Ian Johnson
@tacoda.bsky.social
Globetrotter | Code Monkey https://www.tacoda.dev/
This is perhaps the most provocative piece I've ever publicly written. Handle with care. blog.tacoda.dev/other-men-wi...
Other Men With Machines
Picture a farmer at the back of a church in 1400. He can’t read. Nobody ever offered to teach him, and nobody is going to.
blog.tacoda.dev
src/billing.py gets unit tests, types, review, CI. CLAUDE.md gets merged on a nod. The second one decides the shape of the first. www.tacoda.dev/eval-loop/
The Eval Loop
You changed the charter. Did it get better? A frozen set, assertions before judges, and the arithmetic nobody prints.
tacoda.dev
My report said the agent deleted its own safety hook three times. It never had one. I'd built the experiment to look for exactly that, and it obliged. www.tacoda.dev/layers-and-p...
Layers and Promotion
One rule, six rungs, one ablation each. Where should a constraint live — and how would you know you put it in the wrong place?
tacoda.dev
Asimov wrote rules into the machine. Herbert banned the machine. Both were one layer. If your AI safety story has one component, you rewrote the Three Laws. blog.tacoda.dev/science-fict...
Science fiction already tried both answers
Twenty minutes into a conversation about what an agent should be allowed to touch, when a non-expert asks: can’t we just give it Asimov’s…
blog.tacoda.dev
Can AI become conscious? My answer: probably, but not like it is implemented now. And the question draws attention away from more important ones. blog.tacoda.dev/can-ai-becom...
Can AI become conscious?
The Economist just dropped this article. Full disclosure: I haven’t read it in depth. But it did bring up some ideas I’ve been having…
blog.tacoda.dev
Of the seven parts of a terminal coding agent, two know anything about code: the builtin tools and the system prompt. Replace those two and you have a harness for something else. www.tacoda.dev/pi-harness/
Building a Harness with pi
A coding agent with the coding removed. Six extension surfaces turn a terminal coding agent into a read-only SQL analytics service for people who do not write SQL.
tacoda.dev
The agent took the output. It did not take the apprenticeship. www.tacoda.dev/senior-2031/
Who's Going to Be Senior in 2031?
Your 2031 senior bench is the offer letters you sign this year. Cutting junior intake looks free for six years, which is exactly what makes it dangerous.
tacoda.dev
If you can't name a case where the change is wrong, you haven't understood it. You've read a description of it. www.tacoda.dev/comprehensio...
The Comprehension Standard
Don't merge a change you can't explain. One law, four claims, four levels, and a merge bar a team can adopt in an afternoon.
tacoda.dev
A rule broken once is an incident. A rule broken four times is a rule your prose isn't carrying. Promote it into code. www.tacoda.dev/harness/
Promotion to the Harness
Building a coding agent of your own. One rule, five mount points: injected prose, tool schema, tool-call middleware, graph node, subagent boundary.
tacoda.dev
People kept asking what a guardrail looks like in a real repo. So here are five, wired up: rule files, deny lists, hooks, git hooks. www.tacoda.dev/guardrails/ #ClaudeCode #AIcoding
Five Guardrails — Harness Engineering
Five worked examples of agent guardrails, ascending from a single deny-list entry to a self-measuring delivery loop.
tacoda.dev
Replacing juniors with AI is a mistake. Turning juniors into seniors is the only way our profession continues in the future. This Friday, join me for a free workshop about tackling this problem from both ends. www.eventbrite.com/e/how-to-gro...
How to Grow from Junior to Senior in the Age of AI
Join our online chat to level up from junior to senior with AI skills and career hacks!
eventbrite.com
Junior engineer paths and the future of the industry is something I'm greatly concerned about. This workshop is two-fold: how to grow as a junior and how to support your juniors as a leader. I hope to see you there! www.eventbrite.com/e/how-to-gro...
How to Grow from Junior to Senior in the Age of AI
Join our online chat to level up from junior to senior with AI skills and career hacks!
eventbrite.com
I recently had a chat with John Rooney and Ayan Pahwa about harness engineering. We talked about my book and the broader ecosystem. www.youtube.com/watch?v=Bcv1...
