nix flake check fails with unrecognizable error

[target-san]

Describe the bug

nix flake check --show-trace --no-build --all-systems --print-build-logs -vvvvv --debug reports unrecognizable error. End of most verbose logs:

2024-12-10T13:07:11.1005204Z checking flake output 'apps'...
2024-12-10T13:07:11.1149991Z download thread shutting down
2024-12-10T13:07:13.4659258Z this path will be fetched (0.72 MiB download, 4.61 MiB unpacked):
2024-12-10T13:07:13.4660028Z   /nix/store/dih9dknbvxvi11f5is21pckgnqxnd5pz-nixfmt-unstable-2024-08-16
2024-12-10T13:07:13.4669635Z copying path '/nix/store/dih9dknbvxvi11f5is21pckgnqxnd5pz-nixfmt-unstable-2024-08-16' from 'https://cache.nixos.org'...
2024-12-10T13:07:13.5469788Z <stdin>:1:1:
2024-12-10T13:07:13.5470128Z   |
2024-12-10T13:07:13.5470895Z 1 | <empty line>
2024-12-10T13:07:13.5471231Z   | ^
2024-12-10T13:07:13.5472988Z unexpected end of input
2024-12-10T13:07:13.5473742Z expecting expression
2024-12-10T13:07:13.5474034Z

Steps To Reproduce

Reproduced only on specific CI. My issue is more with inability to debug error.

Expected behavior

nix flake check reports exactly what file it failed to read and where and how it got that file

Metadata

nix (Nix) 2.25.3

Additional context

There are similar issues like #4903 yet error doesn't look the same

Checklist

• checked latest Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

[link2xt]

I have nix fmt failing with

copying path '/nix/store/p2i9dd3fslfhsc593h2xfs4s75lzbpki-elfutils-0.191' from 'http://127.0.0.1:37515/'...
copying path '/nix/store/lnpz4yysm5srb6yls9inw281rv981p8q-nixfmt-unstable-2024-08-16' from 'http://127.0.0.1:37515/'...
<stdin>:1:1:
  |
1 | <empty line>
  | ^
unexpected end of input
expecting expression

at deltachat/deltachat-core-rust#6333

Maybe it is a https://github.com/NixOS/nixfmt bug.