/**
 * PipelineHooks — Strategy Pattern for Execution Observability
 *
 * Defines the hook interface used to instrument the tool execution
 * pipeline without duplicating the core flow. The fast path passes
 * no hooks (zero overhead); debug and traced paths supply their
 * strategy via factory methods.
 *
 * @module
 */
import { type ToolResponse } from '../response.js';
/**
 * Hooks for observability instrumentation on each pipeline step.
 *
 * Each hook is called at the corresponding step of the execution
 * pipeline: route → resolve → validate → middleware → execute.
 */
export interface PipelineHooks {
    /** When true, runChain rethrows exceptions (traced path handles them). */
    readonly rethrow?: boolean;
    onRouteError?(): void;
    onRouteOk?(action: string): void;
    onResolveError?(action: string): void;
    onValidateError?(action: string, durationMs: number): void;
    onValidateOk?(action: string, durationMs: number): void;
    onMiddleware?(action: string, chainLength: number): void;
    onExecuteOk?(action: string, response: ToolResponse): void;
    onExecuteError?(action: string, err: unknown): void;
    /** Wraps every response before returning (used by traced path for span finalization). */
    wrapResponse?(response: ToolResponse): ToolResponse;
}
export declare function computeResponseSize(response: ToolResponse): number;
/**
 * Merge two PipelineHooks into one that calls both in sequence.
 *
 * When both `primary` and `secondary` define the same hook,
 * the merged hook calls `primary` first, then `secondary`.
 *
 * Returns `primary` if `secondary` is undefined (zero allocation).
 *
 * Used to layer telemetry emission on top of debug or traced hooks.
 *
 * @internal
 */
export declare function mergeHooks(primary: PipelineHooks, secondary: PipelineHooks | undefined): PipelineHooks;
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