2026-04-08 08:00:00
Today I’m very happy to share that Mario Zechner is joining Earendil.
First things first: I think you should read Mario’s post. This is his news more than it is ours, and he tells his side of it better than I could. What I want to do here is add a more personal note about why this matters so much to me, how the last months led us here, and why I am so excited to have him on board.
Last year changed the way many of us thought about software. It certainly changed the way I did. I spent much of 2025 building, probing, and questioning how to build software, and in many more ways what I want to do. If you are a regular reader of this blog you were along for the ride. I wrote a lot, experimented a lot, and tried to get a better sense for what these systems can actually do and what kinds of companies make sense to build around them. There was, and continues to be, a lot of excitement in the air, but also a lot of noise. It has become clear to me that it’s not a question of whether AI systems can be useful but what kind of software and human-machine interactions we want to bring into the world with them.
That is one of the reasons I have been so drawn to Mario’s work and approaches.
Pi is, in my opinion, one of the most thoughtful coding agents and agent infrastructure libraries in this space. Not because it is trying to be the loudest or the fastest, but because it is clearly built by someone who cares deeply about software quality, taste, extensibility, and design. In a moment where much of the industry is racing to ship ever more quickly, often at the cost of coherence and craft, Mario kept insisting on making something solid. That matters to me a great deal.
I have known Mario for a long time, and one of the things I admire most about him is that he does not confuse velocity with progress. He has a strong sense for what good tools should feel like. He cares about details. He cares about whether something is well made. And he cares about building in a way that can last. Mario has been running Pi in a rather unusual way. He exerts back-pressure on the issue tracker and the pull requests through OSS vacations and other means.
The last year has also made something else clearer to me: these systems are not only exciting, they are also capable of producing a great deal of damage. Sometimes that damage is obvious; sometimes it looks like low-grade degradation everywhere at once. More slop, more noise, more disingenuous emails in my inbox. There is a version of this future that makes people more distracted, more alienated, and less careful with one another.
That is not a future I want to help build.
At Earendil, Colin and I have been trying to think very carefully about what a different path might look like. That is a big part of what led us to Lefos.
Lefos is our attempt to build a machine entity that is more thoughtful and more deliberate by design. Not an agent whose main purpose is to make everything a little more efficient so that we can produce even more forgettable output, but one that can help people communicate with more care, more clarity, and joy.
Good software should not aim to optimize every minute of your life, but should create room for better and more joyful experiences, better relationships, and better ways of relating to one another. Especially in communication and software engineering, I think we should be aiming for more thought rather than more throughput. We should want tools that help people be more considerate, more present, and more human. If all we do is use these systems to accelerate the production of slop, we will have missed the opportunity entirely.
This is also why Mario joining Earendil feels so meaningful to me. Pi and Lefos come from different starting points. There was a year of distance collaboration, but they are animated by a similar instinct: that quality matters, that design matters, and that trust is earned through care rather than captured through hype.
I am very happy that Pi is coming along for the ride. Me and Colin care a lot about it, and we want to be good stewards of it. It has already played an important role in our own work over the last months, and I continue to believe it is one of the best foundations for building capable agents. We will have more to say soon about how we think about Pi’s future and its relationship to Lefos, but the short version is simple: we want Pi to continue to exist as a high-quality, open, extensible piece of software, and we want to invest in making that future real. As for our thoughts of Pi’s license, read more here and our company post here.
2026-04-04 08:00:00
About five months ago I wrote about Absurd, a durable execution system we built for our own use at Earendil, sitting entirely on top of Postgres and Postgres alone. The pitch was simple: you don’t need a separate service, a compiler plugin, or an entire runtime to get durable workflows. You need a SQL file and a thin SDK.
Since then we’ve been running it in production, and I figured it’s worth sharing what the experience has been like. The short version: the design held up, the system has been a pleasure to work with, and other people seem to agree.
Absurd is a durable execution system that lives entirely inside Postgres. The core is a single SQL file (absurd.sql) that defines stored procedures for task management, checkpoint storage, event handling, and claim-based scheduling. On top of that sit thin SDKs (currently TypeScript, Python and an experimental Go one) that make the system ergonomic in your language of choice.
The model is straightforward: you register tasks, decompose them into steps, and each step acts as a checkpoint. If anything fails, the task retries from the last completed step. Tasks can sleep, wait for external events, and suspend for days or weeks. All state lives in Postgres.
