The Harness — a field journal
Vol. I · Edition 2026 · hienngm.com

Hien Nguyen Production AI agents,
built like a backend engineer.

Senior Backend Engineer / TS · NestJS · AWS / npm 350K dl·mo / AWS Solutions Architect / Remote · Viet Nam / Status: Shipping

Most AI agents are demos. I build the ones that run in production.

Real, scalable agent systems in TypeScript and NestJS — plus the harness, the loops, and the system design that keep them standing. Queues, retries, evals, observability, cost, the failure modes nobody demos. I write it all down here.

№ 01 The Dispatch Subscribe · the asset

One issue a week · for backend engineers

Field notes on shipping agents that don't fall over.

Harness patterns, agent loops, MCP, and the system design behind real, scalable agents. Written by someone who has to keep them running. No fluff, no hype.

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№ 02 Selected Work OSS · SaaS · Essays
nestjs-graceful-shutdownOSS 350K dl/mo  An npm package for seamless, zero-dropped-request NestJS shutdowns. Quietly running in a lot of other people's production. SnapdocSaaS · solo snapdoc.pro  AI document-generation SaaS, designed and built solo on the OpenAI API — section-level editing instead of full regeneration. nestjs-scalable-chat-appReference github  A clean-room reference design for real-time chat under high concurrent load — horizontal scaling, clean architecture, the patterns that hold up. Designing a highly scalable chat appEssay dev.to  The teardown: how to handle high user loads in NestJS without the architecture buckling.
№ 03 The Harness Fig. 1 · agent loop
GATHER state · context ACT tool call · model VERIFY check · evals pass REPEAT  UNTIL  VERIFIED

Every agent I ship is a loop with a verifier — gather, act, check, repeat. The model is the easy part; the harness around it is what makes it reliable at scale.

№ 04 Directory Find me