Why we write our own code

projectMM pulls in no third-party libraries: no FastLED, no ESPAsyncWebServer, no ArduinoJson. A library that is genuinely needed lives behind the platform boundary in src/platform/, never in core or the light domain. The what, with the replacement for each, is in building.md § Third-party libraries. This page is the why.

A dependency is a hole in the test coverage

Every dependency is a part of the system you can observe but cannot reason about. You can test around it, feeding it inputs and checking what comes out, hoping the middle behaves. You cannot test through it: you cannot force it into the state you need, make it fail on demand to see what your code does next, or instrument what it does under memory pressure.

On an embedded target that is exactly backwards. The failures that matter here are timing, fragmentation, and behavior that only appears after four hours of running. Testing around a black box puts the interesting failures precisely where you cannot look.

When everything is ours, the test suite reaches the whole stack with nothing exempt. That is what makes the regression rule affordable: when a bug is found, the fix includes a test that reproduces it, with the root cause named in the test. Regression stops being something to hope about and becomes something to eliminate. The same holds for memory behavior, timing, and what the platform layer does when something goes wrong: when it is all ours, why did it do that is always a question with an answer.

The trade is real. A much larger surface to maintain, every bug ours, and nobody upstream fixing things while we sleep. A bigger surface that can be tested completely is still easier to live with than a smaller one with holes in it.

Why this became possible

This is not a decision that could have been made a few years ago, and it is not the result of better judgment.

Writing your own version of a mature library used to be irrational for a project this size. Not impossible: irrational. The budget was evenings, and libraries exist precisely to buy time that is not there. Taking the dependency was the correct call, and it was taken, repeatedly, for years.

What changed is the effort of writing code, and what changed it is AI agents. That is the whole reason. A rebuild that would have been years of Saturdays became something worth attempting, and the architecture that follows from full ownership, testable end to end with no black boxes, became reachable rather than theoretical. How that work is actually run, and the rules the agents work under, is in Principles & process.

Why agents at all

Using agents to build open-source software is contested, and a page that credits them with making this project possible cannot reasonably skip past that. So, briefly and once: where we stand.

We use AI agents because the technology is not going away, and the only way to learn what a tool really does, where it is strong and where it quietly fails, is to run a real project on it.

The two objections we hear most are that agents take developers' jobs, and that the energy they burn is not worth it. On both we have a position rather than an argument: we think AI changes jobs rather than takes them, the way computers changed office work from the 1990s onward, and we think the energy cost is defensible. We are not going to argue either here, and neither is a claim that everyone should work this way.

What this is not

It is not a verdict on the libraries we moved away from. They work, they have thousands of users, and they were built by people solving real problems on hardware we have never touched.

It is also not arms-length criticism. We built, maintained and contributed to the projects this one descends from, and the code we spent years inside was written by other people and by us. Those lessons are recorded in history.

And it is not a general recommendation. No-dependency is right for this project because of what this project is for: total control of the target, and a test system with no blind spots. For most software it would be a bad trade.

Good theft and bad theft

Austin Kleon's Steal Like an Artist has a chart worth borrowing. Good theft: honor, study, steal from many, credit, transform, remix. Bad theft: degrade, skim, steal from one, plagiarize, imitate, rip off. His own test is whether the person you stole from would shake your hand if you met them in a stalled elevator.

Writing your own implementation of a known idea can land in either column, and which one has nothing to do with the tools used to type it. Four rows carry the weight here.

Study, not skim. This is the row that AI agents genuinely threaten, and it is worth naming rather than glossing. An agent can reproduce a working pattern without anyone involved understanding why it works, which is skimming with better output. The countermeasure is structural: each feature is spec'd from the primary source, the datasheet, the standard, the textbook algorithm, before it is written, and every line and every spec is reviewed. If the reasoning behind a piece of code cannot be stated, it does not go in. That standard is more work, not less.

Ideas, not code. We are not trying to acquire anyone's implementation. What travels is the idea: an approach to a problem, a technique someone proved works on real hardware, a mistake worth not repeating. Most of what projectMM implements is publicly defined. Art-Net, E1.31/sACN, DDP, WS2812 timing, the peripheral datasheets, textbook DSP: those are industry standards, not anyone's property, and we implement them from the primary source. Textbook algorithm, textbook name, our implementation.

Steal from many, not one. A rewrite that is one library with the names changed is a rip-off, whoever or whatever typed it. What is here comes from several sources, from the standards themselves, from what this hardware forces on you, and from years of our own prior work.

Transform, not imitate. The architecture is not the old design retyped. Full testability, a single module model and live reconfiguration force a different shape; an imitation could not have satisfied them.

Credit is the fifth row, and it needs care for a mechanical reason: rewriting removes the easiest form of attribution there is. Take a dependency and the author's name appears in the manifest automatically, as a side effect of the build. Write it yourself and that disappears, even when the idea, the approach or the algorithm came straight from someone else's work. So it has to be deliberate: named in the README's Credits, named in each module's Prior art notes, named in the history digests, in the place where it can be checked against the source.

If something here came from your work and is not credited where it should be, open an issue or find us on Discord. We would much rather hear it directly.