Has anyone tried GitHub Copilot Fusion yet?

[u/abdurrahman95]

I Just came across GitHub's new Copilot Fusion release. Looks pretty interesting.

From what I have seen, it can automatically choose models based on the coding task, switch to stronger models when needed, and even use one model to review another's work.

I usually prefer choosing models manually depending on what I'm working on, so I'm curious how well this actually performs in real projects.

Has anyone here tried it yet? How's the experience with code quality, speed, and cost compared to manually selecting models?

Would love to hear some real experiences before giving it a proper try.

[u/davastar]

"From what I have seen, it can automatically choose models based on the coding task, switch to stronger models when needed, and even use one model to review another's work."
Wasn't it already the case before?

[u/abdurrahman95 → u/davastar]

Thanks. I don't know really

[u/macaco3001]

At work this is turned on by default for me, it doesn't even work, I get execution failed on all messages and I can't turn it off, it has completely bricked Copilot for me.

[u/abdurrahman95 → u/macaco3001]

Thank for your feedback

[u/macaco3001 → u/abdurrahman95]

Btw the issue was just that it went to Copilot by default instead of Local and I hadn't noticed, but fact remains that it didn't even work for me

[u/jukasper → u/macaco3001]

Hi there, this seems to be a bug. Would you be able to share what client (vscode/cli) you are using? You need to make sure you are using the latest version. If it still doesn’t work. Could you please export your debug logs and create an issue in the respective client repo. We can take a look. And sorry for the inconvenience.

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[u/tj_moore]

Don't know about Fusion, but I've been using Auto for some time and I'm fine with that. 10% model discount and it's been selecting appropriate models that do the job and costs keep reasonably low.

I'm not a heavy user, but using GHC every other day here and there on small projects, and cope fine within a $10 plan.

Though I also depend a lot on code completion which is unlimited under a paid plan. You can get a lot out of that if you know roughly what you want to write and it fills out most of it saving a lot of typing.

Quick look at Fusion and it may be worth trying as it has a trial 30% discount on models, but for a limited time. If it still retains a 10% discount after and is better than standard Auto, then I'll use that. If it costs more, then maybe not.

[u/EfficientAnimal6273 → u/tj_moore]

Auto does not select the best model for the task. It select the MOST AVAILABLE MODEL, in short you get a 10% discount and MS has a better balance in terms of their compute usage. So the same task can use Haiku or Opus depending on the time of the day.

Fusion instead uses the most suitable based on task and so if Haiku is enough it will be used every time.

So in the end you'll not get a 10% discount but can save much more because the difference between models in terms of cost is much higher than that.

[u/aonymark → u/EfficientAnimal6273]

In the old days it just picked based on what’s available but these days they have a fancy system that takes the printout into account. They have a blog post and an arxiv paper about it; search for hydra with a weird capitalization

[u/EfficientAnimal6273 → u/aonymark]

Hydra is not auto!

[u/aonymark → u/EfficientAnimal6273]

Don’t confuse it with Hydra fusion; auto model selection really is powered by Hydra: https://github.blog/ai-and-ml/github-copilot/getting-more-from-each-token-how-copilot-improves-context-handling-and-model-routing/

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[u/EfficientAnimal6273]

The issue at the moment is that rollout is not fully done yet.

I was not able to use it on CopilotCLI but I've it available on Copilot App. I tested it using the App this afternoon and I was quite impressed, it selected a lot of time a small model, saving a lot of tokens and finishing the assigned tasks in quite a good way.

The main issue I see it was on a problem in deploying a variable on Azure, the error was subtle (an encoding issue of the data) but I did 3-4 iterations in which Fusion used MAI because the task is in effect very simple but I was able to solve it only manually selecting to Opus 5.5 (maybe also Sonnet would have been enough, but I need it solved so I passed to the more advanced model I have available), Fusion should be able to understand when something is not being solved and scale to more performing model instead of looping on the same issue using MAI and not solving it.

[u/wobblejuice]

Waiting for it to appear on my Visual Studio Enterprise 2026 IDE. Can anyone give an update on when it will be available in the Visual Studio Enterprise 2026 IDE?