If you want the full introduction, the original blog post covers the fundamentals. What follows here is what we’ve learned since.
The project got multiple releases over the last five months. Most of the changes are things you’d expect from a system that people actually started depending on: hardened claim handling, watchdogs that terminate broken workers, deadlock prevention, proper lease management, event race conditions, and all the edge cases that only show up when you’re running real workloads.
A few things worth calling out specifically.
Decomposed steps. The original design only had ctx.step(), where you pass
in a function and get back its checkpointed result. That works well for many
cases but not all. Sometimes you need to know whether a step already ran before
deciding what to do next. So we added beginStep() / completeStep(), which
give you a handle you can inspect before committing the result. This turned out
to be very useful for modeling intentional failures and conditional logic.
This in particular is necessary when working with “before call” and “after call”
type hook APIs.
Task results. You can now spawn a task, go do other things, and later come back to fetch or await its result. This sounds obvious in hindsight, but the original system was purely fire-and-forget. Having proper result inspection made it possible to use Absurd for things like spawning child tasks from within a parent workflow and waiting for them to finish. This is particularly useful for debugging with agents too.
absurdctl. We built this out as a proper CLI tool. You can initialize
schemas, run migrations, create queues, spawn tasks, emit events, retry failures
from the command line. It’s installable via uvx or as a standalone binary.
This has been invaluable for debugging production issues. When something is
stuck, being able to just absurdctl dump-task --task-id=<id> and see exactly
where it stopped is a very different experience from digging through logs.
Habitat. A small Go application that serves up a web dashboard for monitoring tasks, runs, checkpoints, and events. It connects directly to Postgres and gives you a live view of what’s happening. It’s simple, but it’s the kind of thing that makes the system more enjoyable for humans.
Agent integration. Since Absurd was originally built for agent workloads,
we added a bundled skill that coding agents can discover and use to debug
workflow state via absurdctl. There’s also a documented pattern for making
pi agent turns durable by logging each message as a
checkpoint.
The thing I’m most pleased about is that the core design didn’t need to change all that much. The fundamental model of tasks, steps, checkpoints, events, and suspending is still exactly what it was initially. We added features around it, but nothing forced us to rethink the basic abstractions.
Putting the complexity in SQL and keeping the SDKs thin turned out to be a genuinely good call. The TypeScript SDK is about 1,400 lines. The Python SDK is about 1,900 but most of this comes from the complexity of supporting colored functions. Compare that to Temporal’s Python SDK at around 170,000 lines. It means the SDKs are easy to understand, easy to debug, and easy to port. When something goes wrong, you can read the entire SDK in an afternoon and understand what it does.
The checkpoint-based replay model also aged well. Unlike systems that require
deterministic replay of your entire workflow function, Absurd just loads the
cached step results and skips over completed work. That means your code doesn’t
need to be deterministic outside of steps. You can call Math.random() or
datetime.now() in between steps and things still work, because only the step
boundaries matter. In practice, this makes it much easier to reason about
what’s safe and what isn’t.
Pull-based scheduling was the right choice too. Workers pull tasks from Postgres as they have capacity. There’s no coordinator, no push mechanism, no HTTP callbacks. That makes it trivially self-hostable and means you don’t have to think about load management at the infrastructure level.
I had some discussions with folks about whether the right abstraction should have been a durable promise. It’s a very appealing idea, but it turns out to be much more complex to implement in practice. It’s however in theory also more powerful. I did make some attempts to see what absurd would look like if it was based on durable promises but so far did not get anywhere with it. It’s however an experiment that I think would be fun to try!
The primary use case is still agent workflows. An agent is essentially a loop that calls an LLM, processes tool results, and repeats until it decides it’s done. Each iteration becomes a step, and each step’s result is checkpointed. If the process dies on iteration 7, it restarts and replays iterations 1 through 6 from the store, then continues from 7.
But we’ve found it useful for a lot of other things too. All our crons just dispatch distributed workflows with a pre-generated deduplication key from the invocation. We can have two cron processes running and they will only trigger one absurd task invocation. We also use it for background processing that needs to survive deploys. Basically anything where you’d otherwise build your own retry-and-resume logic on top of a queue.
Absurd is deliberately minimal, but there are things I’d like to see.
There’s no built-in scheduler. If you want cron-like behavior, you run your own scheduler loop and use idempotency keys to deduplicate. That works, and we have a documented pattern for it, but it would be nice to have something more integrated.
