/**
 * Warns while a session's context is growing expensive, rather than after the
 * fact (`usage_report` finds the same waste in hindsight).
 *
 * This service deliberately has no database, no sync and no pricing: it runs in
 * a prompt hook that must answer in tens of milliseconds, and the context size
 * is a gauge of the moment, not a record anyone keeps. `UsageService` exposes it
 * for the status line; the hook uses it directly because opening the database
 * is exactly the cost the hook cannot pay.
 */
export interface ContextLimits {
    /** From here the size is a heads-up (yellow). */
    warnAt: number;
    /** From here compacting is advised (red; the hook speaks up). */
    compactAt: number;
}
export type ContextLevel = 'ok' | 'warn' | 'compact';
export interface ContextReading extends ContextLimits {
    /** Tokens the next message will re-read: input + cache read + cache write of the last turn. */
    tokens: number;
    level: ContextLevel;
}
export declare const DEFAULT_CONTEXT_LIMITS: ContextLimits;
/**
 * `150k`, `1.5m` or `150000` as a token count; undefined for anything else, so
 * each caller decides whether that is a usage error (a flag) or ignorable (the
 * environment).
 */
export declare function parseTokenCount(raw: string): number | undefined;
/**
 * Flag, then `AI_USAGE_CTX_WARN` / `AI_USAGE_CTX_LIMIT`, then the defaults.
 *
 * A warn threshold above the compact limit would make the yellow band
 * unreachable, so it is pulled down to the limit instead of being honoured.
 * Throwing is not an option here: this runs in a hook that must never fail.
 */
export declare function resolveContextLimits(flags?: {
    warn?: number | undefined;
    limit?: number | undefined;
}, env?: NodeJS.ProcessEnv): ContextLimits;
export declare function contextLevel(tokens: number, limits: ContextLimits): ContextLevel;
export declare class ContextService {
    /**
     * The session's current context against the limits, or undefined when it is
     * unknown: no transcript path, an unreadable file, no turn yet, or a compact
     * that no new turn has measured. Never throws.
     */
    read(transcriptPath: string | undefined, limits: ContextLimits): ContextReading | undefined;
    /** `read`, for the raw JSON a Claude Code hook receives on stdin. Garbage is no data. */
    readHookPayload(raw: string, limits: ContextLimits): ContextReading | undefined;
}