Dev UI

When this extension is present, the Quarkus Dev UI is extended with an OpenFeature card. The card offers two pages: Feature Flags and Providers.

Both pages share a header that selects the domain to inspect. The header also shows the current state of that domain and the names of the providers bound to it. If the application uses multiple domains, each is inspected separately.

A provider whose flag server has a management console is shown as a link that opens that console in a new tab. This is currently the case for Flipt and Unleash.

Feature Flags

The Feature Flags page lists the flags known to the domain’s providers and lets you search them.

Selecting a flag lets you evaluate it without leaving the browser. You can choose the value type, supply a default value to be returned when evaluation fails, and pass an evaluation context as JSON:

{"targetingKey": "user-123"}

The result shows the resolved value together with the variant, the reason and, when evaluation failed, the error code and message. Evaluating from the Dev UI goes through the same client as your application code, so targeting rules apply exactly as they would at runtime.

Overriding flag values

You can also override the value of an individual flag. An override replaces the value returned for that flag, for every provider in the domain, until you clear it. Flags that are currently overridden are marked in the flag list.

Overrides support the same value types as @TestFlag:

  • boolean — parsed via Boolean.parseBoolean(), so only "true" (case-insensitive) produces true

  • string — used as-is

  • integer — parsed via Integer.parseInt()

  • long — parsed via Long.parseLong()

  • double — parsed via Double.parseDouble()

Object flags cannot be overridden.

Flags that are not overridden fall through to the real provider, so you can override a single flag and leave the rest of the application untouched. Overrides are held in memory by the running application and are discarded when it restarts.

Overrides use the same mechanism as the @TestFlag annotation described in Testing. The Dev UI is the interactive counterpart: use @TestFlag to pin a flag value in a test, and the Dev UI to try values out by hand while the application is running.

Overrides exist only in dev mode and never affect a production build.

Providers

The Providers page shows the lifecycle events recorded by the domain’s providers, most recent first. Each entry has a timestamp, the provider that emitted it, the event (ready, configuration changed, stale, or error) and a message.

This is the fastest way to tell whether a provider actually connected to its flag source, and to see reconnections as they happen.