Vue SDK - API reference

Registration

`provideNexus(app, config): Promise<NexusClient>`

Creates the client, registers it on the application, opens the live stream, and wraps app.unmount so the client is closed on teardown. await it before app.mount(). Throws NexusConfigError for an invalid option and NexusInitError if the first sync fails.

`createNexusPlugin(config): Plugin`

The app.use() form. Registers its handle synchronously during install(), so every component resolves it - including one that mounts before the initial sync finishes. Value composables return their defaults until the client lands, then update reactively. An initialisation failure is not thrown; it is exposed through useNexusError().

Value composables

Each returns a ComputedRef. They register no listener of their own, so they are safe to call from a store, from module scope, or after the first await in an async setup().

Composable	Value	Before the client is ready
`useConfig<T>(key)`	`T \| undefined`	`undefined`
`useFlag(key, defaultValue?)`	`boolean`	`defaultValue`
`useNexusKind()`	`string`	`""`
`useNexusSyncedAt()`	`Date \| null`	`null`
`useNexusBillingOverdue()`	`boolean`	`false`
`useNexusStreamStatus()`	`{ connected, state }`	`{ connected: false, state: 'idle' }`

state is one of idle, connecting, connected, reconnecting, polling.

Readiness

Composable	Returns
`useNexusReady()`	`ComputedRef<boolean>` - `true` once the client is usable
`useNexusError()`	`ComputedRef<Error \| null>` - the initialisation failure, plugin path only
`useNexusClient()`	`ComputedRef<NexusClient \| null>`

Actions

`useNexus(): NexusClient`

The client itself. Throws when the SDK is not registered on the application, and

on the plugin path - while the initial sync is still running. Gate on useNexusReady(), or read values through the composables, which handle the not-ready state themselves.

`useNexusSync(): () => Promise<void>`

Refreshes the cache. Concurrent calls share one request. Resolves without doing anything while the client is still initialising.

`useEvaluateAB(): (keys, userId, attributes?: Record<string, string>) => Promise<Record<string, boolean>>`

Evaluates flags through the AB Testing endpoint. Always a live call. Rejects while the client is not ready, and with NexusAbAddonNotAvailableError when the add-on is not active.

`NEXUS_HANDLE`

The injection key for the handle the SDK provides:

interface NexusHandle {
  client: ShallowRef<NexusClient | null>;
  version: ShallowRef<number>;
  error: ShallowRef<Error | null>;
}

A handle rather than the client itself, for two reasons. It is available synchronously, so the plugin form can provide something real at install time. And the version ref is bumped by a single change listener owned by the handle, so no composable registers one of its own - which is what makes them safe where Vue has no component instance to attach a lifecycle hook to. You rarely need it; the composables are the interface.

`NexusClient`

Member	Returns
`getConfig(key)` / `getConfigAs<T>(key)`	`unknown` / `T \| undefined`
`getFlag(key, defaultValue?)`	`boolean`
`hasFlag(key)`	`boolean` - whether the service defines the flag at all, which `getFlag` cannot express
`getFlagKeys()`	`string[]` - every flag key in the current snapshot
`sync()`	`Promise<void>`, coalesced
`evaluateAB(keys, userId, attributes?, signal?)`	`Promise<Record<string, boolean>>`; `attributes` is `Record<string, string>` - the endpoint compares cohort values as strings
`subscribe(listener)`	an unsubscribe function; fires on any observable change
`connectStream()` / `disconnectStream()`	the live stream
`close()`	final; releases the stream, every timer and every listener
`detectedKeyType`, `kind`, `syncedAt`, `billingOverdue`, `quarantinedUntil`	current state
`streamConnected`, `streamState`, `isClosed`	current state

Types and constants

NexusConfig, NexusHandle, NexusStreamStatus, NexusLogger, NexusLogFields, NexusStreamObserver, NexusStreamState, NexusChangeListener, PublicApiKey. assertPublicKey(key) narrows a string to PublicApiKey, throwing if it is not a public key - the same check the client applies to apiKey. NOOP_LOGGER, NOOP_STREAM_OBSERVER, FALLBACK_REASON_MAX_ERRORS, FALLBACK_REASON_RATE_LIMITED, FALLBACK_REASON_TRANSPORT.

Errors

See Error handling.

Changed in v0.11.0

Was	Now
`NEXUS_CLIENT_KEY` (the client)	`NEXUS_HANDLE` (the handle)
`useNexusSyncedAt(): ComputedRef<Date>`	`ComputedRef<Date \| null>`
`useSecret()`	removed - a public key could only ever return `undefined`

Changed in v0.16.0

Was	Now
`getSecret(key)` on `NexusClient`	removed - a public key could only ever throw. See Error handling.

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

Vue SDK - API reference

Registration

`provideNexus(app, config): Promise<NexusClient>`

`createNexusPlugin(config): Plugin`

Value composables

Readiness

Actions

`useNexus(): NexusClient`

`useNexusSync(): () => Promise<void>`

`useEvaluateAB(): (keys, userId, attributes?: Record<string, string>) => Promise<Record<string, boolean>>`

`NEXUS_HANDLE`

`NexusClient`

Types and constants

Errors

Changed in v0.11.0

Changed in v0.16.0

​Registration

​provideNexus(app, config): Promise<NexusClient>

​createNexusPlugin(config): Plugin

​Value composables

​Readiness

​Actions

​useNexus(): NexusClient

​useNexusSync(): () => Promise<void>

​useEvaluateAB(): (keys, userId, attributes?: Record<string, string>) => Promise<Record<string, boolean>>

​NEXUS_HANDLE

​NexusClient

​Types and constants

​Errors

​Changed in v0.11.0

​Changed in v0.16.0

Registration

`provideNexus(app, config): Promise<NexusClient>`

`createNexusPlugin(config): Plugin`

Value composables

Readiness

Actions

`useNexus(): NexusClient`

`useNexusSync(): () => Promise<void>`

`useEvaluateAB(): (keys, userId, attributes?: Record<string, string>) => Promise<Record<string, boolean>>`

`NEXUS_HANDLE`

`NexusClient`

Types and constants

Errors

Changed in v0.11.0

Changed in v0.16.0