refactor(shells): use native Home Manager Nushell and Nushell login on non-desktop hosts (#513)

* refactor(shells): use native Home Manager Nushell environment

Replace the Bash login-shell wrapper and hand-maintained Nushell PATH with programs.nushell.loadSessionVariables and home.sessionPath. Launch Nushell directly from Kitty, Ghostty, and Zed, with the macOS config-home override and Ghostty's vendor autoload directory.

Upstream feature: https://github.com/nix-community/home-manager/pull/9666

Assisted-by: DeepSeek Harness (deepseek-flash)

* feat(hosts): use Nushell as login shell on Ruby and Kana

Set the per-user shell explicitly and add Nushell to the system shell list. The system default shell and root remain unchanged.

Assisted-by: DeepSeek Harness (deepseek-flash)

* fix(ssh): preserve tuios session marker across SSH

Forward TUIOS_SESSION and accept it on NixOS sshd, so an SSH session opened from inside tuios does not auto-attach a nested remote tuios.

Assisted-by: DeepSeek Harness (deepseek-flash)

* feat(nixos): use Nushell login shell on non-desktop hosts

Enable the Nushell login shell through a shared module imported by the server and agent profiles. Desktop profiles continue to use Bash.

Assisted-by: DeepSeek Harness (deepseek-flash)

* fix(tuios): skip auto-attach in SSH sessions

Remote interactive shells now stay plain Nushell instead of starting a nested TUIOS when the SSH client is already inside a local TUIOS session. Local TUIOS auto-start is unchanged.

Assisted-by: DeepSeek Harness (deepseek-flash)

home/base/core/shells/config.nu

@@ -189,15 +189,6 @@ const NU_PLUGIN_DIRS = [
 
 # As with NU_LIB_DIRS, an $env.NU_PLUGIN_DIRS is searched after the constant version
 
-# The `path add` function from the Standard Library also provides
-# a convenience method for prepending to the path:
-use std/util "path add"
-path add "~/.local/bin"
-# Tools installed outside Nix (go install / cargo install / npm -g).
-path add "~/go/bin"
-path add "~/.cargo/bin"
-path add "~/.npm/bin"
-
 # You can remove duplicate directories from the path using:
 $env.PATH = ($env.PATH | uniq)
 

home/base/core/shells/default.nix

@@ -1,16 +1,19 @@
-{ ... }:
+{ config, ... }:
 {
-  # Kept only for the `~/.profile` it generates: that file sources `hm-session-vars.sh`,
-  # and the terminals launch `bash --login -c 'nu ...'`, so it is how `home.sessionVariables`
-  # reach nushell. Bash itself needs no env/alias setup here — nushell owns those, and a bash
-  # spawned from within nushell inherits the environment.
+  # Bash remains the login shell.
   programs.bash.enable = true;
 
   programs.nushell = {
     enable = true;
-    # Adopt the 26.11 default: source Home Manager's session environment from
-    # env.nu instead of relying only on the bash-login wrapper.
     loadSessionVariables = true;
     configFile.source = ./config.nu;
   };
+
+  # Tools installed outside Nix.
+  home.sessionPath = [
+    "${config.home.homeDirectory}/.local/bin"
+    "${config.home.homeDirectory}/go/bin"
+    "${config.home.homeDirectory}/.cargo/bin"
+    "${config.home.homeDirectory}/.npm/bin"
+  ];
 }

home/base/gui/terminal/ghostty.nix

@@ -1,4 +1,5 @@
 {
+  config,
   lib,
   pkgs,
   ...
@@ -36,11 +37,7 @@
       # Start fullscreen on macOS; window managers control this on Linux.
       fullscreen = pkgs.stdenv.hostPlatform.isDarwin;
 
-      #  To resolve issues:
-      #    1. https://github.com/ryan4yin/nix-config/issues/26
-      #    2. https://github.com/ryan4yin/nix-config/issues/8
-      #  Spawn a nushell in login mode via `bash`
-      command = "${pkgs.bash}/bin/bash --login -c 'nu --login --interactive'";
+      command = "${lib.getExe config.programs.nushell.package} --config-home ${config.programs.nushell.configDir}";
     };
   };
 }

home/base/gui/terminal/kitty.nix

@@ -1,4 +1,5 @@
 {
+  config,
   lib,
   pkgs,
   ...
@@ -32,11 +33,7 @@
       macos_option_as_alt = true; # Option key acts as Alt on macOS
       enable_audio_bell = false;
 
