._task = asyncio.create_task(self._poll_loop())

    def on_stop(self) -> None:
        self._task.cancel()

removeSensor only unregisters the runtime instance — the persisted entity stays and shows as disconnected until the user deletes it in the UI. The host removes camera-bound sensors automatically when a camera is released; your onCameraReleased hook just needs to drop your reference.

5. Storage and configuration schema

User-facing settings live in storage. Storage is split into two scopes — plugin-level and sensor-level — each with its own storage_schema property that returns a list of JSON schema dicts. The host renders the schemas as form fields and persists the values; you read them via self.storage.values["X"] (or await self.storage.getValue("X", default)).

Plugin-level schemas appear on the plugin's settings page. Override the property on your BasePlugin subclass.

from camera_ui_sdk import JsonSchema


class MyPlugin(BasePlugin[MyStorage]):
    @property
    def storage_schema(self) -> list[JsonSchema]:
        return [
            {
                "type": "number",
                "key": "pollIntervalSec",
                "title": "Poll interval (seconds)",
                "description": "How often background work runs",
                "defaultValue": 30,
                "minimum": 5,
                "maximum": 300,
                "step": 5,
                "store": True,
                "required": True,
                "onSet": self._on_interval_changed,
            },
        ]

    async def _on_interval_changed(self, new_value: object, old_value: object) -> None:
        self.logger.log(f"Poll interval {old_value} -> {new_value}")
        self._reschedule()

Sensor-level schemas appear on the camera detail page next to that one sensor. Override the property on your Sensor subclass.

from typing import Literal, TypedDict

from camera_ui_sdk import JsonSchema, MotionDetectorSensor, MotionResult, VideoFrameData


class ConfigurableMotionStorage(TypedDict):
    sensitivity: int
    mode: Literal["fast", "accurate"]


class ConfigurableMotion(MotionDetectorSensor[ConfigurableMotionStorage]):
    @property
    def storage_schema(self) -> list[JsonSchema]:
        return [
            {
                "type": "number",
                "key": "sensitivity",
                "title": "Sensitivity",
                "description": "Higher = trigger on smaller motion",
                "defaultValue": 50,
                "minimum": 0, "maximum": 100, "step": 1,
                "store": True,
                "onSet": lambda *_: self._reconfigure(),
            },
            {
                "type": "string",
                "key": "mode",
                "title": "Mode",
                "description": "Trade-off between speed and accuracy",
                "defaultValue": "fast",
                "enum": ["fast", "accurate"],
                "store": True,
            },
            {
                "type": "button",
                "key": "reset",
                "title": "Reset to defaults",
                "description": "Restore sensitivity / mode",
                "color": "danger",
                "onSet": self._reset_defaults,
            },
        ]

    async def _reset_defaults(self) -> None:
        await self.storage.setValue("sensitivity", 50)
        await self.storage.setValue("mode", "fast")

    async def detectMotion(self, frame: VideoFrameData) -> MotionResult:
        sensitivity = self.storage.values.get("sensitivity", 50)
        _ = sensitivity
        return {"detected": False, "detections": []}

    def _reconfigure(self) -> None: ...  # re-warm caches

Field types:

• number — slider/input with optional minimum, maximum, step.
• string — text input; add "enum": [...] for a dropdown, "format": "password" to mask, "format": "image" / "qrCode" for media display.
• boolean — toggle.
• button — fires onSet() on click; stores no value. Useful for actions like "Test connection" or "Reset".

onSet(new_value, old_value) runs after the host has persisted the new value. Use it to re-warm caches, restart sessions, or anything else that depends on the changed setting. It can be sync or async, but the host doesn't block UI on it — keep work scoped to the plugin.

For the full schema reference (conditional visibility, submit handlers with toast feedback, array fields), see camera_ui_sdk/storage/__init__.py in the SDK.

6. Optional interfaces

BasePlugin covers the lifecycle. Specific capabilities are unlocked by implementing one of the optional interfaces and listing it in contract["interfaces"]. The rest of this section shows each one with a working snippet.

