import type { AgentModelDefinition, UsageTurn } from '../../shared/types.js';
/**
 * Model selection and per-turn usage accounting.
 */
/**
 * The model used for the main agent loop: the one flagged `isDefault`, or the
 * first configured model as a fallback.
 */
export declare function getDefaultModel(models: AgentModelDefinition[]): AgentModelDefinition | undefined;
/**
 * Build a `UsageTurn` from a provider `message_end` event and the model that
 * produced it (for pricing). Returns undefined when token counts are absent,
 * so callers can skip emitting a usage message.
 */
export declare function createUsageTurn(event: {
    inputTokens?: number;
    outputTokens?: number;
    cacheCreationInputTokens?: number;
    cacheReadInputTokens?: number;
}, model: AgentModelDefinition | null | undefined): UsageTurn | undefined;