Microsoft agentically ports Copilot runtime to Rust for $120K

tecoholic

One of the thorniest conversions was the session.ts file, which was over 30,000 lines of TypeScript that touched all aspects of the runtime. This can’t be real. Single file with 30K lines? Which human being is working on it and how much RAM does it take for a code editor to load that with full symbol tree? I am genuinely curious. Is this common? I think most files I come across stretch to maybe 2-3k lines max.

Rexxar

They don't have to tell us they are vibe coding everything. - there are now ridiculous vibe coded localisation in VS2026 - task manager started to not report cpu usage correctly recently (the number becomes stalled) - file explorer display the "loading" icon infinitely on some directories - and many other things!

amelius

Still hoping for a company to agentically port the python ecosystem to GIL-free python.

andrewstuart

Can we not say “agentically” please?

perching_aix

Is that why session compaction stopped working for me in VS Code at the end of this week, or is that just the integrated extension itself having a normal one? Though it's the same extension that can't keep its session timestamps straight, randomly hides sessions I was just in (then suddenly remembers them after going in and out of a session), and completely shits itself visually when using OpenAI's models, so maybe it really is just the latter.

dmix

> agents converted 430,000 lines of TypeScript into 800,000 lines of production Rust The +400k new lines were probably code comments the agents added to everything

hollowturtle

> The original TypeScript implementation completed 7.55 of those lifecycles per second, while Rust running in-process managed 120 per second - representing a 15.9x speedup on that particular workload. Does this impresses/surprises anyone? Two folds: 1) I believe the most optimized JavaScript code could near the performance of this phase 1 port without optimizations. I would have gone with that first, many would think that would not be as cost efficient but: 2) optimizing the rust code will require 10x the effort of the 1 by 1 conversion, just because you now need idiomatic rust code that likely has nothing to do with a plain translation. So defeating the initial gain, there's nothing to do the bottleneck gets just pushed elsewhere

meerita

I wrote to the post of Andrea (a dev from the Copilot team) about their 800K LoC: 128 PRs, shipped incrementally. Existing end-to-end tests ran against the new code at every step. Total: ~1,301,378 lines of Rust. Production: 832,378 Unit tests: ~469,000 Combined: ~1.30 million lines On top of the 832K LoC are mostly tests she answered: > Yeap, 832,378 lines of production Rust. the +800K number is production only; unit tests are another +469K on top. https://x.com/acolombiadev/status/2100660224298193081?s=20

iamgopal

why golang lost to rust ?

baxuz

The fuck does "agentically" mean

jdw64

Now I'm starting to really feel that I should use Rust, but I have no idea where to actually apply it.

Havoc

Can they port their m365 chat UI too? Don't know what tech stack it is but I'm guessing electron judging by how buggy and slow it is

aniceperson

they ported their coding harness, something known for being simply an extensible http and subprocess wrapper, into a monolithic blob. They took their bloated and slow coding harness, and turned into an un-maintanable blob.

turowicz

They really built that shit in TS? Mad!

ChrisArchitect

Source: https://github.blog/ai-and-ml/generative-ai/migrating-the-gi...

mixxit

I'm slowing moving everything to kubuntu and have for some time has it in my non work life Really nothing works anymore as great a product full fat visual studio and windows 7 was I don't have time to deal with your bugs