The Brain Sandwich

Posted by keyle 4 days ago

Comments

Comment by coldtea 3 days ago

The whole actual, not necessarily the "openly admitted", utility of AI is to allow people to ship while not understanding the work, and not caring that much about it.

So such posts will make as much change as "trade, but be ethical" would make on a late 80s Wall Street trading floor:

"Before you tell the agent to start building anything, you go there and read and understand it first."

Yeah, not gonna happen. 1 in 100 might do that.

Comment by uludag 3 days ago

I completely agree. While the best outcome may obviously involve lots of thinking, from what I've seen an experienced, the AI tools we have today put people on a slope to becoming "meat proxies". Some of the brighter, stronger engineers may have a less steep slope, but I'm convinced that with time they too will be meat proxies. AI is attacking on too many fronts for it to be otherwise:

  - AI generates too much code that overwhelms humans
  - AI deskills users concerning the gritty details of coding by having them not do it themselves
  - Having most of one's co-workers become meat proxy will put pressure for others to convert
  - Lack of effort or expertise invested into codebase leads people to care less; caring less -> not caring about optimal outcome -> not expending brain power on problems we don't care about.

I think since we as an industry are still on this slope, we're still having systems propped up by people actually using their brains. I personally think this situation is regrettable. We should as an industry consider if the direction we're going truly is something we want.

Comment by Alive-in-2025 3 days ago

We are clearly getting to the point, or past the point, where humans will not understand the code base very well or at all. I fear we are building a tower of "it kind of works this way" (maybe it does or maybe it doesn't), in a couple years people won't know what they can change, they won't get much of the architecture.

If one can't understand the monstrosity that was built up over time, where the code base is enormous, millions and millions of lines and components, all with a few buggy corners that the tests didn't touch, and a human didn't have the insight to write a test that understands and verifies the corner cases, it will be like a magic machine that we can't change because we don't understand it and we can't afford years of effort. Some may hope their LLM will be able to understand it.

We'll have things that are buggy in ways that become very difficult to understand or fix, and no one can afford the effort. Remember when we had all those huge old programs from the 60s or early 70s, before there were tests maybe, or unit tests. Code written at a lot of human effort, but before the ideas of software engineering made it more tractable to build large programs reliably, testable.

We are creating a new problem for the people that take over our new code, just like the "vast for the time" 1960s huge cobol program can't be changed.

Comment by AIorNot 3 days ago

Well to play the opposite perspective:

If we assume that AI coding is just beginning- we can assume that humans will create systems to help Manage the increasingly complex interactions that machines will code - ie we are still early like when we first introduced the industrial revolution to the peasants (which led to decades of chaos- for sure)

But Just like a 787 is not flown by hand either - doesn't mean anyone is qualified to autopilot it

Complex engineering systems will require sme humans to help manage the underlying complex interactions in way that is comprehensible to human intelligence

No one except for a smaller group of specialists for example these days does much understanding of assembly or compilers.. but we build complex SaaS apps all the time without that knowledge

Comment by coldtea 3 days ago

>when we first introduced the industrial revolution to the peasants

In this case, we're the peasants.

Comment by BobbyTables2 3 days ago

Look at a completely idle Kubernetes system. Can you explain everything that is running?

Humans have been building stuff too complex to understand for a long time.

But yeah, AI is going to accelerate this…

Comment by coldtea 3 days ago

The analogy doesn't make it better. Kubernetes was already an example of pile upon piles on harmful complexity.

Comment by BoggleOhYeah 3 days ago

It's leading us toward the Cult Mechanicus from Warhammer 40k.

Comment by Terr_ 3 days ago

We can look at it as a natural extension of how regular office work gets counterfeited, ex:

1. I wrote a status-update without actually looking at the status.

2. I made a proposal without really knowing the pros and cons.

3. I provided you information without really knowing what your question was.

Comment by fwipsy 3 days ago

Some applications (e.g. a kernel) need to be carefully engineered with every possible edge case considered. Some apps (e.g. a web game) don't. This is a way for careful engineers who need to build dependable software to integrate AI without compromising quality.

