It seems like in some cases Xcode 12.3 launch way to many swift compilers and starts swapping heavily. Check for memory pressure in Activity Monitor. If it's red, try to fall back to Xcode 12.2 (helped me).

Same here. Have info about 1-year old versions, but not later.

I occasionally have the same problem on my MacBook Pro 2019, 16Gb RAM. Most often it happens if I try to do a cold build for simulator (most of the time I use real devices). If I run top -o mem while it's happening I see literally tens of swift-frontend processing each taking ~200Mb. After about a minute or two RAM congestion wears out and it starts to behave normally. I wonder if anyone also see this?

Still not fixed in Xcode 13.2 beta (13C5066c)

Xcode 13.2 beta 2 (13C5081f) - same story. Back to Xcode 12.5.1 again 🙁

Did you get any reply to your bug report?

The release notes of Xcode 13.3 beta 2 mentions "code completion" 12 (!) times. Unfortunately I cannot test it yet, since it requires macOS Monterey. Did anybody tried it?

Answer is here https://stackoverflow.com/a/79342378/2432781

Me too

One year later it's still there. Is an expected behavior after all?

Just checked new Xcode 26.2 with iOS 26.2 and the debug builds startup time indeed improved significantly. We still have ~7 seconds of initial sluggishness (difference between debug executable on/off), but it's way better than it was before! 👍