6.1 DiscoveryProvider

Let users scan and adopt cameras. Three methods: onDiscoverCameras returns adoption candidates, onGetCameraSettings returns the schema for the adoption form, onAdoptCamera resolves the form values into a CameraConfig for the host to persist. Available only for camera-controlling roles (CameraController, CameraAndSensorProvider).

from urllib.parse import quote
from typing import TypedDict

from camera_ui_sdk import (
    API_EVENT, BasePlugin, CameraConfig, CameraDevice, DeviceStorage,
    DiscoveredCamera, DiscoveryProvider, JsonSchemaWithoutCallbacks,
    LoggerService, PluginAPI,
)


class FakeDevice(TypedDict):
    id: str
    name: str
    manufacturer: str
    model: str
    host: str


FAKE_DEVICES: list[FakeDevice] = [
    {"id": "fake-001", "name": "Front Door", "manufacturer": "ACME", "model": "X1", "host": "192.0.2.10"},
]


class CameraProvider(BasePlugin, DiscoveryProvider):
    def __init__(self, logger: LoggerService, api: PluginAPI, storage: DeviceStorage) -> None:
        super().__init__(logger, api, storage)
        self.cameras: dict[str, CameraDevice] = {}
        self.api.on(API_EVENT.SHUTDOWN, self._on_shutdown)

    async def configureCameras(self, cameraDevices: list[CameraDevice]) -> None:
        for c in cameraDevices:
            self.cameras[c.id] = c

    async def onCameraAdded(self, camera: CameraDevice) -> None:
        self.cameras[camera.id] = camera

    async def onCameraReleased(self, cameraId: str) -> None:
        self.cameras.pop(cameraId, None)

    def _on_shutdown(self) -> None:
        self.cameras.clear()

    async def onDiscoverCameras(self) -> list[DiscoveredCamera]:
        adopted = {c.nativeId for c in self.cameras.values()}
        return [
            {"id": d["id"], "name": d["name"], "manufacturer": d["manufacturer"], "model": d["model"]}
            for d in FAKE_DEVICES if d["id"] not in adopted
        ]

    async def onGetCameraSettings(self, camera: DiscoveredCamera) -> list[JsonSchemaWithoutCallbacks]:
        return [
            {"type": "string", "key": "username", "title": "Username", "description": "", "required": True},
            {"type": "string", "key": "password", "title": "Password", "description": "",
             "format": "password", "required": True},
        ]

    async def onAdoptCamera(self, camera: DiscoveredCamera, cameraSettings: dict[str, object]) -> CameraConfig:
        device = next((d for d in FAKE_DEVICES if d["id"] == camera["id"]), None)
        if device is None:
            raise ValueError(f"Unknown device: {camera['id']}")
        u = quote(str(cameraSettings.get("username", "")))
        p = quote(str(cameraSettings.get("password", "")))
        return {
            "name": device["name"],
            "nativeId": device["id"],
            "info": {"manufacturer": device["manufacturer"], "model": device["model"]},
            "sources": [{
                "name": "main",
                "role": "high-resolution",
                "urls": [f"rtsp://{u}:{p}@{device['host']}/stream0"],
                "useForSnapshot": True,
                "hotMode": True,
                "preload": True,
            }],
        }

For asynchronous discovery (cloud OAuth callbacks, mDNS bursts), you can also push candidates directly into the UI without waiting for the next poll: await self.api.deviceManager.pushDiscoveredCameras([...]).

6.2 NotifierInterface

Register as a notification target so the host's NotificationManager can dispatch through you. The plugin owns its device list — the manager queries through these methods rather than maintaining a shared registry.

import uuid
from datetime import datetime, timezone
from typing import Any

from camera_ui_sdk import (
    API_EVENT, BasePlugin, CameraDevice, DeviceStorage, LoggerService,
    Notification, NotifierDevice, NotifierInterface, PluginAPI,
)


class MyNotifier(BasePlugin, NotifierInterface):
    def __init__(self, logger: LoggerService, api: PluginAPI, storage: DeviceStorage) -> None:
        super().__init__(logger, api, storage)
        self.devices: list[NotifierDevice] = []
        self.api.on(API_EVENT.SHUTDOWN, lambda: self.devices.clear())

    async def configureCameras(self, cameraDevices: list[CameraDevice]) -> None: ...
    async def onCameraAdded(self, camera: CameraDevice) -> None: ...
    async def onCameraReleased(self, cameraId: str) -> None: ...

    async def get_devices(self, owner_user_id: str) -> list[NotifierDevice]:
        return [d for d in self.devices if d["ownerUserId"] == owner_user_id]

    async def get_device(self, device_id: str) -> NotifierDevice | None:
        return next((d for d in self.devices if d["id"] == device_id), None)

    async def send_notification(self, device_id: str, n: Notification) -> None:
        device = next((d for d in self.devices if d["id"] == device_id), None)
        if not device or not device["active"]:
            return
        self.logger.log(f"[{device['name']}] {n['title']}: {n.get('body', '')}")

    async def register_device(self, owner_user_id: str, input: dict[str, Any]) -> NotifierDevice:
        device: NotifierDevice = {
            "id": str(uuid.uuid4()),
            "ownerUserId": owner_user_id,
            "type": str(input.get("type", "mobile")),
            "name": str(input.get("name", "Unnamed device")),
            "active": True,
        }
        self.devices.append(device)
        return device

    async def revoke_device(self, device_id: str) -> None:
        self.devices = [d for d in self.devices if d["id"] != device_id]

    async def update_device(self, device_id: str, patch: dict[str, Any]) -> NotifierDevice | None:
        device = next((d for d in self.devices if d["id"] == device_id), None)
        if device is None:
            return None
        if isinstance(patch.get("name"), str):
            device["name"] = patch["name"]
        if isinstance(patch.get("active"), bool):
            device["active"] = patch["active"]
        return device