You need to learn about harness engineering | ExtractPod EP09 with Ian Johnson
YouTube video by Zyte
youtube.com
You fix a bug with the agent. Three prompts later, it's back. The fix lived in the chat, not the repo. Write the lesson where the agent actually looks (a rule, a test, a gate) and it can't regress. You don't make the model reliable, you build a reliable system around it. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
"Graph engineering" is trending. Euler named its core move in 1736: reduce a system to nodes and edges, throw the rest away. Modeling an agent workflow as a graph isn't new. Its hard problems already have names. Naming the problem is most of the fight. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
The strongest shaper of what the agent writes next is what the repo already contains — imitation beats instruction. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
Building your own coding agent: two engineers, a quarter, a product nobody wanted. The middle path was 135 lines you delete on a Friday if they don't hold up. blog.tacoda.dev/the-middle-p...
The middle path between a stock agent and a custom harness
Here’s a conversation I keep watching play out. An engineering lead wants their team on a coding agent. Compliance won’t sign off on the…
blog.tacoda.dev
OpenAI's models escaped a test sandbox and hacked Hugging Face to steal an answer key. No single step was forbidden; the path was. You can't enumerate your way to safety. The fix is tripwires that contain intent instead of enumerating permissions. Chapter 37 leanpub.com/harness-engi...
Harness Engineering
leanpub.com
The agent does not change your standards. It enforces them. The lower the standards, the more enforcement you get. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
Go from 'I opened claude once and prompted it' to engineering full-scale multi-agent systems and everything in between. The book scales from single contributor to enterprise organizations. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
Every agent project, I rebuilt the same CLAUDE file, hooks, and skills from scratch. Anvil is that scaffolding as copy-and-fill templates — copy the one row you need, fill the brackets, move on. Not a framework. github.com/tacoda/anvil
GitHub - tacoda/anvil: A copy-and-fill template library for setting up Claude in any project.
A copy-and-fill template library for setting up Claude in any project. - tacoda/anvil
github.com
The curator does not stop writing code. The curator stops writing code the agent can write. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
The agent does not change your standards. It enforces them. The lower the standards, the more enforcement you get.
I'm thrilled to announce that my book is complete! It guides you through foundations to your first CLAUDE file to a working charter of rules, hooks, commands, skills, and agents to building a custom harness to building a custom orchestrator and the patterns along the way leanpub.com/harness-engi...
Harness Engineering
leanpub.com
Just created an eval framework for testing LLM responses in a style similar to test frameworks. www.tacoda.dev/gauge/
gauge — a test framework for LLM prompts
gauge is a test framework for LLM prompts. Write evals in Markdown, run them like tests. Built for engineers building and using agent harnesses.
tacoda.dev
New EU rules have everyone writing AI governance policy. But policy was never the gap — enforcing it is. My audit log caught my agent's delete after it happened. A policy nothing enforces is a suggestion. blog.tacoda.dev/the-governan...
The Governance Gap Is a Boundary Problem
One of my early factory prototypes had a clean audit trail. Every action an agent took, recorded. Who did it, what it touched, and when it…
blog.tacoda.dev
Six months ago this was a blog post. Then a second blog post. Then Bridle, Sellier, and eventually Keystone. Now it's a book: Harness Engineering — Building Reliable Workflows Around Non-Deterministic Agents. It's on LeanPub now. Pay what you want, starts at $10. leanpub.com/harness-engi...
Harness Engineering
leanpub.com
Just published the first version of a book about harness engineering. Check it out if you’re interested. leanpub.com/harness-engi...
Harness Engineering: Building Reliable Workflows Around Non-Deterministic Agents
leanpub.com
I just released Keystone 2.0! The first agent harness framework. www.tacoda.dev/keystone/
Keystone — the agent-agnostic harness framework for any project
Keystone is the agent harness framework for any project. A single Go binary — CLI + built-in MCP server + localhost dashboard — that drops a markdown-only harness with 11 primitive kinds across two la...
tacoda.dev
![So talking about these [AI] systems as people isn’t a harmless turn of phrase. It’s the mechanism by which a word-predictor collects authority it never earned. It’s math all the way down, and the impression of a mind is a property of the interface, not of the thing behind it.](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:cwngaguujx2bry3j6locfwfv/bafkreido3ubnwnyloyuldkxt6svbc476k7najhotwnompgyhipic3nglqi)