import type { Writable } from 'node:stream';
/**
 * Harden a stdio MCP server against stdout pollution.
 *
 * The MCP stdio transport frames JSON-RPC over `process.stdout`. Any *other* write to
 * stdout — a clack `intro`/`log`, a stray `console.log`, a chatty dependency — injects
 * non-JSON bytes into that stream, and a strict client (e.g. Codex) then drops the
 * connection with "Transport closed". Per-call `silent` flags (see sdk.ts) are easy to
 * miss one-by-one, so this is the backstop: it routes EVERY ambient `process.stdout`
 * write to stderr (still visible for debugging, harmless to the protocol) and returns a
 * dedicated Writable — bound to the real stdout — for the transport to send JSON-RPC on.
 *
 * Call once, before constructing StdioServerTransport, and hand it the returned stream:
 *   const out = installMcpStdoutGuard()
 *   const transport = new StdioServerTransport(process.stdin, out)
 *
 * @returns a Writable wired to the real fd-1 stdout, for the transport only.
 */
export declare function installMcpStdoutGuard(): Writable;