Notification.tag is a collapse key (e.g. "motion:cam-1"). The host uses it to replace an older entry with the same tag in the in-app notification list. Delivery is not throttled: every publish reaches your notifier, so map the tag to a platform collapse-id if you want the same behavior on the device. Notification.severity is Severity.Info | Warn | Error | Critical; map Critical to whatever DND-bypass mechanism your platform offers.

Note: notifier methods are snake_case (get_devices, send_notification, …) — the rest of the SDK uses camelCase for parity with the Node and Go SDKs, but the notifier surface is intentionally Pythonic.

6.3 Detection interfaces

The seven detection capabilities follow a single pattern. Each interface has:

• A required test* method invoked by the UI when the user uploads a clip/image and clicks "Test" — it accepts raw media bytes plus metadata and returns the same result shape the per-frame detector would.
• An optional pre-processed detect* method invoked by automations and benchmarks — it accepts an already-decoded frame.
• An optional *Settings() method that returns a schema for the detection configuration UI.

All seven (MotionDetectionInterface, ObjectDetectionInterface, AudioDetectionInterface, FaceDetectionInterface, LicensePlateDetectionInterface, ClassifierDetectionInterface, ClipDetectionInterface) share that shape. ClipDetectionInterface additionally requires getTextEmbedding(text) for semantic search.

Motion as a worked example:

from typing import Any

from camera_ui_sdk import (
    BasePlugin, JsonSchema, MotionDetectionInterface,
    MotionDetectionPluginResponse, VideoFrameData,
)


class MotionPlugin(BasePlugin, MotionDetectionInterface):
    # ... lifecycle methods omitted ...

    async def testMotionDetection(
        self, video_data: bytes, config: dict[str, Any],
    ) -> MotionDetectionPluginResponse | None:
        detections = await self._run_on_encoded_clip(video_data)
        return {"detected": len(detections) > 0, "detections": detections}

    async def detectMotion(
        self, frames: list[VideoFrameData], config: dict[str, Any] | None = None,
    ) -> MotionDetectionPluginResponse | None:
        detections = await self._run_on_frames(frames)
        return {"detected": len(detections) > 0, "detections": detections}

    async def motionDetectionSettings(self) -> list[JsonSchema] | None:
        return [
            {"type": "number", "key": "minArea", "title": "Min area (%)", "description": "",
             "defaultValue": 1, "minimum": 0, "maximum": 100, "step": 1, "store": True},
        ]

    async def _run_on_encoded_clip(self, v: bytes) -> list: return []
    async def _run_on_frames(self, f: list[VideoFrameData]) -> list: return []

The image-based detection interfaces (ObjectDetectionInterface, FaceDetectionInterface, LicensePlateDetectionInterface, ClassifierDetectionInterface, ClipDetectionInterface) take an extra metadata: ImageMetadata argument with width / height on the test* method. The audio interface takes metadata: AudioMetadata with the mimeType. Otherwise the wiring is identical to the motion example above — add the matching PluginInterface.X flag to the contract and implement the test* / optional detect* / optional settings trio.

A detection plugin almost always implements both halves: the appropriate *DetectorSensor subclass (Section 4) for the live pipeline, AND the matching *DetectionInterface here for UI test dialogs and ad-hoc benchmarks.

7. Logging

self.logger is a LoggerService. The methods are log, warn, error, success, debug, trace, and attention — each accepts a list of arguments joined with spaces by the host. debug and trace are gated by host log level.

self.logger.log("Plugin started")
self.logger.success(f"Connected to vendor cloud as {user}")
self.logger.warn("Falling back to substream")
self.logger.error("Adopt failed:", err)

Every CameraDevice exposes camera.logger — same interface, but the output is prefixed with the camera name. Prefer it over self.logger whenever the message is about a specific camera:

async def onCameraAdded(self, camera: CameraDevice) -> None:
    camera.logger.log("attached")

8. Consuming sensors from other plugins

Bridge plugins (HomeKit, MQTT, automations) don't look at cameras to find sensors — they receive a consumable view: every sensor whose type is listed in contract["consumes"] and that the user exported. The host delivers it through three optional BasePlugin hooks:

• configureSensors(sensors) — once at startup with the view known at that point.
• onSensorAdded(sensor) — a sensor entered the view at runtime: it was created, became exposed, or its type became consumable.
• onSensorReleased(sensorId) — a sensor permanently left the view: deleted or unexposed. Plugin connectivity does NOT fire this; watch sensor.onConnectedChanged for that.

