The Cloud Codex — field notes on building with AI agents

$ cat ./codex/README.md

Field notes on building with AI agents.

The economics and architecture of production AI — the harness around the model, what the tokens actually cost, and the platform engineering that keeps it production-grade.

by Michael Tuszynski — principal architect · ex-AWS · 25 years shipping production systems

107 essays est. 2023

7-part series

Building an AI Assessment System

A field build of AI-graded assessment — grading written answers, testing the judge, red-teaming it, and measuring what actually moved the needle for students. Read in order.

// start here

$ grep -l signal ./essays

  1. An Engineer Costs $250K. Their Tokens Cost $20K. That Math Is a Trap.7 min read
  2. The Coding Agent Stack Has Two Layers6 min read
  3. Your Claude Plugin Marketplace Needs More Than a Git Repo5 min read
  4. The Hidden Infrastructure Cost of Running Local LLMs vs Cloud APIs: A Real-World TCO Analysis for Enterprise Deployments6 min read
  5. AI Agents Are Killing Seat-Based SaaS Pricing. Here's What's Replacing It.5 min read
  6. The Hidden AI Vendor Dependency Crisis: How to Build AI Systems That Survive Platform Wars8 min read

// most recent

$ ls -t ./essays

[ 01 ] Jul 13, 2026 · 4 min read

Try It: A Working Assessment-First Course

#ai-education#llm-evaluation#open-source
[ 02 ] series·7/7 Jul 12, 2026 · 4 min read

Instrument Like a Learning Scientist

#ed-tech#learning-science#product-analytics
[ 03 ] series·6/7 Jul 11, 2026 · 4 min read

The Biggest Effect Size Was the Boring Feature

#ed-tech#learning-science#ai-engineering
[ 04 ] series·5/7 Jul 10, 2026 · 4 min read

The Grader Was Right and the Students Quit Anyway

#ai-assessment#learning-science#ed-tech
[ 05 ] series·4/7 Jul 09, 2026 · 5 min read

Students Are Adversaries: Red-Teaming an LLM Grader

#ai-engineering#ai-security#prompt-engineering
[ 06 ] series·3/7 Jul 08, 2026 · 4 min read

Your LLM Judge Needs a Test Suite

#llm-evaluation#ai-engineering#software-testing
[ 07 ] series·2/7 Jul 07, 2026 · 5 min read

Grading Written Answers with an LLM, Properly

#ai-engineering#ed-tech#llm-applications
[ 08 ] series·1/7 Jul 06, 2026 · 6 min read

The AI Tutor Everyone Builds Is the One Students Ignore

#ai-engineering#ed-tech#llm-applications
[ 09 ] Jul 05, 2026 · 7 min read

Build a Self-Improving Agent Harness in an Afternoon

#ai-agents#prompt-engineering#ai-engineering
[ 10 ] Jul 02, 2026 · 5 min read

Maintainability Is the Last Mile, and It Doesn't Benchmark Away

#ai-agents#ai-engineering#platform-engineering
[ 11 ] Jun 30, 2026 · 4 min read

OpenTelemetry Tells You What Your Agent Did. Not Whether It Was OK.

#ai-agents#observability#open-telemetry
[ 12 ] Jun 27, 2026 · 7 min read

An Engineer Costs $250K. Their Tokens Cost $20K. That Math Is a Trap.

#ai#software-engineering#tech-layoffs