Failure spawning project using a neovim frontend and mise

[badosu]

I have been using expert with neovide (a neovim frontend) and mason for quite a while.

After the last update I noticed a peculiar failure, the "engine" builds but fails to spawn the project child:

expert.log excerpt

21:32:21.960 [info] Engine build available at: /home/badosu/.local/share/Expert/0.1.0-b237fd5/elixir-1.18.4-erts-14.2.5.2/337a120c4a0f3608086a2f2a3a040525/_build/dev_ns
21:32:21.992 [debug] sent notification server -> client $/progress
21:32:22.174 [debug] Node port message: /home/badosu/.local/share/mise/installs/elixir/1.18.4-otp-26/bin/elixir: line 244: exec: erl: not found
21:32:22.176 [info] Port #Port<0.11> has exited due to: :normal

21:32:24.993 [debug] sent notification server -> client $/progress

21:32:24.993 [error] GenServer :"teiserver::node_process" terminating

** (stop) :start_timeout

Last message: :maybe_start_timeout

State: nil

21:32:24.994 [error] Process #PID<0.174.0> terminating

** (exit) {:error, :start_timeout}

(stdlib 6.2.2.1) gen_server.erl:2210: :gen_server.init_it/6

(stdlib 6.2.2.1) proc_lib.erl:329: :proc_lib.init_p_do_apply/3

Initial Call: XPExpert.Project.Node.init/1

Ancestors: [:"teiserver::supervisor", XPExpert.ProjectSupervisor, XPExpert.Supervisor, #PID<0.158.0>]

Message Queue Length: 0

Messages: []

Links: [#PID<0.171.0>]

Dictionary: []

Trapping Exits: false

Status: :running

Heap Size: 28690

Stack Size: 29

Reductions: 21266

21:32:24.994 [error] Process :"teiserver::node_process" (#PID<0.182.0>) terminating

** (exit) :start_timeout

(stdlib 6.2.2.1) gen_server.erl:2476: :gen_server.handle_common_reply/8

(stdlib 6.2.2.1) proc_lib.erl:329: :proc_lib.init_p_do_apply/3

Of particular note is the following line:

21:32:22.174 [debug] Node port message: /home/badosu/.local/share/mise/installs/elixir/1.18.4-otp-26/bin/elixir: line 244: exec: erl: not found

Somehow it found the elixir binary but not the erl one.

Running neovim on the terminal does not present this behavior.

I made a neovim plugin/script to workaround this for now, I load mise env whenever the current directory of the editor changes.

[aseigo]

Seeing the same issue with mise but a different editor, so this is not neovim-speicifc.

[aseigo]

For others running into this issue, I created a small script with the following content:

#!/usr/bin/env fish

eval (mise env)
~/bin/expert --stdio

Replace shell and paths to taste.

[mhanberg]

Can both of you share your editor configurations, shell, project structure (mise, tool versions? Whatever mise toml?) and how you start up your editor for a project.

Basically looking to have a full understanding of your environment and the steps you take to start the editor, as it affects how the PATH will look to expert.

[aseigo]

Mise: 2025.12.0 linux-x64
Erlang: 28.2
Elixir: 1.19.4-ot-28
OS: Linux (OpenSuse Leap 15.6)

mist.toml: The observed behaviour is the same with or without a mise.toml, so this does not seem relevant

Editor: Kate, with the following configuration for Expert

{
    "servers": {
        "elixir": {
            "command": ["/home/aseigo/bin/expert_ls_start"],
            "rootIndicationFileNames": ["mix.exs"],            
            "highlightingModeRegex": "^(Elixir)$"
        }
    }
}

Starting Kate via the application menu, the Run Command interface, desktop shortcut, desktop widget, etc. ... it does not find erl, though it does find elixir even though both are installed using mise.

[mhanberg]

Mise: 2025.12.0 linux-x64
Erlang: 28.2
Elixir: 1.19.4-ot-28
OS: Linux (OpenSuse Leap 15.6)

mist.toml: The observed behaviour is the same with or without a mise.toml, so this does not seem relevant

Editor: Kate, with the following configuration for Expert

{
    "servers": {
        "elixir": {
            "command": ["/home/aseigo/bin/expert_ls_start"],
            "rootIndicationFileNames": ["mix.exs"],            
            "highlightingModeRegex": "^(Elixir)$"
        }
    }
}

Starting Kate via the application menu, the Run Command interface, desktop shortcut, desktop widget, etc. ... it does not find erl, though it does find elixir even though both are installed using mise.

Do you have elixir or Erlang installed globally at all with mise? Or with any package manager?

[netrusov]

I had the same issue right now - fixed by adding mise exec --

#!/usr/bin/env bash

mise exec -- expert --stdio

[aseigo]

Do you have elixir or Erlang installed globally at all with mise? Or with any package manager?

Everything is installed using mise. I have no system packages for Erlang/OTP or Elixir installed on the system.

[aseigo]

I had the same issue right now - fixed by adding mise exec --

#!/usr/bin/env bash

mise exec -- expert --stdio

Ah, that's a very nice trick indeed.

I've modified my Kate config to contain "command": ["mise", "exec", "--", "expert", "--stdio"], and that works without the need for an extra shell script at all. Lovely.

Perhaps this could / should become the recommended way to run expert in mise environments? There have been a few of these regressions in the past requiring the devs working on expert to exert time / effort on fixes .. perhaps mise exec is a more reliable way forward?

[badosu]

I can confirm mise exec -- expert --stdio resolved the issue for me. I sent a PR to better notify the client of initialization errors (this one in particular).