Comment by sublinear 3 days ago

Wrong.

If the software makes money because it's expected to work reliably, every edge case matters. Web games aren't exempt from engineering challenges. In fact, the more trivial the problem seems on the surface, the more likely it is to have edge cases.

Bugs are always prioritized based on how big of a deal it is for the customer. They don't like to wait and they rarely give second chances.

AI doesn't fit into any dev workflow except greenfield or analysis. Everything else needs a lot of close human attention and human discussion. AI doesn't read minds.

Comment by fwipsy 2 days ago

Web games don't make money because they're expected to work reliably, people play them on impulse. If it breaks 1% of the time, that's hardly a problem at all. If a kernel breaks 1% of the time, nobody would use it ever.

A raytracer demo doesn't need to be engineered to the same standard as the Apollo onboard computer software. A $20 paint app doesn't need to work as reliably as banking software that handles millions of dollars of transfers every day. All software exists on a scale from trivial to critical. It's like saying a toy drone needs to be designed the same way as a F-16.

Comment by NewsaHackO 3 days ago

I think you are misssing the economics of the situation, which the GP is implicitly referring to. You have 24 hours in a day. A person that is making a web game that he wants to release cannot spend all of his effort chasing one in a million bugs, as that would eat into the time he has to actually make a great and engaging game. He can’t worry about how the game renders on Internet Explorers running in PowerPC. If you are making a kernel, a single RCE in an edge case (worse, even in a adversarially induced edge case) can equate to an emergency patch and general loss of trust in your system. The kernel programmer is even incentivized to do the opposite of the web game guy, which is remove functionality that they do not think they can reasonably completely test. So yes, edge case importance matters differently in different applications.

Comment by sublinear 3 days ago

> The kernel programmer is even incentivized to do the opposite of the web game guy, which is remove functionality that they do not think they can reasonably completely test.

Why wouldn't a game dev do the same? It's pretty common for initial game releases to lack features.

Comment by AIorNot 3 days ago

No that is not a correct read -it might be based on this past few months or so state of the art, while instead that state of the art is moving forward every month- and at the rate these ai coding systems are improving and our harnesses for managing them- bug handling and brownfield codebases are becoming increasingly accessible to AI coding

Ie you are making the mistake of assuming the tech is static when it most assuredly is not

Comment by coldtea 3 days ago

Aside from having incremental new releases, it has stopped moving that fast, in evolutionary jumps, for over a year now.

Comment by AIorNot 2 days ago

That is not true for AI coding at all: ie the evidence is the massive difference between Claude code in opus 4.6 vs opus 5.5

That difference is enough to unlock AI coding for so many real life teams

Comment by 3 days ago

Comment by kpmcc 3 days ago

Like the concept.

Pedantic addendum: this is an AI sandwich, not a brain sandwich.

Comment by derpyzza 3 days ago

Meh, the rules for what an "X sandwich" refers to tends to differ by types of sandwiches. In terms of normal sandwiches, an "X sandwich" does indeed refer to X being in between two types of bread, like a chicken sandwich, or an ice cream sandwich, or a knuckle sandwich, etc. But on the other hand, sometimes an "X sandwich" refers to two things sandwiching some other thing, like a compliment sandwich — where you sandwich criticism between two bits of compliments, or a croissant sandwich — which refers to a sandwich that uses a sliced croissant as the bread. So calling it a "brain sandwich" works fine I think

Comment by etcetcetcetceta 3 days ago

the latter only exists because of this misunderstanding.

Besides don't most people refer to the croissant in substitute for sandwich "ham and cheese croissant"?

Comment by passive 3 days ago

The basic concept here, that you take personal responsibility for the input and output being transmitted to/from the LLM, is an obvious but critical one, so I appreciate this terminology as a way to convey it.

I'll try using Brain Sandwich as guidance for less technical folk.

Comment by themgt 3 days ago

I have a very simple framework I use for working with John von Neumann ... the idea is very simple, and can be summarized by: whenever you work on something with John von Neumann, you should use:

1. Your brain, and then

2. John von Neumann, and then

3. Your brain

Explaining a bit more… Before you tell John von Neumann to start working on anything, you go there and read and understand it first. And when John von Neumann brings you the solution, you will know if it’s right, or if it’s too much, or if it’s completely solving the wrong problem, etc.

