/**
 * Cost Cap Gate
 *
 * Pre-call gate that checks the accumulated cost for the current session
 * against a configured cap. Returns a COST_LIMIT_EXCEEDED error response
 * when the cap is reached (block mode) or fires a warn hook and proceeds
 * (warn mode).
 *
 * Requires:
 * - hazo_llm_api_log table to exist (ensure_api_log_table must be called first)
 * - A session_id available via hazo_logs ALS (safe_get_log_context)
 * - cost_cap.enabled = true in LLMApiConfig
 */
import type { Logger, LLMResponse, CostCapConfig } from '../llm_api/types.js';
import type { HazoConnect } from '../hazo_connect/types.js';
/**
 * Ensure the session_id + created_at composite index exists on hazo_llm_api_log.
 * Idempotent — safe to call on every initialization.
 * Errors are swallowed to avoid crashing initialization.
 */
export declare function ensure_cost_cap_index(connect: HazoConnect, logger: Logger): Promise<void>;
/**
 * Query the total cost_usd accumulated for a session within the given window.
 *
 * Returns 0 if connect has no raw_sql, if there are no matching rows, or if
 * any DB error occurs (errors are swallowed).
 */
export declare function query_session_cost(connect: HazoConnect, session_id: string, window_start: string, logger: Logger): Promise<number>;
/**
 * Pre-call cost cap gate.
 *
 * Returns:
 * - `null`         if the gate should not block (cap disabled, no session, current < cap, or warn mode)
 * - `LLMResponse`  if the call should be blocked (block mode, cap exceeded)
 *
 * In warn mode the `cost_cap_exceeded` hook is called (errors swallowed) and null is returned
 * so the call proceeds.
 */
export declare function check_cost_cap_gate(connect: HazoConnect | null, cap_config: CostCapConfig | undefined, logger: Logger): Promise<LLMResponse | null>;
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