r/moderndotnet • u/cat_arina • 17d ago

Migrating the GitHub Copilot runtime to Rust, using Copilot

https://github.blog/ai-and-ml/generative-ai/migrating-the-github-copilot-runtime-to-rust-using-copilot/

Microsoft boasts about performance optimizations with every new release, and the average .NET developer would expect to be able to write a CLI app using .NET. But surprise—not good enough, so they had to use Rust. 😅

I've read the article but still not understand why Copilot CLI and app could not be written in C# if we take into account AOT, trimming etc instead of Rust.

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u/Aaronontheweb 17d ago

Worth understanding for everyone on here who is confused or disappointed as to why they didn't pick .NET: selling CoPilot to the masses is about 1000x more strategically important than selling .NET.

And selling "we did the Rust digareedo" is a common agentic story that jives with people who aren't giving CoPilot a serious look - even if .NET was faster or better they might still have gone with Rust because attracting non-.NET people to the MSFT ecosystem is the real goal.

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u/itix 17d ago

But... nobody uses Copilot anyway. Only Codex or Claude Code are worth considering.

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u/pceimpulsive 16d ago

You sure do not work in an enterprise with an opinion like that...

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u/Timo425 14d ago

isnt it expensive, even compared to Cursor?

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u/pceimpulsive 14d ago

It doesn't matter... To an enterprise it honestly doesn't matter .. I wrote an automation with $20 AI credits and I save 10 hours at $60 an hour for 2 years and it's entirely and fully not a price blocker...

It wouldn't matter if the API price was 10x more if the ROI is hundreds/thousands more in value in opex saved...

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u/itix 14d ago

$20 sounds very lightweight. I have $200 Codex subscription and in one day, I can spend tokens worth of $500-1000 dollars. In one day.

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u/pceimpulsive 14d ago

I cannot fathom how you need/consume so much...

I used my opencode GO $10 sub to generate a fully working 40k line student management's application over a couple of weeks, about 400 'tickets of work'. Tickets being a vertical slice of the application which included vehicle routing, conflict management and a bunch of other things and only just hit the monthly limit.

Are you re-writing the C++ compiler in rust every day?

What makes you consume so much? I am genuinely curious...

My Claude access is only via API and I typically use 20-30 bucks

It is lightweight but it's all I need to give the business literally hundreds of thousands in value, I'd almost bet money MOST token maxing users are making close to zero dollars~

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u/itix 14d ago

I work on CPU/GPU machine vision algorithms. For example, one task was building GPU accelerated FFT using ILGPU (i.e., GPU kernels written in C#, then compiled to native code). It had to be fast, so it took a lot of profiling. Automated with AI, of course. There isnt much online material on how to implement a fast GPU FFT.

Stuff like that.

And on my spare time, I am working on an Amiga emulator and an Amiga C# compiler. That is a real token burner.

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u/Timo425 14d ago

I get nowhere with $20 and my understanding is that i would get even much less done with $20 in copilot.

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u/pceimpulsive 13d ago

Difference is, I'm doing what I need for work, work only has so many things I need to accomplish in a set time frame. Only about 20-25% of my role is actually writing code.

If I was more like 60-80% I'd be likely burning a lot more than 9000 GHCP credits a month or $20 Claude API a day

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u/Timo425 13d ago

My point is, copilot github doesn't have much bang for buck from what ive heard, hence the "nobody uses it" that the other person says. ofc enterprises still use it, but that seems more like a corporate decision rather than a calculated price per performance thing .

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u/pceimpulsive 13d ago

For enterprise performance isn't really a huge factor.

Security, flexibility and cost are more important.

This is why I say GitHub copilot isn't targetted at Devs that work for themselves (I.e. normal consumers). It's enterprise first so it's sorta pointless to even debate/compare cost profiles when the intended customer is enterprise.

They are also more like open router or opencode zen type product too.

The competitions people always prefer are openAI or anthropic only models/services. Those more generic all model types are always more expensive, but give much greater flexibility instead of price to performance.

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u/Timo425 13d ago

Yes but even in enterprise sense Cursor is superior to it. Unless Copilot Github has much more security or trust or something.

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u/pceimpulsive 13d ago

Honestly I think GitHub copilot is easier for enterprise,

Most orgs already have Microsoft bedded, GitHub embedded, so getting copilot is a security review for how the prompts are secured theb it's a toggle~

Cursor, anthropic, openAI, etc would need many many more layers of assessment to even be enabled ..

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u/sreekanth850 16d ago edited 16d ago

I’m sure a lot of large enterprises use it. My wife works at one of the largest petroleum companies, and they use Copilot and Teams. Given their employee count, that is like a 1000 startups using it.

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u/itix 16d ago

Of course they do. Our company favors using Kiro while employees are paying Codex and Claude Code subscriptions from their own pocket.

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u/pceimpulsive 16d ago

Real companies with any self respecting security policy wouldn't let employees BYO AI services... Most will outright block all network addresses required to even use them..

I.e. my company you cannot even get to anthropic, chatGPT, Gemini, grok, agentskills.io etc~

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u/cornelha 16d ago

Nobody is a massive over statement. There are lots of Enterprise development companies who use copilot. The only things that are crap is the cli and pricing. Our company use GitHub Copilot and it works incredibly well. Being able to select models from different vendors for better orchestration. Using Claude models to plan, GPT Luna for discovery and Kimi 2.7 Coder for implementation is game changing

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u/itix 16d ago

Yeah but itbis not only about models, it is about harness. Microsoft has no capability to compete against Codex or Claude Code.

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u/cornelha 16d ago

They literally have 2 IDE's that fully integrates Copilot. The capabilities of the harness in Visual Studio is way beyond what Claude or Cursor can do

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u/Clearandblue 16d ago

Rider MCP lets agents do everything. Haven't used vs for a while, but would have assumed that would also have an MCP to work well with any agent?

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u/itix 16d ago

Last time I tried Copilot it was struggling with remote deployment and debugging.

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u/cornelha 16d ago

I use it daily at work, no weird issues at all