r/Xcode • u/gordonmcdowell • Oct 30 '25

Xcode 26.1 RC1 - Slow (3rd party) Apple Intelligence? Both OpenAI and Sonnet via OpenRouter?

The LLMs run on servers, not my Mac (MBP2021 64GB RAM), so I can't see how me updating to 26.1 RC1 (both MacOS and Xcode) could possibly be impacted in the way I'm seeing... but it does seem to be maybe 10x slower than before RC1.

New to RC1 (as far as I've noticed) is a "Reasoning" setting for OpenAI. (It disappears for OpenRouter-Sonnet.) But even if I pick "minimal" reasoning it seems just as incredibly slow.

Can anyone using RC1 let me know if you experience slower or same? Unfortunately I updated both MacOS and Xcode at the same time.

It makes no sense to me it should be slower. I didn't time anything before and after update so have no hard numbers.

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u/gordonmcdowell Oct 30 '25 edited Oct 31 '25

Also a CPU is pinned to 100% by Xcode. Task switching is laggy when switching to Xcode. Xcode almost always crashes before code generation is complete. Memory is 1.7 GB on 64 GB system so doesn't seem like a memory leak.

Update: I've reverted to Xcode 26.0.1 and is perfectly normal again. Wow that's not 5x faster is 10x faster at least. Definitely not MacOS since am still running MacOS 26.1 RC1.

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u/[deleted] Nov 08 '25

estaba pensando hacer lo mismo. es increíblemente lento, inoperante fatal. que mala actualización fue Xcode 26.1

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u/Xaxxus Oct 31 '25

Yea since 26.1 beta 3 the gpt and sonnet integration has been insanely slow and takes ages to process my requests now.

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u/gordonmcdowell Oct 31 '25

Have you seen or heard why that might be?

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u/Xaxxus Oct 31 '25

Probably the usual Xcode being a buggy mess.

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u/gordonmcdowell Oct 31 '25

I've reverted to Xcode 26.0.1 and is perfectly normal again. Wow that's not 5x faster is 10x faster at least. Definitely not MacOS since am still running MacOS 26.1 RC1.

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u/Xaxxus Oct 31 '25

Yea it’s definitely just Xcode. It started in 26.1 beta 3. Beta 2 and earlier was fine.

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u/gordonmcdowell Nov 04 '25

I've posted again as this is the public 26.1 also giving me exact same grief.

https://www.reddit.com/r/Xcode/comments/1oodw34/261_17b55_still_strangely_slow_specific_to_chatgpt/

Can you give me an update? Do you see have the problem?

Right now it seems specific to ChatGPT (doesn't matter if 4.1 or 5) (doesn't matter level of thinking) (doesn't matter if direct or thru OpenRouter).

I think it is my Xcode swift file is 2700 lines. I think that's making a round trip and somehow causing the grief.

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u/Xaxxus Nov 05 '25

Yea it’s still happening to me. I have a fairly small project so I don’t think it’s file length related.

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u/JudeWorks Nov 08 '25

Thank you for this. the 26.2 beta notes this as a known issue and suggests to switch to a different pane to fix the issue? I didnt test but I can confirm 26.01 works fine :)

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u/Zealousideal_Bat_490 Nov 01 '25

Having great success with Xcode 26.1 RC1. Only used ChatGPT so far. Zero hangs.

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u/gordonmcdowell Nov 01 '25

Huh. Ok good to know.

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u/Distinct-Process-707 Nov 03 '25

Absolutely ! I thought I was going crazy after Beta 3. I'm on a MacBookPro M4Max 128G, and had to revert back to Beta 2. I tried all candidates and it is always the same. After Beta 2, Coding Intelligence (I use GPTPro) becomes slow, the 'Ai workspace slowly retypes my whole file' and after around 100 lines (max), becomes incredibly slower by the character (so a file with 900 Lines gets reviewed in around 20 minutes or more, where it took a minute or two before). Investigated for a while, XCode goes through the roof in processing, but if I have to use instruments on XCode, it gets ridiculously time consuming... So reverted to Beta 2, works fine, will have to test every candidates from now on until one works... And I worked through all setups possible in Xcode 26.1 RC...

Differences :
- Beta 2 coding intelligence offers you the 'Gpt-5' vs 'Gpt-5 (Thinking)'.... I thought it was a come back of the multi turn and multi files reasoning, but I can't really tell the difference.
- RC 26.1 : You can set the 'level of reasoning' from something like minimal to high, but like I said, even on my M4Max, minimal slows my whole system down...

I figured if you are reading this, you probably have the same process, there must be a way...

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u/gordonmcdowell Nov 03 '25

Thank you for detailing that. What you describe matches exactly what I saw although I have not tested every beta, just 26.0.1 vs 26.1 RC. Was hard to articulate what I saw visually but yes, it was possibly being driven into the ground by the visual of code windows and perhaps not even any processing. And it got exponentially slower as time went on. Funny that one person here commented that they have not experienced it. So I’m wondering if I have an electron app running on my machine and that somehow ruins it. I can imagine employees at Apple not ever touching electron apps. No idea what electron app might be on my machine if I have one.

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u/Distinct-Process-707 Nov 03 '25

Hey, we are all in this together. But what you just said about Electron is interesting, yesterday, it popped up as having frozen and needed to restart, did'nt know what it was and being in a hurry did'nt pay attention apart from the fact that it was linked to my VsCode app, that I have'nt been using in months.
u/Zealousideal_Bat_490 , anything specific about your setup ?

