/**
 * @license
 * Copyright 2026 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */
/**
 * Feature names.
 */
export declare enum FeatureName {
    PROGRESSIVE_SSE_STREAMING = "PROGRESSIVE_SSE_STREAMING"
}
/**
 * Feature lifecycle stages.
 */
export declare enum FeatureStage {
    WIP = "wip",
    EXPERIMENTAL = "experimental",
    STABLE = "stable"
}
/**
 * Feature configuration.
 */
export interface FeatureConfig {
    stage: FeatureStage;
    defaultOn: boolean;
}
/**
 * Get the configuration of a feature from the registry.
 *
 * @param featureName The feature name.
 * @returns The feature config from the registry, or undefined if not found.
 */
export declare function getFeatureConfig(featureName: FeatureName): FeatureConfig | undefined;
/**
 * Register a feature with a specific config.
 *
 * @param featureName The feature name.
 * @param config The feature config to register.
 */
export declare function registerFeature(featureName: FeatureName, config: FeatureConfig): void;
/**
 * Programmatically override a feature's enabled state.
 *
 * This override takes highest priority, superseding environment variables
 * and registry defaults.
 *
 * @param featureName The feature name to override.
 * @param enabled Whether the feature should be enabled.
 */
export declare function overrideFeatureEnabled(featureName: FeatureName, enabled: boolean | undefined): void;
/**
 * Check if a feature is enabled at runtime.
 *
 * Priority order (highest to lowest):
 * 1. Programmatic overrides
 * 2. Environment variables (ADK_ENABLE_* / ADK_DISABLE_*)
 * 3. Registry defaults
 *
 * @param featureName The feature name.
 * @returns True if the feature is enabled, false otherwise.
 */
export declare function isFeatureEnabled(featureName: FeatureName): boolean;
/**
 * Temporarily overrides a feature for the duration of a callback.
 */
export declare function withTemporaryFeatureOverride<T>(featureName: FeatureName, enabled: boolean, callback: () => Promise<T> | T): Promise<T>;