Jan Brennenstuhl Principal Engineer, Berlin

Security that makes the secure path the easy one.

Essays, a field guide and research notes on application security, identity, and the agents that now act on our behalf.

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What I Learned Building an Identity Broker With Coding Agents

Magnus Jungsbluth and I built the open-source Agentic Identity Broker with coding agents from the first prototype. Over 10 months, I switched agent harnesses 6 times and used 9 models, and most of my lessons are about specs, tests, and review.

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Recent essays

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  1. Guest Lecture at HTW Berlin: AppSec in the Age of Agentic Engineering AppSec for Agentic Engineering
  2. Shift Down: Why Agentic Engineering Demands Platform-Level Security AppSec for Agentic Engineering
  3. Dependency Updates: latest Is Not a Security Strategy AppSec for Agentic Engineering
  4. AppSec in the Age of Agentic Engineering AppSec for Agentic Engineering
  5. Goodbye Big Tech: My European JAMstack Migration

Topics

Essays, field-guide entries, talks and projects by subject. All topics Search

Field guide

Short reference entries on identity, authentication and account security. Each one answers a question with a claim, shows the evidence behind it and states its review status. All entries Glossary

  1. Should an agent use a robot account or delegated access? Field Guide
  2. What should a password policy require? Field Guide
  3. What is inside a JWT? Field Guide
  4. How does OAuth 2.0 Token Exchange keep provider tokens away from agents? Field Guide
  5. How should people grant and revoke an agent's access? Field Guide
  6. How does authorization work for MCP servers? Field Guide