import { type ReasoningEffort } from "../shared/reasoning-effort.js";
/**
 * First-party hosted A/B: the Builder default (`engine.defaultModel` at
 * DEFAULT_REASONING_EFFORT) versus Haiku 5.5 at medium effort. Chat clients
 * send the default model and effort explicitly, so this keys off the resolved
 * values rather than the explicit-request flag the DB experiment path uses.
 * Any other model or effort is a deliberate choice and is left alone.
 */
export declare const HOSTED_MODEL_EXPERIMENT_ID = "hosted-default-haiku-5-5-medium-vs-luna-high-2026-10";
export declare const HOSTED_MODEL_EXPERIMENT_CONTROL: {
    readonly id: "luna-high";
};
export declare const HOSTED_MODEL_EXPERIMENT_TREATMENT: {
    readonly id: "haiku-5-5-medium";
    readonly model: "claude-haiku-5-5";
    readonly effort: "medium";
};
export interface HostedModelExperimentAssignment {
    experimentId: string;
    variantId: string;
}
export interface HostedModelExperimentResolution {
    /** True only for the Haiku arm; control keeps the request's model and effort. */
    treatment: boolean;
    model: string;
    /** Undefined for the control arm: the request's own effort stands. */
    effort?: ReasoningEffort;
    assignment: HostedModelExperimentAssignment;
}
/**
 * `setting` is `observability.hostedModelExperiment` from app config. `auto`
 * follows the caller's first-party hosted check; `on` forces it for preview;
 * `off` is the emergency rollback.
 */
export declare function isHostedModelExperimentEnabled(args: {
    setting: "auto" | "on" | "off";
    firstParty: boolean;
}): boolean;
/**
 * Stable across apps and processes: the same user lands in the same arm in
 * every hosted template for the life of this experiment id. No DB write needed.
 */
export declare function hostedModelExperimentBucket(userEmail: string): number;
export declare function resolveHostedModelExperiment(args: {
    enabled: boolean;
    userEmail: string | null | undefined;
    engineName: string;
    defaultModel: string;
    model: string;
    /** The request's effort as submitted; anything but default means a choice. */
    effort: unknown;
}): HostedModelExperimentResolution | null;
/**
 * The hosted arm's variant, found by id so it is reported even when the turn
 * is also in another experiment. The singular experiment tags only cover a
 * turn with exactly one assignment.
 */
export declare function hostedModelExperimentVariant(assignments: readonly HostedModelExperimentAssignment[] | undefined): string | undefined;
/**
 * The singular experiment tags predate the hosted test. They keep naming only
 * the other experiment on a turn, so the hosted arm never changes them.
 */
export declare function singleNonHostedAssignment(assignments: readonly HostedModelExperimentAssignment[] | undefined, selectedAssignment?: HostedModelExperimentAssignment): HostedModelExperimentAssignment | undefined;