bug: tmux with 'sensibleOnTop' option no longer uses the correct shell

[cixel]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

The upstream version of tmux was updated last week to 3.5a (commit). One of the changes in this version (from 3.5) is that /bin/sh is used for run-shell.

With this version of tmux, all panes/windows/etc use sh instead of the configured default shell (in my case, zsh).

My rough guess is that this change in tmux has introduced some ordering issues when sensibleOnTop is set, as run-shell will now use sh regardless of how tmux's default-shell is set.

The problem goes away if I do:

  package = pkgs.tmux.overrideAttrs (old: rec {
    version = "3.5";
    src = pkgs.fetchFromGitHub {
      owner = "tmux";
      repo = "tmux";
      rev = version;
      hash = "sha256-8CRZj7UyBhuB5QO27Y+tHG62S/eGxPOHWrwvh1aBqq0=";
    };
  });

or if I set sensibleOnTop = false;

Maintainer CC

@jorsn @rycee (cc based on a7cdfaa).

System information

- system: `"aarch64-darwin"`
 - host os: `Darwin 23.6.0, macOS 14.7`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.18.8`
 - channels(ehdens): `"home-manager, nixpkgs"`
 - nixpkgs: `/Users/ehdens/.nix-defexpr/channels/nixpkgs`

[x123]

I'm also experiencing the same issue. The notes for tmux 3.5a here tmux/tmux#4162 say the following:

"Note that a fix in 3.5 and 3.5a to correctly set SHELL for run-shell and if-shell reveals a bug in the tmux-sensible script, causing it to set default-shell to /bin/sh. This can be worked around by adding this to .tmux.conf after the tmux-sensible script is invoked:"

 - system: `"aarch64-darwin"`
 - host os: `Darwin 24.0.0, macOS 15.0.1`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.18.8`
 - channels(root): `"nixpkgs"`
 - nixpkgs: `/nix/store/60sn02zhawl3kwn0r515zff3h6hg6ydz-source`

EDIT: Using the following in extraConfig to make sure it's run after tmux-sensible loads seems to fix the issue on darwin and is the updated recommendation from tmux/tmux#4162 (comment)

set -gu default-command
set -g default-shell "$SHELL"

[gshpychka]

Same here. Having set -g default-shell "$SHELL" as the last line in my tmux.conf does not fix the issue, only disabling the sensible plugin by setting sensibleOnTop to false does.

EDIT: using set -g default-command "$SHELL" does fix the issue on darwin (with the sensible plugin enabled)

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/tmux-use-bash-instead-defined-zsh-in-home-manager/54763/2

[YorikSar]

Quick and (very) dirty workaround for this:

  nixpkgs.overlays = [
    (final: prev: {
      tmuxPlugins = prev.tmuxPlugins // {
        sensible = prev.tmuxPlugins.sensible.overrideAttrs (prev: {
          postInstall = prev.postInstall + ''
            sed -e 's:\$SHELL:/bin/zsh:g' -i $target/sensible.tmux
          '';
        });
      };
    })
  ];

It hardcodes /bin/zsh (replace it with what you like to use) and rebuilds tmux-sensible with it.

[art1es23]

I'm also experiencing the same issue. The notes for tmux 3.5a here tmux/tmux#4162 say the following:

"Note that a fix in 3.5 and 3.5a to correctly set SHELL for run-shell and if-shell reveals a bug in the tmux-sensible script, causing it to set default-shell to /bin/sh. This can be worked around by adding this to .tmux.conf after the tmux-sensible script is invoked:"

 - system: `"aarch64-darwin"`
 - host os: `Darwin 24.0.0, macOS 15.0.1`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.18.8`
 - channels(root): `"nixpkgs"`
 - nixpkgs: `/nix/store/60sn02zhawl3kwn0r515zff3h6hg6ydz-source`

EDIT: Using the following in extraConfig to make sure it's run after tmux-sensible loads seems to fix the issue on darwin and is the updated recommendation from tmux/tmux#4162 (comment)

set -gu default-command
set -g default-shell "$SHELL"

This solved the root problem, but after running tmux I got another issue:
/Users/qmpwwsd/.config/tmux/tmux.conf:91: not a suitable shell: zsh

After pressing the 'Enter' key:

• if this is a new session: zsh is used
• if the session is saved: all panels use bash by default, not zsh, only after closing the panel and opening it again zsh is used. So I need to reopen every time all panes which I saved

And I don't know how to fix it

[zoriya]

SHELL needs to be an absolute path, not a binary name. You'd need to set it to something like /run/current-system/sw/bin/zsh

[gen740]

I encountered the same issue, and at that time, I noticed that home-manager's tmux automatically loads the sensible plugin.
I love having plentiful options, but is it necessary to load this plugin by default?

[gshpychka]

I encountered the same issue, and at that time, I noticed that home-manager's tmux automatically loads the sensible plugin. I love having plentiful options, but is it necessary to load this plugin by default?

It's supposed to be a sensible default, hence the name ;)

[gen740]

It’s supposed to be a sensible default, hence the name ;)

This is simply the origin of the plugin’s name. Regardless of the name, it’s still just a plugin.

Who would expect that setting tmux.enable = true would also load an additional tmux plugin?

[gen740]

And unfortunately, it seems that tmux-sensible is no longer being maintained...

tmux-plugins/tmux-sensible#70 (comment)

[gshpychka]

It’s supposed to be a sensible default, hence the name ;)

This is simply the origin of the plugin’s name. Regardless of the name, it’s still just a plugin.

Who would expect that setting tmux.enable = true would also load an additional tmux plugin?

I don't disagree, was mostly joking.

Yeah, considering the last commit was over 2 years ago - could be worth considering changing the default.

[gen740]

Are there any problems in creating the PR on this?

I think a bit more discussion is needed, but it is inconvenient to discuss in this thread.