Description

Currently, in the OpenFeature React SDK (@openfeature/react-sdk), the flagKey parameter in hooks such as useFlag, useBooleanFlag, useStringFlag, etc. is typed as a plain string.

This results in:

• no autocomplete for available flag keys,
• no compile-time validation for typos,
• potential drift between code and actual feature flag definitions.

It would be very valuable to have a way to make flagKey type-safe, for example via string literal types or generics.

Current behavior

useBooleanFlag('my-feature-flag');

flagKey is typed as string, so TypeScript cannot:

• suggest valid keys,
• catch misspellings at compile time.

Desired behavior

Ability to restrict flagKey to a known set of feature flag keys:

type FeatureFlagKey =
  | 'new-dashboard'
  | 'beta-checkout'
  | 'enable-ai';

useBooleanFlag('new-dashbord'); // ❌ TS error
useBooleanFlag('new-dashboard'); // ✅

Or via a generic API:

useBooleanFlag<FeatureFlagKey>('new-dashboard');

Possible approaches

1. Generic parameter for flagKey

   function useBooleanFlag<K extends string>(
     flagKey: K,
     defaultValue?: boolean
   ): boolean;

2. Typed provider / context

   const FeatureFlagProvider = createFeatureFlagProvider<FeatureFlagKey>();

3. Module augmentation
   Allow teams to extend flag key types in their own codebase without forking the SDK.

Why this matters

• Feature flags are part of business logic; mistakes in flag keys can be critical
• Type-safe flags:
  • reduce runtime errors,
  • improve developer experience,
  • align well with contract-first approaches
• Especially valuable in large React codebases