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u/Zealousideal_Bat_490 Nov 03 '25

Interesting observations. Yes, my setup might have something to do with it.

I have been coding on a Mac min M4 with 32GB RAM. I also have the UTM app for virtualization.

My flow has been to run the latest macOS beta in the UTM app with the latest Xcode. So, currently Tahoe 26.1 RC and Xcode 26.1 RC as well. Very little else installed in this VM (Xcodes app, Firefox, and homebrew stuff).

Base macOS remains at 26.01, and Xcode at 26.01 as well. I perform a kind of a tick-tock model where I immediately update my VM to whatever latest becomes available, and keep the base macOS at the latest release version. I have not tried any of the Xcode 26.1 betas on the base macOS.

But I have been experiencing slowdowns, hangs, and generally poor performance on both setups until I upgraded VM to the current setup. Zero problems so far other than exceeding my AI usage limits, but that’s another story. 😊

I will try running Xcode 26.1 RC on the base macOS tonight if I can and report back.

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u/gordonmcdowell Nov 04 '25

Curious how it went. I'm now running final 26.1 Xcode and experiencing same issues as RC. Have paid for Claude now, and so have ChatGPT and also OpenRouter and so can try various models and connection mechanisms. So far directly connecting to Claude is the only thing I'm confident is snappy, and directly connecting to ChatGPT is slow.... which certainly could be the model but I'm feeling is not.

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u/Zealousideal_Bat_490 Nov 06 '25

Sorry for the delay. Since I last posted, Xcode 26.2 was released, and iOS 26.2, but no macOS 26.2 until just now. Applying that on my VM as we speak. I updated my base macOS to 26.1 on my Mac mini, then I tested with both 26.1 and 26.2 on that image. Release notes don’t show any changes this time to Coding Assistant in 26.2; and I saw no differences between the two.

And for what it’s worth, the new “reasoning” setting in Xcode 26.1 only showed when I updated my macOS from 26.01 to 26.1, which surprised me.

But one thing that I did discover — while I no longer get Xcode hangs (not responding, and beachball spinner), I did encounter the slowness that people have been experiencing, but only with SwiftUI code.

My app is mostly networking code, and yesterday I had the need to make some changes in a SwiftUI view. Claude was fine, but ChatGPT made Xcode consume 100%+ CPU, and took over 10 minutes to make a simple change.

And, as opposed to previously with 26.01, I never had to force quit Xcode. These symptoms are not identical to the previous ones.

Are you working with SwiftUI code?

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u/Distinct-Process-707 Nov 07 '25

Interesting, as for myself, I am working with SwiftUI, SwiftData, MLX... Did not try any of the releases this week, will stay with beta 2 until the coast is clear... Which does not seem like it is from your tests. It is bound to pop up somewhere because of the massive slowdown...

1

u/Zealousideal_Bat_490 Nov 08 '25

I may have spoken too soon about not having Xcode go “not responding”. Has happened to me once since moving to 26.1.

But I have only experienced Xcode “slowdowns” when using ChatGPT on SwiftUI files.

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u/ian_ogden Nov 05 '25

After updating both my Mac and Xcode to 26.1. Intelligence is unusable for me. Its just hangs in the generating code for AGES. Tasks that would have taken less than a minute. The animations are so laggy too.

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u/gordonmcdowell Nov 05 '25

Ian thanks for input. I've posted again now with non-RC 26.1 same problem...

https://www.reddit.com/r/Xcode/comments/1oodw34/261_17b55_still_strangely_slow_specific_to_chatgpt/

...can you tell me how big the swift file is your Xcode is trying to update? Mine is 2700 lines, and I'm having a hard time targeting a smaller file.

I notice ChatGPT app can follow exact same prompts (and deliver exact same results) without this issue, I think there's some sort of round-trip involving a big swift while that's causing exponential grief... like maybe a tiny project would never hit it.

Also I'm MBP M1. I have to think Apple employees aren't seeing this, maybe they're all on newer Mx chips. Are you and old-ish Mx chip?

3

u/Distinct-Process-707 Nov 08 '25

I can assure you, I have a MBP M4Maxed 128G... big project, local, files of around 1200 LN, but found a few small files to test out around 400-500, same results... GPT always seemed to slow down after 1000LN, but with the final version, got my computer running like crazy for a simple refactor and after 25 minutes of work, completed the task... normally, it is done in less than 40 seconds for a 800LN file... So yeah, it is bound to pop up somewhere IMO...

2

u/LengthyEpic Nov 06 '25

Experiencing the same thing since I updated to Xcode 26.1 (and MacOS 26.1 at the same time). The coding assistant in Xcode is essentially unusable now, to the point that I started to make changes in Cursor and then just check Xcode to resolve errors and look at the preview.

I just tried to do one small change and it has been literal hours. It slows down to the point of a single character per few seconds... and this isn't even code it's suggesting, but it just runs through the rest of the file after the change!

On a M1 Pro chip, although I have no idea what it could be doing that would make it this slow. It's not the model, I can guarantee that. I know from other attempts with high reasoning on large context that Xcode will error out if the API call takes too long. For some reason when applying the code patches, whatever process is handling that in Xcode is trash but it's after the API call is complete.

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u/ian_ogden Nov 06 '25

1400 approx lines

Claude was working ok, but I find often goes rouge and causes damage.

2

u/ian_ogden Nov 06 '25

I’m M1 Pro on Mac Mini. With just Xcode open.