nh os info silently exited when running nixos is a specialisation generation

[cloud-yu]

I have confirmed that this is a bug related to nh

• This is a bug, and not an user error or a support request. I understand that my issue will be closed if it is not a bug in NH.
• I have checked the issues tab and confirmed that my issue has not yet been reported. I understand that my issue will be closed if it is a duplicate.

Description

When nixos running in a generation with specialisation, nh os info silently exited.

❯ NH_LOG='nh=DEBUG' nh os info
DEBUG Main {
    verbosity: Verbosity {
        verbose: 0,
        quiet: 0,
        phantom: PhantomData<clap_verbosity_flag::InfoLevel>,
    },
    elevation_program: None,
    command: Os(
        OsArgs {
            subcommand: Info(
                OsGenerationsArgs {
                    profile: Some(
                        "/nix/var/nix/profiles/system",
                    ),
                },
            ),
        },
    ),
} (nh/src/main.rs:29)
DEBUG NH_VERSION=4.2.0 NH_REV=Some("v4.2.0") (nh/src/main.rs:30)
DEBUG cmd=Exec { nix --version } (nh/src/commands.rs:577)
DEBUG cmd=Exec { nix --version } (nh/src/commands.rs:577)
DEBUG Version normalized: 'nix (Lix, like Nix) 2.93.3' -> '2.93.3' (nh/src/util.rs:106)
DEBUG Got the following output for nix path-info: Output {
    status: ExitStatus(
        unix_wait_status(
            0,
        ),
    ),
    stdout: "[{\"closureSize\":3997111848,\"deriver\":\"/nix/store/y44h6mscrp56bvcsc14klij20vw30m58-nixos-system-nixos-25.11.20251130.8bb5646.drv\",\"narHash\":\"sha256-SHZ6tGE0/yt1JcBBl4+BBoBSoEjtYpRFNCfiSNLVuk8=\",\"narSize\":19280,\"path\":\"/nix/store/858h0rzja79l9m18m02yi98niw4b1zfh-nixos-system-nixos-25.11.20251130.8bb5646\",\"references\":[\"/nix/store/35yc81pz0q5yba14lxhn5r3jx5yg6c3l-bash-interactive-5.3p3\",\"/nix/store/3c6r8gh8zrqw8xmncmlj9vivz9rz6r30-util-linux-2.41.2-bin\",\"/nix/store/48p58ls5qwfpn6qwd0ls61akcr97w4rz-switch-to-configuration-0.1.0\",\"/nix/store/522vd4hl7dyk98cbi0y57vrhrlpg4sfp-local-cmds\",\"/nix/store/7gs397m7lpj02q8ag566bqsch4q7mdvq-etc\",\"/nix/store/7sb1nkpf82nb5kj7qc4bbqkwj1l1mdv9-update-users-groups.pl\",\"/nix/store/858h0rzja79l9m18m02yi98niw4b1zfh-nixos-system-nixos-25.11.20251130.8bb5646\",\"/nix/store/914x32c982bs3i1998yxvkg9svm3ycr5-shadow-4.18.0\",\"/nix/store/9fdfn5ra4ji67f4ifp6lyfjsww5c4nxx-perl-5.40.0-env\",\"/nix/store/9msqnxihyqc1qckwlsjixzz78xpav0hr-users-groups.json\",\"/nix/store/9vmxdn26pggj3glazmb68vhcf4smflvz-glibc-locales-2.40-66\",\"/nix/store/av4xw9f56xlx5pgv862wabfif6m1yc0a-findutils-4.10.0\",\"/nix/store/dl7wg5yg8h12a5bc97aqj4mdlywhihy1-getent-glibc-2.40-66\",\"/nix/store/imad8dvhp77h0pjbckp6wvmnyhp8dpgg-coreutils-9.8\",\"/nix/store/l9pbwhp06c7b122dj7km9j68zqwrka67-users-groups.json\",\"/nix/store/mhiwv5wazpj5kbvxnxxj4wnvyag6i0vc-sh\",\"/nix/store/mhxn5kwnri3z9hdzi3x0980id65p0icn-lib.sh\",\"/nix/store/pn5f4sck8ff0mdkqn21cl0zqij1r721l-pre-switch-checks\",\"/nix/store/q26j77br78jg5f4jh5n9wy1yk36grgk7-nixos-wsl-recovery\",\"/nix/store/q6wgv06q39bfhx2xl8ysc05wi6m2zdss-glibc-2.40-66-bin\",\"/nix/store/rg5rf512szdxmnj9qal3wfdnpfsx38qi-setup-etc.pl\",\"/nix/store/rlq03x4cwf8zn73hxaxnx0zn5q9kifls-bash-5.3p3\",\"/nix/store/vzr65nawnnqj58vwdf01cg15xyjyyazh-mounts.sh\",\"/nix/store/x3zjxxz8m4ki88axp0gn8q8m6bldybba-gnugrep-3.12\",\"/nix/store/xn2vzkk0ab5gn9d1h20yaghb652i34v1-perl-5.40.0-env\",\"/nix/store/yk1kqigwvvmh1v8yqwqg5xh4vyaq8zny-system-path\",\"/nix/store/ywnz6hd3afxkhg4j0mysfm77yzfvk0s3-nixos-wsl-utils-1.0.0\",\"/nix/store/zf8qy81dsw1vqwgh9p9n2h40s1k0g2l1-systemd-258.2\"],\"registrationTime\":1764744131,\"ultimate\":true,\"valid\":true}]",
    stderr: "",
} (nh/src/generations.rs:206)
DEBUG current_generation=None (nh/src/generations.rs:242)

