import type { ModelUsage } from '../shared/model-pricing.js';
/**
 * Most-recent-turn input-context size from a codex per-turn usage object.
 * codex's `cached_input_tokens` is a SUBSET of `input_tokens` (OpenAI semantics),
 * so the window fill is `input_tokens` alone — summing would double-count.
 * Best-effort: returns undefined on any shape mismatch.
 */
export declare function extractCodexContextTokens(usage: unknown): number | undefined;
export interface CodexTokenUsage {
    inputTokens: number;
    cachedInputTokens: number;
    outputTokens: number;
}
export declare function extractCodexTokenUsage(usage: unknown): CodexTokenUsage | undefined;
export declare function codexUsageDelta(start: CodexTokenUsage, end: CodexTokenUsage): ModelUsage;
export declare function lastCodexTranscriptContextTokens(sessionId: string, root?: string): number | undefined;
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