Comment by rbongers 3 days ago

Hard to truly understand the work unless if you're actually doing it.

Comment by mcculley 3 days ago

This is the same problem a lot of leaders have in all kinds of work. It is often possible to delegate a task. But if one delegates understanding, one is at a disadvantage when compared to an organization where leadership understands the task.

When I was in charge of companies, I understood the technical tasks, but delegated understanding of things like tax law. This was okay, but I was definitely at a disadvantage compared to companies that could better optimize capital allocation around understanding of tax law.

AI means more humans in every organization are having to learn how to be managers/leaders of these agents. Those who actually understand the work they delegate will maintain an advantage over those who do not.

Comment by rbongers 3 days ago

Unfortunate for those of us who really dislike that work.

Comment by tonyedgecombe 3 days ago

Yes, the temptation to skip forward is going to be to great for most people.

Comment by algernonramone 3 days ago

Wait, so this isn't about the pride of my hometown? (https://en.wikipedia.org/wiki/Fried_brain_sandwich)

But the Fall Festival just ended, it's the perfect time to bring it up!

Comment by jonathanlydall 4 days ago

> Before you tell the agent to start building anything, you go there and read and understand it first.

The sentence is maybe ambiguous, but it sounds like it's saying to not use the AI at all until you understand what's happening in the area that needs to change.

I don't agree with this as you can spend quite a bit of time digging around to first find the correct place which needs to be updated and then more time reading the code (likely in multiple files or places) to build up a mental model of what's going on.

I typically have more than one AI conversation on the go at any given time, so I'll always start by asking it to make a plan to solve a problem and while it's busy exploring to make a plan I review some other AI conversation's work in the meantime, when the AI's plan is ready I review it.

If at this point there is anything that is unclear to me about its approach to implement the plan, or I don't already have familiarity with the part of the system it's proposing to update, I start questioning the AI on how the system works. I will scrutinize the AI's plan until I'm absolutely sure that it's going to implement something that is sound from a system design perspective and as a senior software developer with architecture level experience I am capable of making such judgments.

I'm not sure what it might be like for comparitively inexperienced developers, but I would expect that AI's capacity for infinite patience allows them to ask as many questions as they need to get a clear mental model of what's happening, so if I were mentoring such a person in this age of AI I would drill into them on how to interact with AIs to ensure they have this clarity before the AI starts implementing anything.

The difference between vibe coding and highly accelerated agentic development is having the expertise and judgment to ensure you're building properly sound software.

Comment by stefan_lec 3 days ago

Yeah this resonates with me. I think of it more as an “understanding” sandwich:

1) While pointing the agent at the task, poke it with annoying questions until I understand the problem and its context well enough to explain it.

2) Have it write the solution, help it work past problems it encounters during testing, then go through simplification, performance and correctness reviews.

3) Have the agent draft a pr, then poke it with annoying questions about the PR until I understand where we’re at, and why we don’t need to do more work. Also try to rewrite it into readable prose instead of Claud-ish while doing so.

#2 and #3 can repeat quite a bit, depending on how stubborn the problem is.

Comment by ewy1 3 days ago

in the post, the brain sandwich gets explained as "brain, ai, brain" but sandwich experts note that a sandwich is usually named after its contents and not the bread

Comment by SubiculumCode 3 days ago

Yep, it's AI - Meat - AI

Comment by fluxusars 3 days ago

I fully agree with the approach, but sadly that doesn't make the overwhelming amount of code reviews in the AI age much better. At best, it might slow down your colleagues' deluge of review requests a little. But also, you still have to spend time reviewing your own LLM code, of which there is more of and you're naturally less familiar with than if you'd hand-written it, so it takes longer to review.

Comment by bzmrgonz 3 days ago

I agree completely, I recently went thru this. Customer API session/journey security is a beast to secure, so many layers, so many moving parts, so many approaches.

Comment by aozgaa 4 days ago

> before sending your stuff to other people for review, you need to make the work reviewable.