There’s no push model. Everything is pull. If you need an HTTP endpoint to receive webhooks and wake up tasks, you build that yourself. I think that’s the right default as push systems are harder to operate and easier to overwhelm but there are cases where it would be convenient. In particular there are quite a few agentic systems where it would be super nice to have webhooks natively integrated (wake on incoming POST request). I definitely don’t want to have this in the core, but that sounds like the kind of problem that could be a nice adjacent library that builds on top of absurd.
The biggest omission is that it does not support partitioning yet. That’s unfortunate because it makes cleaning up data more expensive than it has to be. In theory supporting partitions would be pretty simple. You could have weekly partitions and then detach and delete them when they expire. The only thing that really stands in the way of that is that Postgres does not have a convenient way of actually doing that.
The hard part is not partitioning itself, it’s partition lifecycle management under
real workloads. If a worker inserts a row whose expires_at lands in a month
without a partition, the insert fails and the workflow crashes. So you need a
separate maintenance loop that always creates future partitions far enough ahead
for sleeps/retries, and does that for every queue.
On the delete side, the safe approach is DETACH PARTITION CONCURRENTLY, but
getting that to run from pg_cron doesn’t work because it cannot be run within a
transaction, but pg_cron runs everything in one.
I don’t think it’s an unsolvable problem, but it’s one I have not found a good solution for and I would love to get input on.
This brings me a bit to a meta point on the whole thing which is what the point of Open Source libraries in the age of agentic engineering is. Durable Execution is now something that plenty of startups sell you. On the other hand it’s also something that an agent would build you and people might not even look for solutions any more. It’s kind of … weird?
I don’t think a durable execution library can support a company, I really don’t. On the other hand I think it’s just complex enough of a problem that it could be a good Open Source project void of commercial interests. You do need a bit of an ecosystem around it, particularly for UI and good DX for debugging, and that’s hard to get from a throwaway implementation.
I don’t think we have squared this yet, but it’s already much better to use than a few months ago.
If you’re using Absurd, thinking about it, or building adjacent ideas, I’d love your feedback. Bug reports, rough edges, design critiques, and contributions are all very welcome—this project has gotten better every time someone poked at it from a different angle.
2026-03-20 08:00:00
Trees take quite a while to grow. If someone 50 years ago planted a row of oaks or a chestnut tree on your plot of land, you have something that no amount of money or effort can replicate. The only way is to wait. Tree-lined roads, old gardens, houses sheltered by decades of canopy: if you want to start fresh on an empty plot, you will not be able to get that.
Because some things just take time.
We know this intuitively. We pay premiums for Swiss watches, Hermès bags and old properties precisely because of the time embedded in them. Either because of the time it took to build them or because of their age. We require age minimums for driving, voting, and drinking because we believe maturity only comes through lived experience.
Yet right now we also live in a time of instant gratification, and it’s entering how we build software and companies. As much as we can speed up code generation, the real defining element of a successful company or an Open Source project will continue to be tenacity. The ability of leadership or the maintainers to stick to a problem for years, to build relationships, to work through challenges fundamentally defined by human lifetimes.
The current generation of startup founders and programmers is obsessed with speed. Fast iteration, rapid deployment, doing everything as quickly as possible. For many things, that’s fine. You can go fast, leave some quality on the table, and learn something along the way.
But there are things where speed is actively harmful, where the friction exists for a reason. Compliance is one of those cases. There’s a strong desire to eliminate everything that processes like SOC2 require, and an entire industry of turnkey solutions has sprung up to help — Delve just being one example, there are more.
There’s a feeling that all the things that create friction in your life should be automated away. That human involvement should be replaced by AI-based decision-making. Because it is the friction of the process that is the problem. When in fact many times the friction, or that things just take time, is precisely the point.
There’s a reason we have cooling-off periods for some important decisions in one’s life. We recognize that people need time to think about what they’re doing, and that doing something right once doesn’t mean much because you need to be able to do it over a longer period of time.
AI writes code fast which isn’t news anymore. What’s interesting is that we’re pushing this force downstream: we seemingly have this desire to ship faster than ever, to run more experiments and that creates a new desire, one to remove all the remaining friction of reviews, designing and configuring infrastructure, anything that slows the pipeline. If the machines are so great, why do we even need checklists or permission systems? Express desire, enjoy result.
