Fabraix

Fabraix is a red-teaming service for teams shipping customer-facing AI agents, whether chat, voice, browser, or coding assistants. Its product Nyx probes a live agent from the outside without requiring access to source code, then reports the specific prompts, tool calls, and responses that produced a failure so engineers can reproduce and patch each finding. The pitch to security teams is that reading a system prompt is not enough when the underlying agent is nondeterministic and can reach untrusted files, websites, and MCP servers on its own. Rather than cycling through a fixed list of jailbreak payloads, Nyx draws from a library of more than 10,000 attack strategies and adapts multi-turn attempts based on how the target agent defends itself. Fabraix reports a 78 percent attack success rate on the AgentHarm benchmark and says Nyx has surfaced exploitable failures in public-facing agents at dozens of Fortune 500 companies. The team has also published ACE (Adversarial Cost to Exploit), a benchmark that scores AI systems by how expensive they are for a rational attacker to break. The company was founded in 2026 by Ahmed Aly (CEO), previously on the international payments fraud team at Monzo and the first data scientist at Sequoia-backed Two, and Ibrahim Abdu (CTO), who red-teamed AI agents inside Meta's Privacy org and built compilers for trade surveillance at TradingHub before that. Fabraix is part of Y Combinator's S26 batch, and this launch coincides with Aly publicly sharing that the company reached a $1.04M annualized run rate three months after joining YC with zero revenue.