error: failed to read compressed data (Truncated zstd input)

[timhae]

Hey, thanks a lot for maintaining this great tool, I have recently started seeing this error when updating my local system with a harmonia cache as substituter:

❯ nixos-rebuild switch --flake . --use-remote-sudo
building the system configuration...
error: failed to read compressed data (Truncated zstd input)
..
error: failed to read compressed data (Truncated zstd input)
error: some substitutes for the outputs of derivation '/nix/store/1c3qmlg3j1ldwf09gjqpbyy77l0gjq3y-initrd-linux-6.6.71.drv' failed (usually happens due to networking issues);
 try '--fallback' to build derivation from source
error: 1 dependencies of derivation '/nix/store/m8vvzn45j5z6jw8azy64xn6vymf6x6kg-nixos-system-desktop1-25.05.20250116.5df4362.drv' failed to build

My local nix config:

  nix.settings.substituters = [
    "https://cache.ts.my.domain?priority=39"
  ];
  nix.settings.trusted-public-keys = [
    "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
    "cache.ts.my.domain:II5Re1ZjWdDCZBSXWC2gA35H57r5eJTRl5bv++delZ4="
  ];

Server harmonia/nginx config:

  services.nginx = {
    virtualHosts = {
      "cache.ts.my.domain" = {
        forceSSL = true;
        useACMEHost = "main";
        kTLS = true;
        extraConfig = ''
          allow 100.64.0.0/10;
          allow fd7a:115c:a1e0::/48;
          deny all;
        '';
        locations."/".extraConfig = ''
          proxy_pass http://127.0.0.1:${toString harmoniaPort};
          proxy_set_header Host $host;
          proxy_redirect http:// https://;
          proxy_http_version 1.1;
          proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
          proxy_set_header Upgrade $http_upgrade;
          proxy_set_header Connection $connection_upgrade;
        '';
      };
    };
  };

  services.harmonia = {
    enable = true;
    signKeyPaths = [ config.age.secrets.cacheKey.path ];
    settings = {
      bind = "[::]:${toString harmoniaPort}";
      priority = 39;
    };
  };

Do you happen to have an idea what I might be doing wrong here?