Because we now believe it is important for us to just do everything faster. But increasingly, I also feel like this means that the shelf life of much of the software being created today — software that people and businesses should depend on — can be measured only in months rather than decades, and the relationships alongside.
In one of last year’s earlier YC batches, there was already a handful that just disappeared without even saying what they learned or saying goodbye to their customers. They just shut down their public presence and moved on to other things. And to me, that is not a sign of healthy iteration. That is a sign of breaking the basic trust you need to build a relationship with customers. A proper shutdown takes time and effort, and our current environment treats that as time not wisely spent. Better to just move on to the next thing.
This is extending to Open Source projects as well. All of a sudden, everything is an Open Source project, but many of them only have commits for a week or so, and then they go away because the motivation of the creator already waned. And in the name of experimentation, that is all good and well, but what makes a good Open Source project is that you think and truly believe that the person that created it is either going to stick with it for a very long period of time, or they are able to set up a strategy for succession, or they have created enough of a community that these projects will stand the test of time in one form or another.
Relatedly, I’m also increasingly skeptical of anyone who sells me something that supposedly saves my time. When all that I see is that everybody who is like me, fully onboarded into AI and agentic tools, seemingly has less and less time available because we fall into a trap where we’re immediately filling it with more things.
We all sell each other the idea that we’re going to save time, but that is not what’s happening. Any time saved gets immediately captured by competition. Someone who actually takes a breath is outmaneuvered by someone who fills every freed-up hour with new output. There is no easy way to bank the time and it just disappears.
I feel this acutely. I’m very close to the red-hot center of where economic activity around AI is taking place, and more than anything, I have less and less time, even when I try to purposefully scale back and create the space. For me this is a problem. It’s a problem because even with the best intentions, I actually find it very hard to create quality when we are quickly commoditizing software, and the machines make it so appealing.
I keep coming back to the trees. I’ve been maintaining Open Source projects for close to two decades now. The last startup I worked on, I spent 10 years at. That’s not because I’m particularly disciplined or virtuous. It’s because I or someone else, planted something, and then I kept showing up, and eventually the thing had roots that went deeper than my enthusiasm on any given day. That’s what time does! It turns some idea or plan into a commitment and a commitment into something that can shelter and grow other people.
Nobody is going to mass-produce a 50-year-old oak. And nobody is going to conjure trust, or quality, or community out of a weekend sprint. The things I value most — the projects, the relationships, the communities — are all things that took years to become what they are. No tool, no matter how fast, was going to get them there sooner.
We recently planted a new tree with Colin. I want it to grow into a large one. I know that’s going to take time, and I’m not in a rush.
2026-03-05 08:00:00
Because code gets cheaper and cheaper to write, this includes re-implementations. I mentioned recently that I had an AI port one of my libraries to another language and it ended up choosing a different design for that implementation. In many ways, the functionality was the same, but the path it took to get there was different. The way that port worked was by going via the test suite.
Something related, but different, happened with chardet. The current maintainer reimplemented it from scratch by only pointing it to the API and the test suite. The motivation: enabling relicensing from LGPL to MIT. I personally have a horse in the race here because I too wanted chardet to be under a non-GPL license for many years. So consider me a very biased person in that regard.
Unsurprisingly, that new implementation caused a stir. In particular, Mark Pilgrim, the original author of the library, objects to the new implementation and considers it a derived work. The new maintainer, who has maintained it for the last 12 years, considers it a new work and instructs his coding agent to do precisely that. According to author, validating with JPlag, the new implementation is distinct. If you actually consider how it works, that’s not too surprising. It’s significantly faster than the original implementation, supports multiple cores and uses a fundamentally different design.
What I think is more interesting about this question is the consequences of where we are. Copyleft code like the GPL heavily depends on copyrights and friction to enforce it. But because it’s fundamentally in the open, with or without tests, you can trivially rewrite it these days. I myself have been intending to do this for a little while now with some other GPL libraries. In particular I started a re-implementation of readline a while ago for similar reasons, because of its GPL license. There is an obvious moral question here, but that isn’t necessarily what I’m interested in. For all the GPL software that might re-emerge as MIT software, so might be proprietary abandonware.
For me personally, what is more interesting is that we might not even be able to copyright these creations at all. A court still might rule that all AI-generated code is in the public domain, because there was not enough human input in it. That’s quite possible, though probably not very likely.
