export interface VerifiedDownloadSpec {
    readonly url: string;
    /** Expected byte count (pinned). */
    readonly bytes: number;
    /** Expected lowercase hex sha256 (pinned). */
    readonly sha256: string;
}
export interface VerifiedDownloadOptions {
    readonly spec: VerifiedDownloadSpec;
    readonly destPath: string;
    readonly fetchImpl?: typeof fetch | undefined;
    readonly timeoutMs?: number | undefined;
    /** Progress callback (best-effort). */
    readonly onProgress?: ((phase: 'skip' | 'download' | 'verify' | 'done', message?: string) => void) | undefined;
}
export type VerifiedDownloadResult = {
    readonly ok: true;
    readonly path: string;
    readonly bytes: number;
    readonly skipped: boolean;
} | {
    readonly ok: false;
    readonly reason: 'download-failed' | 'checksum-mismatch' | 'size-mismatch';
    readonly error: string;
};
/**
 * The lowercase hex sha256 of a file, or null when it cannot be read. For
 * honest "got X, want Y" mismatch reporting; never throws.
 */
export declare function fileSha256(path: string): string | null;
/** True when an existing file already matches the pinned size + checksum. */
export declare function fileMatches(path: string, spec: VerifiedDownloadSpec): boolean;
/**
 * Like {@link fileMatches} but cached by (path, size, mtime): repeated status
 * polls do not synchronously re-read and re-hash a 63MB model on every call.
 * A file whose size or mtime changed is re-verified with the full hash,
 * provisioning decisions (download skip/replace) always use the full hash.
 */
export declare function fileMatchesCached(path: string, spec: VerifiedDownloadSpec): boolean;
/**
 * Download a component to `destPath` atomically, verifying size + sha256.
 * Skips (returns skipped:true) when the file already matches, this is what
 * makes a re-run resumable. Never leaves a partial or unverified file in place.
 */
export declare function downloadVerifiedFile(options: VerifiedDownloadOptions): Promise<VerifiedDownloadResult>;
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