Tools and writing
for developers
Kumizhi builds developer tools and publishes weekly technical writing on API design, contract testing, and AI engineering.
Writing
Recent posts
Building a customer support chatbot in a weekend
Phase 1 of my AI engineering curriculum. A naive chatbot with every help article stuffed into the system prompt — and what it taught me about streaming, system messages, and where the simple approach starts to break.
Building an eval suite (and catching my own tests being wrong)
Phase 4 of my AI engineering curriculum. Golden set, LLM-as-judge, self-hosted LangFuse — and the finding that the most useful thing I built was the judge of the judge.
Building my first AI agent — and the one way it actually broke
Phase 3 of my AI engineering curriculum. The chatbot becomes an agent: it can look up orders, open tickets, escalate to humans. Plus one real failure mode — and why most edge cases turned out fine.