But this all causes some interesting new developments we are not necessarily ready for. Vercel, for instance, happily re-implemented bash with Clankers but got visibly upset when someone re-implemented Next.js in the same way.
There are huge consequences to this. When the cost of generating code goes down that much, and we can re-implement it from test suites alone, what does that mean for the future of software? Will we see a lot of software re-emerging under more permissive licenses? Will we see a lot of proprietary software re-emerging as open source? Will we see a lot of software re-emerging as proprietary?
It’s a new world and we have very little idea of how to navigate it. In the interim we will have some fights about copyrights but I have the feeling very few of those will go to court, because everyone involved will actually be somewhat scared of setting a precedent.
In the GPL case, though, I think it warms up some old fights about copyleft vs permissive licenses that we have not seen in a long time. It probably does not feel great to have one’s work rewritten with a Clanker and one’s authorship eradicated. Unlike the Ship of Theseus, though, this seems more clear-cut: if you throw away all code and start from scratch, even if the end result behaves the same, it’s a new ship. It only continues to carry the name. Which may be another argument for why authors should hold on to trademarks rather than rely on licenses and contract law.
I personally think all of this is exciting. I’m a strong supporter of putting things in the open with as little license enforcement as possible. I think society is better off when we share, and I consider the GPL to run against that spirit by restricting what can be done with it. This development plays into my worldview. I understand, though, that not everyone shares that view, and I expect more fights over the emergence of slopforks as a result. After all, it combines two very heated topics, licensing and AI, in the worst possible way.
2026-02-13 08:00:00
Historically, writing code was slower than reviewing code.
It might not have felt that way, because code reviews sat in queues until someone got around to picking it up. But if you compare the actual acts themselves, creation was usually the more expensive part. In teams where people both wrote and reviewed code, it never felt like “we should probably program slower.”
So when more and more people tell me they no longer know what code is in their own codebase, I feel like something is very wrong here and it’s time to reflect.
Software engineers often believe that if we make the bathtub bigger, overflow disappears. It doesn’t. OpenClaw right now has north of 2,500 pull requests open. That’s a big bathtub.
Anyone who has worked with queues knows this: if input grows faster than throughput, you have an accumulating failure. At that point, backpressure and load shedding are the only things that retain a system that can still operate.
If you have ever been in a Starbucks overwhelmed by mobile orders, you know the feeling. The in-store experience breaks down. You no longer know how many orders are ahead of you. There is no clear line, no reliable wait estimate, and often no real cancellation path unless you escalate and make noise.
That is what many AI-adjacent open source projects feel like right now. And increasingly, that is what a lot of internal company projects feel like in “AI-first” engineering teams, and that’s not sustainable. You can’t triage, you can’t review, and many of the PRs cannot be merged after a certain point because they are too far out of date. And the creator might have lost the motivation to actually get it merged.
There is huge excitement about newfound delivery speed, but in private conversations, I keep hearing the same second sentence: people are also confused about how to keep up with the pace they themselves created.
Humanity has been here before. Many times over. We already talk about the Luddites a lot in the context of AI, but it’s interesting to see what led up to it. Mark Cartwright wrote a great article about the textile industry in Britain during the industrial revolution. At its core was a simple idea: whenever a bottleneck was removed, innovation happened downstream from that. Weaving sped up? Yarn became the constraint. Faster spinning? Fibre needed to be improved to support the new speeds until finally the demand for cotton went up and that had to be automated too. We saw the same thing in shipping that led to modern automated ports and containerization.
As software engineers we have been here too. Assembly did not scale to larger engineering teams, and we had to invent higher level languages. A lot of what programming languages and software development frameworks did was allow us to write code faster and to scale to larger code bases. What it did not do up to this point was take away the core skill of engineering.
While it’s definitely easier to write C than assembly, many of the core problems are the same. Memory latency still matters, physics are still our ultimate bottleneck, algorithmic complexity still makes or breaks software at scale.
When one part of the pipeline becomes dramatically faster, you need to throttle input. Pi is a great example of this. PRs are auto closed unless people are trusted. It takes OSS vacations. That’s one option: you just throttle the inflow. You push against your newfound powers until you can handle them.
But what if the speed continues to increase? What downstream of writing code do we have to speed up? Sure, the pull request review clearly turns into the bottleneck. But it cannot really be automated. If the machine writes the code, the machine better review the code at the same time. So what ultimately comes up for human review would already have passed the most critical possible review of the most capable machine. What else is in the way? If we continue with the fundamental belief that machines cannot be accountable, then humans need to be able to understand the output of the machine. And the machine will ship relentlessly. Support tickets of customers will go straight to machines to implement improvements and fixes, for other machines to review, for humans to rubber stamp in the morning.
