Aikido Zen is a runtime application security protection library that embeds directly into applications to detect and block attacks in real-time. The tool operates as an in-app security layer that monitors application behavior during execution and stops threats before they reach the database. Zen provides protection against OWASP Top 10 vulnerabilities including SQL injection, NoSQL injection, command injection, and path traversal attacks. The embedded library analyzes incoming requests and data flows within the application context to identify malicious activity with reduced false positives compared to traditional WAF solutions. The tool includes traffic filtering capabilities that allow blocking of known threat actors through CrowdSec integration, bot traffic, country-based restrictions, and Tor network access. Rate limiting can be configured at the user level rather than solely IP-based restrictions. Installation requires a single npm or yarn command and one line of code integration. The library runs within the application runtime without external dependencies on Aikido servers, operating with minimal performance impact. No rule updates are required as the tool uses contextual analysis rather than signature-based detection. Zen automatically discovers and documents APIs by analyzing inbound traffic, including undocumented endpoints. The tool integrates with Aikido's broader security platform to adjust vulnerability risk scores based on runtime exploitation attempts. Available for Node.js applications with support for multiple database types including MySQL, MongoDB, and PostgreSQL.