/**
 * rate-limit-headers.ts
 *
 * A single, provider-agnostic parser for the rate-limit / quota headers that
 * upstream LLM providers return on EVERY response (success and 429 alike), so
 * the runtime can maintain a quota snapshot and warn before a limit is hit
 * rather than only reacting after a 429.
 *
 * Covers the three families seen in the wild:
 *   - Anthropic: `anthropic-ratelimit-{requests,tokens}-{limit,remaining,reset}`
 *     (reset is an ISO-8601 timestamp) plus `anthropic-ratelimit-unified-*`.
 *   - OpenAI / OpenAI-compatible: `x-ratelimit-{limit,remaining,reset}-{requests,tokens}`
 *     (reset is a duration like `1s`, `6m0s`, or `1h2m3s`).
 *   - IETF draft `RateLimit` (`ratelimit-limit`, `ratelimit-remaining`,
 *     `ratelimit-reset`, reset is delta-seconds).
 * Plus the universal `retry-after` (delta-seconds or an HTTP-date).
 *
 * HONESTY IDIOM: a field is populated ONLY when a header actually carried it.
 * `parseRateLimitHeaders` returns null when NO recognized header was present, so
 * a caller records a signal only for a genuine observation, never a fabricated
 * "full quota". The requests dimension is preferred for limit/remaining (the
 * fan-out assessment reasons over request counts); the tokens dimension is used
 * only as a fallback when no requests header is present.
 */
/** A normalized rate-limit observation parsed from one response's headers. */
export interface ParsedRateLimit {
    /** Observed window limit (requests preferred, else tokens), when a header carried it. */
    readonly limit?: number | undefined;
    /** Observed remaining in the window (requests preferred, else tokens), when a header carried it. */
    readonly remaining?: number | undefined;
    /** Epoch ms the window resets, when a reset header carried it. */
    readonly resetAt?: number | undefined;
    /** Retry-after the provider asked for (ms), when a `retry-after` header carried one. */
    readonly retryAfterMs?: number | undefined;
}
/** A minimal, header-shape-agnostic reader: Headers, a plain record, or an array of pairs. */
export type HeaderSource = Headers | Record<string, string | string[] | undefined> | ReadonlyArray<readonly [string, string]>;
/** Parse an OpenAI-style duration (`1s`, `6m0s`, `1h2m3s`, `500ms`) to milliseconds. */
export declare function parseOpenAiResetDurationMs(value: string | undefined): number | undefined;
/** Parse a `retry-after` value (delta-seconds or an HTTP-date) to milliseconds. */
export declare function parseRetryAfterMs(value: string | undefined, now: number): number | undefined;
/**
 * Parse rate-limit headers from a response. Returns null when no recognized
 * header was present (nothing observed). `now` is injectable for testing.
 */
export declare function parseRateLimitHeaders(source: HeaderSource, now?: number): ParsedRateLimit | null;
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