/**
 * Binary-output kit — write tool-generated bytes (images, maps, exports) to a
 * configurable directory instead of dumping megabytes of base64 into a tool
 * result.
 *
 * Consolidates the duplicated trio in gemini (`images.ts#resolveOutputDir` /
 * `uniquePath` / `writeImage`) and flightaware (`shared.ts#resolveOutputDir` /
 * `writePng`): per-call dir → `<SVC>_OUTPUT_DIR` env → cwd, non-overwriting
 * filenames, extension derived from the MIME type. The fleet convention (see
 * the mcp-fleet-builder skill) is that every binary-output tool uses this shape.
 */
import { type EnvSource } from '../config/index.js';
/**
 * Resolve the directory a binary-output tool should write into:
 * the per-call argument → the named env var → the current working directory.
 * `~` and relative paths are expanded ({@link expandPath}) and the directory is
 * created recursively so the subsequent write can't ENOENT.
 */
export declare function resolveOutputDir(perCall: string | undefined, envVar: string, opts?: {
    env?: EnvSource;
}): string;
/**
 * A non-overwriting path for `base.ext` in `dir`: the bare name when free,
 * else `base-2.ext`, `base-3.ext`, … (gemini's numbering). `ext` is passed
 * without the dot. `base` is sanitized to a single path component
 * ({@link sanitizeBaseName}) so a `../…` stem can't write outside `dir`.
 */
export declare function uniquePath(dir: string, base: string, ext: string): string;
/** Options for {@link writeBinaryOutput}. */
export interface WriteBinaryOutputOptions {
    /** Directory to write into (already resolved — see {@link resolveOutputDir}). */
    dir: string;
    /** Filename stem (no extension). */
    baseName: string;
    /** The bytes, base64-encoded (as returned by generation APIs). */
    base64: string;
    /** MIME type used to derive the extension when `extension` is not given. */
    mimeType?: string;
    /** Explicit extension (no dot); overrides the MIME lookup. */
    extension?: string;
}
/**
 * Decode `base64` and write it to a **non-overwriting** file in `dir`, deriving
 * the extension from `extension` → the MIME type → `'bin'`. Returns the
 * absolute path written. The caller returns that path from the tool result
 * (with an `inline` flag for base64 via `imageResult` when the user asks).
 */
export declare function writeBinaryOutput(opts: WriteBinaryOutputOptions): string;
/**
 * Magic-byte MIME sniff for the image formats the fleet passes around
 * (PNG / JPEG / WebP / GIF). Returns `undefined` for anything else — callers
 * decide their own default. Pairs with `readFileHead` for on-disk files;
 * consolidates gemini's `sniffMimeBytes` (and evite's dimension sniffer uses
 * the same signatures).
 */
export declare function sniffMimeBytes(bytes: Uint8Array): string | undefined;
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