A lot of this sounds both unappealing and reminiscent of the textile industry. The individual weaver no longer carried responsibility for a bad piece of cloth. If it was bad, it became the responsibility of the factory as a whole and it was just replaced outright. As we’re entering the phase of single-use plastic software, we might be moving the whole layer of responsibility elsewhere.
But to me it still feels different. Maybe that’s because my lowly brain can’t comprehend the change we are going through, and future generations will just laugh about our challenges. It feels different to me, because what I see taking place in some Open Source projects, in some companies and teams feels deeply wrong and unsustainable. Even Steve Yegge himself now casts doubts about the sustainability of the ever-increasing pace of code creation.
So what if we need to give in? What if we need to pave the way for this new type of engineering to become the standard? What affordances will we have to create to make it work? I for one do not know. I’m looking at this with fascination and bewilderment and trying to make sense of it.
Because it is not the final bottleneck. We will find ways to take responsibility for what we ship, because society will demand it. Non-sentient machines will never be able to carry responsibility, and it looks like we will need to deal with this problem before machines achieve this status. Regardless of how bizarre they appear to act already.
I too am the bottleneck now. But you know what? Two years ago, I too was the bottleneck. I was the bottleneck all along. The machine did not really change that. And for as long as I carry responsibilities and am accountable, this will remain true. If we manage to push accountability upwards, it might change, but so far, how that would happen is not clear.
2026-02-09 08:00:00
Last year I first started thinking about what the future of programming languages might look like now that agentic engineering is a growing thing. Initially I felt that the enormous corpus of pre-existing code would cement existing languages in place but now I’m starting to think the opposite is true. Here I want to outline my thinking on why we are going to see more new programming languages and why there is quite a bit of space for interesting innovation. And just in case someone wants to start building one, here are some of my thoughts on what we should aim for!
Does an agent perform dramatically better on a language that it has in its weights? Obviously yes. But there are less obvious factors that affect how good an agent is at programming in a language: how good the tooling around it is and how much churn there is.
Zig seems underrepresented in the weights (at least in the models I’ve used) and also changing quickly. That combination is not optimal, but it’s still passable: you can program even in the upcoming Zig version if you point the agent at the right documentation. But it’s not great.
On the other hand, some languages are well represented in the weights but agents still don’t succeed as much because of tooling choices. Swift is a good example: in my experience the tooling around building a Mac or iOS application can be so painful that agents struggle to navigate it. Also not great.
So, just because it exists doesn’t mean the agent succeeds and just because it’s new also doesn’t mean that the agent is going to struggle. I’m convinced that you can build yourself up to a new language if you don’t want to depart everywhere all at once.
The biggest reason new languages might work is that the cost of coding is going down dramatically. The result is the breadth of an ecosystem matters less. I’m now routinely reaching for JavaScript in places where I would have used Python. Not because I love it or the ecosystem is better, but because the agent does much better with TypeScript.
The way to think about this: if important functionality is missing in my language of choice, I just point the agent at a library from a different language and have it build a port. As a concrete example, I recently built an Ethernet driver in JavaScript to implement the host controller for our sandbox. Implementations exist in Rust, C, and Go, but I wanted something pluggable and customizable in JavaScript. It was easier to have the agent reimplement it than to make the build system and distribution work against a native binding.
New languages will work if their value proposition is strong enough and they evolve with knowledge of how LLMs train. People will adopt them despite being underrepresented in the weights. And if they are designed to work well with agents, then they might be designed around familiar syntax that is already known to work well.
So why would we want a new language at all? The reason this is interesting to think about is that many of today’s languages were designed with the assumption that punching keys is laborious, so we traded certain things for brevity. As an example, many languages — particular modern ones — lean heavily on type inference so that you don’t have to write out types. The downside is that you now need an LSP or the resulting compiler error messages to figure out what the type of an expression is. Agents struggle with this too, and it’s also frustrating in pull request review where complex operations can make it very hard to figure out what the types actually are. Fully dynamic languages are even worse in that regard.
The cost of writing code is going down, but because we are also producing more of it, understanding what the code does is becoming more important. We might actually want more code to be written if it means there is less ambiguity when we perform a review.