Yes, but the amount of work needed here is overstated. With good orchestration/prompting in the task[1] (and token budget), the work on this end is significantly reduced.

… and then the brain drain issue returns.

[1] https://claude.dev/blog/solving-code-review-at-anthropic/

Comment by beej71 4 days ago

This is far better than just hitting return, but there's zero chance it's as good as doing things the hard way. Tradeoffs, of course.

Comment by StilesCrisis 4 days ago

If you're saying AI has _never_ found a more elegant solution than your original idea, you're not using it right or you're only using the cheapo models.

(Before someone asks: "not using it right" could mean a lot of things, but intentionally constraining its search by telling it how to do everything is one example. Or by not giving it a way to hill-climb: no tests, no iteration on a solution, etc.)

Comment by sowhat1 3 days ago

A lot of devs are micromanagers who think they’re smarter than everyone else. You’ve probably at least met a couple if you’ve had a long career. They typically leave lots of nits on code that is mostly meaningless noise or personal preference.

These types of people will get the least out of AI as their ego prevents them from letting it outshine themselves.

Comment by StilesCrisis 3 days ago

Shoot, I'm very much the "lots of nits" reviewer but I have no inclination to be a manager and get lots of benefit from AI. What does that make me?

Comment by 0c3ca83 3 days ago

If you've given up on understanding your code base, AI will give you a better solution than you could come up with. Not because AI is better, but because you've become a low performer.

AI is reasonable at reviewing code, with only a 50-60% false-positive rate, and its persistence at broadening scope often finds things human reviewers would miss. It's still actually still pretty shitty at writing code, though, again, with enough ground truth and persistence, it'll often generate something that's a functional turd. It will sometimes come up with better suggestions if you prompt for it, but it needs a ton of hand-holding at the moment. And usually the suggestions are still overly complicated messes that you can trim down to 1/10th the size, while keeping the core idea.

Comment by StilesCrisis 3 days ago

Congrats to you if you're working in a codebase small enough to know it all. Do you know every knob in your database? Every tuning option on your webserver? Every warning and lint setting on your compiler? Wish I did! Do you read every PR that comes through the system, every day? You must keep busy.

Comment by 0c3ca83 3 days ago

Do you know anything about your codebase? How?

Comment by StilesCrisis 3 days ago

Generally, I know a LOT about my team's code, and then in concentric circles I know less and less of the periphery. I work on <feature X> and know almost everything. That's a subsystem of <project Y> which I know well. That's part of <product Z> which I know in varying amounts.

And of course, there are things like build systems (CMake, ninja, blaze) where I know the basics, but I've never been an expert and don't care to be. Before I'd offload build features to another team; now I'd offload it to an AI. It's not something I need to be an expert in. I just want builds to work well.

Comment by 0c3ca83 3 days ago

And, how do you learn it?

Comment by StilesCrisis 3 days ago

That is a wonderful question. I think you might be confusing "full vibe mode" with "using AI as a tool." I don't know where some code paths lead, so I can use AI to help ("who ingests .XYZ outputs? where are the tests?"). I don't always know if policies exist so I can ask ("do we have guards around XYZ going offline? where?"). After learning the lay of the land, I decide what we need and how it fits in with the current design, and ask the agent to verify that my understanding of the flow makes sense. I'll of course review all the code that comes out.

Sometimes in review I'll be surprised that my understanding was flawed and the AI subtly misled me during the discussion, but that's super rare and that's honestly still helping me learn and understand.

Frankly it's no different than if I were pair-coding with a teammate who happened to type 25,000 wpm, and who never takes a day off.

Comment by 0c3ca83 3 days ago

If you had an electrician that told you "Oh, I don't learn by running wires, but if I didn't immediately see where a wire lead, I'd ask someone who knew, and then I read wiring diagrams after the other person did the work", would you hire them?

Comment by StilesCrisis 3 days ago

I dunno, man. At some point an experienced electrician thinks about the blueprints and hires apprentices to run the wires.

Comment by 0c3ca83 3 days ago

When they stop working at the site when they make the blueprints -- or worse, only look at them, you should run, or at least make sure they're only involved in management, and not any important technical decision making.

