How to Security-Test a LangChain Agent Using a 15-Line FastAPI Wrapper

Developers often ship AI agents to production after a successful demo without conducting adversarial security testing, leaving a critical gap between functional validation and real-world safety. Functional tests only verify expected inputs and miss scenarios like prompt injection, scope violations, tool misuse, and goal hijacking — threats categorized in the OWASP Top 10 for Agentic Applications. The article demonstrates how a tool called Humanbound red-teams a live agent using OWASP-aligned attack scenarios, grading transcripts into a security posture score. Because Humanbound operates as a black-box HTTP tester, agents built with frameworks like LangChain must first be wrapped in a lightweight HTTP service, such as a FastAPI endpoint, to be compatible. The post walks through a sample LangChain support agent with order lookup and refund tools, then shows how a minimal server wrapper bridges the gap between a local .invoke() agent and the security testing interface.