I also want to point out that we are heading towards a world where some code is never seen by a human and is only consumed by machines. Even in that case, we still want to give an indication to a user, who is potentially a non-programmer, about what is going on. We want to be able to explain to a user what the code will do without going into the details of how.
So the case for a new language comes down to: given the fundamental changes in who is programming and what the cost of code is, we should at least consider one.
It’s tricky to say what an agent wants because agents will lie to you and they are influenced by all the code they’ve seen. But one way to estimate how they are doing is to look at how many changes they have to perform on files and how many iterations they need for common tasks.
There are some things I’ve found that I think will be true for a while.
The language server protocol lets an IDE infer information about what’s under the cursor or what should be autocompleted based on semantic knowledge of the codebase. It’s a great system, but it comes at one specific cost that is tricky for agents: the LSP has to be running.
There are situations when an agent just won’t run the LSP — not because of technical limitations, but because it’s also lazy and will skip that step if it doesn’t have to. If you give it an example from documentation, there is no easy way to run the LSP because it’s a snippet that might not even be complete. If you point it at a GitHub repository and it pulls down individual files, it will just look at the code. It won’t set up an LSP for type information.
A language that doesn’t split into two separate experiences (with-LSP and without-LSP) will be beneficial to agents because it gives them one unified way of working across many more situations.
It pains me as a Python developer to say this, but whitespace-based indentation is a problem. The underlying token efficiency of getting whitespace right is tricky, and a language with significant whitespace is harder for an LLM to work with. This is particularly noticeable if you try to make an LLM do surgical changes without an assisted tool. Quite often they will intentionally disregard whitespace, add markers to enable or disable code and then rely on a code formatter to clean up indentation later.
On the other hand, braces that are not separated by whitespace can cause issues too. Depending on the tokenizer, runs of closing parentheses can end up split into tokens in surprising ways (a bit like the “strawberry” counting problem), and it’s easy for an LLM to get Lisp or Scheme wrong because it loses track of how many closing parentheses it has already emitted or is looking at. Fixable with future LLMs? Sure, but also something that was hard for humans to get right too without tooling.
Readers of this blog might know that I’m a huge believer in async locals and flow execution context — basically the ability to carry data through every invocation that might only be needed many layers down the call chain. Working at an observability company has really driven home the importance of this for me.
The challenge is that anything that flows implicitly might not be configured. Take for instance the current time. You might want to implicitly pass a timer to all functions. But what if a timer is not configured and all of a sudden a new dependency appears? Passing all of it explicitly is tedious for both humans and agents and bad shortcuts will be made.
One thing I’ve experimented with is having effect markers on functions that are added through a code formatting step. A function can declare that it needs the current time or the database, but if it doesn’t mark this explicitly, it’s essentially a linting warning that auto-formatting fixes. The LLM can start using something like the current time in a function and any existing caller gets the warning; formatting propagates the annotation.
This is nice because when the LLM builds a test, it can precisely mock out these side effects — it understands from the error messages what it has to supply.
For instance:
fn issue(sub: UserId, scopes: []Scope) -> Token
needs { time, rng }
{
return Token{
sub,
exp: time.now().add(24h),
scopes,
}
}
test "issue creates exp in the future" {
using time = time.fixed("2026-02-06T23:00:00Z");
using rng = rng.deterministic(seed: 1);
let t = issue(user("u1"), ["read"]);
assert(t.exp > time.now());
}
Agents struggle with exceptions, they are afraid of them. I’m not sure to what degree this is solvable with RL (Reinforcement Learning), but right now agents will try to catch everything they can, log it, and do a pretty poor recovery. Given how little information is actually available about error paths, that makes sense. Checked exceptions are one approach, but they propagate all the way up the call chain and don’t dramatically improve things. Even if they end up as hints where a linter tracks which errors can fly by, there are still many call sites that need adjusting. And like the auto-propagation proposed for context data, it might not be the right solution.
Maybe the right approach is to go more in on typed results, but that’s still tricky for composability without a type and object system that supports it.
The general approach agents use today to read files into memory is line-based, which means they often pick chunks that span multi-line strings. One easy way to see this fall apart: have an agent work on a 2000-line file that also contains long embedded code strings — basically a code generator. The agent will sometimes edit within a multi-line string assuming it’s the real code when it’s actually just embedded code in a multi-line string. For multi-line strings, the only language I’m aware of with a good solution is Zig, but its prefix-based syntax is pretty foreign to most people.
