/**
 * Normalization and caps for vision images attached to tool results.
 *
 * Actions opt in by returning a well-known optional `_agentImages` field on
 * their result object; external MCP tools opt in by returning standard MCP
 * `image` content parts. Both funnel through `normalizeToolResultImages` so
 * the caps live in exactly one place:
 *
 *   - at most {@link MAX_TOOL_RESULT_IMAGES} images per tool result,
 *   - at most {@link MAX_TOOL_RESULT_IMAGE_BASE64_CHARS} base64 chars each.
 *
 * Dropped images become model-readable text notes instead of failing the tool
 * call. Accepted images become `EngineToolResultImagePart`s that live only on
 * the in-memory turn — the run ledger persists the string result (which
 * carries a compact `[image: …]` note per image), never base64 payloads.
 */
import type { EngineToolResultImagePart } from "./engine/types.js";
/** Well-known optional field on action results carrying result images. */
export declare const AGENT_IMAGES_FIELD = "_agentImages";
export declare const MAX_TOOL_RESULT_IMAGES = 4;
/** ~2MB of base64 (≈1.5MB decoded) per image; larger becomes a text note. */
export declare const MAX_TOOL_RESULT_IMAGE_BASE64_CHARS = 2000000;
export interface NormalizedToolResultImages {
    images: EngineToolResultImagePart[];
    /** Model-readable notes for images that were dropped (oversize/invalid). */
    notes: string[];
}
/**
 * Validate and cap a raw `_agentImages`-shaped array. Never throws; anything
 * invalid or over-cap becomes a note the model can read.
 */
export declare function normalizeToolResultImages(raw: unknown): NormalizedToolResultImages;
/**
 * Detect and strip the `_agentImages` field from an action result object.
 * Returns the value to stringify for the model (field removed) plus the
 * normalized images and drop notes. Non-objects pass through untouched.
 */
export declare function extractAgentImagesFromActionResult(value: unknown): {
    value: unknown;
    images: EngineToolResultImagePart[];
    notes: string[];
};
/**
 * Compact per-image notes appended to the string result. This is what the
 * run ledger / journal persists — URLs survive verbatim; base64 becomes a
 * `[image: <mediaType>, <n> …]` placeholder (never the payload).
 */
export declare function describeToolResultImages(images: EngineToolResultImagePart[]): string[];
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