`cabal` crashes in HLS CI while copying files

[fendor]

Describe the bug

cabal 3.16.{0,1}.0 crashes in the HLS CI (logs)

The error in question:

2026-01-07T14:53:53.6355558Z copyFile:atomicCopyFileContents:withReplacementFile:CreateFile "D:\\a\\haskell-language-server\\haskell-language-server\\.\\dist-newstyle\\build\\x86_64-windows\\ghc-9.14.1\\hls-2.12.0.0\\t\\hls-qualify-imported-names-plugin-tests\\build\\hls-qualify-imported-names-plugin-tests\\autogen\\.copyFile-da8b2aac-21ce-4e49-8a1b-8f41d1393bf2.tmp": does not exist (does not exist

The same error seems to happen for various other packages with long names and this path is 260 characters long, perhaps an indicator for long path issues?

To Reproduce
Steps to reproduce the behavior:

On windows only (and I have not tried reproducing locally, might be a GHA CI only thing):

$ cabal-3.16.1.0 build test:hls-alternate-number-format-plugin-tests

Expected behavior

Should not crash, just like cabal 3.14

System Information

Seems to only happen on windows, and I haven't tried reproducing locally.

[ulysses4ever]

@fendor i'm getting "AuthenticationFailed" when following your link to the logs. Also, filling "system information" in the issue template would be helpful.

[fendor]

I pressed "Create" too early 😬
Added the missing information and uploaded the logs so they don't expire.

[fendor]

I was able to reproduce this locally on windows 11 and the issue is most likely not cabal 3.16 specific, with long --build-dirs, cabal-3.14 also crashes. Perhaps something caused the HLS CI to finally overflow, but it sounds like cabal or something that it uses still suffers from long path issues.

Actually, my gut feeling is currently that it is caused by a third-party tool, as cabal does, in theory, use long path syntax on windows.