/**
 * Prompt Injection Sanitizer for MCP Tool Outputs
 *
 * Implements SEC-H9: Sanitizes user-controlled content returned by MCP tools
 * to prevent prompt injection attacks where attacker-controlled data
 * (contact names, group names, message previews) could manipulate LLM behavior.
 *
 * Defense strategy:
 * 1. Boundary markers clearly delineate user data from system output
 * 2. Tool name references are defanged to prevent tool-call injection
 * 3. Markdown control characters that could be interpreted as instructions are stripped
 */
/**
 * Sanitize user-controlled content before embedding in MCP tool output.
 *
 * @param text - Raw user content (contact name, group name, message preview, etc.)
 * @returns Sanitized string wrapped in boundary markers, or empty string for nullish input
 */
export declare function sanitizeUserContent(text: string | null | undefined): string;
//# sourceMappingURL=sanitizer.d.ts.map