They are not going to do a good job.

Software engineers used to mock non-coding architects for good reason.

Comment by StilesCrisis 3 days ago

Again, it sounds like you are against vibe coding ("stop working at the site") and so am I. There's a middle ground worth acknowledging: we've built an automatic wire pulling machine and there's no reason to hand-pull anymore unless it's a really weird bend. If you just load up the machine with a spool and come back in 24 hours, though, it'll make a mess of wire all over the place.

Comment by 0c3ca83 3 days ago

My point is that reading and inspection is not enough to learn.

Comment by StilesCrisis 3 days ago

I'm past the point in my career where I need to worry about learning C++. The rules of the system are what matter.

Comment by 0c3ca83 3 days ago

My point is that reading is not enough for learning the rules of the system. Again, architects that don't write code were mocked for the entire history of software engineering.

Comment by StilesCrisis 3 days ago

They were mocked because they became mentally detached from the actual rules of the system, and because they weren't in the trenches landing PRs. Trust me, I know, I worked with one. (He was also a huge proponent of AI)

Comment by beej71 2 days ago

I'm not saying that at all. What I am saying is that I've never grown more mentally sharp by punting to AI. Learning a better solution is not the same as becoming more sharp.

Comment by spuz 4 days ago

This is the same approach I use. I don't know if it actually produces good results yet as I've only been doing this for about three months. At the very least it feels like I have some agency in my work which I think is one of the things people complain they lose to AI.

Comment by nk_kolja 3 days ago

Do people not use AI this way in prod?

Comment by RunSet 4 days ago

"Other people use slop the wrong way."

https://en.wikipedia.org/wiki/Third-person_effect

Comment by tehnoslow 3 days ago

I like this concept

Comment by pazimzadeh 3 days ago

sounds like 'design' is back

Comment by etcetcetcetceta 3 days ago

>Your brain, and then

>AI, and then

>Your brain

I'm sorry but this is not a "brain sandwich" this is an ai sandwich...when a slice of ham is between two slices of bread do we call it a "bread sandwich"?

Comment by thedailymail 3 days ago

If we follow deli conventions, this is more of a slop-on-brain (akin to a ham-on-rye) than a brain sandwich on your bread of choice.

Comment by jmarlow47 4 days ago

This approach appears valuable for personal growth as an engineer, yet it demands discipline that may not yield returns in corporate settings. Specifically:

> The rule of thumb is: if you can’t explain what’s changing and why, it’s not ready for someone else to take a look

I have observed firsthand that the metric or "understanding" can be irrelevant to management. When delivery dominates, understanding can be deferred to future agents who will gladly consume your codebase and convince you they grasp it, and further, that you do too. If I invest substantial effort in my PRs only for them to be /review'd, does it still matter? Perhaps reviewers should practice brain sandwich as well.

The worst offenders seem to sit at either extreme: fully AI firms that treat understanding as a human weakness and prioritize outcomes alone, or large corporate teams building internal CRUD apps whose middle management merely pretends to value good engineering to satisfy finicky senior engineers.

Not a criticism on the authors work at all, I like the idea (and I don't think they were trying to solve anything to do with work culture), but ultimately if my company doesn't find my practice valuable, I can't easily justify taking it on. Especially if I have to sell to them that I'm going to be spending _more_ time delivering. Fun times!

Comment by apical_dendrite 3 days ago

Our CEO, COO, etc are starting to see non-technical work go to customers with huge mistakes (committing to things that don't exist for instance). I also think seeing the Claude-style of writing everywhere has become tiresome for execs. That seems to have helped force a bit of an attitude change from always wanting to know how we could use AI in every process, to insisting that certain things should never be done by AI.

This is anecdotal of course, but at least at my company it's getting a bit easier to advocate for humans to do the thinking and understanding.

Comment by ThrowawayR2 3 days ago

The return is that the developer doesn't get washed out of the industry 10-20 years into their career because they are a senior with no or weak understanding.

Comment by AnaMaria09 1 day ago

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Comment by hncbw02z5a 4 days ago

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