Field Notes
Notes on event-driven Java, Spring Boot, Kafka, and secure systems for regulated banking.
I gave three agents a worktree each and watched what landed on disk — the pid inside the lock file, the worktree that erased itself completely, and the shared site-packages that no amount of git isolation was ever going to protect.
Switching branches is a destructive operation on your files. git worktree removes that coupling — here is the model underneath, the plumbing that makes it cheap, and the three rules Git only mentions when you break them.
Security and privacy, in practice
RFC 9116 answers the one question a stranger needs answered about your site: who do I tell about a vulnerability. What the file must contain, why the expiry date belongs in a test, and the routing trap that makes an SPA host serve it as HTML at 200.
Security and privacy, in practice
I put an MCP server on the public internet so an AI client could file todos onto my private kanban board. The interesting part wasn't the protocol — it was making the dangerous call unrepresentable.
Shipping an AI feature into my own product · Part 4
Adding browser dictation to my AI concierge took twenty minutes. Making it behave in a real composer, refuse to leave a microphone running, and tell the truth about where the audio goes took the rest of the day.
Building agents on the JVM with Embabel · Part 10
When an Embabel action needs two objects of the same type, binding becomes two declarations that must agree — and nothing cross-checks them. Get them out of step and you get a startup exception, an unreachable goal, or a confident wrong answer, depending on which half you forgot.
Building agents on the JVM with Embabel · Part 9
Ask the same question twice in one session and the planner drops a step. Not a cache — a consequence of A* refusing to schedule an action whose output is already on the blackboard, for better and for worse.
Security and privacy, in practice
My kanban board had no authentication at all and handed its entire database to any caller. Putting it on focus.zakaria.lu meant a fourth host on the jar that was already running - plus a disclosure bug caught in review, and one cookie dot that 500'd every sign-in.
Building agents on the JVM with Embabel · Part 8
An Embabel blackboard lives and dies with a single agent process. A Context is the thing that outlives it - and because it seeds the blackboard before planning starts, it changes which actions actually run.
I had written the same rule three times, which is a diagnostic, not a wording problem. Splitting my Claude Code config across the layer that fits each instruction: CLAUDE.md 250 to 163 lines, six path-scoped rules, and two hooks that cannot be talked out of it.