Each sensor arrives as a SensorLike: a read-only view with type, displayName, connected, assignedCameraIds, assignmentLocked, plus getValue() / getValues() and the observables onPropertyChanged, onConnectedChanged, onAssignmentChanged. Consumers decide rendering purely from that data — e.g. a light with assignmentLocked is camera hardware, an unassigned contact sensor is a standalone device.

A complete Hub consumer that reacts to motion state and connectivity:

from typing import Any

from camera_ui_sdk import (
    API_EVENT, BasePlugin, CameraDevice, DeviceStorage, Disposable,
    LoggerService, PluginAPI, SensorLike, SensorType,
)


class HubConsumer(BasePlugin):
    def __init__(self, logger: LoggerService, api: PluginAPI, storage: DeviceStorage) -> None:
        super().__init__(logger, api, storage)
        self.subs: dict[str, list[Disposable]] = {}
        self.api.on(API_EVENT.SHUTDOWN, self._dispose_all)

    async def configureCameras(self, cameraDevices: list[CameraDevice]) -> None: ...
    async def onCameraAdded(self, camera: CameraDevice) -> None: ...
    async def onCameraReleased(self, cameraId: str) -> None: ...

    async def configureSensors(self, sensors: list[SensorLike]) -> None:
        for sensor in sensors:
            self._bind(sensor)

    async def onSensorAdded(self, sensor: SensorLike) -> None:
        self._bind(sensor)

    async def onSensorReleased(self, sensorId: str) -> None:
        for sub in self.subs.pop(sensorId, []):
            sub.dispose()

    def _bind(self, sensor: SensorLike) -> None:
        def on_property(event: dict[str, Any]) -> None:
            if sensor.type == SensorType.Motion and event["property"] == "detected" and event["value"]:
                self.logger.log(f"{sensor.displayName}: motion started")

        def on_connected(connected: bool) -> None:
            self.logger.log(f"{sensor.displayName}: {'online' if connected else 'offline'}")

        props = sensor.onPropertyChanged.subscribe(on_property)
        conn = sensor.onConnectedChanged.subscribe(on_connected)
        self.subs[sensor.id] = [props, conn]

    def _dispose_all(self) -> None:
        for subs in self.subs.values():
            for sub in subs:
                sub.dispose()
        self.subs.clear()

Two things to notice:

• The bridge keeps one list[Disposable] per sensor and disposes it in onSensorReleased. subscribe() keeps the subscription alive until you call .dispose().
• The bind happens in both configureSensors AND onSensorAdded for sensors that show up after startup. Same shape as the camera lifecycle.

For direct plugin-to-plugin RPC (e.g. asking a face plugin to compute embeddings on demand), use api.coreManager.connectToPlugin(name). It returns a typed proxy of the target plugin including any optional interfaces it implements:

face = await self.api.coreManager.connectToPlugin("Face Plugin")
if face is not None:
    result = await face.testFaceDetection(jpeg_bytes, {"width": 640, "height": 480}, {})

Use await self.api.coreManager.getPluginsByInterface(PluginInterface.FaceDetection) to discover candidate plugins by capability rather than by name.

9. Common pitfalls

• Always release per-camera state in onCameraReleased. Timers, vendor sessions, RTP sockets, Disposables from subscribe() — drop them all. Leaking them keeps the camera object alive forever and prevents reassignment from working.
• Don't block in configureCameras. It runs on the host's startup path; a slow vendor handshake delays every other plugin. Do the network work in API_EVENT.FINISH_LAUNCHING instead.
• Don't import from camera_ui_sdk.internal. The internal subpackage exposes types the host uses to talk to plugins via RPC. The shapes there are not part of the stable public surface and may change without notice.
• Don't construct sensors in __init__. The host hasn't finished wiring up api / storage until super().__init__() returns and configureCameras is called. Construct sensors inside the lifecycle hooks.
• Don't log frame data. Detection paths run dozens of times per second per camera. Use logger.debug / logger.trace (host-gated) for anything per-frame, and prefer aggregated counters over per-event logs.

10. Next steps

For complete production plugins to read alongside this guide, see plugins/ in the camera.ui repo. They cover everything documented above — discovery, notifier, detection, hub bridges — wired into a real UI.

For the full module-by-module surface, browse the API Reference — it's auto-generated from the SDK source and stays in sync with whatever version of camera-ui-sdk you have installed.