import { type Dispose, type FeatureId, type GenerationHandoff, type SnapshotState } from '@zhin.js/plugin-runtime';
import type { FeatureProvider } from '@zhin.js/feature-kit';
export type ProjectionState = Omit<SnapshotState, 'projections'>;
export interface ProjectedFeatures {
    readonly state: SnapshotState;
    readonly disposers: ReadonlyMap<FeatureId, Dispose>;
    readonly handoff?: GenerationHandoff;
}
/** Builds selected Feature projections against one coherent candidate snapshot. */
export declare class FeatureProjector {
    private readonly providers;
    constructor(providers: Iterable<FeatureProvider>);
    project(generation: number, base: ProjectionState, signal: AbortSignal, retained?: ReadonlyMap<FeatureId, unknown>): Promise<ProjectedFeatures>;
}
export declare function composeGenerationHandoffs(...handoffs: readonly (GenerationHandoff | undefined)[]): GenerationHandoff | undefined;