/**
 * The ONE admission an image's bytes pass before they reach the model as an `ImageContent` block —
 * whether a file supplied them (the Read tool's image lane) or a caller did (`TaskSpec.images`' inline
 * arm). Four steps, in this order:
 *
 *   ① the claimed type is one the content API accepts (png / jpeg / gif / webp — the four
 *      {@link imageMagicMatches} can verify);
 *   ② the raw bytes are within the read cap (5 MiB without a downsampler, 64 MiB with one);
 *   ③ the bytes carry the claimed type's signature — an empty / text / mis-named "png" would
 *      otherwise become a malformed block that 400s the NEXT whole provider request;
 *   ④ optional downsample (when a downsampler is supplied; a processing failure keeps the original
 *      bytes, CC's catch → createImageResponse(original)), then the provider's hard limit, which is on the
 *      BASE64 length, not raw bytes.
 *
 * The answer is structured; each carrier words its own refusal (the Read tool speaks to the model, the
 * task door to the caller). The block it admits is built from the bytes it checked — never from a
 * caller's string it did not decode.
 */
import type { ImageContent } from "../../internal/llm.js";
import { type ImageDimensions, type ImageDownsampler } from "../../core/mcp.js";
/** The image types the content API accepts — the only ones a signature check can verify. */
export declare const ADMITTED_IMAGE_MIME_TYPES: readonly ["image/png", "image/jpeg", "image/gif", "image/webp"];
/** The raw-byte read cap for an image, with or without a downsampler. */
export declare function imageReadCap(downsampler: ImageDownsampler | undefined): number;
export type ImageAdmission = {
    ok: true;
    block: ImageContent;
    /** The raw byte count of the bytes checked (before any downsample). */
    originalSize: number;
    /** Measured by the downsampler; absent without one (never fabricated). */
    dimensions?: ImageDimensions;
    /** True when the downsampler actually changed the pixel size. */
    resized: boolean;
} | {
    ok: false;
    reason: "mime_unsupported" | "magic_mismatch";
    rawBytes: number;
} | {
    ok: false;
    reason: "raw_too_large";
    rawBytes: number;
    cap: number;
}
/** `base64` is the encoding that failed the limit (the caller words the refusal from its length). */
 | {
    ok: false;
    reason: "base64_too_large";
    rawBytes: number;
    base64: string;
};
export declare function admitImageBytes(bytes: Uint8Array, claimedMime: string, downsampler: ImageDownsampler | undefined): Promise<ImageAdmission>;