WHA'S HAPPENING

When nixos switch to a generations with specialisation, /run/current-system not directly link to basement generations in /nix/var/nix/profiles/, it link to basement_generation/specialisation/xxx

Check if this generation is the current one should compare /nix/var/nix/profiles/system with /nix/var/nix/profiles/system-xx-link

❯ realpath /run/current-system
/nix/store/858h0rzja79l9m18m02yi98niw4b1zfh-nixos-system-nixos-25.11.20251130.8bb5646
❯ eza -lah /nix/var/nix/profiles
Permissions Size User Date Modified Name
drwxr-xr-x     - root 18 Aug 16:26  per-user
lrwxrwxrwx     - root 13 Dec 15:41  system -> /nix/var/nix/profiles/system-105-link
lrwxrwxrwx     - root 23 Oct 19:19  system-101-link -> /nix/store/aysfapyky8qsgm11bbzsig6rwlam6v20-nixos-system-nixos-25.05.20251021.481cf55
lrwxrwxrwx     - root 28 Oct 21:03  system-102-link -> /nix/store/1k35q6l0y4lr4dwfi9raxaf95h0dys9h-nixos-system-nixos-25.05.20251026.78e34d1
lrwxrwxrwx     - root  4 Nov 11:37  system-103-link -> /nix/store/jg7w59ikgdb81b4ra23aca455vh7bhc0-nixos-system-nixos-25.05.20251101.3de8f8d
lrwxrwxrwx     - root  3 Dec 14:23  system-104-link -> /nix/store/rjcyvc45fd9w6dbqmfxr7sc0mm612p4a-nixos-system-nixos-25.05.20251201.6c8f0cc
lrwxrwxrwx     - root  3 Dec 14:42  system-105-link -> /nix/store/j2hnzjjd676sjcz1svc48yb0kdjy96n2-nixos-system-nixos-25.11.20251130.8bb5646
❯ eza -lah /nix/var/nix/profiles/system/specialisation
Permissions Size User Date Modified Name
lrwxrwxrwx     - root  1 Jan  1970  lix -> /nix/store/858h0rzja79l9m18m02yi98niw4b1zfh-nixos-system-nixos-25.11.20251130.8bb5646

Installation Method

Stable Release (nixpkgs, pkgs.nh from nixos-unstable or nixos-yy-mm)

Installation Method (Other)

No response

NH Version

v4.2.0

System Information

• system: "x86_64-linux"
• host os: Linux 6.6.87.2-microsoft-standard-WSL2, NixOS, 25.11 (Xantusia), 25.11.20251130.8bb5646
• multi-user?: yes
• sandbox: yes
• version: nix-env (Lix, like Nix) 2.93.3 System type: x86_64-linux Additional system types: i686-linux, x86_64-v1-linux, x86_64-v2-linux, x86_64-v3-linux, x86_64-v4-linux Features: gc, signed-caches System configuration file: /etc/nix/nix.conf Store directory: /nix/store State directory: /nix/var/nix Data directory: /nix/store/kg6pv5f01vj5w6k7scy2zfvnkcgbifcw-lix-2.93.3/share
• nixpkgs: /nix/store/dgp9wmspgm6zhl66f0c81rvg3v7wwbsb-source