@code-signal/signal

Feature flag management SDK for modern web applications.

Ship faster, reduce risk, and control every release — without redeployment.

Features

• Server-side evaluation — local flag evaluation for zero-latency (Node.js / SSR)
• Client-side sync — lightweight browser client with real-time updates via WebSocket
• React bindings — hooks and context provider out of the box
• OpenFeature support — drop-in providers for the OpenFeature standard
• A/B testing — built-in variant management and conversion tracking
• Type-safe flag keys — define flags as typed constants, no magic strings

Installation

npm install @code-signal/signal

Quick start

Server-side (Node.js / SSR)

import { initializeServer, getServerInstance } from '@code-signal/signal';

await initializeServer({
  apiKey: process.env.SIGNAL_API_KEY,
  projectId: process.env.SIGNAL_PROJECT_ID,
  apiUrl: process.env.SIGNAL_API_URL,
});

const signal = getServerInstance();
const enabled = await signal.isEnabled('my-feature', { userId: 'user-123' });

Client-side (browser)

import { initializeClient, getClientInstance } from '@code-signal/signal';

await initializeClient({
  apiKey: process.env.NEXT_PUBLIC_SIGNAL_API_KEY,
  projectId: process.env.NEXT_PUBLIC_SIGNAL_PROJECT_ID,
  apiUrl: process.env.NEXT_PUBLIC_SIGNAL_API_URL,
  websocket: { enabled: true },
});

const signal = getClientInstance();
const enabled = await signal.isEnabled('my-feature');

React

import { FeatureFlagsProvider, useFeatureFlag } from '@code-signal/signal';

function App() {
  return (
    <FeatureFlagsProvider config={{ apiKey: '...', projectId: '...', apiUrl: '...' }}>
      <MyComponent />
    </FeatureFlagsProvider>
  );
}

function MyComponent() {
  const { enabled, loading } = useFeatureFlag('my-feature');

  if (loading) return null;
  return enabled ? <NewUI /> : <OldUI />;
}

OpenFeature

import { OpenFeature } from '@openfeature/server-sdk';
import { SignalServerProvider } from '@code-signal/signal';

await OpenFeature.setProviderAndWait(
  new SignalServerProvider({
    apiKey: process.env.SIGNAL_API_KEY,
    projectId: process.env.SIGNAL_PROJECT_ID,
    apiUrl: process.env.SIGNAL_API_URL,
  })
);

const client = OpenFeature.getClient();
const enabled = await client.getBooleanValue('my-feature', false);

Type-safe flag keys

Define your flags once and reference them safely across your codebase:

import { createFeatureFlag } from '@code-signal/signal';

export const FLAGS = {
  NEW_CHECKOUT: createFeatureFlag('new-checkout'),
  DARK_MODE: createFeatureFlag('dark-mode'),
} as const;

// Usage
const enabled = await signal.isEnabled(FLAGS.NEW_CHECKOUT);

Real-time updates

Enable WebSocket sync to receive flag changes instantly without polling:

await initializeClient({
  // ...
  websocket: { enabled: true },
  onUpdate: (flags) => console.log('Flags updated:', flags),
});

Configuration

| Option | Type | Default | Description | |---|---|---|---| | apiKey | string | required | Your Signal API key (sig_live_...) | | projectId | string | required | Your Signal project ID | | apiUrl | string | required | Signal API base URL | | environment | string | production | Target environment | | syncInterval | number | 30000 | Polling interval in ms (server) | | websocket.enabled | boolean | false | Enable real-time WebSocket sync | | analytics.enabled | boolean | false | Enable analytics tracking | | abTesting.enabled | boolean | false | Enable A/B testing |

License

MIT