Peter Naur in 1985 wrote that programming is the act of building a working theory of the system in our minds, and this often takes form as tacit knowledge in the head of programmers. Even if you handed the complete codebase and perfect documentation to a completely new team, they would often need to go back to the old team and ask questions.

And before agents, we often built this working theory of the system by writing the code by hand. It helps us figure out the "grain" of the codebase so we have a better idea of how to extend it.

So what happens when agents are writing the code? The main avenue with which we built the working theory of the system in our mind is now taken away, and we're left feeling like our understanding of the system is blinded.

I ended up more or less changing my entire workflow. Four main principles:

1. Interrogation/interview-based design and specification

2. Make the decisions that matter and leave the rest to the agent.

3. Use agent to generate explainers, quizzes, and simulations.

4. Use verifiers and guardrails in the coding loop.

Interview-based design and spec

When I tell the agent what I want to build or extend, there's naturally ambiguity. But the agent knows what is ambiguous to it, so it can ask me. /grill-me is one way to do this. You'd think this would be commonplace now, but it's actually not. Some people are still wondering why they're getting bad results. It's because they're not resolving the ambiguity.

Making the decisions that matter

Not every decision matters in a product. Agents are fast at writing code and pretty good at some of the nitty gritty details, so I let it make those decisions. Also, if a particular subsystem is commonplace and undifferentiating, such as login, then I also let it make architectural decisions for that subsystem.

For decisions that are product differentiators, where that differentiation is supported by technology, I make decisions on the stack, the architecture, and the approach. This is the design phase. Because agents tend to make the mainstream decisions, they almost always take a midwit approach which doesn't leverage the technology in a way that makes a difference for the customer.

Some try to build this understanding from code reviews. I personally don't think it's the way to go, because it's not motivating. I find that I'm more motivated to learn how the system works today, because I want to change how it works tomorrow--and it sticks in my head better too (no different than pre-agents).

Generating explainers, quizzes, and simulations

As I'm doing design for an improvement and I don't know how a part of the system works, I can ask questions of the agent in chat. If I still don't get it, I can ask for diagrams (either ASCII or mermaid). But if it's an entire subsystem, I have a skill in which I can ask for visual and interactive explainers. It'll generate a markdown page (or html) that has these interactive components that help demonstrate a concept.

To help make the concept stick, there are quizzes after each section and at the end.

With the computational simulations, I generate a throwaway tool in which I can explore the state space. This doesn't happen as often, as I try to keep state spaces small, and for those explainers tend to work well.

With the design simulations, a same-model agent and a cross-model agent and I will talk about an explainer, and we'll name things that we understand or notice about the design and the intended direction we want to extend it. Then, we'll use subagents to generate options and then discuss the pros and cons. I find this is a good way for me to understand the dead-ends of a design.

Using Verifiers and Guardrails

I define guardrails as mechanistic checks that doesn't change with the feature. such as linters, typecheckers, and pre-commit hooks are all guardrails. Verifiers are mechanistic checks that will be different with each feature, such as unit/integration tests.

For more complicated states or concurrent parts, I'll ask the agent to use formal methods to write a proof. Then use the proof to generate a trace (a series of steps that demonstrate a happy or unhappy path). Then I run that trace in unit tests (kinda like property-based testing--so I guess this can be called trace-based testing), and the code has to adhere to the trace.

I also wrote a design verifier, where the requirements in the spec can be converted into a series of mechanically checkable rules. Then during testing, the verifier fires up the headless browser and uses the DOM measurements of the page to see if it matches up to the rules. This was completely impractical before agents.

All of this so a) I can be sure that the agent is doing what it's supposed to with the decisions that it's making b) I can be out of the coding loop, so that I'm not up at 2am begging, "you fixed this, but you broke that. pls fix." The agent can check for itself.

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If any of this sounds helpful, lemme know. I've been wondering if other engineers care about understanding the code that's being written, or if people just don't care anymore. I've spoken to a few, and it seems to be split. And it may just be a matter of degree and detail. Some like it at a higher level. Some like it nitty gritty.