Brief, mostly facts

Harness Engineering 101: a free book on building agent harnesses

A GitHub-hosted series with 16 chapters that grows a 300-line Python toy harness from first principles.

Read the source at github.com Discussion

What the research found

A free GitHub-hosted book series, Harness Engineering 101 (v1.0, September 2026), teaches agent building from first principles across 16 chapters, growing a roughly 300-line plain Python toy harness.

Claims and how well the evidence supports them

The book is Version 1.0, dated September 2026 99%
The series has 16 chapters 91%
The series grows a roughly 300-line toy agent in plain Python 99%
An LLM API is stateless and the full conversation is resent each turn 99%

Evidence

github.com https://github.com/IsuruMaduranga/harness-engineering-101
isuruwijesiri.com https://isuruwijesiri.com/harness-engineering-101/
news.ycombinator.com https://news.ycombinator.com/item?id=50151390

Actionability rated low.