Reformatting also often causes constructs to move to different lines. In many languages, trailing commas in lists are either not supported (JSON) or not customary. If you want diff stability, you’d aim for a syntax that requires less reformatting and mostly avoids multi-line constructs.
What’s really nice about Go is that you mostly cannot import symbols from
another package into scope without every use being prefixed with the package
name. Eg: context.Context instead of Context. There are escape hatches
(import aliases and dot-imports), but they’re relatively rare and usually
frowned upon.
That dramatically helps an agent understand what it’s looking at. In general,
making code findable through the most basic tools is great — it works with
external files that aren’t indexed, and it means fewer false positives for
large-scale automation driven by code generated on the fly (eg: sed, perl
invocations).
Much of what I’ve said boils down to: agents really like local reasoning. They want it to work in parts because they often work with just a few loaded files in context and don’t have much spatial awareness of the codebase. They rely on external tooling like grep to find things, and anything that’s hard to grep or that hides information elsewhere is tricky.
What makes agents fail or succeed in many languages is just how good the build tools are. Many languages make it very hard to determine what actually needs to rebuild or be retested because there are too many cross-references. Go is really good here: it forbids circular dependencies between packages (import cycles), packages have a clear layout, and test results are cached.
Agents often struggle with macros. It was already pretty clear that humans struggle with macros too, but the argument for them was mostly that code generation was a good way to have less code to write. Since that is less of a concern now, we should aim for languages with less dependence on macros.
There’s a separate question about generics and comptime. I think they fare somewhat better because they mostly generate the same structure with different placeholders and it’s much easier for an agent to understand that.
Related to greppability: agents often struggle to understand barrel files and they don’t like them. Not being able to quickly figure out where a class or function comes from leads to imports from the wrong place, or missing things entirely and wasting context by reading too many files. A one-to-one mapping from where something is declared to where it’s imported from is great.
And it does not have to be overly strict either. Go kind of goes this way, but not too extreme. Any file within a directory can define a function, which isn’t optimal, but it’s quick enough to find and you don’t need to search too far. It works because packages are forced to be small enough to find everything with grep.
The worst case is free re-exports all over the place that completely decouple the implementation from any trivially reconstructable location on disk. Or worse: aliasing.
Agents often hate it when aliases are involved. In fact, you can get them to even complain about it in thinking blocks if you let them refactor something that uses lots of aliases. Ideally a language encourages good naming and discourages aliasing at import time as a result.
Nobody likes flaky tests, but agents even less so. Ironic given how particularly good agents are at creating flaky tests in the first place. That’s because agents currently love to mock and most languages do not support mocking well. So many tests end up accidentally not being concurrency safe or depend on development environment state that then diverges in CI or production.
Most programming languages and frameworks make it much easier to write flaky tests than non-flaky ones. That’s because they encourage indeterminism everywhere.
In an ideal world the agent has one command, that lints and compiles and it tells the agent if all worked out fine. Maybe another command to run all tests that need running. In practice most environments don’t work like this. For instance in TypeScript you can often run the code even though it fails type checks. That can gaslight the agent. Likewise different bundler setups can cause one thing to succeed just for a slightly different setup in CI to fail later. The more uniform the tooling the better.
Ideally it either runs or doesn’t and there is mechanical fixing for as many linting failures as possible so that the agent does not have to do it by hand.
I think we will. We are writing more software now than we ever have — more websites, more open source projects, more of everything. Even if the ratio of new languages stays the same, the absolute number will go up. But I also truly believe that many more people will be willing to rethink the foundations of software engineering and the languages we work with. That’s because while for some years it has felt you need to build a lot of infrastructure for a language to take off, now you can target a rather narrow use case: make sure the agent is happy and extend from there to the human.
I just hope we see two things. First, some outsider art: people who haven’t built languages before trying their hand at it and showing us new things. Second, a much more deliberate effort to document what works and what doesn’t from first principles. We have actually learned a lot about what makes good languages and how to scale software engineering to large teams. Yet, finding it written down, as a consumable overview of good and bad language design, is very hard to come by. Too much of it has been shaped by opinion on rather pointless things instead of hard facts.
Now though, we are slowly getting to the point where facts matter more, because you can actually measure what works by seeing how well agents perform with it. No human wants to be subject to surveys, but agents don’t care. We can see how successful they are and where they are struggling.
