I am not sure how "long term" you are thinking about. Making big architectural changes does not necessarily lead to better performance. JSC has been the fastest JS engine in the past 5-10 years as I remember. If google had a solution, they would have it now.

> Google has a lot more incentive than Apple to make the fastest engine

What are those incentives? I see no incentive for Google to make something fast.

A significant part of Google’s business (Ads, YouTube, Workspace) runs inside a browser, so if the web is slow, Google loses money

What are the marginal gains in business for them from the likely improvement of the runtime? It's not like the web (or: web-technology-based apps) don't capture a lot of time already.

And the faster that a page finishes rendering on an iphone, the faster that the cpu can idle, which hugely benefits battery life. That's a pretty strong motivation on Apple's side. I don't think the proposed motivation on google's side is stronger.

Faster page load times increases engagement with the web. More engagement on the web leads to more engagement with Google's ads.

I don't agree. Page load times do not matter when everything is so locked down that most people don't even know there's an alternative.

But this was always true. True for last 40 years.

What’s changed in 2026 that will motivate Google to overtake JSCore?

Bun's original marketing used JSCore's superior performance as a main benefit over Node.js.[0]

Why would Google have more incentive than Apple to make the fastest engine? Safari being the fastest mobile browser is important to Apple.

If Google had a stronger incentive than Apple, we would have seen V8 being more performant by now.

[0]https://web.archive.org/web/20220724110148/https://bun.sh/

Because tech debt is real... V8 exists and likely isn't going to be completely displaced as a whole. That said, I can't speak for what are or aren't priorities for Google... I'd say they and Apple both have every incentive to give a good experience, and how far that is from the "best" experience will vary.

> Bun.js uses the JavaScriptCore engine, which tends to start and perform a little faster than more traditional choices like V8.

Little faster? Like I said, that's not a *main* benefit as it's not why Bun can be 5 to 10x faster than Node.js

For a long time v8 was the fastest on a set of benchmarks but not on real world work load. That was the time when SpiderMonkey and JSC decided to go on a different path. I believe it was Mozilla that make the move first.

If we believe there is limit to everything, then the only sane conclusion would be v8 and JSC would both perform nearly the same with negligible difference in the long term. So choosing something that is fast, simple to integrate now makes a lot more sense.

Of course that is assuming memory usage, security and others being equal.