-      #  To resolve issues:
-      #    1. https://github.com/ryan4yin/nix-config/issues/26
-      #    2. https://github.com/ryan4yin/nix-config/issues/8
-      #  Spawn a nushell in login mode via `bash`
-      shell = "${pkgs.bash}/bin/bash --login -c 'nu --login --interactive'";
+      shell = "${lib.getExe config.programs.nushell.package} --config-home ${config.programs.nushell.configDir}";
     };
 
     # macOS specific settings

home/base/gui/zed-editor.nix

@@ -1,4 +1,8 @@
-{ lib, ... }:
+{
+  config,
+  lib,
+  ...
+}:
 {
   catppuccin.zed.enable = true;
 
@@ -39,11 +43,10 @@
 
       # Terminal
       terminal.shell.with_arguments = {
-        program = "bash";
+        program = lib.getExe config.programs.nushell.package;
         args = [
-          "--login"
-          "-c"
-          "nu --login --interactive"
+          "--config-home"
+          config.programs.nushell.configDir
         ];
       };
 

home/base/tui/tuios/default.nix

@@ -14,7 +14,8 @@ in
   xdg.configFile."tuios/config.toml".source =
     config.lib.file.mkOutOfStoreSymlink "${configDir}/config.toml";
 
-  # auto-start tuios in interactive shells, except when already inside tuios.
+  # auto-start tuios in local interactive shells, except when already inside
+  # tuios or connected over SSH.
   # `work` for the ~/work tree, `personal` for everything else (a host with no
   # ~/work gets `personal` everywhere).
   programs.nushell.extraConfig = ''
@@ -27,7 +28,7 @@ in
       $env.TERM = "xterm-kitty"
     }
 
-    if $nu.is-interactive and (not ("TUIOS_SESSION" in $env)) {
+    if $nu.is-interactive and (not ("TUIOS_SESSION" in $env)) and (not ("SSH_CONNECTION" in $env)) {
       # Exit 3 means the daemon is stopped; stdout still lists saved sessions.
       let listing = (^tuios ls --json | complete)
       if $listing.exit_code not-in [0 3] {

home/darwin/shell.nix

@@ -1,22 +1,14 @@
-{ config, lib, ... }:
-let
-  envExtra = ''
-    export PATH="/opt/homebrew/bin:/usr/local/bin:$PATH"
-  '';
-in
+{ config, ... }:
 {
-  # Homebrew's default install location:
-  #   /opt/homebrew for Apple Silicon
-  #   /usr/local for macOS Intel
-  # The prefix /opt/homebrew was chosen to allow installations
-  # in /opt/homebrew for Apple Silicon and /usr/local for Rosetta 2 to coexist and use bottles.
-  programs.bash = {
-    enable = true;
-    bashrcExtra = lib.mkAfter envExtra;
-  };
+  # Homebrew install locations for Apple Silicon and Intel.
+  home.sessionPath = [
+    "/opt/homebrew/bin"
+    "/usr/local/bin"
+  ];
+
+  programs.bash.enable = true;
   programs.zsh = {
     enable = true;
     dotDir = "${config.xdg.configHome}/zsh";
-    inherit envExtra;
   };
 }

modules/nixos/nushell-login.nix

@@ -0,0 +1,5 @@
+{ myvars, pkgs, ... }:
+{
+  users.users.${myvars.username}.shell = pkgs.nushell;
+  environment.shells = [ pkgs.nushell ];
+}

modules/nixos/server/server-aarch64.nix

@@ -11,6 +11,7 @@
     (mylib.relativeToRoot "hardening/kernel-hardening.nix")
     ../base/monitoring.nix
     ../base/nix.nix
+    ../nushell-login.nix
     ../base/packages.nix
     ../base/ssh.nix
     ../base/user-group.nix

modules/nixos/server/server.nix

@@ -2,6 +2,7 @@
 {
   imports = [
     ../base
+    ../nushell-login.nix
     ../../base
   ];