Vercel Flags now supports JSON values

Source: Vercel Blog

May 7, 2026

You can now store JSON values in Vercel Flags, extending the existing support for boolean, string, and number values. This allows you to collapse what used to take several related flags into a single feature flag.

Example

To A/B test how a different model performs, you can define a single model flag that holds the full configuration object instead of managing separate flags such as ai_model, ai_temperature, and ai_max_tokens.

// Variant A
{
  "id": "claude-sonnet-4-6",
  "temperature": 0.7,
  "maxTokens": 1024,
  "systemPrompt": "You are a helpful shopping assistant."
}

// Variant B
{
  "id": "claude-opus-4-6",
  "temperature": 0.8,
  "maxTokens": 2048,
  "systemPrompt": "You help with shopping."
}

A feature flag holding JSON configuration in its variants enables you to progressively route traffic to a new model, run A/B tests, or quickly switch models if a provider experiences issues.

Try it out or learn more about Vercel Flags.