Memory and concurrency safety the compiler checks
Our crates compile with #![forbid(unsafe_code)], so the compiler rules out out-of-bounds writes, use-after-free and data races. Nobody has to take a reviewer's word for it, human or AI. SIMD goes through two small primitive crates, archmage and magetypes, that wrap the intrinsics once; a few older crates still carry unsafe code, and we treat it as debt.
Limits on everything
Decoders and encoders take resource limits (dimensions, pixel counts, memory) and fail cleanly instead of taking the process down. Long jobs accept cooperative cancellation, so a server can stop one that runs too long. We also predict CPU cost before doing the work, so a pipeline can refuse or reroute an expensive request up front.
Bytes in, bytes out
Our domain is bytes and configuration in, bytes out, which makes it unusually testable. When a C reference implementation exists, we test against it bit for bit: zenav1-aom is checked module by module against libaom, and zenjpegai reproduces the JPEG AI reference encoder byte for byte on 25 of 32 reference encodes. Where pixels are allowed to differ, psychovisual metrics tell us whether a person would see it.
Fuzzing, continually, on every platform
Every product is fuzzed continually, on every platform we ship. Crashes become minimized regression files that every later build has to pass.
Millions of test files
Testing at this depth takes data: millions of test files, and 4 to 6 TB of data churned on an average day. That is why we run servers at home and in the cloud. Creative testing (new oracles, differential checks against other decoders, synthetic stress images) is most of the work, more than writing the codecs themselves.
Six machines, every target
AI agents work on six dedicated development machines with different CPUs and operating systems, so the fast paths are built and tested for macOS, Windows, Linux and WebAssembly, on x86-64 and ARM, instead of on whatever one laptop happens to have.
Metrics we can trust
Bit-exact tests say whether the bytes match; they can't say whether an image looks better. For that we built zensim, our perceptual metric, which we consider the front of the image-quality-assessment field. To get there we ported 141 image-quality metrics to Rust (what each costs to run is on metric-brief.imazen.org), gathered over a terabyte of compressed IQA datasets, and scored millions of image encodes, including synthetic training data, so the metric isn't overfitted to one benchmark. A metric we trust does two jobs: it tells us when a codec change is a real breakthrough, and it steers the encoders' own decisions from the inside.
Why this makes AI safe to use
Provable memory and concurrency safety, hard resource limits and exhaustive testing are what let us use frontier AI models here. A model proposes a change; the compiler rules out whole classes of bugs, and the bit-exact tests, fuzzers and metrics catch most of the rest before anything ships. That is how a small team is building what we intend to be the best collection of codecs and imaging software in the world.
What it replaces
ImageMagick has 913 published vulnerabilities (OpenCVE, checked October 28, 2026). We don't think it belongs on servers that process images from the internet. This toolset is built to replace it there: memory-safe, far faster, with better compression, and generally more capable. It covers most of what people reach for ffmpeg or libvips to do as well.
What would help
Access to the models' cybersecurity capabilities would make me faster. Codec work is parsing hostile input, so even safe-Rust codec work trips the models' security filters often. The same access would let me help other projects in the field improve: I've contributed security-relevant fixes to most of the codecs that ship with Google Chrome.
Owner's account, 2026-10-28. Figures in this chapter are the owner's statements unless marked as measured; the measured ones link to their source on this page.