import type { TokenUsage } from "./types.js";
/** Normalize exact provider-reported token counters. Never estimates usage. */
export declare function tokenUsageFromRecord(raw: unknown): TokenUsage | undefined;
/**
 * Merge later counters over earlier ones without letting an absent field erase a present one.
 *
 * `tokenUsageFromRecord` returns every key and sets the ones it did not find to `undefined`,
 * so a spread merge overwrites good values with `undefined`. Anthropic's streaming
 * `message_delta` carries `output_tokens` only, which made a spread wipe the input and cache
 * counters captured at `message_start`.
 *
 * This deliberately does not recompute `totalTokens`. Whether a cache counter is additive
 * depends on the provider (Anthropic reports it outside `input_tokens`, OpenAI inside
 * `prompt_tokens`), and that distinction is gone by the time usage has been normalised. The
 * caller knows its provider and owns the total.
 */
export declare function mergeTokenUsage(base: TokenUsage | undefined, next: TokenUsage | undefined): TokenUsage | undefined;
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