Subflag SDKs

Official OpenFeature-compliant SDKs for Subflag feature flag management.

Packages

Package	Language	Install
@subflag/openfeature-web-provider	TypeScript/JavaScript	npm install @subflag/openfeature-web-provider
@subflag/openfeature-node-provider	TypeScript/JavaScript	npm install @subflag/openfeature-node-provider
subflag-openfeature-provider	Ruby	gem install subflag-openfeature-provider
@subflag/api-types	TypeScript	npm install @subflag/api-types

Quick Start

Web/Browser (React, Vue, vanilla JS)

npm install @subflag/openfeature-web-provider @openfeature/web-sdk

import { OpenFeature } from '@openfeature/web-sdk';
import { SubflagWebProvider } from '@subflag/openfeature-web-provider';

const provider = new SubflagWebProvider({
  apiUrl: 'https://api.subflag.com',
  apiKey: 'sdk-prod-...',
});

await OpenFeature.setProviderAndWait(provider);
const client = OpenFeature.getClient();

// Flags are cached - synchronous evaluation, no network call
const enabled = client.getBooleanValue('new-feature', false);

Node.js/Server (Express, Fastify, etc.)

npm install @subflag/openfeature-node-provider @openfeature/server-sdk

import { OpenFeature } from '@openfeature/server-sdk';
import { SubflagNodeProvider } from '@subflag/openfeature-node-provider';

const provider = new SubflagNodeProvider({
  apiUrl: 'https://api.subflag.com',
  apiKey: 'sdk-prod-...',
});

await OpenFeature.setProviderAndWait(provider);
const client = OpenFeature.getClient();

// Each evaluation makes an API call - always gets latest value
const enabled = await client.getBooleanValue('new-feature', false);

Ruby (Rails, Sinatra, etc.)

gem install subflag-openfeature-provider openfeature-sdk

require "openfeature/sdk"
require "subflag"

provider = Subflag::Provider.new(
  api_url: "https://api.subflag.com",
  api_key: "sdk-prod-..."
)

OpenFeature::SDK.configure do |config|
  config.set_provider(provider)
end

client = OpenFeature::SDK.build_client
enabled = client.fetch_boolean_value(flag_key: "new-feature", default_value: false)

What is OpenFeature?

OpenFeature is an open standard for feature flag management, providing:

• Vendor-neutral API — Switch providers without changing application code
• Standardized evaluation — Consistent flag evaluation across platforms
• Ecosystem integration — Works with existing hooks, extensions, and tooling

Supported Flag Types

All providers support the five OpenFeature value types:

Type	TypeScript	Ruby
Boolean	getBooleanValue()	fetch_boolean_value()
String	getStringValue()	fetch_string_value()
Integer	getNumberValue()	fetch_integer_value()
Float	getNumberValue()	fetch_float_value()
Object	getObjectValue()	fetch_object_value()

Getting Started with Subflag

1. Sign up at subflag.com
2. Create a project with environments (dev, staging, production)
3. Create feature flags and configure variants
4. Generate an API key (Settings → Applications → Create)
5. Install an SDK and start evaluating flags

API keys follow the format sdk-{environment}-{app-name}-{random} and are scoped to a specific project and environment.

Documentation

• Subflag Documentation
• OpenFeature Specification

Development

# Install dependencies
pnpm install

# Build all packages
pnpm build

# Run tests
pnpm test

# Type check
pnpm typecheck

Project Structure

packages/
├── openfeature-web-provider/     # Browser/client-side provider
├── openfeature-node-provider/    # Node.js server provider
├── openfeature-ruby-provider/    # Ruby provider
└── api-types/                    # Shared TypeScript types

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

MIT