/**
 * Per-session token state tracker.
 *
 * Bridges the gap between:
 * - `chat.params` hook → provides model context limit (maxTokens)
 * - `message.updated` event → provides latest input token usage (usedTokens)
 *
 * Uses an in-memory Map keyed by sessionId. State resets on plugin restart,
 * which is acceptable — data rebuilds on the next `chat.params` + `message.updated` pair.
 */
export interface SessionTokenEntry {
    maxTokens: number;
    usedTokens: number;
}
/**
 * Store the model's context limit for a session.
 * Called from the `chat.params` hook when a session starts.
 * Does NOT overwrite existing `usedTokens`.
 */
export declare function setContextLimit(sessionId: string, maxTokens: number): void;
/**
 * Update the latest input token usage for a session.
 * Called from `message.updated` events with AssistantMessage tokens.
 * Stores the latest value — NOT cumulative across messages.
 * Does NOT overwrite existing `maxTokens`.
 * Only updates when inputTokens > 0 (guards against partial streaming updates).
 */
export declare function updateUsage(sessionId: string, inputTokens: number): void;
/**
 * Get the current token state for a session.
 * Returns undefined if the session is unknown.
 */
export declare function getState(sessionId: string): SessionTokenEntry | undefined;
/**
 * Remove a session from the tracker.
 * Called on `session.deleted` events.
 */
export declare function clearSession(sessionId: string): void;
/**
 * Clear all session state. Used in tests only.
 */
export declare function clear(): void;