Building and testing a config management orchestrator for Windows
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
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Jane Street Tech Blog
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15 posts in the last 90 days · newest 6 Oct
Scaling and benchmarking a critical message bus using a new indexing strategy
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
How recurring network maintenance exposed 6 bugs
Jane Street does a lot of network maintenance over the weekends. In each maintenance, a cabinet may lose connectivity for 15 to 25 minutes. Our internal Kafka infrastructure is supposed to be resilient to these partitions, and reconnect when connectivity resumes. For several…
A resilient kernel log reporter
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
A FUSE server for our in-house storage backend
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
What the interns have wrought, special jumbo 2026 edition
It’s time again to review some of what Jane Street’s interns built over the summer, though this year we’re going to try to cover more projects and in more depth. In particular we’re including projects from teams and roles whose work has historically been hard to talk about…
Trading off compute for memory with activation checkpointing
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
What the TDOE interns have wrought, 2026 edition
The following is part of a series of posts about 2026 summer intern projects—for more, see “What the interns have wrought, special jumbo 2026 edition”
Mitigating memorization in LLMs
The following is part of a series of posts about 2026 summer intern projects – for more, see “What the interns have wrought, special jumbo 2026 edition”
Can you use autoregressive diffusion to generate market data?
The following is part of a series of posts about 2026 summer intern projects – for more, see “What the interns have wrought, special jumbo 2026 edition”
A study of sequence weighting at scale
TL;DR: We study the scaling laws of data weighting across in-house and open-weight LMs, finding non-monotonic behavior across scales. We vary the weight assigned to sequences during training and measure how strongly the model’s loss reduction on a sequence depends on the…
Using OxCaml to implement type-safe reference counting between OCaml and Python
Jane Street is known for being an OCaml shop, but for years now Python has been our second major programming language, acting as the primary tool for data analysis and (especially importantly these days) machine learning. Most of our traders and researchers think and write in…
Formal methods and the future of programming
I’ve been telling people for the last 25 years that Jane Street as an organization was just not interested in formal methods.
strace-ui, Bonsai_term, and the TUI renaissance
We’ve always found strace useful but somewhat hard to work with. Its output is often inscrutable, it’s hard to follow subprocesses or threads, and if you want to filter syscalls you have to rerun the trace with a flag for each one. What you want in debugging is a tool for…
Using group theory to explore the space of positional encodings for attention
Attention is a computational primitive at the core of modern language models, allowing internal representations to reference and influence each other. It’s how these models handle sequential data in the first place.
Can you reverse engineer our neural network?
A lot of “capture-the-flag” style ML puzzles give you a black box neural net, and your job is to figure out what it does. When we were thinking of creating our own ML puzzle early last year, we wanted to do something a little different. We thought it’d be neat to give users a…